WO2004024394A1

WO2004024394A1 - Control of removal profile in electrochemically assisted cmp

Info

Publication number: WO2004024394A1
Application number: PCT/US2003/029230
Authority: WO
Inventors: Lizhong Sun; Liang-Yuh Chen; Siew Neo; Feng Q. Liu; Alain Duboust; Stan D. Tsai; Rashid A. Mavliev
Original assignee: Applied Materials, Inc.
Priority date: 2002-09-16
Filing date: 2003-09-15
Publication date: 2004-03-25
Also published as: KR20050043972A; TW200409225A; JP2005539384A

Abstract

Aspects of the invention generally provide a method and apparatus for polishing a substrate using electrochemical deposition techniques. In one aspect, an apparatus for polishing a substrate (104) comprises a counter-electrode (166) and a pad (160) positioned between a substrate (104) and the counter-electrode (166) and a pad (160) positioned between a substrate (104) and the counter-electrode (166). The counter-electrode (166) and/or the pad (160) each comprise a plurality of electrically isolated zones (924, 926, 628, 424, 426, 428). An electrical connector is separately coupled to each of the conductive elements. Separate bias may be applied in each of the electrically isolated zones. A substrate having a material layer may be moved in a relative motion from the counter-electrode (166), the pad (160), or both. Determining the separate biases may comprise determining a time that at least one portion of the material layer is associated with each of the zones of the counter-electrode (166).

Description

CONTROL OF REMOVAL PROFILE IN ELECTROCHEMICALLY ASSISTED CMP

BACKGROUND OF THE INVENTION Field of the Invention

[0001] Embodiments of the present invention relate to a method and apparatus for planarizing a surface of a substrate and, more particularly, to a method for controlling the removal rates of materials disposed on the substrate surface and the removal or polishing profile in electrochemically assisted chemical mechanical polishing (ECMP).

Background of the Related Art

[0002] Chemical mechanical polishing (CMP) is a common technique used to planarize substrates. CMP utilizes a chemical composition, typically a slurry or other fluid medium, for selective removal of material from substrates. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate urging the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. The CMP apparatus effects polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a polishing composition to effect chemical activity and/or mechanical activity and consequential removal of material from the surface of the substrate.

[0003] One material increasingly utilized in integrated circuit fabrication is copper due to its desirable electrical properties. However, copper has its own special fabrication problems. Copper material is removed at different removal rates along the different surface topography of the substrate surface, which makes effective removal of copper material from the substrate surface and planarity of the substrate surface difficult to achieve.

[0004] One solution for polishing copper is by polishing copper by electrochemical mechanical polishing (ECMP) techniques. ECMP techniques remove conductive material from a substrate surface by electrochemical dissolution while concurrently polishing the substrate with reduced mechanical abrasion compared to conventional CMP processes. The electrochemical dissolution is performed by applying an electrical bias between an electrode and a substrate surface to remove conductive materials from a substrate surface into a surrounding electrolyte. During electrochemical dissolution, the substrate typically is placed in motion relative to a polishing pad to enhance the removal of material from the surface of the substrate. In one embodiment of an ECMP system, the electrical bias is applied by a ring of conductive contacts in electrical communication with the substrate surface in a substrate support device, such as a substrate carrier head. In other ECMP systems, a bias is applied between an electrode and conductive pad that is in contact with the substrate surface. Unfortunately, these conventional ECMP systems fail to provide a method for adjusting and controlling the polishing profile across the surface of the substrate to be polished during the ECMP process.

[0005] As a result, there is a need for a method and apparatus for controlling the rate of removal and the polishing profile (i.e., polishing rate) during ECMP.

SUMMARY OF THE INVENTION

[0006] Aspects of the invention generally provide a method and apparatus for polishing a layer on a substrate using electrochemical deposition techniques, electrochemical dissolution techniques, polishing techniques, and/or combinations thereof. In one aspect, an apparatus for depositing or removing material from a substrate, comprises a counter-electrode and a pad having a substrate-contacting surface positioned between a substrate and the counter-electrode, and the pad may have a plurality of pad zones and the electrode may have a plurality of electrode zones.

[0007] In another aspect of the invention, a method is provided for polishing a substrate including a conductive layer comprising separately applying a plurality of biases between the conductive layer and a plurality of zones of an electrode. The electrode is generally a counter-electrode to the material layer and may comprise a plurality of conductive elements separated by a dielectric material. [0008] In another aspect, an apparatus is provided for processing a substrate having a conductive layer including a substrate support, an electrode, and a pad positioned between the substrate support and the electrode, wherein the pad includes a plurality of zones adapted to provide an adjustable current density between the electrode and a substrate disposed on the substrate support for the at least one zone of the plurality of zones.

[0009] In another aspect, an apparatus for processing a substrate, including a conductive layer including a substrate support, an electrode, and a pad positioned between the substrate support and the electrode, wherein the pad includes a plurality of zones adapted to provide an adjustable current density between the electrode and a substrate disposed on the substrate support for the at least one zone of the plurality of zones. The polishing pad may include a first reference electrode and a second reference electrode. A method may comprise applying a first bias between the first reference electrode and the conductive layer. A first bias is applied between the first reference electrode and the substrate. A second bias is applied between the second reference electrode and the substrate. The second bias may be applied during the application of the first bias.

[0010] In another aspect, a method of processing a substrate is provided including contacting a pad to the substrate in a processing chamber having an electrode disposed therein, wherein the pad comprises a plurality of pad zones adapted to have a separate bias control in each pad zone and the electrode comprises a plurality of electrode zones adapted to have a separate bias control in each electrode zone, flowing an electrolyte between the electrode and the substrate, applying a separate bias between each pad zone and each electrode zone, and removing at least a portion of the metal layer therefrom.

[0011] In one aspect, a method is provided for processing a substrate including disposing a substrate containing a conductive material layer in a process apparatus comprising an electrode having a plurality of zones and a polishing pad, contacting the substrate and the polishing pad, moving the substrate relative to the plurality of zones of the electrode with at least one portion of the substrate passes through more than one zone of the plurality of zones of the electrode, applying a bias to each of the plurality of zones of the electrode, wherein the bias to each of the plurality of zones of the electrode is modified by the time that the at least one portion of the substrate layer is associated with more than one zone of the electrode, and removing conductive material from the conductive material layer.

[0012] In another aspect, a method is provided for processing a surface of a material layer including disposing a substrate containing a conductive material layer in a process apparatus comprising an electrode having a plurality of zones and a polishing pad having a plurality of zones corresponding to the plurality of zones of the electrode, providing relative motion between the polishing pad and the substrate, and separately applying a bias to each of the plurality of zones of the polishing pad and the plurality of zones of the electrode, wherein each bias causes conductive material from the conductive material layer to be removed at a rate that varies for each of the plurality of zones of the polishing pad.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and, therefore, are not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0014] Figure 1A is a sectional view of one embodiment of a processing cell that may be used to practice aspects described herein;

[0015] Figure 1 B is a sectional view of another embodiment of a processing cell that may be used to practice embodiments described herein;

[0016] Figure 2 is a bottom view of one embodiment of a counter-electrode;

[0017] Figure 3 is a bottom view of one embodiment of a dielectric insert;

[0018] Figure 4 is a schematic cross sectional view of the dielectric insert of Figure 3 exposed to a flow of electrolyte; [0019] Figure 5 is a schematic cross-sectional view of a dielectric insert depicting open and closed states of various zones;

[0020] Figure 6 is a bottom perspective view of one embodiment of a conductive pad that may be used to practice embodiments described herein;

[0021] Figure 7 is a bottom perspective view of a portion of another embodiment of a conductive pad that may be used to practice embodiments described herein;

[0022] Figure 8 is a cross-sectional view of the conductive pad of Figure 6;

[0023] Figure 9 is a bottom view of another embodiment of a conductive pad that may be used to practice embodiments described herein;

[0024] Figure 10 is a cross-sectional view of the conductive pad of Figure 8;

[0025] Figure 11A-B are sectional views of embodiments of a processing cell of the present invention;

[0026] Figure 12A-12B are top perspective views of a substrate having a material layer thereon, wherein the material layer may be polished in order to develop a relationship between removal rate and applied bias, consistent with embodiments described herein;

[0027] Figures 13A-13B depict two different removal rate profiles that may be generated using embodiments described herein; and

[0028] Figure 14 is a schematic, cross-sectional view of a material layer that may be polished using embodiments described herein.

[0029] To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] The words and phrases used herein should be given their ordinary and customary meaning in the art by one skilled in the art unless otherwise further defined herein. Chemical-mechanical polishing should be broadly construed and includes, but is not limited to, abrading a substrate surface by chemical activity, mechanical activity, or a combination of both chemical and mechanical activity. Electropolishing should be broadly construed and includes, but is not limited to, planarizing a substrate by the application of electrochemical activity. Electrochemical mechanical polishing (ECMP) should be broadly construed and includes, but is not limited to, planarizing a substrate by the application of electrochemical activity, or a combination of both electrochemical and mechanical activity to remove material from a substrate surface. Electrochemical mechanical plating process (ECMPP) should be broadly construed and includes, but is not limited to, electrochemically depositing material on a substrate and concurrently planarizing the deposited material by the application of electrochemical activity, or a combination of both electrochemical and mechanical activity.

[0031] Anodic dissolution should be broadly construed and includes, but is not limited to, the application of an anodic bias to a substrate directly or indirectly which results in the removal of conductive material from a substrate surface and into a surrounding electrolyte solution. Aperture should be broadly construed and includes, but is not limited to, a perforation, hole, opening, groove, channel, or passage formed partially or completely through an object. Additionally, the term substantially as used to modifying the term planar is intended to describe a surface on a macroscopic or global level and not surface roughness.

[0032] Figure 1A depicts a sectional view of one embodiment of a process cell 100 in which at least one or more processes including plating and polishing, or combinations thereof may be practiced. The process cell 100 may be used to practice electrochemical mechanical polishing (ECMP). The process cell 100 may be used to polish a substrate that includes a conductive layer, such as a conductive layer formed on a wafer substrate, through an anodic dissolution process. In an anodic dissolution process, an anodic bias is applied to the substrate, directly or indirectly, resulting in removal of conductive material from a substrate surface into a surrounding electrolyte. The process cell 100 may also be used to electrochemically deposit material onto a substrate. The electrochemical deposition may be concurrent with the application of various forms of activity used to polish the substrate. The concurrent activity may be electrochemical activity, mechanical activity, or a combination of both electrochemical and mechanical activity, such as are used in an electrochemical mechanical plating process (ECMPP).

[0033] The process cell 100 generally includes a basin assembly 152 and a polishing head 106. A substrate 104 may be retained in the basin assembly 152 during processing in a face-up (e.g., backside down) orientation. An electrolyte is flowed over a feature side (surface) 138 of the substrate 104 during processing. The polishing head 106 is placed in contact with the substrate 104, and the polishing head 106 and the substrate are moved relative to each other to provide a polishing motion. The polishing motion generally comprises at least one motion defined by an orbital, rotary, linear or curvilinear motion, or combinations thereof, among other motions. The polishing motion may be achieved by moving either or both of the polishing head 106 and the basin assembly 152.

[0034] The basin assembly 152 generally includes a basin 102 having a substrate support or carrier 116 disposed therein. The carrier 116 generally supports the substrate 104 within the basin 102 during processing. The basin 102 is generally non-electrically conductive and can be a bowl shaped member made of a plastic such as fluoropolymers, TEFLON^® polymers, perfluoroalkoxy resin, PFA, polyethylene-based plastics, PE, sulfonated polyphenylether sulfones, PES, or other materials that are compatible or non-reactive with electrolyte compositions that may be used in electroplating or electropolishing. The basin 102 generally includes sidewalls 108 and a bottom 110 that generally defines a container or electrolyte cell in which a conductive fluid such as the electrolyte can be confined. The bottom 110 generally includes a drain 142 to facilitate removal of fluids from the bottom of the basin 102, while the sidewalls 108 generally include an outlet 140 to facilitate removal of excess electrolyte from the basin 102 during processing.

[0035] The basin 102 may be stationary or be driven to provide at least a portion of a relative motion between the substrate 104 and the polishing head 106. In the embodiment depicted in Figure 1A, an optional shaft 112 is coupled to the bottom 110 of the basin 102 and is coupled to a drive system (not shown) to provide the basin 102 with a rotary, orbital, sweep motion or a motion comprising combinations thereof, among other motions. The shaft 112 additionally provides a conduit for ground leads 144 and other control or supply lines to be routed into or out of the basin 102. In embodiments wherein the basin 102 is rotated by the shaft 112, the drain 142 may also be routed through the shaft 112.

[0036] A spacer 114 is disposed on the bottom 110 of the basin 102. The spacer 114 is typically annular in form and is comprised of a material compatible with process chemistries. In one embodiment, the spacer 114 is fabricated from the same material as the basin 102. The spacer 114 may optionally be fabricated with the basin 102 as a single member from a unitary mass of material.

[0037] The carrier 116 is generally disposed in the basin 102 and supported by the spacer 114. The carrier 116 is typically fabricated from a dielectric material such as a polymer or a ceramic material. The carrier 116 generally includes a first side 118 and a second side 120. The first side 118 includes a flange 122 substantially circumscribing a projecting center section 124. The flange 122 is disposed on the spacer 114 and supports the carrier 116 above the bottom 110 of the basin 102. The center section 124 projects into the open area defined within the spacer 114 to locate the carrier 116 within the basin 102 and prevent movement of the carrier 116 during processing.

[0038] The second side 120 of the carrier 116 includes a projecting support surface 126 that extends towards the top of the basin 102. The support surface 126 generally supports the substrate 104 during processing. The support surface 126 includes at least one vacuum port 132 formed therein and coupled to a vacuum passage 128 disposed through the carrier 116. The vacuum passage 128 is fluidly coupled through the shaft 112 to a vacuum source 146. Vacuum, drawn through the vacuum port 132, retains the substrate 104 on the support surface 126 during processing. Optionally, the support surface 126 may include topography that enhances the distribution of vacuum between the substrate 104 and support surface 126 so that the substrate 104 is uniformly pulled towards the carrier 116. [0039] A plurality of lift pins 154 (only one is shown for clarity) is disposed through respective holes formed through the carrier 116. A lift plate 156 disposed between the carrier 116 and the chamber bottom 110 is coupled to an actuator rod 158. The actuator rod 158 is routed through the shaft 112 to a lift mechanism (not shown). The lift mechanism may be actuated to move the rod 158 and lift plate 156 towards the carrier 116. The lift plate 156 contacts the pins 154 and causes the pins 154 to extend above the support surface 126 of the carrier 116, thus placing the substrate 104 in a spaced-apart relation relative to the carrier 116 that facilitates access to the substrate 104 by a substrate transfer device (not shown).

[0040] An annular retaining ring 130 is generally disposed on the flange 122 of the carrier 116. The retaining ring 130 generally snugly circumscribes and extends above a plane of the support surface 126. The thickness of the retaining ring 130 is configured so that a top surface 136 of the retaining ring 130 is substantially co-planar (i.e., within about ±1 mil) with the feature side 138 of the substrate 104 to be processed. The sidewalls 108 generally extend above the retaining ring 130 to define a processing area 150. The outlet 140 is typically located in the sidewall 108 near the elevation of the top surface 136 of the retaining ring 130 to allow the removal of electrolyte from the processing area 150 during or after processing.

[0041] The top surface 136 of the retaining ring 130 is typically fabricated from a material that does not adversely affect the polishing head 106 which may periodically contact the top surface 136. In one embodiment, the retaining ring 130 is fabricated from a material compatible with processing chemistries, for example, a thermoplastic such as polyphenylene sulfide (PPS) among other polymers. The retaining ring 130 may be grounded by the ground lead 144 that is routed out of the process cell 100 through the shaft 112. If the retaining ring 130 is a thermoplastic or other dielectric, there is no need to ground it since it is an electrical insulator.

[0042] Alternatively, the ring 130 may be metallic to promote uniformity across the wafer (particularly at the edge of the substrate). For example, an ungrounded copper retaining ring 130 may be used that has the same potential as the substrate during processing of the electrical field.

[0043] The polishing head 106 generally includes a pad 160, an optional zone control insert 165, an optional membrane 162, a support disk 164 and a counter- electrode 166 coupled to a housing 168. The pad 160 is generally exposed at the bottom of the polishing head 102 and contacts the substrate 104 and, in some embodiments, the retaining ring 130 during processing. The pad 160 may have one or more conductive elements formed therein. The membrane 162 is sandwiched between the pad 160 and the support disk 164. The counter- electrode 166 is disposed between the support disk 164 and the interior of the housing 168. The pad 160, membrane 162, disk 164 and the counter-electrode 166 are permeable, perforated, or contain passages formed therethrough that allow the electrolyte to flow into and out of the polishing head 102.

[0044] The polishing head 106 may be stationary or driven to provide at least a portion of the relative motion between the substrate 104 and the polishing head 106. In the embodiment depicted in Figure 1A, the housing 168 is coupled to a drive system (not shown) by a column 170. The drive system moves the column 170 thereby providing the polishing head 106 with a rotary, orbital, sweep motion or a motion comprising combinations thereof, among other motions. The column 170 additionally provides a conduit for electrical leads and other control or supply lines to be routed into or out of the polishing head 106.

[0045] The housing 168 is generally fabricated from a rigid material compatible with process chemistries. The housing 168 generally includes a top 178 which is coupled to the column 170 and sides 180 extending therefrom. The sides 180 typically are coupled to the support disk 164, enclosing the counter-electrode 166 within the housing 168. A plurality of spacing members (not shown) generally extend from the top 178 into the interior of the housing 168. The spacing members keep the counter-electrode 166 in a spaced-apart relation relative to the top 178. The spacing members generally support the counter-electrode 166 in an orientation parallel to the surface of the substrate 104. The spacing members are configured to allow fluids to move laterally within the housing 168. [0046] The counter-electrode 166 comprises an electrically conductive material. The counter-electrode 166 and the substrate 104 define a region between which an electrical bias (e.g. a potential difference) is established. The bias may be applied between the counter electrode 166 and the pad 160 that is placed in contact with the surface 138 of the substrate 104. The pad 160 may be at least partially conductive and may act as an electrode in combination with the substrate 104 during electrochemical processes, such as an electrochemical mechanical plating process (ECMPP), which includes electrochemical deposition and chemical mechanical polishing, or electrochemical dissolution. The counter- electrode 166 may be an anode or cathode depending upon the positive bias (anode) or negative bias (cathode) applied between the counter-electrode 166 and the pad 160.

[0047] For example, when depositing material from an electrolyte onto the substrate surface, the counter-electrode 166 acts as an anode and the substrate surface and/or conductive pad 160 acts as a cathode. A reaction takes place at the cathode causing material to deposit on the substrate surface. When removing material from a substrate surface, the counter-electrode 166 functions as a cathode and the substrate surface and/or the pad 160 acts as an anode. The removal may result from material on the substrate surface dissolving into the surrounding electrolyte due to the application of the electrical bias.

[0048] The level of the electrolyte within the basin 102 is maintained at a level that ensures that the counter-electrode 166 is immersed in the electrolyte during processing. The counter-electrode 166 is permeable to the electrolyte and gases, and can be a plate-like member, a plate having multiple holes formed therethrough or a plurality of counter-electrode pieces disposed in a permeable membrane or container.

[0049] The counter-electrode 166 typically is comprised of the material to be deposited or removed, such as copper, aluminum, gold, silver, tungsten and other materials which can be electrochemically deposited on the substrate 104. For electrochemical removal processes, such as anodic dissolution, the counter- electrode 166 may include a non-consumable electrode of a material other than the deposited material, such as platinum for copper dissolution. The non- consumable electrode is used in planarization processes combining both electrochemical deposition and removal.

[0050] Figure 2 shows a bottom view of a counter-electrode 166 consistent with embodiments of the invention described herein. The counter-electrode has a surface 990 that generally is positioned to face the surface 138 of the material layer 105 to be polished. The counter-electrode 166 may be characterized as having a plurality of distinct zones. Three zones, an outer zone 924, an intermediate zone 926, and an inner zone 928 are shown by way of example in Figure 2 (the zones 924, 926, 928 are separated by zone boundaries 980 that are shown in phantom in Figure 2).

[0051] Each zone of the counter-electrode 166 generally comprises at least one conductive element (three conductive elements 950, 952, 954 are shown by way of example in Figure 2) that is electrically isolated from the conductive elements in the other zones. Each conductive element may be, for example, a ring or a radially-oriented conductive element. Alternatively, other shapes and orientations, such as linear, curved, concentric, involute curves or other shapes and orientations are possible for the conductive elements. The conductive elements may be of substantially equal sizes and shapes from one zone to the next, or the sizes and shapes may vary depending upon the particular zone of concern. So that the zones may be separately biased, the conductive elements are separated by insulating material such as a solid, liquid, or gaseous (e.g. air) dielectric material, or combinations thereof. The counter electrode 166 may have perforations 960 therethrough to facilitate the flow of electrolyte through the counter-electrode 166.

[0052] The support disk 164 is perforated or permeable to the electrolyte and gases. The support disk 164 is made from a material compatible with the electrolyte that would not detrimentally affect polishing. The support disk 164 may be fabricated from a non-electrically conductive polymer, for example a plastic such as fluoropolymers, TEFLON^® polymers, perfluoroalkoxy resin, PFA, polyethylene-based plastics, PE, sulfonated polyphenylether sulfones, PES, or other materials that are compatible or non-reactive with electrolyte compositions that may be used in electroplating or electropolishing. The support disk 164 is typically secured in the housing 168 of the polishing head 106 using adhesives, fasteners or other devices or methods that substantially ensure the parallelism of the support disk 164 and the carrier 116. The support disk 164 may be spaced from the counter-electrode 166 to provide a wider process window, thus reducing the sensitivity of depositing material and removing material from the substrate surface to the counter-electrode 166 dimensions.

[0053] In one embodiment, the support disk 164 includes a plurality of perforations or channels (not shown) formed therein. The size and density of the channels are selected to provide uniform distribution of the electrolyte through the support disk 164 to the substrate 104. In one aspect, the support disk 164 includes channels having a diameter between about 0.5 mm and about 10 millimeters. The channels may have a density between about 30% and about 80% of the polishing media. A channel density of about 50% has been observed to provide electrolyte flow with minimal detrimental effects to polishing processes. Generally, the channels of the support disk 164 and the pad 160 may be aligned to provide for sufficient mass flow of electrolyte through the support disk 164 and pad 160 to the substrate surface.

[0054] A dielectric insert 165 may be positioned between the counter electrode 166 and the pad 160. Figure 3 depicts a bottom view of one embodiment of the dielectric insert 165 and Figure 4 depicts a cross sectional view of the dielectric insert 165 taken along line 4-4 of Figure 3. While the following description of the dielectric insert is for a circular insert, the invention contemplates that the dielectric insert may have other shapes and geometrical configurations, such as a square shape.

[0055] Regarding Figure 3, the dielectric insert 165 may have a circular outer surface or diameter 500 (shown in phantom). The diameter 500 may be greater or lesser than a diameter of the pad 160 disposed adjacent thereto. In one embodiment, the dielectric insert 165 has a diameter 500 generally corresponding to a diameter of the pad 160. An outer portion or zone 504 of the dielectric insert including the diameter 500 is exposed to and adapted to allow flow of electrolyte therethrough. The diameter 500 of the dielectric inset 165 may be less than the diameter or width of the portion of the apparatus disposed therein to allow electrolyte flow therearound from pad 160 to counter-electrode 166 or counter- electrode 166 to pad 160.

[0056] The dielectric insert 165 may also have a thickness (not shown to scale) necessary for use in inhibiting flow through the process cell 100. For example, the dielectric insert may have a thickness between about 0.1 mm and about 5 mm. Additionally, the thickness of portions of the dielectric insert 165 may vary across the dielectric insert 165. For example, the dielectric insert 165 may have a concave or convex shape for a desired removal profile or to mate with adjacent articles in the processing cell 100.

[0057] The dielectric insert 165 has a cross-sectional area that may modify or vary, i.e., impede or encourage, the flow of electrolyte between the pad 160 and the counter-electrode 166. For example, a dielectric insert may be adapted as a flow control insert and reduce or impede electrolyte flow through one or more portions of the dielectric insert 165 (arrows are used in Figure 4 to indicate the direction of flow of electrolyte). The dielectric insert may also have an adaptable cross sectional area that by mechanical or other means controls the amount of electrolyte therethrough for different processes or different times during the same process.

[0058] In one aspect, the dielectric insert 165 may comprises a plurality of zones. The zones may be, for example, concentric circular or annular segments, as depicted in Figure 2, or other geometrical configurations. For example, three zones, an outer zone 504, an intermediate zone 506, and an inner zone 508 are shown by way of example in Figures 3 and 4.

[0059] The insert 165 is adjustable such that each zone of the insert 165 may be switched between an open electrolyte flow state, such a full or 100% electrolyte flow, closed or blocked electrolyte flow state, such as about 0% electrolyte flow, or with the ability to have some electrolyte flow state or permeability between, such as 50% closed or blocked state, e.g., 50% electrolyte flow, therethrough. Greater than 50% electrolyte flow is considered a high electrolyte flow state or high permeability state, and 50% or less electrolyte flow is considered a low electrolyte flow state or low permeability state. For example, in Figure 4, all zones are open and anodically dissolved material is allowed to flow freely from an outer zone 514, an intermediate zone 516, and an inner zone 518 of the substrate 104.

[0060] The state of each zone of the insert 165 may be adjusted between a blocked an open state by various ways. For example, the insert 165 may comprise a plurality of retractable, rotatable, or sliding plates that permit zones to be opened or closed. In another embodiment, the insert 165 comprises one or more detachable concentric rings that can be selectively removed or positioned so as to open or block a particular zone. Alternatively, the dielectric insert 165 may comprise a series of membranes that have an adjustable permeability to the electrolyte. In at least one embodiment the insert 165 is detachable from the polishing head 106 to facilitate adjustment of one or more zones from one state to another. While Figures 2-4 depict a zone in either one of two discrete states (i.e. blocked or open), it is within the scope of the invention for a zone to be switched between a plurality of partially blocked or partially permeable states as described above.

[0061] Limiting the electrolyte flow through the respective zone also correspond to a reduction in the current density therethrough. When the electrolyte is inhibited from flowing, such as by a low electrolyte flow state (low permeability state), the corresponding current density is reduced and any electrochemical activity, such as electroplating or electropolishing is reduced. In an open or high permeability state, the zone is occupied by either a material with low electrical resistance and/or high permeability to electrolyte or is unobstructed such that electrolyte may pass unimpeded and current density is higher than in zones with limited flow or limited current density.

[0062] The amount or thickness of dielectric material disposed in the respective zone of the dielectric insert 165 may also be increased to reduce the current density through the zone by an increase in electrical resistance between the counter-electrode 166 and the pad 160 or material layer 105. The dielectric insert 165 may also control the current density through one or more portions or zones by application of different dielectric materials for different portions or zones of the insert between the counter-electrode and pad or substrate in a similar manner as controlling the electrolyte flow therethrough.

[0063] The dielectric insert may comprise electrically resistive materials, such as a non-electrically conductive polymer, including, for example, a plastic such as fluoropolymers, TEFLON^® polymers, perfluoroalkoxy resin, PFA, polyethylene- based plastics, PE, sulfonated polyphenylether sulfones, PES, or other materials that are compatible or non-reactive with electrolyte compositions that may be used in electroplating or electropolishing, such as dielectric materials used in conventional polishing pads, such as polyurethane. The dielectric insert 165 may comprise one or more materials dielectric to provide a desired dielectric of the entire dielectric insert or to provide the desired dielectric or electrical properties for each of the respective zones.

[0064] Figure 5 depicts the annular dielectric insert 165 that has an open or permeable inner zone 508 (e.g. an opening) that allows current/electrolyte such as, for example, anodically dissolved material from the inner zone 518 of the substrate 104 to pass from through the inner zone 508 of the insert 165. Similarly, the insert 165 has an open outer zone 504 that permits material from an outer zone 514 of the substrate 104 to pass through the outer zone 504 of the insert 165. The insert 165 has a blocked intermediate zone 506 that reduces or inhibits the current moving across an intermediate zone 516 of the substrate 104 through the intermediate zone 506 of the insert 165.

[0065] While Figures 4 and 5 depict an insert 165 that has a diameter 530 that is about the same size as a diameter of the substrate 104, the diameter of the insert 165 may be larger or smaller than the diameter of the substrate 104. In one embodiment, the insert 65 has a diameter that is about 3 to about 5 times larger than that of the substrate 104.

[0066] To facilitate control of polishing uniformity, a microprocessor controller 194, as shown in Figure 1A may be electrically coupled to the optional dielectric insert 165 and the various components of the process cell 100 to facilitate control of the polishing process. The controller 196 comprises a central processing unit (CPU) 244, a memory 242, and support circuits 246 for the CPU 244. The CPU 244 may be one of any form of a general purpose computer processor that can be used in an industrial setting for controlling various process equipment and sub- processors. The memory 242 is coupled to the CPU 244. The memory 242, or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits 246 are coupled to the CPU 244 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. A polishing process is generally stored in the memory 242 as a software routine. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU 244.

[0067] The software routine is executed after the substrate is positioned in the process cell 100. The software routine when executed by the CPU 244, transforms the general purpose computer into a specific purpose computer (controller) 196 that controls the process cell 100 such that the polishing process is performed. Although the process of the present invention is discussed as being implemented as a software routine, some of the method steps that are disclosed therein may be performed in hardware as well as by the software controller. As such, the invention may be implemented in software as executed upon a computer system, in hardware as an application specific integrated circuit or other type of hardware implementation, or a combination of software and hardware.

[0068] The membrane 162 is generally permeable, thereby allowing the electric field lines, electrolyte and other liquids and gases to pass therethrough. The membrane 162 generally prevents particles or sludge released from the counter-electrode 166 from passing through the electrolyte and contacting the substrate 104. The membrane 162 is typically fabricated from a porous ceramic or polymer that is compatible with process chemistries and does not increase the cell resistance. For example, a spunbonded polyolefin (such as TYVEK®, available from E. I. DuPont de Nemours Inc. of Wilmington, Delaware) may be used. [0069] The pad 160 can be a pad, a web or a belt of material, which is compatible with the fluid environment and the processing specifications. In the embodiment depicted in Figure 1A, the pad 160 is circular in form and is adhered or otherwise retained to the optional dielectric insert 165 or the membrane 162 at the bottom of the polishing head 106 opposite the housing 168 of the polishing head 106. The pad 160 may include one or more conductive elements (not shown in Figure 1A) for contacting the feature side 135 of the substrate 104 during processing. A backing material (not shown) may be disposed between the membrane 162 and the pad 160 to tailor the compliance and/or durometer of the pad 160 during processing. Examples of a conductive pad that may be adapted to benefit from the invention are disclosed in United States Patent Application 10/033,732, filed December 27, 2001 , which paragraphs 41-157 are incorporated herein incorporated by reference to the extent not inconsistent with the claims aspects and description herein.

[0070] Figure 6 depicts a bottom perspective view of one embodiment of a pad that may be used to practice embodiments described herein. The pad 400 is a conductive pad comprising a body 406 having a polishing surface 402 adapted to contact the substrate while processing. The polishing surface 402 has a plurality of conductive elements 414, each of which may be formed within a pocket 404 within the polishing surface 402. The conductive elements 414 generally have a contact surface 408 that may extend above a plane defined by the polishing surface 402. The contact surface 408 is typically compliant to maximize electrical contact with the substrate without scratching. During polishing, the substrate generally provides a bias force that urges the contact surface 408 into a position co-planar with the polishing surface 402.

[0071] The body 406 is generally permeable to the electrolyte by a plurality of channels or perforations 410 formed therein. The plurality of perforations 410 allow electrolyte to flow through the body 406 and contact the surface of the substrate 104 during processing. Perforations 410 formed in the conductive pad 400 may include apertures, channels, or holes in the body 406. The aperture size and density is selected to provide uniform distribution of electrolyte, as well as current distribution, through the conductive pad 400 to a substrate surface. [0072] The body 406 of the conductive pad 400 is generally made of a dielectric material. Examples of materials suitable for use in the body 406 include conventional polishing materials typically comprised of polymeric materials, such as polyurethane, polycarbonate, polyphenylene sulfide (PPS), or combinations thereof, and other polishing materials, such as ceramic material, used in polishing substrate surfaces. A conventional polishing media typically comprises polyurethane and/or polyurethane mixed with fillers. Conventional polishing media, such as the Freudenberg FX 9 pad is commercially available from Freudenberg & Company of Weinheim, Germany or the IC-1000 pad commercially available from Rodel Inc., of Phoenix, Arizona. Other conventional polishing materials, such as a layer of compressible material, for example felt leeched in urethane as in a Suba IV polishing pad commercially available from Rodel Inc., of Phoenix, Arizona, may also be utilized for the body 406.

[0073] The pockets 404 generally are configured to retain the conductive elements 414 while processing, and accordingly may vary in shape and orientation. In the embodiment depicted in Figure 5, the pockets 404 are grooves of rectangular cross section and are disposed across the polishing surface 402 coupling two points on the perimeter of the conductive pad 160. Alternatively, the pockets 404 (and conductive elements 414 disposed therein) may be disposed at irregular intervals, be orientated radially, perpendicular and may additionally be linear, curved, concentric, involute curves or other orientation.

[0074] Typically, the conductive elements 414 may include conductive polymers, polymer composites with conductive materials, conductive metals or polymers, conductive fillers, graphitic materials, or conductive doping materials, or combinations thereof. The conductive elements 214 generally have a bulk resistivity or a bulk surface resistivity of about 10 Ω-cm or less.

[0075] The pad 400 may be characterized as having a plurality of distinct zones (three are shown, in phantom, by way of example in Figure 5), such as an outer zone 424, an intermediate zone 426, and an inner zone 428. The zones 424 may have linear boundaries 430, as depicted in Figure 5. Alternatively, the zones 424 may have radial boundaries 430, or boundaries 430 with other geometries. [0076] One or more connectors 412 couple the conductive elements 414 to a power source 190 (or alternatively, a potentiostat) to electrically bias the conductive elements 414 while processing. The connectors 412 are generally wires, tapes or other conductors compatible with process fluids or having a covering or coating that protects the connector 412 from the process fluids. The connectors 412 may be coupled to the conductive elements 414 by soldering, stacking, brazing, clamping, crimping, riveting, fastening, conductive adhesive or by other methods or devices. Examples of materials that may be utilized in the connectors 412 include insulated copper, graphite, titanium, platinum, gold, and HASTELOY® among other materials. The connectors 412 may be coated with, for example, a polymer. In the embodiment depicted in Figure 5, one connector 412 is coupled to each conductive element 414 at the perimeter of the conductive pad 400. Alternatively, the connectors 412 may be disposed through the body 406 of the conductive pad 400.

[0077] Figure 7 depicts a three-dimensional bottom perspective view of another embodiment of a conductive pad 300 and Figure 8 is a cross-sectional view of the pad 300 of Figure 7 taken along line 8-8 of FIG. 7. The pad 300 includes a support 302 that comprises a perforated base 306. The perforated base 306 has a contact surface 338 and an opposing surface 358 opposed to the contact surface 338. The support 302 is generally constructed of a dielectric material similar to the dielectric materials described above for body 406 with reference to Figure 5. Apertures or perforations 312 formed through the perforated base 306 allow fluid, such as electrolyte fluid, to pass through the pad 300.

[0078] The pad 300 may further include one or more reference electrodes disposed in a plurality of posts 308 extending from the surface 338 of the perforated base 306. The posts comprise a base portion 309 and a contact portion 311. A contact pad 304 comprising a conductive material is formed on the contact portion 311 of each post 308. The contact pads 304 may have an area that is substantially uniform amongst all of the contact pads 304 on the bottom surface 338 of the polishing pad 330. A conductive element 310, such as a wire or other conductive means, is formed through each post 308 to provide electrical contact with each contact pad 304 and one or more external power sources. Each wire 310 and contact pad 304 attached thereto form a continuous conductive pathway through pad 300. The plurality of posts 308 may be configured into a plurality of rings or are oriented radially, linearly, curved, concentrically, involuted, or combinations thereof.

[0079] The posts described are illustrative, and the invention contemplated posts of different geometries, such as square or conical bases, different heights, different thicknesses, and different numbers of conductive elements disposed therein.

[0080] The conductive pad 300 may further comprises a plurality of zones as discussed above with reference to Figure 6 including one or more of the plurality of posts 308. The zones may contain the same or different number of posts, same or different density of posts, or the same or variable heights of the posts. The zones may further include posts 308 that do not have conductive elements or posts isolated from an electrical source. The configuration and number of posts in each zone may be varied or adapted to provide the desired amount of electrical bias for the individual post 308 in each zone or to provide a desired electrical bias for the entire zone.

[0081] The zones may be oriented radially from a center 380 of the conductive pad 300, (i.e., the zones may be defined as portions of the pad within a specific range of distance from the center 380 of the pad 300). The plurality of zones may also be configured into a plurality of rings or are oriented radially, linearly, curved, concentrically, involuted, or combinations thereof

[0082] An electrical connector 316 may be attached to each conductive element 310 by, for example, soldering, to form an electrical connection thereto. Each zone generally includes at least one connector 316 electrically connected to the potentiostat or power supply 190.

[0083] Figure 9 depicts a bottom view of another embodiment of a conductive pad 804 having a contact surface 838 and an opposing surface 859. Figure 10 depicts a cross sectional view of the conductive pad 804 of Figure 9 taken through line 10-10. A plurality of contacting elements for contacting the substrate 104 may be formed in the pad 804. The contacting elements may be arranged in a pattern such as concentric circles, as shown in Figure 9 and 10 (a first contacting element 854, a second contacting element 856 and a third contacting element 858 are shown by way of example in Figures 9 and 10) or in other configurations. The number of contacting elements is variable and may be selected to facilitate electrical contact between the pad 804 and the substrate 104.

[0084] A plurality of reference elements are also formed in the conductive pad 804 (a first reference element 864, a second reference element 866 and a third reference element 868 are shown by way of example in Figures 9 and 10). While Figures 9 and 10 depict contacting elements and reference elements arranged in similar patterns (i.e. concentric circles), the patterns may be dissimilar. The reference elements each comprise conductive material. Each reference element is generally separately connected by a connector 816 to the potentiostat 190 to facilitate the application of a separate bias in each zone and across a thickness 815 of the pad. Each reference element may be positioned proximate to a perforation 810 in the pad 804 to facilitate the flow of electrolyte and the establishment of the separate biases across the thickness 815 of the pad 804.

[0085] Furthermore, while Figure 1A depicts the pad 160 as having a diameter larger than that of the substrate 104, the pad 160 may, alternatively, have a diameter smaller or substantially similar in size compared to the substrate 104. In one embodiment of the invention, the pad 160 and the counter-electrode 166 have a diameter that is in a range from about 3 to about 5 times as large as a diameter of the substrate 104 and the material layer 105 thereon.

[0086] While the polishing apparatus described above in Figure 1A depicts a "face-up" polishing apparatus, it is also within the scope of the invention to use a face-down polishing apparatus in which a substrate is supported face down above a polishing pad.

[0087] Figure 1B depicts a sectional view of one embodiment of a "face-down" process cell 200. The process cell 200 generally includes a basin 204 and a polishing head 202. A substrate 208 is retained in the polishing head 202 and lowered into the basin 204 during processing in a face-down (e.g., backside up) orientation. An electrolyte is flowed into the basin 204 and in contact with the substrate's surface while the polishing head 202 places the substrate 208 in contact with a pad assembly 222. The substrate 208 and the pad assembly 222 disposed in the basin 204 are moved relative to each other to provide a polishing motion (or motion that enhances plating uniformity). The polishing motion generally comprises at least one motion defined by an orbital, rotary, linear or curvilinear motion, or combinations thereof, among other motions. The polishing motion may be achieved by moving either or both of the polishing heads 202 and the basin 204. The polishing head 202 may be stationary or driven to provide at least a portion of the relative motion between the basin 204 and the substrate 208 held by the polishing head 202. In the embodiment depicted in Figure 1B, the polishing head 202 is coupled to a drive system 210. The drive system 210 moves the polishing head 202 with at least a rotary, orbital, sweep motion or combinations thereof.

[0088] The polishing head 202 generally retains the substrate 208 during processing. In one embodiment, the polishing head 202 includes a housing 214 enclosing a bladder 216. The bladder 216 may be deflated when contacting the substrate to create a vacuum therebetween, thus securing the substrate to the polishing head 202. The bladder 216 may additionally be inflated to press the substrate in contact with the pad assembly 222 retained in the basin 204. A retaining ring 238 is coupled to the housing 214 and circumscribes the substrate 208 to prevent the substrate from slipping out from the polishing head 202 while processing. One polishing head that may be adapted to benefit from the invention is a TITAN HEAD™ carrier head available from Applied Materials, Inc., located in Santa Clara, California. Another example of a polishing head that may be adapted to benefit from the invention is described in United States Patent No. 6,159,079, issued December 12, 2001 , which is hereby incorporated herein by reference in its entirety.

[0089] The basin 204 is generally fabricated from a plastic such as fluoropolymers, TEFLON^® polymers, perfluoroalkoxy resin, PFA, polyethylene- based plastics, PE, sulfonated polyphenylether sulfones, PES, or other materials that are compatible or non-reactive with electrolyte compositions that may be used in electroplating or electropolishing. The basin 204 includes a bottom 244 and sidewalls 246 that define a container that houses the pad assembly 222.

[0090] The sidewalls 246 include a port 218 formed there through to allow removal of electrolyte from the basin 204. The port 218 is coupled to a valve 220 to selectively drain or retain the electrolyte in the basin 204.

[0091] The basin 204 is rotationally supported above a base 206 by bearings 234. A drive system 236 is coupled to the basin 204 and rotates the basin 204 during processing. A catch basin 228 is disposed on the base 206 and circumscribes the basin 204 to collect processing fluids, such as an electrolyte, that flow out of port 218 disposed through the basin 204 during and/or after processing.

[0092] An electrolyte delivery system 232 is generally disposed adjacent the basin 204. The electrolyte delivery system 232 includes a nozzle or outlet 230 coupled to an electrolyte source 242. The outlet 230 flows electrolyte or other processing fluid from the electrolyte source 242 to into the basin 204. During processing, the electrolyte generally provides an electrical path for biasing the substrate 208 and driving an electro-chemical process to remove and/or deposit material on the substrate 208. Alternatively, the electrolyte delivery system may provide electrolyte through the bottom 244 of the process cell and flow electrolyte through the pad assembly, including the dielectric insert 207, to contact the polishing pad and substrate.

[0093] A conditioning device 250 may be provided proximate the basin 204 to periodically condition or regenerate the pad assembly 222. Typically, the conditioning device 250 includes an arm 252 coupled to a stanchion 254 that is adapted to position and sweep a conditioning element 258 across pad assembly 222. The conditioning element 258 is coupled to the arm 252 by a shaft 256 to allow clearance between the arm 252 and sidewalls 246 of the basin 204 while the conditioning element 258 is lowered to contact the pad assembly 222. The conditioning element 258 is typically a diamond or silicon carbide disk, which may be patterned to enhance working the surface of the pad assembly 222 into a predetermined surface condition/state that enhances process uniformity. One conditioning element 258 that may be adapted to benefit from the invention is described in United States Patent Application Serial No. 09/676,280, filed September 28, 2000 by Li et al., which is incorporated herein by reference to the extent not inconsistent with the claims aspects and description herein.

[0094] A power source 224 is coupled to the pad assembly 222 by electrical leads 212 (shown as 212A-B). The power source 224 applies an electrical bias to the pad assembly 222 to drive an electrochemical process as described further below. The leads 212 are routed through a slip ring 226 disposed below the basin 204. The slip ring 226 facilitates continuous electrical connection between the power source 224 and the pad assembly 222 as the basin 204 rotates. The leads 212 typically are wires, tapes or other conductors compatible with process fluids or having a covering or coating that protects the leads 212 from the process fluids. Examples of materials that may be utilized in the leads 212 include insulated copper, graphite, titanium, platinum, gold, and HASTELOY® among other materials. Coatings disposed around the leads 212 may include polymers such as fluorocarbons, PVC, polyamide, and the like.

[0095] As the pad assembly 222 includes elements comprising both an anode and cathode of an electrochemical cell, both the anode and cathode may be replaced simultaneously by simply removing a used pad assembly 222 from the basin 204 and inserting a new pad assembly 222 with fresh electrical components into the basin 204.

[0100] The pad assembly 222 depicted includes a conductive pad 203 coupled to a backing 207. The backing 207 may be coupled to an electrode 209. The dielectric insert 205 as described above may be disposed between the polishing pad 203 and the backing 207 or electrode 209. Typically, the conductive pad 203, the backing 207, optionally the dielectric insert 205, and the electrode 209 are secured together forming a unitary body that facilitates removal and replacement of the pad assembly 222 from the basin 204. Typically, the conductive pad 203, the backing 207, optionally the dielectric insert 205, and the electrode 209 are adhered or bonded to one another. Alternatively, the conductive pad 202, the backing 207, optionally the dielectric insert 205, and the electrode 209 may be coupled by other methods or combination thereof, including sewing, binding, heat staking, riveting, screwing and clamping among others.

[0101] The face-down polishing apparatus is more fully disclosed in U.S. patent application entitled "Method and Apparatus for Substrate Polishing," serial number 10/151 ,538, filed May 16, 2002 (Attorney Docket No. 6906), commonly assigned and which paragraphs 25-81 are incorporated herein by reference to the extent not inconsistent with the claims aspects and description herein. Similarly to face-up polishing, relative motion is provided between the substrate and the electrode and/or pad.

POLISHING METHODS

[0102] Using embodiments described herein, the polishing uniformity of an ECMP process may be improved by selectively adjusting a current density between a substrate and specific zones of an electrode. Referring to Figures 1-5, the substrate 104 is transferred to the support surface 126 of the carrier 116 in a typical lift pin assisted transfer operation. The polishing head 106 is lowered into the basin 102 to place the substrate 104 in contact with the pad 160 or at least proximate thereto. Electrolyte is supplied to the basin 102 and to a level such that the electrolyte may contact the counter-electrode 166, the pad 160, and the optional insert 165. Alternatively, the substrate 104 is positioned in a face-down polishing apparatus such that the substrate 104 may contact the pad 106 disposed beneath the substrate 104.

[0103] The electrolyte used in processing the substrate 104 can include metals such as copper, aluminum, tungsten, gold, silver or other materials that can be electrochemically deposited onto or electrochemically removed from the substrate 104. Electrolyte solutions may include commercially available electrolytes. For example, in copper containing material removal, the electrolyte may include between about 2 and about 30% by volume or weight of sulfuric acid based electrolytes or phosphoric acid based electrolytes, such as potassium phosphate (K₃PO₄), phorphoric acid, or combinations thereof. Additionally, the invention contemplates using electrolyte compositions conventionally used in electroplating or electropolishing processes. [0104] The electrolyte may comprise one or more chelating agents, one or more corrosion inhibitors, and one or more pH adjusting agents. The chelating agents may include one or more groups selected from the group consisting of amine groups, amide groups, carboxylate groups, dicarboxylate groups, tri- carboxylate groups, and combinations thereof, for example, ethylenediamine. The chelating agents may be present in a concentration between about 0.1 % and about 15% by volume or weight.

[0105] The one or more corrosion inhibitors may include an organic compound having azole groups, including benzotriazole, mercaptobenzotriazole, and 5- methyl-1-benzotriazole. The electrolyte composition may include between about 0.01% and about 2.0% by volume or weight of the organic compound having azole groups.

[0106] The pH adjusting agents that may be an acid, for example, acetic acid, citric acid, oxalic acid, phosphate-containing components, a base, such as potassium hydroxide (KOH), or combinations thereof, to provide a pH between about 3 and about 10. The electrolyte composition may include, for example, between about 0.2% and about 25% by volume or weight of the one or more pH adjusting agents. The composition may further comprise up to 15% one or more additives selected from the following group: suppressors, enhancers, levelers, inhibitors, brighteners, chelating agents, and stripping agents. An example of a suitable electrolyte is more fully described in United States Patent Application No. 10/032,275, filed December 21 , 2001 , which paragraphs 14-40 are incorporated herein incorporated by reference to the extent not inconsistent with the claims aspects and description herein

[0107] The electrolyte flow rate is typically constant, for example between about 0.1 gallons per minute (GPM) and about 20 GPM, but may vary according to the desires of the operator. Additionally, the invention contemplates that the electrolyte may be introduced from multiple inlets to provide variable electrolyte flow rates over portions of the substrate surface.

[0108] Figure 11 A is a sectional view of the process cell 100 that may be used to practice a polishing method consistent with embodiments of the invention described herein. Referring to Figure 11A and to Figure 1A, the substrate 104 disposed on the substrate support 126 and the pad 160 may be moved (e.g. rotated, translated, orbited, etc.) relative to one another to polish the surface 138 of the substrate 104. The counter electrode 166 is generally moved along with the pad 160. The counter electrode 166 may comprise a plurality of zones. An outer zone 1014, an intermediate zone 1016, and an inner zone 1018 are shown by way of example in Figure 11A. The counter-electrode 166 has optional perforations 960 formed therethrough. The counter-electrode 166 is positioned, for example, proximate to the pad 160 during polishing.

[0109] Power from the potentiostat or power source 190 may be applied to the pad 160 and the counter-electrode 166 through electrical leads to provide a bias therebetween. Three leads 192a, 192b, 192c connected to the respective zones 924, 926, 928 of the counter electrode 166 and the power source 190 are shown by way of example in Figure 11A. A lead 199 is connected to the pad 160 through one or more conductive elements 1090 formed in the pad 160. Each conductive element 1090 may have an individual lead and a series of conductive elements may be connected to the same lead as desired by the operator. The one or more conductive elements 1090 may have a surface that is substantially coplanar with a polishing surface 1098 of the pad 160. The conductive elements 1090 may comprise post conductive elements as shown in Figures 7-8 or may comprise concentric ring elements as shown in Figure 9.

[0110] While the description herein for the power source 190 indicates one power source, the invention contemplates that a plurality of power sources may be used including an individual power source for each lead or conductive element in the processing cell 100, 200.

[0111] The polishing motion may be applied before, after, or simultaneously with the application of the electrical bias. When contacting the surface 138 of the substrate 104, the pad 160 typically applies a pressure of about 2 psi or less, such as between about 0.01 psi and about 0.5 psi, for example, about 0.2 psi, to the substrate surface. The relative motion between the pad 160 and the substrate 104 may include rotational, linear or curvilinear motion, orbital motion or combinations thereof, among other motions. [0112] In anodic dissolution, the bias may be applied to the counter-electrode 166, performing as a cathode, and the substrate 104 (as well as the conductive pad, for embodiments in which a conductive pad is used) performing as the anode. The application of the bias allows removal of deposited material from the substrate surface.

[0113] Generally the bias is applied to provide a current density between about 0.1 milliamps/cm² and about 50 milliamps/cm², or between about 0.1 amps to about 20 amps for a 200 mm substrate. By varying the bias applied between each zone of the counter electrode 166 and the substrate 104, the rate of material removal from the substrate surface 138 may be varied. For example, a bias of a voltage of about 15 volts or less, such as between 1 volt and 15 volts, including between about 2 and about 6 volts, to a surface of the substrate 104 may be used with the processes described herein for 200 mm and 300 mm substrates. Additionally, each bias may be zero or "off' for a portion or all of a planarizing process. Further, the voltages described herein may be the voltages applied prior to any mechanical polishing and may be the voltages applied during mechanical polishing as described as follows.

[0114] The bias applied to perform the anodic dissolution process may be varied in power and application depending on the user requirements in removing material from the substrate surface. For example, a time varying anodic potential may be provided to the pad 160. The pulses may have a pulse width in a range of about 0.1 seconds to about 20 seconds. The time-varying potential may range from about -10 volts to about 10 volts. By way of example, the pulses may be cycled between 0 volts and 3 volts. The pulses of anodic potential may be repeated for a number of cycles ranging, for example, from about 1 to about 100 cycles or more.

Bias Change by Physical Aspects

[0115] In one embodiment, the current density is spatially varied between the surface 138 of the material layer 105 to be polished and the counter-electrode 166. The current density is varied by varying the electrical resistance between the substrate 104 and the counter-electrode 166. The varying of electrical resistance may be effectuated by adjusting the flow or permeability of electrolyte between the substrate 104 and the counter-electrode 166. This adjustment in permeability translates into a change in current density because the rate of anodic dissolution from the substrate 104 and the current density between the counter- electrode 166 and the substrate 104 is directly related to the motion of charge carriers (e.g. copper ions) between the substrate 104 and the counter-electrode 166. By providing increased uniformity of permeability of electrolyte between the counter-electrode 166 and the substrate 104, the current density and the rate of material removal from the substrate 104 are thereby made more uniform across the substrate 104. Alternatively, electrical resistance may be varied across the surface 138 to be polished without varying the permeability of electrolyte between the counter-electrode 166 and the substrate 104.

[0116] The electrical resistance between the counter-electrode 166 and the substrate 104 may be adjusted using one or more inserts, such as the dielectric insert 165 discussed above with respect to Figures 3-5. The permeability of one or more zones of the dielectric insert 165 is adjusted to provide an increased uniformity in flow of electrolyte among all of the zones of the substrate 104. For example, in a first polishing period, the dielectric insert 165 is not inserted between counter-electrode 166 and the substrate 104. Alternatively, the dielectric insert 165 may be inserted, but all zones are open or unrestricted with respect to electrolyte flow. It may be observed, for example, that copper is being removed from an intermediate zone 516 of the substrate 104 at a faster rate than for other zones of the substrate 104. The flow control 165 is inserted between inserted between counter-electrode 166 and the substrate 104 or otherwise manipulated to decrease the permeability of the electrolyte through the intermediate zone 516 of the dielectric insert 154. This reduces the flow of electrolyte and the current density from the intermediate zone 516 of the substrate 104 through the intermediate zone 506 of the insert 165, thus making the rate of copper removal in the intermediate zone 516 closer to the rate of copper removal in the other zones.

[0117] While the above description details using the dielectric insert 165 to vary the flow rate of electrolyte, the dielectric insert 165 may deliver a variable current density through other mechanisms. For example, the dielectric insert 165 may have a dielectric material with a dielectric constant in one zone that differs from a dielectric material having a different dielectric constant of another zone, thereby resulting in varying current densities through the various zones of the insert 165. Additionally, the thickness of the dielectric material for the zone may also be used to adjust the dielectric constant of the material of the zone to control current density. Additionally, the shape of the zone may also be modified to control the electrolyte flow or current density passing therethrough.

[0118] The above description details one example of a non-uniformity pattern that is often observed in ECMP processes, in which an intermediate zone 516 exhibits a faster removal rate than for other zones. Other observed non- uniformity patterns may be corrected as well. For example, it may be observed that material is being removed faster in the outer zone 514 and the inner zone 518 with respect to the intermediate zone 516. In another non-uniformity pattern, the inner zone 518 may exhibit slower removal that either the intermediate zone 516 or the outer zone 514. Other non-uniformity patterns are possible as well. Any of these non-uniformity patterns may be corrected using the technique of adjusting the flow rate of electrolyte through the appropriate zones of the dielectric insert 165 to provide a removal profile to result in a planarized substrate surface.

[0119] In another embodiment of the invention, instead of using the optional dielectric insert 165 to control the flow rate of the electrolyte, the flow rate of electrolyte may be adjusted by altering a pattern of perforations such as the perforations 410 in the conductive pad 400. Specifically, the conductive pad 400 may have a plurality of perforations 410 formed therethrough, the perforations 410 located in one or more zones such as the zones 424, 426, 428 of the pad 400. The flow rate of electrolyte through, for example, the outer zone 424 of the pad 400 is altered by, for example, plugging or sealing one or more the perforations 410 in order to reduce flow in the outer zone 424. Plugging the perforations 410 may be accomplished by inserting, for example, plugs of dielectric material into the perforations 410. Alternatively, the flow rate of electrolyte may be altered through the zone 424 of the pad by adding one or more new perforations 410 through the pad 400 in the zone 424. The process of plugging or adding the perforations 410 may be repeated for other zones of the pad 400. By altering the number of the perforations 410 in, for example, the zone 424 of the pad 400, the flow rate through the zone 424 is altered, thereby altering the polishing rate of the pad 400 in the zone 424.

[0120] While the insert 165 and the pad 160 described above are discussed in the context of an electrochemical-mechanical polishing (ECMP) process, the invention contemplates using the insert 165 and the pad 160 in other fabrication processes involving electrochemical activity. Examples of such processes using electrochemical activity include electrochemical deposition, which involves a pad 160 being used to apply bias to a substrate surface for depositing a conductive material, and electrochemical mechanical plating processes (ECMPP) that include a combination of electrochemical deposition and chemical mechanical polishing.

Bias Change by Process Application

[0121] In another exemplary polishing process, current density between a substrate 104 and zones of an electrode is adjusted by applying a bias such as a potential difference between one zone of an electrode such as the counter- electrode 166 and the substrate 104. A second bias is independently applied between a second zone of the counter-electrode 166 and the substrate 104. The second bias may be unequal to the first bias. Additional zones, such as a third zone, a fourth zone, and the like, may also be independently biased.

[0122] In one example of a power application process, a first bias, V1 is applied via the potentiostat or power source 190 between the outer zone 924 of the counter-electrode 166, performing as a cathode, and the pad 160, performing as the anode. Similarly, a second bias, V2 is applied between the intermediate zone 926 of the counter-electrode 166 and the pad 160. A third bias, V3 is applied between the inner zone 928 of the counter-electrode 166 and the pad 160. The application of the first bias V1 , the second bias V2, and the third bias V3 urges removal of material from the surface 138 of a material layer. Each bias V1 , V2, and V3, may include the application of a voltage of about 10 volts or less to the surface 138 of the substrate 104. [0123] The independent bias may be used to provide for effective planarization of the substrate surface 138. For example, referring to Figure 11 A, if it is observed that material from a copper layer is being removed (polished) faster in the intermediate zone 516 of the material layer 105 on the substrate 104 than the outer zone 514 and the inner zone 518, a first bias, V1 may be applied between an outer zone 514 of the substrate 104 and the counter electrode 166 using the power source or potentiostat 190. The bias may be applied, for example, using connectors 192a-c, 199 that provide the bias V1 between the first conductive element 850 formed in an outer zone 924 of the counter-electrode 166 and, for example, a conductive element 1090 formed in the pad 160. A bias V2 of smaller magnitude than V1 may be separately applied between the second conductive element 852 in the intermediate zone 926 of the counter-electrode 166 and the pad 160. A bias V3, applied to the third conductive element 854 in the inner zone 928 may, for example, be set to a value similar to the bias applied between the outer zone 1014 and the material layer 105 to maintain a similar bias.

[0124] Separate biasing of different zones of the counter-electrode 166 with respect to the substrate 104 allows one to correct a problem of unequal material removal rates that may have existed previously between the two zones of the substrate 104. The separate biases V1 , V2, V3 may be applied simultaneously, or in a staggered, an overlapping, or a non-overlapping fashion, in time. Note that arrows in Figure 11 A depict linear, rotational, orbital, sweep, and other forms of relative motion that may be provided between the substrate 104 with respect to the counter-electrode 166 and the pad 160, for example, during the application of the biases V1 , V2, and V3. To facilitate the application of the biases V1 , V2, and V3, the pad 160 may have perforations 1026 to allow electrolyte to flow between the substrate 104 and the counter electrode 166.

[0125] Referring to Figure 11B, in another exemplary polishing process, the current density between a zone of the substrate and electrodes is adjusted in a similar manner as described above with reference to Figure 11 A. However, the potential differences are applied using a multiple electrode configuration. The multiple reference electrodes (three reference electrodes 1034, 1036, and 1038 are shown by way of example in Figure 11 B) may be, for example, formed within a conductive pad 1000. Alternatively, the reference electrodes may be spaced apart from the pad 1000. In this embodiment, the counter electrode 166 may be a continuous conductive material that is not separated into different zones by dielectric material, as depicted in Figure 2.

[0126] For example, if it is observed that copper is being removed faster in the intermediate zone 516 than the outer zone 514 and the inner zone 518 of a substrate 104, a first bias, V1 , may be applied between the substrate 104 and a first reference electrode 1034 in outer zone 1114 of the pad 1000. The potential difference V1 may be applied using the potentiostat 190. Electrical contact with the substrate 104 may be made, for example, using an electrical connector 1080 that is coupled to a contact ring or other device for contacting the substrate 104. The connector 1080 may alternatively be electrically coupled to the substrate 104 by one or more conductive elements, such as the contacting elements 854, 856, 858 in Figure 6, that are formed within the pad 1000 and adapted to contact the substrate 104.

[0127] The first bias, V1 , may be applied between the first reference electrode 1034 and the substrate 104, for example, using a connector 1072 that is connected between the potentiostat 190 and the first reference electrode 1034 within an outer zone 1114 of the pad 1000. A second bias, V2, may be separately applied between the substrate 104 and a second reference electrode 1036 in an intermediate zone 1116 of the pad 160. A third bias, V3, applied between the substrate 104 and a third reference electrode 1038 in an inner zone 1118 of the pad 160. The third bias, V3, may be similar in magnitude to V1 in order to maintain a similar potential between the outer zone 1114 and the inner zone 1118.

[0128] While the above detailed description makes reference to polishing the substrate 104 or the material layer 105 uniformly (i.e., provide a polishing rate that does not vary substantially across the surface to be polished), alternatively the biases may be applied to different zones of the counter-electrode 166 or the pad 160 so as to generate a removal rate or polishing rate that is non-uniform across the surface 138 to be polished. In this alternative embodiment, the biases may be applied, for example, in order to correct for a non-uniformity in thickness that may be present in the material layer 105 or substrate to be polished. In general, using embodiments of the invention, the polishing rate across the surface to be polished (i.e. the removal profile) may be controlled.

[0129] The separate biases to be applied to the zones of the counter-electrode 166, or alternatively to the multiple reference electrodes, may be determined empirically, i.e., by polishing a plurality of material layers 105 and adjusting the separate biases in order to make the polishing rate more uniform or to make the polishing rate match a pre-determined profile. Alternatively, the biases may be selected using an algorithm that determines the amount of time during a polishing process that various parts, points, or zones of the material layer 105 to be polished are associated with various zones of the pad 160. In this manner, removal rate from regions of the material layer may be optimized.

[0130] In one aspect of the bias application per time process, a selection of appropriate values for V1 , V2, and V3, may be determined by a relationship between a rate of removal of material from the substrate surface 138 to be polished and a bias applied between the counter-electrode 166 and the substrate surface is utilized. The relationship may be a mathematical or statistical relationship such as a functional relationship.

[0131] The relationship between removal rate and bias may be determined empirically, for example, by polishing a plurality of test material layers 105 using a process cell such as the process cell 100. The test material layers 105 may be polished according to a specific set of instructions that is communicated via software to the controller 194. The controller 194 relays the set of instructions to components of the process cell 100. The set of instructions may comprise providing relative motion between the pad 160 and the substrate 104. The relative motion may be, for example, linear, rotational, orbital, or combinations thereof. A test bias, V_t is applied between the test material layer 105 and the counter electrode 166. The test bias, V_t, may be applied such that a substantially uniform potential is generated across the counter electrode 166 with respect to the surface 138 to be polished. The bias may be applied to the test material layer 105 using, for example, a pad such as the pad 160 described above. [0132] For example, referring to Figure 12A, a top perspective view of a substrate 604 shows a first test material layer 605 formed thereon. Similarly, Figure 12B shows a second substrate 704 having a second test material layer 705 formed thereon. The first test material layer 605 is polished by applying a first test bias such as a uniform test bias across the test material layer 605 relative to the counter electrode 166.

[0133] After polishing the test material layer 605 for a pre-determined period of time (a first polishing time), the substrate 604 is, for example, removed from the process cell 100 and an amount of material removed from the test material layer 605 is then measured. The amount of material removed may be determined, for example, using conventional methods of measuring layer thicknesses, such as sheet resistance (Rs) measurements. Alternatively, the amount of material removed may be measured using electron microscopy, or similar methods for analyzing thickness and composition of material layers. The material removal may be determined by measuring a thickness 680 of the test material layer 605 before polishing and the thickness 680 after polishing. The thickness 680 may be measured at a first point 620. Additional thickness measurements of the first test material layer 605 may be taken at one or more additional points 622 in order to obtain a statistically representative value for material removal.

[0134] Alternatively, a property other than thickness may be measured. For example, a mass of material removed or a material removal rate may be measured directly or indirectly. The one or more additional points 622 on the test material layer 605 may be chosen such that the points lie within a region or zone of the test material layer 605 that experiences a relatively uniform rate of polishing (material removal). For example, the first point 620 and the additional points 622 may be chosen such that they all lie in an intermediate region 616 of the test material layer 605. Alternatively, the first point 620 and the additional points 622 may be chosen such that they each are a distance from a center 630 of the test material layer 605 that is substantially the same. A first rate of material removal may be determined by, for example, dividing mass or thickness of the material removed by the first polishing time. [0135] The second test material layer 705 may be polished using the same geometry and configuration of the cell 100 as for the polishing of the first test material layer 605. The second test material layer 705 may be polished by applying a second bias applied to the second test material layer 705. Thereafter, the step of determining material removal may be performed for one or more points 720 on the second test material layer 705. Furthermore, the process of determining removal rate may be repeated for additional test material layers (not shown), if desired.

[0136] The one or more points 720 on the test material layer 705 may lie within a region such as an intermediate region 716 of the material layer 105. The intermediate region 716 may have a similar shape and define a similar range of distances from a center 730 of the material layer 705 as is defined by the intermediate region 616 with respect to the center 630.

[0137] By matching the material removal from each test material layer 605, 705 with the corresponding bias applied to the test material layer, a relationship, such as a mathematical relationship between rate of material removal and bias may be determined. The relationship thus determined may be relevant for a specific configuration of the process cell 100, including a specific polishing composition as well as specific composition of material layer. Therefore, the relationship between material removal and bias may be used to determine optimal bias voltages to be applied when polishing a material layer using a process cell that has a similar geometry/polishing composition to the process cell 100 used to polish the test material layers 605, 705. The relationship may be a linear relationship, an exponential relationship, or other mathematical relationship as determined between the rate of material removal and any applied bias. The mathematical relationship may also be modified or adjusted to compensate for any effects of the type, shape, geometry, or limitations of the processing cell on the processes being performed therein.

[0138] Referring again to Figures 12A-12B, after determining the relationship between bias and rate of material removal, a set of biases V1 , V2, V3 that may be desirably applied between the zones 924, 926, 928 of the counter-electrode 166 and the material layer 105 are determined. The set of desirable biases V1 , V2, V3 may be selected in order to generate a pre-determined removal profile, i.e. generate a separate rate of material removal for different regions of the material layer 105. For example, Figure 13A shows one example of a removal profile 900 that may be desirably generated. The removal profile 900 is substantially uniform across the material layer 105 to be polished (i.e. does not vary across surface 138 of the material layer 105, such as, for example, vary with a distance from a center such as the center 630 of the test material layer 105 shown in Figure 5A).

[0139] In an alternative embodiment of the invention, as shown in Figure 13B, the set of biases V1 , V2, V3 are selected to generate a removal profile 902 that varies across the surface 138 to be polished. The alternative embodiment depicted in Figure 13B, may be employed, for example, in cases in which the surface 138 of the substrate 104 and/ or material layer 105 is irregular (e.g. either the substrate 104 or the material layer 105 is bowed, warped, uneven, not flat, or otherwise has a variable thickness). For example, Figure 14 shows a cross- sectional view of the substrate 104 having a material layer 1105 formed thereon, wherein the material layer 1105 has a thickness 1180 that varies substantially across the surface 1138 to be polished). By applying biases that generate the non-uniform removal profile 902, material can be removed more rapidly from, for example, an edge region 1124 of the material layer 1105 than for a center region 1128.

[0140] For a known set of biases, V1 , V2, V3 applied to zones of the counter- electrode 166, a corresponding set of removal rates, R1 , R2, R3, can be estimated, calculated, or modeled using the pre-determined relationship, between applied bias and removal rate. The removal rates R1 , R2, R3, associated with the zones of the counter-electrode 166 can be used to determine removal rates that will be experienced by the material layer to be polished. Optimal values for biases V1 , V2, V3 can be determined using techniques described below.

[0141] The material layer 105 is polished, for example, by providing a predetermined set of instructions to the components of the process cell 100 using the controller 194. The predetermined set of instructions defines a specific sequence of relative motion between the pad 160 and the substrate 104. Using an appropriate algorithm, the location of any point on the material layer 105 as a function of time relative to the pad 160 can be calculated. Furthermore, the amount of time that any point on the material layer 105 is associated with each zone of the counter electrode 166 may also be determined by the algorithm. Because each zone of the pad 160 has a removal rate that is a function of the bias applied to that zone, it can therefore be determined the amount of time that any point on the material layer 105 is associated with each removal rate. The removal rate for any point on the material layer 105 can then be calculated as, for example, as an average of the removal rates of each zone, wherein the average is weighted by the amount or fraction of time that the point on the material layer 105 spends in each zone. In general, the material layer 105 may be polished in the process cell 100 used to polish the test material layers 605, 705. Alternatively, the material layer 105 may be polished in a process cell having similar geometry (e.g., substantially similar size and shape at the counter-electrode 166, a substantially similar distance between the counter-electrode 166 and the substrate 104, and the like).

Exemplary polishing method

[0142] A counter-electrode such as the counter-electrode 166 was divided into five zones: an inner zone, an inner-central zone, a central zone, an outer-central zone and an outer zone (Z1 , Z2, Z3, Z4 and Z5) respectively. The zones were arranged in a concentric circular manner similar to the zones depicted for the counter-electrode 166 shown in Figure 2. Each of the zones was capable of receiving a separate bias with respect to a material layer to be polished. One hundred twenty one points, representing a broad sampling of various locations on the material layer were selected. A pre-determined set of instructions (i.e., a polishing program) that encoded a sequence of relative motion between the counter-electrode 166 (as well as the pad 160) and the material layer 105 was provided to controller 194. An algorithm based on the polishing program was used to determine the sequence of relative positions between the material layer 105 and the counter-electrode 166 as a function of time throughout the polishing process. The algorithm calculated the location of each point relative to the five zones of the counter-electrode 166 for each of a total of 2400 instants in time (time steps). [0143] The algorithm also calculated the number of time steps each point was associated with each of the five zones (e.g. the number of times the point would be facing or under each of the zones of the counter-electrode 166). Note that for embodiments in which the process cell 100 comprises the pad 160, a point on the material layer 105 only experiences a bias when the point on the material layer 105 is facing a perforation 410in the pad 160. If the point is not facing a perforation 410 in the pad 160, no bias will be experienced by the point on the material layer 105.

[0144] Based upon the program to be used to polish the material layer, the algorithm determined that a first point in the center of the material layer was associated with Z2 for 1080 time steps (i.e. 45% of the total number of time steps), associated with Z1 , Z3, Z4, Z5 for 0 time steps, and associated with none of the zones (i.e., the point was not under a perforation 960 in the pad and therefore zero bias was experienced by the point) for the remaining 1320 time steps. Therefore, for 45% of time, point A was associated with Z2, and the expected removal rate would be 0.45 X R2.

[0145] From the algorithm it was further determined that a second point B, away from the center of the material layer) was associated with Z2 for 570 time steps (or 23.75% of the total number of time steps), associated with Z3 for 774 time steps (or 32.35% of the total number of time steps), and associated with no zones (i.e., not under a perforation in the pad) for 1056 time steps. The expected removal rate for point B is therefore given by an average of the removal rates for Z1 , Z2, Z3, Z4, and Z5, weighted by the percentage of the time spent in each zone. Expressed in mathematical terms, the expected removal rate for point B is given by the mathematical expression, [.2375 x R2] + [.3235 x R3].

[0146] The algorithm further calculated the expected removal rate for the remainder of the 121 points on the material layer in a similar manner. Specifically, for each point an expected removal rate was calculated as [A1 X R1] + [A2 X R2] + [A3 X R3] + [A4 X R4] + [A5 X R5]. A1 , A2, A3, A4, and A5 are the percentage of times that the particular point was associated with the zones Z1 , Z2, Z3, Z4, and Z5 respectively. [0147] The material layer to be polished had a non-uniform surface to be polished. In order to compensate for the non-uniform surface 138, the desired removal profile was similar to the removal profile 902, shown in Figure 13B. A least-squares regression was performed to optimize the values for R1 , R2, R3, R4, and R5 such that the removal profile of the material layer 105 after polishing would closely match the desired removal profile. The optimal biases to be applied to each of the zones was then determined using a pre-determined (linear) relationship between removal rate and bias (specifically bias in volts equals removal rate in thousands of Angstroms per minute). The results of the regression and the assumption of the linear relationship between bias and removal rate yielded a value of V1 of 2.0222 volts, a value of V2 of 1.8569 volts a value of V3 of 2.0028 volts, and a value of V4 of 3.7397 volts a value of V5 of 6.7937 volts. The material layer 105 was polished using these biases and the resultant removal profile was similar to the desired removal profile.

[0148] While Figures 11A-11B depict the use of the counter-electrode 166 that is divided into three radial zones, each of which may be separately biased with respect to the material layer 105, other pad configurations are possible. The counter-electrode 166 may be divided into zones of any number greater than one. Similarly, the zones of the counter-electrode 166 need not be radial as depicted in Figure 11 A. The zones may be may be of any geometrical configuration, such as, for example, linear sections.

[0149] Furthermore, in addition to the counter-electrode 166, one or more reference electrodes may be used to apply the separate biases to the material layer 105. Examples of methods that may be used to apply a plurality of biases between one or more electrodes and a material layer to be polished are provided in the previously cross-referenced, co-pending U.S. patent application entitled "Control Of Removal Profile In Electrochemically Assisted CMP", commonly assigned with the present invention and herein incorporated by reference to the extent not inconsistent with the claims aspects and description herein.

[0150] While the method described above is discussed in the context of an electrochemical-mechanical polishing (ECMP) process, the invention contemplates using the method in other fabrication processes involving electrochemical activity. Examples of such processes using electrochemical activity include electrochemical deposition, which involves a pad 160 being used to apply a uniform bias to a substrate surface for depositing a conductive material without the use of a conventional bias application apparatus, such as edge contacts, and electrochemical mechanical plating processes (ECMPP) that include a combination of electrochemical deposition and chemical mechanical polishing.

[0151] While the foregoing is directed to various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is Claimed is:

1. An apparatus for processing a substrate having a conductive layer, comprising: a substrate support; an electrode; and a pad positioned between the substrate support and the electrode, wherein the pad includes a plurality of zones adapted to provide an adjustable current density between the electrode and a substrate disposed on the substrate support for the at least one zone of the plurality of zones.

2. The apparatus of claim 1 , wherein the plurality of zones are configured into a plurality of rings, oriented radially, linearly, curved, concentrically, involuted, or combinations thereof.

3. The apparatus of claim 1 , wherein each zone of the plurality of zones comprises one or more reference electrodes adapted to provide a separate bias in each zone.

4. The apparatus of claim 3, wherein the plurality of reference electrodes are configured into a plurality of rings or are oriented radially, linearly, curved, concentrically, involuted, or combinations thereof.

5. The apparatus of claim 1 , wherein the electrode comprises a plurality of zones adapted to provide a separate bias control in each zone.

6. The apparatus of claim 5, wherein each zone of the electrode comprises a conductive element electrically isolated from conductive elements disposed in adjacent zones by an insulating material.

7. The apparatus of claim 6, wherein the conductive element comprises a ring, a radially orientated conductive element, or a combination thereof.

8. The apparatus of claim 7, wherein the conductive elements are disposed concentrically.

9. The apparatus of claim 1 , wherein the plurality of zones of the pad are formed by positioning a dielectric insert between the counter electrode and the pad and the dielectric insert comprises a plurality of zones and at least one zone of the plurality of zones is adapted to provide an adjustable current density between the electrode and the substrate for the at least one zone of the plurality of zones.

10. The apparatus of claim 9, wherein the dielectric insert comprises one or concentric rings or annular rings.

11. The apparatus of claim 9, wherein the dielectric insert is adapted to adjust the current density for each zone of the plurality of zones by modifying the permeability for the zone, modifying the dielectric material for the zone, modifying the thickness of the dielectric material for the zone, modifying the shape for the zone.

12. A method of processing a substrate having a metal layer formed thereon, comprising: contacting a pad to the substrate in a processing chamber having an electrode disposed therein, wherein the pad comprises a plurality of pad zones adapted to have a separate bias control in each pad zone and the electrode comprises a plurality of electrode zones adapted to have a separate bias control in each electrode zone; flowing an electrolyte between the electrode and the substrate; applying a separate bias between each pad zone and each electrode zone; and removing at least a portion of the metal layer therefrom.

13. The method of claim 12, wherein the pad comprises three concentric pad zones, the electrode comprises three concentric electrode zones, and the three concentric pad zones disposed adjacent the three concentric electrode zones.

14. The method of claim 12, further comprising providing relative motion between the substrate and the electrode, the pad, or both.

15. The method of claim 13, wherein applying the separate bias comprises applying a first bias between a first concentric pad zone and a first concentric electrode zone, applying a second bias between a second concentric pad zone and a second concentric electrode zone, and applying a third bias between a third concentric pad zone and a third concentric electrode zone.

16. The method of claim 15, wherein the first, second, and third biases are applied to provide a non-uniform removal rate across a surface of the substrate.

7. A method of processing a substrate, comprising: disposing a substrate containing a conductive material layer in a process apparatus comprising an electrode having a plurality of zones and a polishing pad; contacting the substrate and the polishing pad; moving the substrate relative to the plurality of zones of the electrode with at least one portion of the substrate passes through more than one zone of the plurality of zones of the electrode; applying a bias to each of the plurality of zones of the electrode, wherein the bias to each of the plurality of zones of the electrode is modified by the time that the at least one portion of the substrate layer is associated with more than one zone of the electrode; and removing conductive material from the conductive material layer.

18. The method of claim 17, further comprising determining a substrate removal rate profile by determining the removal rates for each of the plurality of zones of the electrode by application of one or more test biases for each of the plurality of zones of the electrode.

19. The method of claim 18, wherein determining the removal rates for each of the plurality of zones of the electrode by application of one or more test biases for each of the plurality of zones of the electrode is achieved by measuring a property of the one or more polished test material layers selected from the group consisting of material removal, rate of material removal, layer thickness, and combinations thereof.

20. The method of claim 18, wherein the bias is modified by the substrate removal rate profile to remove conductive material at a rate that varies for each of the plurality of zones of the electrode.

21. The method of claim 20, wherein the bias is modified by the substrate removal rate profile to remove conductive material at a rate that varies for each of the plurality of zones of the electrode to provide a substantially uniform removal profile or a substantially non-uniform removal profile to planarize the substrate surface.

22. The method of claim 20, wherein the substrate removal rate profile compensates for a variation in thickness of the material layer on the substrate, compensates for a variation in thickness of the substrate, or both.

23. The method of claim 17, wherein the substrate is contacted with the polishing pad at a pressure of about 0.5 psi or less.

24. A method of processing a surface of a material layer, comprising: disposing a substrate containing a conductive material layer in a process apparatus comprising an electrode having a plurality of zones and a polishing pad having a plurality of zones corresponding to the plurality of zones of the electrode; providing relative motion between the polishing pad and the substrate; and separately applying a bias to each of the plurality of zones of the polishing pad and the plurality of zones of the electrode, wherein each bias causes conductive material from the conductive material layer to be removed at a rate that varies for each of the plurality of zones of the polishing pad.

25. The method of claim 24, wherein the bias to each of the plurality of zones removes conductive material at a rate that varies for each of the plurality of zones to provide a substantially uniform removal profile or a substantially non-uniform removal profile to planarize the substrate surface.

26. The method of claim 24, wherein the polishing pad has a plurality of perforations formed therethrough.

27. The method of claim 24, wherein applying the bias between each of the plurality of zones of the polishing pad and the plurality of zones of the counter- electrode compensates for a variation in thickness of the material layer, compensates for a variation in thickness of the substrate, or both, to planarize the substrate surface.

28. The method of claim 24, further comprising determining a time that at least one portion of the conductive material layer is associated with each of the plurality of zones of the electrode, each of the plurality of zones of the polishing pad, or both.

29. The method of claim 28, wherein applying the bias between each of the plurality of zones of the polishing pad and the plurality of zones of the counter- electrode compensates for a variation in the time that at least one portion of the conductive material layer is associated with each of the plurality of zones of the electrode, each of the plurality of zones of the polishing pad, or both, to planarize the substrate surface.

30. The method of claim 24, further comprising determining a distribution of time that at least one portion of the conductive material layer is associated with each of the plurality of zones of the electrode, each of the plurality of zones of the polishing pad, or both.

31. The method of claim 30, wherein applying the bias between each of the plurality of zones of the polishing pad and the plurality of zones of the counter- electrode compensates for a variation in the distribution of time that at least one portion of the conductive material layer is associated with each of the plurality of zones of the electrode, each of the plurality of zones of the polishing pad, or both, to planarize the substrate surface.

32. The method of claim 24, further comprising contacting the substrate with the polishing pad at a pressure of about 0.5 psi or less.