WO2006110864A2

WO2006110864A2 - Method for improving surface roughness during electro-polishing

Info

Publication number: WO2006110864A2
Application number: PCT/US2006/013804
Authority: WO
Inventors: Hui Wang; Fredrick Ho; Jian Wang
Original assignee: Acm Research, Inc.
Priority date: 2005-04-12
Filing date: 2006-04-12
Publication date: 2006-10-19
Also published as: WO2006110864A3

Abstract

A surface is electropolished using a stream of electrolyte. A nozzle is used to apply the stream of electrolyte to the surface. The nozzle has an insulator wall and a partial electrode. The insulator wall and the partial electrode form a flow channel for the stream of electrolyte. The stream of electrolyte contacts the insulator wall and the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode. The insulator wall is less electrically conductive than the partial electrode. A power supply is connected to the partial electrode. The power supply is configured to apply a charge to the stream of electrolyte through the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode.

Description

IMPROVING SURFACE ROUGHNESS DURING ELECTRO-POLISHING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application Serial No. 60/672,111, titled METHOD FOR IMPROVING SURFACE ROUGHNESS DURING ELECTRO-POLISHING, filed April 12, 2005, which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field

[0002] The present application generally relates to an electropolishing process used in integrated circuit (IC) fabrication, and, in particular, to a multi-step electropolishing process of a metal layer formed on a wafer used in IC fabrication.

2. Related Art

[0003] IC devices are manufactured or fabricated on wafers using a number of different processing steps to create transistor and interconnection elements. To electrically connect transistor terminals associated with the wafer, conductive (e.g., metal) trenches, vias, pads, and the like are formed in dielectric materials as part of IC devices. The trenches, vias, and pads couple electrical signals and power between transistors, internal circuits of the IC devices, and circuits external to the IC devices.

[0004] In forming the interconnection elements, the wafer may undergo, for example, masking, etching, and deposition processes to form the desired electronic circuitry of the IC devices. In particular, multiple masking and etching steps can be performed to form a pattern of recessed areas in a dielectric layer on a wafer that serve as trenches, vias, and/or pads for the interconnections. A deposition process may then be performed to deposit a metal layer over the wafer to deposit metal both in the trenches and vias and also on the non-recessed areas of the wafer. To isolate the interconnections, such as patterned trenches and vias, the metal deposited on the non-recessed areas of the wafer is removed. [0005] The metal layer deposited on the non-recessed areas of the dielectric layer can be removed using an electropolishing process. In particular, a nozzle can be used to apply an electrolyte solution to electropolish the metal layer. Surface roughness or striation, however, can be produced on the metal layer after electropolishing. To remove metal residue caused by poor surface roughness or striation, much longer over-polishing may to be performed, which can cause larger metal recess on metal structure such as trench, pad, or via. The larger the metal recess, the higher line resistance for metal trench, which can cause more circuit delay. Furthermore, larger metal recess on wide trench may impact global planarity of interconnect structure, which can cause yield loss during lithography.

SUMMARY

[0006] In one exemplary embodiment, a surface is electropolished using a stream of electrolyte. A nozzle is used to apply the stream of electrolyte to the surface. The nozzle has an insulator wall and a partial electrode. The insulator wall and the partial electrode form a flow channel for the stream of electrolyte. The stream of electrolyte contacts the insulator wall and the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode. The insulator wall is less electrically conductive than the partial electrode. A power supply is connected to the partial electrode. The power supply is configured to apply a charge to the stream of electrolyte through the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIGs. 1A-1F are block diagrams of exemplary electropolishing tools; [0008] FIG. 2 depicts another exemplary electropolishing tool; [0009] FIG. 3 depicts a surface being electropolished; [0010] FIG. 4A depicts a cross section of a stream of electrolyte; [0011] FIG. 4B depicts an area of a surface electropolished by the stream of electrolyte depicted in FIG. 4A;

[0012] FIG. 5A depicts another cross section of a stream of electrolyte; [0013] FIG. 5B depicts an area of a surface electropolished by the stream of electrolyte depicted in FIG. 5A;

[0014] FIG. 6A depicts an area of a surface electropolished by a stream of electrolyte; [0015] FIGs. 6B and 6C are optical microscopic pictures of portions of the area depicted in FIG. 6A;

[0016] FIG. 7A depicts a surface electropolished by a stream of electrolyte; [0017] FIG. 7B depicts an optical microscopic picture of a portion of the area depicted in FIG. 7A;

[0018] FIG. 7C depicts a portion of the area depicted in FIG. 7A;

[0019] FIG. 7D depicts profile measurements taken within the portion depicted in FIG. 7C; [0020] FIG. 8 A depicts a surface electropolished by a stream of electrolyte; [0021] FIGs. 8B-8E depict optical microscopic pictures of portions of the surface depicted in FIG. 8A; [0022] FIGs. 9 A and 9B depict an exemplary nozzle used to electropolish a surface;

[0023] FIGs. 1OA, 1OB to 19A, 19B depict various exemplary nozzles used to electropolish a surface;

[0024] FIG. 20 depicts another exemplary nozzle used to electropolish a surface; and

[0025] FIGs. 21A, 21B to 4OA, 40B depict various exemplary nozzles used to electropolish a surface.

DETAILED DESCRIPTION

[0026] With reference to FIG. IA, as part of an IC fabrication process, an exemplary electropolishing tool is configured to electropolish a metal layer 102 formed on a wafer 100. Metal layer 102 can include copper, which is increasingly being used to replace aluminum. It should be recognized, however, that metal layer 102 can include any electrically conductive material. Additionally, it should be recognized that the term "wafer" can be used to refer to substrate 104 on which subsequent layers are formed, or to refer collectively to substrate 104 and the subsequent layers formed on substrate 104.

[0027] In one exemplary embodiment, the electropolishing tool includes a nozzle 106 configured to apply a stream of electrolyte 108 to metal layer 102 at different radial locations on wafer 100. A power supply 110 is connected to nozzle 106 to apply a negative electropolishing charge to stream of electrolyte 108. Power supply 110 is also connected to wafer 100 to apply a positive electropolishing charge to wafer 100. Thus, during the electropolishing process, nozzle 106 acts as a cathode, and wafer 100 acts as an anode. When stream of electrolyte 108 is applied to metal layer 102, the difference in potential between electrolyte 108 and metal layer 102 results in the electropolishing of metal layer 102 from wafer 100. Although power supply 110 is depicted as being directly connected to wafer 100, it should be recognized that any number intervening connection can exist between power supply 110 and wafer 100. For example, power supply 110 can be connected to chuck 112, which is then connected to wafer 100, and, more particular to metal layer 102. [0028] For additional descriptions of electropolishing, see U.S. Patent No. 6,395,152, entitled METHODS AND APPARATUS FOR ELECTROPOLISHING METAL INTERCONNECTIONS ON SEMICONDUCTOR DEVICES, filed on July 2, 1999, the entire content of which is incorporated herein by reference. See also, U.S. Provisional Application Ser. No. 60/462,642, entitled METHODS AND APPARATUS FOR OPTIMIZING ELECTROPOLISHER, filed on April 14, 2003, the entire content of which is incorporated herein by reference, disclosing a variety of nozzle shape designs to enhance removal rate profile of nozzle during an electrical polishing process. See also, U.S. Provisional Application Ser. No. 60/579,980, entitled METHODS FOR IMPROVEING SURFACE ROUGHNESS DURING ELECTRO-POLISHING, filed on June 15, 2004, the entire content of which is incorporated herein by reference.

[0029] In the exemplary embodiment depicted in FIG. IA, the electropolishing tool includes a chuck 112 that holds and positions wafer 100. The electropolishing tool also includes a motor 114 that rotates chuck 112, and thus wafer 100, during the electropolishing process. By rotating wafer 100, electrolyte 108 is applied in a spiral pattern on metal layer 102. In particular, in the present exemplary embodiment, chuck 112, and thus wafer 100, is translated along a guide rod 116 to translate wafer 100 in a lateral direction relative to nozzle 106 and stream of electrolyte 108. The relative motion between nozzle 106 and wafer 100 produced by rotating and translating wafer 100 results in electrolyte 108 being applied in a spiral pattern. It should be recognized, however that the relative motion between nozzle 106 and wafer 100 can achieved in various manners. For example, nozzle 106 and wafer 100 can be moved in a straight or curved trajectory in the lateral direction,

[0030] Although in the exemplary embodiment depicted in FIG. IA wafer 100 is rotated and translated while nozzle 106 is kept stationary, it should be recognized that nozzle 106 and wafer 100 can be moved relative to each other in various manners using various mechanisms. For example, in the exemplary embodiment depicted in FIG. IB, wafer 100 is only rotated, while nozzle 106 is translated. Although in the exemplary embodiment depicted in FIG. IA nozzle 106 is disposed below wafer 100 to apply stream of electrolyte 108 vertically up to metal layer 102, it should be recognized that nozzle 106 and wafer 100 can be oriented in various manners. For example, in the exemplary embodiment depicted in FIG. 1C, nozzle 106 is disposed above wafer 100 to apply stream of electrolyte 108 vertically down to metal layer 102. In the exemplary embodiment depicted in FIG. 1C, chuck 112, and thus wafer 100, is rotated and translated, while nozzle 106 is kept stationary. In the exemplary embodiment depicted in FIG. ID, nozzle 106 is translated, while chuck 112, and thus wafer 100, is rotated. In the exemplary embodiment depicted in FIG. IE, nozzle 106 is disposed horizontally adjacent to wafer 100 to apply stream of electrolyte 1OS horizontally to metal layer 102. In the exemplary embodiment depicted in FIG. IE, chuck 112, and thus wafer 100, is rotated and translated, while nozzle 106 is kept stationary. In the exemplary embodiment depicted in FIG. IF, nozzle 106 is translated, while chuck 112, and thus wafer 100, is rotated. It should be recognized that in the exemplary embodiments depicted in FIGs. 1A-1F, both nozzle 106 and chuck 112, and thus wafer 100, can be translated. [0031] With reference to 2, in one exemplary embodiment, nozzle 106 includes an electrode 202 configured to apply a negative electropolishing charge to stream of electrolyte 108. In the present exemplary embodiment, the metal layer on wafer 100 makes contact with one or more electrode contacts located near the edge of wafer 100 (i.e., around the outer circumferential area of the surface on which the metal layer and IC structures are formed). In the present exemplary embodiment, before the electropolishing process begins, the metal layer is continuous from the center to near the edge, where the metal layer makes contact with the one or more electrode contacts. Thus, an electric current flows from stream of electrolyte 108 radially outward toward the edge of wafer 100. See, U.S. Patent No. 6,188,222, entitled METHODS AND APPARATUS FOR HOLDING AND POSITIONING SEMICONDUCTOR WORKPIECES DURING ELECTROPOLISHING AND/OR ELECTROPLATING OF THE WORKPIECES, issued June 19, 2001, which is incorporated herein by reference in its entirety.

[0032] In the present exemplary embodiment, during the electropolishing process, nozzle 106 is positioned adjacent to wafer 100 with a gap between nozzle 106 and wafer 100. As noted above, the term "wafer" can be used to refer collectively to substrate 104 (FIG. IA) and any subsequent layers formed on substrate 104 (FIG. IA). Thus, the gap between nozzle 106 and wafer 100 can also be viewed as the gap between nozzle 106 and the metal layer, which is formed on substrate 104 (FIG. IA), either directly or on any number of intermediate layers. For the sake of convenience and clarity, the gap will be referred to as being defined between nozzle 106 and wafer 100 rather than between nozzle 106 and the metal layer. [0033] FIG. 3 depicts a surface 300 being electropolished using the tool described above. As depicted in FIG. 3, the stream of electrolyte is applied at a contact area 302 on surface 300. As also depicted in FIG. 3, as the wafer is rotated and the wafer and/or the nozzle applying the stream of electrolyte is translated, portions of surface 300 are subsequently electropolished. In particular, FIG. 3 depicts surface 300 having a portion 304, which has yet to be electropolished, and a portion 306, which has been electropolished. [0034] With reference again to FIG. 2, when the surface being electropolished is a metal layer, particularly when electropolishing Cu in an acid bath, the electrical chemical reaction is described as follows:

Cathode or nozzle: H ⁺ + e ^" > H₂ (1)

Cu²⁺+ 2 e -> Cu (2)

Anode or wafer: 2H₂O > O₂ + 4H ⁺ + 4 e ^" (3)

Cu -- > Cu²⁺ + 2 e ^" (4) [0035] On the anode or wafer surface, the voltage can be adjusted to an adequate value so that only Cu metal is electropolished out and no oxygen is generated. However, on the cathode (electrode 202) or surface of nozzle 106, low concentration of Cu ion in typical acid bath is not enough to transfer all charges. Therefore, hydrogen is plated out and acts as an electrical path to the electropolishing process.

[0036] As shown in FIG. 2, hydrogen bubbles 206 generated in electrode 202 or nozz\<s 106 rises up as stream of electrolyte 108 reaches the surface being electropolished. FIG. 4A depicts a cross section 402 of the stream of electrolyte. As depicted in FIG. 4A, hydrogen bubbles 206 are located around the perimeter of cross section 402. When hydrogen bubbles 206 reach the surface being electropolished, they block the electrical path of the polishing process locally, which results in a rough surface. In particular, as depicted in FIG. 4B, a portion 404 on the surface being electropolished that corresponds to the portion of cross section 402 (FIG. 4A) with hydrogen bubbles 206 is characterized by a rougher surface than a portion 406 that corresponds to the portion of cross section 402 (FIG. 4A) without hydrogen bubbles 206.

[0037] For example, with reference to FIGs. 6A and 6B, an optical microscopic picture is depicted in FIG. 6B of portion 406. The surface roughness of portion 406 depicted in FIG. 6B is 9.3 nm. With reference to FIGs. 6A and 6B, an optical microscopic picture is depicted in FIG. 6C of portion 404. The surface roughness of portion 404 depicted in FIG. 6C is 24.6 nm. The inner diameter of the nozzle used to produce the surface roughness depicted in FIG. 6B and 6C was 20 mm. The polishing current used was 2.5 Amperes. The current density used was 796 mA/cm². The polishing time was 30 seconds. The electrolyte used consisted of 65% phosphoric acid, 25% of glycol, and 10% water. The electrolyte temperature was set at 27 ⁰C.

[0038] With reference again to FIG. 3, a relative motion exists between the surface being electropolished and the stream of electrolyte being applied to the surface. For example, as described above, in one exemplary embodiment, the surface is being rotated, while the nozzle that applies the stream of electrolyte is laterally translated. Alternatively, the surface is rotated and laterally translated, while the nozzle remains stationary. [0039] With reference to FIG. 5A, the relative motion between the surface being electropolished and the stream of electrolyte results in movement of the electrolyte within cross section 402. For example, as depicted in FIG. 5A, the electrolyte can move right and downward across cross section 402 as indicated by the directional arrows in FIG. 5A. Hydrogen bubbles 206 located around the perimeter of cross section 402 also moves across cross section 402. In particular, as depicted in FIG. 5A, some hydrogen bubbles 206 located in the upper left portion of cross section 402 can move right and downward across cross section 402. As depicted in FIG. 5B, the movement of hydrogen bubbles 206 across cross section 402 (FIG. 5A) can cause surface striations 502 in portion 406 of the surface being electropolished.

[0040] For example, FIG. 7A depicts a cross section 402 of the stream of electrolyte scanned across a portion of the surface being electropolished. For the purpose of this example, the position of the nozzle was fixed at a radial location of R=30mm. Thus, cross section 402 was scanned along a circumferential path 700 around the surface. FIG. 7B depicts an optical microscopic picture of surface striations 502 on the post electropolished surface. As depicted in FIG. 7C, profile measurements were made using a profiler scanned from location 704 to 712. FIG. 7D depicts the profiles measured by the profiler. The peak- valley value of surface striations 502 reached a high of 1000 A at location 710. For the purpose of this example, an electrolyte flow rate of 6.0 slm (stewarded liter per minute) was used. A nozzle diameter of 20 mm was used. A rotation speed of 200 rpm was used. A polishing current of 2.5 was used. An electrolyte temperature of 27 ⁰C was used. A polishing time of 70 seconds was used. The electrolyte used consisted of 65% phosphoric acid, 25% of glycol, and 10% water.

[0041] FIG. 8 A depicts a top view of a surface electropolished using the same conditions as described above except the nozzle was moved in a radial direction outward from the center of the surface to the edge of the surface rather than being fixed at R=30 mm as the surface is rotated. FIG. 8B depicts an optical microscopic picture of the surface at location 802. FIG. 8C depicts an optical microscopic picture of the surface at location 804. FIG. 8D depicts an optical microscopic picture of the surface at location 806. FIG. 8E depicts an optical microscopic picture of the surface at location 808.

[0042] As can be seen from FIGs. 8B, 8C, 8D, and 8E, the direction of the surface striations follow the direction of the electrolyte flowing on the surface during the polishing process. As described above in the background section, in order to metal residue caused by poor surface roughness or striation, much longer over-polishing may to be performed, which causes larger metal recess on a metal structure such as trench, pad, or via. The larger the metal recess, the higher line resistance for metal trench, which can cause more circuit delay. Furthermore, larger metal recess on wide trench may impact global planarity of interconnect structure, which can cause yield loss during lithography. [0043] With reference to FIG. 9 A and 9B, in accordance with one exemplary embodiment, nozzle 106 includes an insulator wall 902 and a partial electrode 904. As depicted in FIG. 9B, insulator wall 902 and partial electrode 904 of nozzle 106 form a flow channel for stream of electrolyte 108. As also depicted in FIG. 9B, stream of electrolyte 108 contacts both insulator wall 902 and partial electrode 904 when stream of electrolyte 108 flows through the flow channel formed by insulator wall 902 and partial electrode 904. [0044] In the present exemplary embodiment, insulator wall 902 is less electrically conductive than partial electrode 904. For example, insulator wall 902 can be formed from an electrically insulating material, while partial electrode 904 can be formed from an electrically conducting material.

[0045] In the present exemplary embodiment, partial electrode 904 is connected to power supply 110 (FIGs. 1A-1F). When stream of electrolyte 108 flows through the flow channel formed by insulator wall 902 and partial electrode 904, power supply 110 (FIGs. IA- IF) applies an electrical charge to stream of electrolyte 108 through partial electrode 904. In particular, as described above, a negative charge is applied to stream of electrolyte 108 through partial electrode 904, which, thus, acts as a cathode.

[0046] In the present exemplary embodiment, insulator wall 902 is not connected to power supply 110 (FIGs. 1 A-IF). Additionally, because insulator wall 902 is formed from an electrically insulating material, the charge applied to partial electrode 904 is not transmitted through insulator wall 902. Thus, as depicted in FIG. 9B, hydrogen bubbles 206 form only along partial electrode 904 and not along insulator wall 902. [0047] In the present exemplary embodiment, a chuck 114 rotates the substrate on which the surface to be electropolished is disposed. As depicted in FIG. 9A, partial electrode 904 is disposed adjacent to a radially outward position from the center of the substrate, while insulator wall 902 is disposed adjacent to a radially inward position from the center of the substrate. Thus, since hydrogen bubbles 206 are only generated on the surface of partial electrode 904, hydrogen bubbles 206 spin off toward the edge of the substrate as the substrate is rotating. Therefore, hydrogen bubbles 206 will not move across the center portion of nozzle 106, which reduces or eliminates surface striation.

[0048] Another advantage of nozzle 106 having partial electrode 904 is to generate a stronger electrical field at outer portion 906 of stream of electrolyte 108 (i.e., closer to the edge of the surface being electropolished). Since the surface velocity at the location on the surface adjacent to outer portion 906 is higher than at the location on the surface adjacent to inner portion 908, a higher electrical field is desirable to generate electropolishing double layer at outer portion 906 rather than at inner portion 908 since linear velocity at outer portion 906 is higher than at inner portion 908. A double layer is an electric charged layer formed close to the surface being electropolished during electropolishing process, which is desirable to generate a smooth surface.

[0049] FIGs. 1OA and 1OB depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 9 A and 9B except that more than half of the flow channel is comprised of partial electrode 904, and less than half of the flow channel is comprised of insulator wall 902. Thus, in FIG. 1OB, the coverage angle α of partial electrode 904 is smaller than 180 degree.

[0050] FIGs. 1 IA and 1 IB depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 9A and 9B except that less than half of the flow channel is comprised of partial electrode 904, and more than half of the flow channel is comprised of insulator wall 902. Thus, in FIG. 1 IB, the coverage angle α of partial electrode 904 is larger than 180 degree.

[0051] FIGs. 12A and 12B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 9A and 9B except that more than half of the flow channel is comprised of partial electrode 904, less than half of the flow channel is comprised of insulator wall 902, and the shape of nozzle 106 is elliptical rather than circular. In FIG. 12B, the coverage angle α of partial electrode 904 is smaller than 180 degree.

[0052] FIGs. 13A and 13B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 9A and 9B except that the shape of nozzle 106, and thus the shape of the flow channel, is square rather than circular. It should be recognized that the shape of nozzle 106 can be rectangular or a slip. [0053] FIGs. 14A and 14B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 13 A and 13B except that insulator wall 902 has a symmetric shape as partial electrode 904. Thus, half of the flow channel is comprised of partial electrode 904, and half of the flow channel is comprised of insulator wall 902. [0054] FIGs. 15A and 15B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 13A and 13B except that insulator wall 902 has less surface area than partial electrode 904. Thus, more than half of the flow channel is comprised of partial electrode 904, and less than half of the flow channel is comprised of insulator wall 902.

[0055] FIGs. 16A and 16B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. As depicted in FIG. 16A, in this exemplary embodiment, an angle β is defined between insulator wall 902 and partial electrode 904 in an interior portion of nozzle 106.

Angle β can be used to tune the hydrogen generation distribution profile and electric field distribution profile.

[0056] FIGs. 17A and 17B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 16A and 16B except that angle β is smaller.

[0057] FIGs. 18A and 18B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 17A and 17B except that angle β is smaller.

[0058] FIGs. 19A and 19B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 13 A and 13B except that insulator wall 902 is a half circle and angle β is zero.

[0059] With reference to FIG. 20, in accordance with one exemplary embodiment, nozzle

106 includes electrode 202. As depicted in FIG. 20, electrode 202 of nozzle 106 forms a flow channel for stream of electrolyte 108. Nozzle 106 also includes a mesh tube 2002 disposed within the flow channel formed by electrode 202.

[0060] In the present exemplary embodiment, electrode 202 is connected to power supply

110 (FIGs. 1 A-IF). When stream of electrolyte 108 flows through the flow channel formed by electrode 202, power supply 110 (FIGs. 1 A-IF) applies an electrical charge to stream of electrolyte 108 through electrode 202. In particular, as described above, a negative charge is applied to stream of electrolyte 108 through electrode 202, which, thus, acts as a cathode. [0061] In the present exemplary embodiment, mesh tube 2002 is configured to block or prevent hydrogen bubbles from flowing into mesh tube 2002. In particular, hydrogen bubbles generated during the electro-polishing process by electrode 202 are prevented from entering into the portion of the stream of electrolyte flowing within mesh tube 2002, and then the hydrogen bubbles are pushed out of nozzle 106. Meanwhile, the electrical charge applied to electrode 202 can pass through mesh tube 2002.

[0062] As depicted in FIG. 20, in the present exemplary embodiment, a first flow path 2004 for a portion of stream of electrolyte 108 is defined within mesh tube 2002. A second flow path 2006 for another portion of stream of electrolyte 108 is defined between mesh tube 2002 and electrode 202. As also depicted in FIG. 20, the portion of stream of electrolyte 108 in first flow path 2004 contacts the surface being electropolished, while the portion of stream of electrolyte 108 in second flow path 2006 does not contact the surface. [0063] Because mesh tube 2002 prevents hydrogen bubbles in second flow path 2006 from entering first flow path 2004, hydrogen bubbles generated during the electropolishing process are prevented from reaching the surface being electropolished. Thus,, surface striation can be reduced or eliminated by using an adequate polishing current or voltage. Adequate voltage or current is set at an appropriate value such that no oxygen is generated on anode or the surface being electropolished. At the same time, the double layer can be formed on the surface to facilitate the electro-polishing process instead of electro-etching process. As noted above, a double layer is an electric charged layer formed close to the surface being electropolished during electropolishing process, which is desirable to generate a smooth surface.

[0064] In the present exemplary embodiment, mesh tube 2002 is preferably made of an insulating material, such as Teflon, PVDF, ceramics, and the like. Mesh tube 2002 can also be made of conductors, such as Pt, stainless steel, other metals and alloys, and the like. Although mesh tube 2002 has been depicted as being cylindrical, and mesh tube 2002 is described as a tube, it should be recognized that mesh tube 2002 can have various cross sectional shapes. For example, mesh tube 2002 can have a square cross sectional shape. [0065] FIGs . 21 A and 21 B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 includes insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 also includes mesh tube 2002 disposed within the flow channel. As described above, hydrogen bubbles generated during the electro-polishing process can be blocked by mesh tube 2002. Potential distribution profile can be tuned by adjusting the gap between nozzle 106 and the surface being electropolished. The smaller the gap is, the bigger the difference of electrical field strength.

[0066] FIGs. 22A and 22B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in

FIG.20 except that mesh tube 2002 is longer and extended out of electrode 202. Extending mesh tube 2002 out of electrode 202 better prevents the hydrogen bubbles from reaching the portion of stream of electrolyte 108 in first flow path 2004, which contacts the surface being. electropolished.

[006?] Additionally, in the present exemplary embodiment, stopper 2202 is placed between mesh tube 2002 and electrode 202 at the bottom of electrode 202 to help create a flow path 2204 from inside of mesh tube 2002 to outside of mesh tube 2002. Flow path 2204 can further reduce or prevent hydrogen bubbles from getting inside of mesh tube 2002, which can reduce the amount or prevent hydrogen bubbles from reaching the surface being electropolished.

[0068] FIGs. 23 A and 23B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in

FIG. 20 except that a tube 2302 extends from mesh tube 2002. Extending tube 2302 better prevents the hydrogen bubbles from reaching the portion of stream of electrolyte 108 in first flow path 2004, which contacts the surface being electropolished.

[0069] In the present exemplary embodiment, tube 2302 is preferably made of an electrically insulating material, such as plastics, ceramics, and the like. Tube 2302 can also be made of an electrically conducting material, such as Pt, stainless steel, other metals and alloys, and the like.

[0070] Additionally, in the present exemplary embodiment, stopper 2202 is placed between mesh tube 2002 and electrode 202 at the bottom of electrode 202 to help create a flow path 2204 from inside of mesh tube 2002 to outside of mesh tube 2002. Flow path 2204 can reduce or prevent hydrogen bubbles from getting inside of mesh tube 2002, which can reduce the amount or prevent hydrogen bubbles from reaching the surface being electropolished.

[0071] FIGs. 24 A and 24B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in

FIGs. 23A and 23B except that tube 2302 includes a guide portion 2402 to better flow hydrogen bubbles down to the bottom of the outside of electrode 202. As depicted in FIG.

24 A, guide portion 2402 extends from tube 2302 and over the end of electrode 202. [0072] FIGs. 25 A and 25B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 24A and 24B except that guide portion 2402 of tube 2302 extends to the bottom of the outside of electrode 202.

[0073] FIGs. 26A and 26B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 includes a tube 2602 that forms a flow channel for the stream of electrolyte. Tube 2302 extends from tube 2602. Guide portion 2402 extends from tube 2302, over the end of tube 2602, and along the side of tube 2602.

[0074] In the present exemplary embodiment, tube 2602 is less electrically conductive than guide portion 2402. For example, tube 2602 can be formed from an electrically insulating material, while guide portion 2402 can be formed from an electrically condμcting material.

[0075] In the present exemplary embodiment, guide portion 2402 is connected to power supply 110 (FIGs. 1A-1F). When a portion of stream of electrolyte 108 flows between the sides of tube 2602 and guide portion 2402, power supply 110 (FIGs. 1A-1F) applies an electrical charge to the portion of stream of electrolyte 108 through guide portion 2402. In particular, as described above, a negative charge is applied to the portion of stream of electrolyte 108 through guide portion 2402, which, thus, acts as a cathode. [0076] As depicted in FIG. 26A, in the present exemplary embodiment, first flow path 2004 for a portion of stream of electrolyte 108 is defined within mesh tube 2002 and extending out of tube 2302. Second flow path 2006 for another portion of stream of electrolyte 108 is defined between mesh tube 2002 and tube 2602. The portion of stream of electrolyte 108 in first flow path 2004 contacts the surface being electropolished, while the portion of stream of electrolyte 108 in second flow path 2006 does not contact the surface. [0077] FIGs. 27 A and 27B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 26A and 26B except that tube 2602 is covered by another tube 2702 that is electrically conductive. Thus, in the present exemplary embodiment, tube 2702 and guide portion 2402 jointly act as cathodes.

[0078] FIGs. 28A and 28B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 27A and 27B except that guide portion 2402 is formed from an electrically insulating material. Thus, only tube 2702 acts as a cathode. [0079] FIGs. 29A and 29B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 28A and 28B except that mesh tube 2002 is removed from nozzle 106. In the present exemplary embodiment, since hydrogen bubbles are generated on the outside surface of tube 2702, the electrolyte flowing through outside surface of tube 2702 will push hydrogen bubbles out of nozzle 106.

[0080] FIGs. 30A and 30B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 29A and 29B except that guide portion 2402 is electrically conductive. [0081] FIGs. 31A and 3 IB depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 25A and 25B except that mesh tube 2002 (FIG. 25A) is omitted and tube 2302 extends to the bottom of electrode 202.

[0082] FIGs. 32A and 32B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 31A and 3 IB except that tube 2302 extends into electrode 202 but does not extend all the way down to the bottom of electrode 202. Also, in the present exemplary embodiment, tube 2302 has a square cross sectional shape. Furthermore, electrode 202 includes an electrically insulating portion 3202. It should be recognized that the shape of tube 2302 can be rectangular or a very long slit, which can be used to polish laterally moving large surfaces, such as on a stainless foil or Aluminum foil. The electropolished metal foils can be potentially used as substrates for fabricating flexible displays.

[0083] FIGs. 33A and 33B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. In the present exemplary embodiment, the flow channel formed by insulator wall 902 and partial electrode 904 is angled at an angle γ. In the present exemplary embodiment, angle γ is in the range of 30 degree to -30 degree. Angled nozzle 106 can provide another nub to adjust electrical filed strength distribution and electrolyte flow pattern to optimize the electropolishing process with minimum striation or surface roughness. [0084] FIGs. 34A and 34B depict another exemplary embodiment of nozzle 106 having insulator wall 902 and partial electrode 904 that form a flow channel for the stream of electrolyte. Nozzle 106 is similar to that depicted in FIGs. 33A and 33B except that mesh tube 2002 is disposed within the angled flow channel of nozzle 106. [0085] With reference to FIGs. 35 A and 35B, in accordance with one exemplary embodiment, nozzle 106 includes a first flow channel 3502 for a first portion of the stream of electrolyte. Nozzle also includes a second flow channel 3504 for a second portion of the stream of electrolyte.

[0086] As depicted in FIG. 35B, first flow channel 3502 has a first end, second end, and sides. Second flow channel 3504 also has a first end, second end, and sides. As also depicted in FIG. 35B, the first portion of the stream of electrolyte enters first flow channel 3502 through the first end of first flow channel 3502, and exits first flow channel 3502 through the second end of first flow channel 3502. The second portion of the stream of electrolyte enters second flow channel 3504 through the first end of second flow channel 3504, and exits second flow channel 3504 through the second end of second flow channel 3504.

[0087] In the present exemplary embodiment, first end of second flow channel 3504 is connected to first flow channel 3502. In particular, second flow channel 3504 extends from one side of first flow channel 3502.

[0088] In the present exemplary embodiment, an electrode 3506 is disposed on second flow channel 3504. In particular, electrode 3506 is disposed on the second end of second flow channel 3504. Electrode 3506 is connected to power supply 110 (FIGs. 1 A-IF). When a portion of the stream of electrolyte flows through second flow channel 3504, power supply 110 (FIGs. IA- IF) applies an electrical charge to the portion of the stream of electrolyte flowing through second flow channel 3504 through electrode 3506. In particular, as described above, a negative charge is applied to electrode 3506, which, thus, acts as a cathode.

[0089] As depicted in FIG. 35B, in the present exemplary embodiment, a first flow path 3508 for a portion of stream of electrolyte 108 is defined within first flow channel 3502. A second flow path 3510 for another portion of stream of electrolyte 108 is defined with second flow channel 3504. In the present exemplary embodiment, the portion of stream of electrolyte 108 in first flow path 3508 contacts the surface being electropolished, while the portion of stream of electrolyte 108 in second flow path 3510 does not contact the surface. [0090] FIGs. 36A and 36B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 35A and 35B except that nozzle 106 includes a third flow channel 3602 for another portion of the stream of electrolyte and another electrode 3604. [0091] In the present exemplary embodiment, third flow channel 3602 is connected to first flow channel 3502. In particular, third flow channel 3602 extends from another side of first flow channel 3502.

[0092] In the present exemplary embodiment, another electrode 3604 is disposed on third flow channel 3602. Electrode 3604 is connected to power supply 110 (FIGs. 1A-1F). The use of electrodes 3506 and 3604 increases the effective surface area over which the charge is applied to the stream of electrolyte.

[0093] In the present exemplary embodiment, a third flow path 3606 for a portion of the stream of electrolyte is defined within third flow channel 3602. In the present exemplary embodiment, the portion of the stream of electrolyte in third flow path 3606 does not contact the surface being electropolished.

[0094] Fig. 37 A and 37B depicts another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 36A and 36B except that nozzle 106 includes a fourth flow channel 3702 for another portion of the stream of electrolyte and a fifth flow channel 3708 for yet another portion of the stream of electrolyte.

[0095] In the present exemplary embodiment, fourth flow channel 3702 and fifth flow channel 3708 are both connected to first flow channel 3502. In particular, fourth flow channel 3702 and fifth flow channel 3708 extend from sides of first flow channel 3502. [0096] In the present exemplary embodiment, a third electrode 3704 is disposed on fourth flow channel 3702, and a fourth electrode 3710 is disposed on fifth flow channel 3708. Third and fourth electrodes 3704, 3710 are connected to power supply 110 (FIGs. 1 A-IF). [0097] In the present exemplary embodiment, a fourth flow path 3706 for a portion of the stream of electrolyte is defined within third flow channel 3702. A fifth flow path 3712 for another portion of the stream of electrolyte is defined within fourth flow channel 3708. In the present exemplary embodiment, the portions of stream of electrolyte in fourth flow path 3706 and fifth flow path 3712 do not contact the surface being electropolished. [0098] FIGs. 38A and 38B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to. that depicted in FIGs. 37A and 37B except that the flow channels and the electrodes are cylindrical. The shape of the first flow channel 3502 can be elliptical, square, rectangular, or a very long slit, which can be used to polish laterally moving large surfaces, such as on stainless foils or Aluminum foils. The electropolished metal foils can be potentially used as substrates for fabricating flexible displays. [0099] FIGs. 39A and 39B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 35A and 35B except that electrode 3506 is disposed adjacent to the second end of second flow channel 3504 rather than disposed on the second end of second flow channel 3504. In particular, a gap is defined between electrode 3506 and the second end of second flow channel 3504. As depicted in FIG. 39B, a portion of the stream of electrolyte in second flow channel 3504 flows down to electrode 3506 to form an electrical connection between the portion of the stream of electrolyte in second flow channel 3504 and electrode 3506. [00100] FIG. 40A and 40B depict another exemplary embodiment of nozzle 106 configured to reduce or eliminate hydrogen bubbles. Nozzle 106 is similar to that depicted in FIGs. 39A and 39B except that nozzle 106 includes a third flow channel 3602 for another portion of the stream of electrolyte and another electrode 3604. [00101] The above detailed description of various device, methods, and systems is provided to illustrate exemplary embodiments and is not intended to be limiting. It will be apparent to those skilled in the art that numerous modifications and variations within the scope of the present inventions are possible. Therefore, the present invention should not be construed as being limited to the specific forms depicted in the drawings and described above.

[00102] For example, although nozzle 106 and the exemplary electropolishing tools have been described in connection with electropolishing a wafer, it should be recognized that nozzle 106 and the exemplary electropolishing tools described above can be used to electropolish various surfaces on various substrates in various applications. One application is to electropolish metal foils, such as stainless steel or Aluminum. The electropolished metal foils can be potentially used as substrates for fabricating flexible displays. Another application is to make mirrors using the electro-polished Aluminum to focus or reflect solar light on solar cells to increase efficiency.

Claims

CLAIMS What is claimed is:

1. A system to electropolish a surface using a stream of electrolyte, the system comprising: a nozzle having an insulator wall and a partial electrode, wherein the insulator wall and the partial electrode form a flow channel for the stream of electrolyte, wherein the stream of electrolyte contacts the insulator wall and the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode, and wherein the insulator wall is less electrically conductive than the partial electrode; and a power supply connected to the partial electrode, wherein the power supply is configured to apply a charge to the stream of electrolyte through the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode.

2. The system of claim I₅ wherein the power supply is not connected to the insulator wall.

3. The system of claim 1 , further comprising: a chuck configured to rotate a substrate on which the surface to be electropolished is disposed, wherein the partial electrode of the nozzle is disposed adjacent to a radially outward position from a center of the substrate, and wherein the insulator wall of the nozzle is disposed adjacent to a radially inward position from the center of the substrate.

4. The system of claim 1, wherein hydrogen bubbles are generated at the partial electrode and not at the insulator wall when the charge is applied to the stream of electrolyte.

5. The system of claim 1 , wherein half of the flow channel is comprised of the partial electrode, and wherein half of the flow channel is comprised of the insulator wall.

6. The system of claim 1 , wherein more than half of the flow channel is comprised of the partial electrode, and wherein less than half of the flow channel is comprised of the insulator wall.

7. The system of claim 1 , wherein less than half of the flow channel is comprised of the partial electrode, and wherein more than half of the flow channel is comprised of the insulator wall.

8. The system of claim 1 , wherein the flow channel formed by the insulator wall and partial electrode is circular in shape.

9. The system of claim 1, wherein the flow channel formed by the insulator wall and partial electrode is elliptical in shape.

10. The system of claim 1 , wherein the flow channel formed by the insulator wall and partial electrode is square, rectangular, or slit in shape.

11. The system of claim 1 , wherein an angle is defined between the insulator wall and partial electrode in an interior portion of the flow channel.

12. The system of claim 1, further comprising: a mesh tube disposed within the flow channel, wherein the mesh tube is configured to prevent hydrogen bubbles from flowing into the mesh tube.

13. The system of claim 12, wherein the flow channel formed by the insulator wall and the partial electrode is angled, and wherein the mesh tube disposed within the flow channel is angled.

14. The system of claim 1, wherein the flow channel formed by the insulator wall and the partial electrode is angled.

15. The system of claim 14, wherein the angle is between positive 30 degrees and negative 30 degrees.

16. A method of electropolishishing a surface using a stream of electrolyte, the method comprising: applying a stream of electrolyte through a nozzle having an insulator wall and a partial electrode, wherein the insulator wall and the partial electrode form a flow channel for the stream of electrolyte, wherein the stream of electrolyte contacts the insulator wall and the partial electrode as the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode, and wherein the insulator wall is less electrically conductive than the partial electrode; and applying a charge to the stream of electrolyte through the partial electrode when the stream of electrolyte flows through the flow channel formed by the insulator wall and the partial electrode, wherein the charge is applied to the partial electrode from a power supply connected to the partial electrode.

17. A system to electropolish a surface using a stream of electrolyte, the system comprising: a nozzle having: an electrode, wherein the electrode forms a flow channel for the stream of electrolyte; and a mesh tube disposed within the flow channel formed by the electrode; and a power supply connected to the electrode, wherein the power supply is configured to apply a charge to the stream of electrolyte through the electrode when the stream of electrolyte flows through the flow channel formed by the electrode.

18. The system of claim 17 , wherein the mesh tube is configured to prevent hydrogen bubbles formed on the electrode from flowing into the mesh tube.

19. The system of claim 17, wherein a first flow path for a portion of the stream of electrolyte is defined within the mesh tube, and wherein a second flow path for another portion of the stream of electrolyte is defined between the mesh tube and the electrode.

20. The system of claim 19, wherein the portion of the stream of electrolyte in the first flow path contacts the surface to be electropolished, and wherein the portion of the stream of electrolyte in the second flow path does not contact the surface.

21. The system of claim 17, wherein the mesh tube extends beyond the electrode.

22. The system of claim 17, wherein the flow channel formed by the electrode has a first end and a second end, wherein the stream of electrolyte enters the flow channel from the first end and exits the flow channel from the second end, and further comprising: a stopper disposed at the first end of the flow channel between the electrode and the mesh tube.

23. The system of claim 22, wherein a first flow path for a portion of the stream of electrolyte is defined within the mesh tube, and wherein a second flow path for another portion of the stream of electrolyte is defined between the mesh tube and the electrode.

24. The system of claim 17, wherein the electrode has a first end, second end, and sides extending from the first end to the second end, and wherein the stream of electrolyte enters the electrode from the first end and exits the electrode from the second end, and further comprising: a tube having solid walls extending from the mesh tube at the second end of the electrode.

25. The system of claim 24, further comprising: a guide portion extending from the tube having solid walls, wherein the guide portion extends over the second end of the electrode.

26. The system of claim 25, wherein the guide portion extends along the sides of the electrode to the first end of the electrode.

27. The system of claim 17, wherein the flow channel formed by the electrode is circular in shape.

28. The system of claim 17, wherein the flow channel formed by the electrode is elliptical in shape.

29. The system of claim 17, wherein the flow channel formed by the electrode is square, rectangular, or slit in shape.

30. A method of electropolishishing a surface using a stream of electrolyte, the method comprising: applying a stream of electrolyte through a nozzle having an electrode, wherein the electrode forms a flow channel for the stream of electrolyte, and a mesh tube disposed within the flow channel formed by the electrode; and applying a charge to the stream of electrolyte through the electrode when the stream of electrolyte flows through the flow channel formed by the electrode, wherein the charge is applied to the electrode from a power supply connected to the electrode.

31. A system to electropolish a surface using a stream of electrolyte, the system comprising: a nozzle having: a first tube that forms a flow channel for the stream of electrolyte, the first tube having a first end, second end, and solid sides extending from the first end to the second end, wherein the stream of electrolyte enters the first tube through the first end and exits the first tube from the second end; a second tube that extends from the second end of the first tube; and a guide portion that extends from the second tube, over the second end of the first tube, and along the solid sides of the first tube; and a power supply configured to apply a charge to the stream of electrolyte when the stream of electrolyte flows through the nozzle.

32. The system of claim 31 , further comprising: a mesh tube disposed within the first tube, and wherein the second tube extends from the mesh tube.

33. The system of claim 32, wherein a first flow path for a portion of the stream of electrolyte is defined within the mesh tube and the second tube, and wherein a second flow path for a portion of the stream of electrolyte is defined between the sides of the first tube and the guide portion.

34. The system of claim 33, wherein the portion of the stream of electrolyte in the first flow path contacts the surface, and wherein the portion of the stream of electrolyte in the second path does not contact the surface.

35. The system of claim 32, wherein the first tube is less electrically conductive than the guide portion, wherein the guide portion is connected to the power supply, wherein the guide portion is configured to be a first electrode to apply the charge to the stream of electrolyte.

36. The system of claim 35, further comprising: a second electrode disposed between the sides of the first tube and the guide portion, wherein the power supply is connected to the second electrode, and wherein the second electrode is configured to apply the charge to the stream of electrolyte.

37. The system of claim 32, further comprising: an electrode disposed between the sides of the first tube and the guide portion, wherein the power supply is connected to the electrode, and wherein the electrode is configured to apply the charge to the stream of electrolyte.

38. The system of claim 37, wherein a first flow path for a portion of the stream of electrolyte is defined within the mesh tube and the second tube, wherein a second flow path for a portion of the stream of electrolyte is defined between the electrode and the guide portion, wherein the portion of the stream of electrolyte in the first flow path contacts the surface, and wherein the portion of the stream of electrolyte in the second path does not contact the surface.

39. The system of claim 31 , further comprising: an electrode disposed between the sides of the first tube and the guide portion, wherein the power supply is connected to the electrode, and wherein the electrode is configured to apply the charge to the stream of electrolyte.

40. The system of claim 39, wherein a first flow path for a portion of the stream of electrolyte is defined within a portion of the first tube and the second tube, wherein a second flow path for a portion of the stream of electrolyte is defined between the electrode and the guide portion, wherein the portion of the stream of electrolyte in the first flow path contacts the surface, and wherein the portion of the stream of electrolyte in the second path does not contact the surface.

41. The system of claim 39, wherein the guide portion is connected to the power supply, wherein the guide portion is configured to be another electrode to apply the charge to the stream of electrolyte

42. The system of claim 31 , wherein the second tube extends into the first tube, and wherein the second tube is electrically conductive and connected to the power supply.

43. The system of claim 42, wherein the second tube extends into a bottom of the first tube.

44. The system of claim 42, wherein the second tube includes an electrically conducting portion and an electrically insulating portion.

45. The system of claim 31 , wherein the second tube is circular in shape.

46. The system of claim 31 , wherein the second tube is elliptical in shape.

47. The system of claim 31 , wherein the second tube is square, rectangular, or slit in shape.

48. A method of electropolishishing a surface using a stream of electrolyte, the method comprising: applying a stream of electrolyte through a nozzle having: a first tube that forms a flow channel for the stream of electrolyte, the first tube having a first end, second end, and solid sides extending from the first end to the second end, wherein the stream of electrolyte enters the first tube through the first end and exits the first tube from the second end; a second tube that extends from the second end of the first tube; and a guide portion that extends from the second tube, over the second end of the first tube, and along the solid sides of the first tube; and applying a charge to the stream of electrolyte through the electrode when the stream of electrolyte flows through the nozzle.

49. A system to electropolish a surface using a stream of electrolyte, the system comprising: a nozzle having: a first flow channel for a first portion of the stream of electrolyte, the first flow channel having a first end, second end, and sides, wherein the first portion of the stream of electrolyte enters the first flow channel through the first end and exits the first flow channel through the second end; a second flow channel for a second portion of the stream of electrolyte, the second flow channel having a first end, second end, and sides, wherein the second portion of the stream of electrolyte enters the second flow channel through the first end and exits the second flow channel through the second end, wherein the first end of the second flow channel is connected to the first flow channel; an electrode disposed on or adjacent to the second flow channel; and a power supply connected to the electrode, wherein the power supply is configured to apply a charge to the second portion of the stream of electrolyte through the electrode when the second portion of the stream of electrolyte flows through the second flow channel.

50. The system of claim 49, wherein the second flow channel extends from one side of the first flow channel.

51. The system of claim 50, wherein the first portion of the stream of electrolyte contacts the surface, and wherein the second portion of the stream of electrolyte does not contact the surface.

52. The system of claim 50, wherein the electrode is disposed on the second end of the second flow channel.

53. The system of claim 50, wherein the electrode is disposed adjacent to the second end of the second flow channel to define a gap between the electrode and the second end of the second flow channel, and wherein the electrolyte flows between the gap to form an electrical connection between the second portion of the stream of electrolyte in the second flow channel and the electrode.

54. The system of claim 49, further comprising: a third flow channel for a third portion of the stream of electrolyte, the third flow channel having a first end, second end, and sides, wherein the third portion of the stream of electrolyte enters the third flow channel through the first end and exits the third flow channel through the second end, wherein the first end of the third flow channel is connected to the first flow channel

55. The system of claim 54, wherein the second flow channel extends from one side of the first flow channel, and wherein the third flow channel extends from another side of the first flow channel.

56. The system of claim 54, wherein the first portion of the stream of electrolyte contacts the surface, and wherein the second and third portions of the stream of electrolyte do not contact the surface.

57. The system of claim 54, wherein the electrode comprises: a first electrode disposed on the second end of the second flow channel; and a second electrode disposed on the second end of the third flow channel.

58. The system of claim 54, wherein the electrode comprises: a first electrode disposed adjacent to the second end of the second flow channel to define a gap between the first electrode and the second end of the second flow channel, and wherein the electrolyte flows between the gap to form an electrical connection between the second portion of the stream of electrolyte in the second flow channel and the first electrode; and a second electrode disposed adjacent to the second end of the third flow channel to define a gap between the second electrode and the second end of the third flow channel, and wherein the electrolyte flows between the gap to form an electrical connection between the third portion of the stream of electrolyte in the third flow channel and the second electrode.

59. The system of claim 54, further comprising: a fourth flow channel for a fourth portion of the stream of electrolyte, the fourth flow channel having a first end, second end, and sides, wherein the fourth portion of the stream of electrolyte enters the fourth flow channel through the first end and exits the fourth flow channel through the second end, wherein the first end of the fourth flow channel is connected to the first flow channel; and a fifth flow channel for a fifth portion of the stream of electrolyte, the fifth flow channel having a first end, second end, and sides, wherein the fifth portion of the stream of electrolyte enters the fifth flow channel through the first end and exits the fifth flow channel through the second end, wherein the first end of the fifth flow channel is connected to the first flow channel.

60. The system of claim 59, wherein the second, third, fourth, and fifth flow channels extend from sides of the first flow channel.

61. The system of claim 60, wherein the first portion of the stream of electrolyte contacts the surface, and wherein the second, third, fourth, and fifth portions of the stream of electrolyte do not contact the surface.

62. The system of claim 49, wherein the first flow channels is circular in shape.

63. The system of claim 49, wherein the first flow channel is elliptical in shape.

64. The system of claim 49, wherein the first flow channel is square, rectangular, or slit in shape.

65. A method of electropolishishing a surface using a stream of electrolyte, the method comprising: applying a stream of electrolyte through a nozzle having: a first flow channel for a first portion of the stream of electrolyte, the first flow channel having a first end, second end, and sides, wherein the first portion of the stream of electrolyte enters the first flow channel through the first end and exits the first flow channel through the second end; a second flow channel for a second portion of the stream of electrolyte, the second flow channel having a first end, second end, and sides, wherein the second portion of the stream of electrolyte enters the second flow channel through the first end and exits the second flow channel through the second end, wherein the first end of the second flow channel is connected to the first flow channel; and