WO2008151918A1

WO2008151918A1 - A process for polishing patterned and unstructured surfaces of materials and an aqueous polishing agent to be used in the said process

Info

Publication number: WO2008151918A1
Application number: PCT/EP2008/056395
Authority: WO
Inventors: Yuzhuo Li; Vivek R. Duvvuru
Original assignee: Basf Se
Priority date: 2007-06-12
Filing date: 2008-05-26
Publication date: 2008-12-18
Also published as: TW200911970A

Abstract

Process for the polishing of patterned and unstructured surfaces of materials, wherein an aqueous polishing agent is used, which aqueous polishing agent comprises (A) at least one bi- or multifunctional compound (a1 ) capable of forming out of its aqueous solution and/or dispersion a passivating film on top of a surface of a metal M or of an alloy of the metal M, the said metal M having a standard reduction potential E0 > -0.1 V for the half-reaction M - Mn+ + n e-, wherein n = integer of from 1 to 4 and e- = electron; and, at the same time, (a2) capable of forming chelate complexes with the said metal M and/or its ions in aqueous solution and/or dispersion; and (B) at least one oxidizing agent; and an aqueous polishing agent, containing (A) at least one bi- or multifunctional compound (a1 ) capable of forming out of its aqueous solution and/or dispersion a passivating film on top of a surface of a metal M or of an alloy of the metal M, the said metal M having a standard reduction potential E0 > -0.1 V for the half-reaction M - Mn+ + n e-, wherein n = integer of from 1 to 4 and e- = electron; and, at the same time, (a2) capable of forming chelate complexes with the said metal M and/or its ions in aqueous solution and/or dispersion; (B) at least one oxidizing agent; and (C) at least one solid, finely divided abrasive.

Description

A process for polishing patterned and unstructured surfaces of materials and an aqueous polishing agent to be used in the said process

Field of the Invention

The invention is directed to a novel process for polishing, in particular for the chemical mechanical polishing (CMP) of patterned and unstructured surfaces of materials, wherein at least one bi- or multifunctional compound is used.

Moreover, the invention is directed to an novel aqueous polishing agent, in particular a CMP agent containing at least one bi- or multifunctional compound.

Background of the Invention

Integrated circuits (IC) consist of structured electrically semiconducting, non-conducting and conducting thin layers. These patterned layers are customarily prepared by applying a layer material, for example, by vapor deposition and patterning it by a microlithographic process. By way of the combination of the various electrically semiconducting, non-conducting and conducting layered materials the electronic circuit elements such as transistors, capacitors, resistors and wirings are fabricated.

The quality of an IC and of its function depends particularly on the precision with which the various layer materials can be applied and patterned.

However, with an increasing number of layers the planarity of the layers decreases significantly. This leads to the failure of one or more functional elements of the IC and, therefore, to the failure of the complete IC after a certain number of layers has been reached.

The decrease of the planarity of the layers is caused by the buildup of new layers on top of layers already patterned. By the patterning altitude differences are created which can add up to 0.6 μm per layer. These altitude differences add up from layer to layer and bring about that the next following layer can no longer be applied onto a planar surface but only onto an uneven surface. The first result is that the layer subsequently applied has an irregular thickness. In extreme cases, imperfections, defects in the electronic functional elements and lacking electrical contacts are caused. Moreover, uneven surfaces lead to problems with the patterning. In order to be able to create sufficiently small patterns, an extremely acute depth of focus is a necessary in the microlithographic process step. However, these patterns can only be imaged with acuity on a planar surface. The more the locations deviate from the planarity, the murkier the image becomes.

In order to solve this problem, a so-called chemical mechanical polishing (CMP) is carried out. The CMP causes a global planarization of the patterned surface by the removal of protruding features of the layer until a planar layer is obtained. Because of this, the subsequent buildup can take place on top of a planar surface exhibiting no altitude differences, and the precision of the patterning and of the functionality of the elements of the IC is maintained.

Typical examples for the global planarization are dielectric CMP, nickel phosphide CMP and silicium or polysilicium CMP.

In addition to the global planarization to overcome lithographical difficulties, there are two other important applications for CMP. One is to fabricate microstructures. Typical examples for this application are copper CMP, tungsten CMP or shallow trench isolation (STI) CMP, in particular the Damascene process described below. The other is defect correction or elimination, as for example sapphire CMP.

A CMP process step is carried out with the help of special polishers, polishing pads and polishing agents which are also referred to in the art as polishing slurries or CMP slurries. A CMP slurry is a composition, which in combination with the polishing pad causes the removal of the material to be polished.

In case that wafers with semiconductor layers are to be polished, the precision requirements for the process step and, thus, the requirements set for the CMP slurry are particularly strict.

A series of parameters are used for evaluating the efficiency of CMP slurries and for characterizing their activity. The material removal rate (MRR), that is the speed with which the material to be polished is removed, the selectivity, that is the ratio of the removal rate of the material to be polished to the removal rates of other materials present, the removal uniformity within a wafer (WIWNU; within wafer non-uniformity) and the removal uniformity from wafer to wafer (WTWNU; wafer to wafer non- uniformity) as well as the number of defects per unit of area rank among these parameters.

The copper Damascene process is increasingly used for the fabrication of IC (cf., for example, the European patent application EP 1 306 415 A2, page 2, paragraph

[0012]). In order to produce the copper circuit paths, it is necessary to remove a copper layer chemically mechanically in this process with the help of a CMP slurry, which process is also called "copper CMP process" in the art. The completed copper circuit paths are embedded in a dielectric. Customarily, a barrier layer is located between the copper and the dielectric.

A two-step process is known for the copper CMP process. This means that the copper layer is polished in the first step with a CMP slurry which guarantees a high copper removal rate. In the second step, a second CMP slurry is used in order to produce the final planar surface with a dielectric polished bare and smooth and with the embedded copper circuit paths.

The first step is often divided into two phases.

During the first phase, the step heights of the copper structures are significantly reduced or eliminated. A flat copper surface is the desired result.

During the second phase, the remaining copper film is removed.

Therefore, the key objective for the first phase is step height reduction. The relative removal rate selectivity is not important. As during the second phase barrier and possibly dielectric materials will be reached, the removal rate selectivity is important. The key objectives for the second phase are to prevent step height redevelopment, minimize surface defects, and clear all copper residues.

For the first polishing step a CMP slurry having a high selectivity is used. This means that the the removal rate for the copper is as high as possible and the removal rate for the underlying barrier layer is as low as possible. The polishing process is automatically stopped as soon as the barrier layer is excavated from under the copper. However, because the complete removal of the copper residues from the barrier layer takes some time, which is also called "over polishing" in the art, the copper of the circuit paths is continuously removed at the locations, where the copper circuit paths are embedded in the dielectric. This effect is also called "dishing" in the art. Depending on the design and the quality of the surface produced in the first polishing step, a CMP slurry which is selective or nonselective with regard to the materials to be polished, namely copper, barrier layer and dielectric, is used in the second polishing step.

In case that a uniform removal of copper leaving only little copper residues behind on the barrier layer can be achieved in the first polishing step, a CMP slurry having a very high selectivity for the barrier layer is used in the second polishing step in order to obtain a uniformly polished surface.

In case that in the first polishing step a surface still containing copper on the barrier layer is produced, the use of a CMP slurry being nonselective with regard to the barrier layer is recommended. In the case of using a nonselective CMP slurry, that is in the case of an approximately equal removal rate for the copper, the barrier layer and the dielectric, the complete surface of the wafer is uniformly planarized by the polishing process. However, a part of the dielectric layer has to be sacrificed which is disadvantageous because of the necessity to deposit thicker dielectric and copper layers. It is essential for the nonselective CMP slurry to have essentially the same planarizing efficiency for all the three materials to be polished. Moreover, the copper circuit paths produced must have a minimum thickness, which means that care has to be taken that not too much material is removed from the dielectric layer and the copper circuit paths. Therefore, the removal has to be carefully monitored during the polishing process.

In the case of using a selective CMP slurry in the second polishing step, the removal rate for the barrier layer is higher than the removal rate for the copper. In this case, the dishing of the copper circuit paths is alleviated by the selective removal of the barrier layer. Therefore, the loss of the dielectric, i.e. the erosion, and the diminishing of the layer thickness of the copper circuit paths associated therewith is much lesser.

From all this, it can be concluded that the material composition of the CMP slurries, in particular of the copper CMP slurries, is of extraordinary importance for the CMP processes described afore.

A copper CMP slurry containing a solid, finely divided abrasive, as for example, colloidal silica, an oxidizing agent, as for example, hydrogen peroxide, a chelating agent capable of forming watersoluble copper chelate complexes, such as glycine, and a corrosion inhibitor, passivating agent or film building agent, as for example, benzotriazole is known from the international patent application WO 2004/063301 A1. The balancing act among the four components (abrasive, oxidizing agent, passivating agent and chelating agent) provides the needed mechanism for the step hight reduction.

However, there are numerous disadvantages associated with such a classic design for the copper CMP slurry including the corrosive effects of the chelates, the defectivity introduced by the typical passivating agents, and the surface defects such as scratching and pitting caused by larger abrasive particles induced by the passivating agent. It has also been shown that the use of abrasive free CMP slurries can reduce surface defects such as scratching, however this has resulted in complications such as corrosion due to strong chemical components in the system which are necessary for compensating for the lack of the abrasives.

The American patent application US 2002/0183498 A1 discloses aqueous slurries containing polyglucosamines such as chitosan and an oxidizing agent such as hydrogen peroxide. Due to the addition of copper ions, the chitosan concentration of these aqueous slurries can be increased significantly. The pH of these aqueous slurries is preferably in the range of from 4 to 6 and can be adjusted with the help of organic and inorganic acids. These prior art aqueous slurries are used as fungicides. No mention is made whatsoever in the patent application that they could be used as or in polishing agents.

Objects of the Invention

It was the object of the present invention to provide a novel aqueous polishing agent for the polishing, in particular for the CMP of patterned and unstructured surfaces of materials, preferably of patterned surfaces of materials, more preferably of metal and metal-dielectric patterns, in particular copper containing patterns, which novel polishing agents do not exhibit the disadvantages of the prior art.

In particular, the novel aqueous polishing agent ought to have a less complex material composition so that it can be adapted to the requirements of each individual case much better than the copper CMP slurries of the prior art. The novel aqueous polishing agent ought to have an excellent polishing efficiency without causing dishing during the copper damascene process. The novel aqueous polishing agent ought to exhibit no undesired corrosive effects and ought not to effectuate defects, scratches and pitting in the materials to be polished.

Moreover, it was the object of the invention to provide a novel polishing process, preferably a novel CMP process of the patterned and unstructured, preferably patterned surfaces of materials, most preferably of metal and metal-dielectric structures, and particularly of copper containing structures, which novel polishing process does no longer exhibit the disadvantages of the prior art and does not effectuate dishing in the materials to be polished and does not lead to undesired corrosion and to defects, scratches and pitting in the materials to be polished.

Summary of Invention

Accordingly, the novel process for the polishing of patterned and unstructured surfaces of materials has been found, wherein an aqueous polishing agent is used, which aqueous polishing agent comprises

(A) at least one bi- or multifunctional compound

(a1 ) capable of forming out of its aqueous solution and/or dispersion a passivating film on top of a surface of a metal M or of an alloy of the metal M, the said metal M having a standard reduction potential E⁰ > -0.1 V for the half-reaction

M ♦+ Mⁿ⁺ + n e", wherein n = integer of from 1 to 4 and e" = electron;

and, at the same time,

(a2) capable of forming chelate complexes with the said metal M and/or its ions in aqueous solution and/or dispersion; and

(B) at least one oxidizing agent.

Hereinafter, the said novel polishing process is referred to as "the polishing process of the invention".

Additionally, the novel aqueous polishing agent was found, containing (A) at least one bi- or multifunctional compound

M ♦+ Mⁿ⁺ + n e", wherein n = integer of from 1 to 4 and e" = electron;

and, at the same time,

(a2) capable of forming chelate complexes with the said metal M and/or its ions in aqueous solution and/or dispersion;

(B) at least one oxidizing agent; and

(C) at least one solid, finely divided abrasive.

Hereinafter, the novel aqueous polishing agent is referred to as "the polishing agent of the invention".

Advantages of the Invention

In view of the prior art discussed above, it was surprising and could not be expected by the skilled artisan that the objects underlying the present invention could be solved by the process of the invention and the polishing agent of the invention.

In particular, it was surprising that the novel use of the bi- or multifunctional compounds A permitted the manufacture of aqueous polishing agents, preferably the polishing agents of the invention, which were excellently suited for the polishing, preferably the CMP, of the patterned and unstructured surfaces of materials, preferably of the patterned surfaces of materials, most preferably of metal and metal-dielectric patterns, particularly of copper containing patterns, in conjunction with the polishing process of the invention.

More specifically, the concerned polishing agent for the CMP, in particular the polishing agents for the CMP of the invention, were well-suited for the CMP of metal and of metal-dielectric structures containing or consisting of a metal M or of an alloy of the metal M, the said metal M having a standard reduction potential E⁰ > -0.1 V for the half- reaction

M ♦+ Mⁿ⁺ + n e", wherein n = integer of from 1 to 4 and e" = electron;

in particular however copper. Particularly, the polishing agents used in the polishing process of the invention were excellently suited for the CMP in the copper damascene fabrication process for IC.

Moreover, it was surprising that the novel use of the bi- or multifunctional compounds A permitted the simple, highly specific and excellently reproducible adjustment and adaption of the material composition of the aqueous polishing agents used in the polishing process of the invention, in particular the polishing agents of the invention, to the requirements of the individual case, in particular in terms of the material removal rate (MRR) and the selectivity. Most notably, it was accomplished to adapt the material composition of the aqueous polishing agent in a simple, directed and excellently reproducible manner to the requirements of the polishing process of the invention. Specifically, the concerned aqueous polishing agents could be excellently adapted to the requirements of the CMP in the copper damascene fabrication process for IC.

Because of the novel use of the bi- or multifunctional compounds A, the polishing process of the invention and the polishing agent of the invention exhibited an excellent polishing efficiency. In particular, they exhibited a very high material removal rate (MRR) and a very high selectivity and yielded polished surfaces free of corrosion, scratches, pitting or other defects. Most notably however, they caused no or only a negligibly small dishing in the copper damascene process.

Last but not least, the novel use of the bifunctional compounds A permitted to carry out the polishing process of the invention with aqueous polishing agents containing no solid, finely dispersed abrasives so that the disadvantages frequently associated therewith, such as scratches or pitting, no longer occurred. Nevertheless, the concerned aqueous polishing agents developed the same or nearly the same excellent polishing efficiency as the aqueous polishing agents containing abrasives without causing corrosion. All in all, the polishing process of the invention and the polishing agent of the invention exhibited an excellent balance between a particularly high material removal rate (MRR) for protruding patterns or structures on the one hand and a particularly strong protective effect for the lowered or recessed patterns or structures on the other hand.

Consequently, because of the novel use of the bi- or multifunctional compounds A in the polishing process of the invention and in the polishing agent of the invention, wafers with IC could be fabricated having no or only a negligibly small WIWNU and no or only a negligibly small WTWNU. Therefore, an extraordinarily high fabrication efficiency could be achieved.

Detailed Description of the Invention

In its broadest aspect, the invention is directed to the novel use of at least one bi- or multifunctional compound A as hereinafter defined in the aqueous polishing agent used in the polishing process of the invention and in the polishing agent of the invention.

Therefore, the aqueous polishing agent used in the polishing process of the invention as well as the polishing agent of the invention comprises at least one, preferably one, bi- or multifunctional, preferably bifunctional compound A.

Basically, the term "bi- or multifunctional" means that the compound A can fulfill at least two, in particular, two functions in an aqueous polishing agent, the two functions being different from each other in chemical and physicochemical terms.

In its first function a1 the bi- or multifunctional compound A is capable of forming out of its aqueous solution and/or dispersion a passivating film on top of a surface of a metal M or of an alloy of the metal M, the said metal M having a standard reduction potential E⁰ > -0.1 V, preferably > 0 V, most preferably > 0.1 V and in particular > 0.2 V for the half-reaction

M ♦+ Mⁿ⁺ + n e", wherein n = integer of from 1 to 4 and e" = electron.

Examples for such standard reduction potentials E⁰ > -0.1 are listed in the CRC Handbook of Chemistry and Physics, 79th edition, 1998-1999, CRC Press LLC, Electrochemical Series, 8-21 to 8-31. In the context of the present invention the term "passivating film" designates a mono or multilayered film essentially or completely consisting of at least one, preferably one, of the bi- or multifunctional compounds A. The passivating film adheres to the surface of the metal M or its alloy so that the surface is protected from detrimental chemical and mechanical effects, in particular from corrosion and ablation, under the conditions of the polishing process of the invention. In its second function a2, the bi- or multifunctional compound A is capable of forming chelate complexes with a metal M and/or its ions in aqueous solution and/or dispersion. As regards the term "chelate complexes", reference is made to Roempp Online 2006, "chelates".

The following surprising advantageous effects of the bi- or multifunctional compound A have been found.

It is known in the art that a passivating film usually consists of two layers. The first layer is an adhesion layer that bridges the oxidized or non-oxidized metal surface and the hydrophobic stack film. The hydrophobic stack film is the key for the passivating effect.

However, it is also the source of many disadvantages of a conventional passivating agent such as organic residue and promotion of the formation of large defect causing particles. As is known in the art, the function of a complexing agent is twofold. The first is to soften the hydrophobic stack by expanding the adhesion layer. The other is to quickly dissolve the metal oxide or hydroxide of the oxidized metal surface that are surrounded by the hydrophobic passivating agent.

However, surprisingly so, the bi- or multifunctional compound A to be used according to the invention, preferably a hydrophilic bi- or multifunctional compound A, does not require any additional complexing agent to free the metal oxide or hydroxide of the oxidized metal surface from forming large defect causing particles. In addition, the preferably hydrophilic nature of the bi- or multifunctional compound A also surprisingly and advantageously simplifies the structure of the passivating film. The adhesion layer and hydrophobic stack found in the passivating layer of a conventional CMP slurry is replaced with a simple film that consists of a complex layer and a stack held together by hydrogen bonding.

Preferably, the metal M is selected from the group consisting of Ag, Au, Bi, Cu, Ge, Ir, Os, Pd, Pt, Re, Rh, Ru, Tl and W, most preferably Ag, Au, Cu, Ir, Os, Pd, Pt, Re, Rh, Ru and W. In particular, the metal M is copper. Therefore, in the case that an aqueous solution and/or dispersion of the bifunctional compound A to be used according to the invention and a metal M or its alloy are in direct contact with each other, the bifunctional compound A forms according to its first function a1 a passivating film on the surface of the metal M or its alloy and, at the same time, forms according to its second function a2 chelate complexes with the metal M and/or its ions present in the aqueous solution and/or dispersion.

According to the invention, all the bi- or multifunctional compounds A can be used in the aqueous polishing agents of the polishing process of the invention or in the polishing agents of the invention as long as they are stable in aqueous solutions or dispersions and are capable of fulfilling the functions a1 and a2. The term "stable" means that the concerned bi- or multifunctional compounds A are not irreversibly chemically transformed, in particular not decomposed by water or other constituents present in the aqueous polishing agents.

Preferably, the bi- or multifunctional, in particular bifunctional compound A is selected from the group consisting of amino sugars and their oligomers and polymers, more preferably amino sugars and polyglucosamines, most preferably D-glucosamine, D- galactosamine and polyglucosamines, and in particular D-glucosamine and chitosan.

The aqueous polishing agent of the polishing process of the invention and the polishing agent of the invention can contain broadly varying amounts of the bi- or multifunctional compound A. Therefore, the concerned amounts can be excellently adjusted and adapted to the requirements of the individual case. Preferably, the polishing agents contain of from 0.1 to 5% by weight, most preferably 0.1 to 3% by weight and in particular 0.25 to 2% by weight, each value being based on the weight of the complete polishing agent concerned, of the bifunctional compound A.

The aqueous polishing agent of the polishing process of the invention optionally contains and the polishing agent of the invention obligatorily contains at least one, preferably one oxidizing agent B. In the case that the aqueous polishing agent of the polishing process of the invention is used for the CMP, it also comprises the oxidizing agent B.

The oxidizing agent B can be selected from the group of oxidizing agents customarily used in the art for the CMP. Examples of suitable oxidizing agents B are known from the international patent application WO 2004/063301 , page 13, paragraph [0028] or from the European patent application EP 1 306 415 A2, page 4, paragraph [0050], the disclosures of which are included by reference. In particular, hydrogen peroxide is used as the oxidizing agent B.

The aqueous polishing agents of the polishing process of the invention and the polishing agents of the invention can contain broadly varying amounts of the oxidizing agent B. Therefore, the concerned amounts can be excellently adjusted and adapted to the requirements of the individual case. Preferably, the polishing agents contain of from 0.1 to 8% by weight and in particular 0.25 to 5% by weight, each value being based on the weight of the complete polishing agent concerned, of the oxidizing agent B.

The aqueous polishing agent of the polishing process of the invention optionally contains and the polishing agent of the invention obligatorily contains at least one, in particular one solid, finely divided abrasive C.

It is a particular advantage of the polishing process of the invention that it can also be carried out in many cases with aqueous polishing agents containing no solid, finely divided abrasives C. Consequently, the disadvantages, such as scratches or pitting in the polished materials, which are sometimes associated with such abrasives, can be avoided from the start without jeopardizing the polishing efficiency. It is an additional special advantage of the polishing process of the invention that no compensation by highly active, in particular strongly corroding compounds is necessary.

However, because of their content of solid, finely divided abrasives C, the polishing agents of the invention exhibit an extraordinarily high MRR for protruding patterns or structures on the one hand without jeopardizing the particularly strong protective effect for the lowered patterns or structures on the other hand.

Preferably, the solid, finely divided abrasives C are having particle sizes of from 1 to 300 nm, most preferably 5 to 200 nm and particularly 10 to 100 nm. The particle size distribution depends on the requirements of the individual case and can be monomodal, bimodal or multimodal, in particular monomodal, and it can be broad or narrow, in particular narrow. Preferably, the mean particle diameter dso is in the range of 5 to 50 nm. The particle size distribution can be determined by laser diffraction. The particles C can have different shapes. For example, they can have the shape of cubes, cubes with champfered edges, octahedrons, icosahedrons, nodules or spheres with or without protrusions or indentations. In particular, they are spherical without protrusions and indentations.

Moreover, the particles C can be homogeneous materials or inhomogeneous materials such as composite materials. They can have hollows or they can be compact. They can also be surface modified. In particular, they are homogeneous and compact.

Preferably, the solid, finely dispersed abrasives C are selected from the group consisting of organic and inorganic materials which are inert under the conditions of the CMP. The term "inert" means that the concerned solid, finely divided abrasives C are neither partially nor completely destroyed by the chemical action of the other constituents of the polishing agents of the invention and of the materials to be polished and by the mechanical effects during the polishing, in particular by the shearing under pressure.

Preferably, the organic and inorganic materials C are selected from the group consisting of solid elements, in particular metals and carbon, borides, carbides, nitrides, phosphides, oxides, sulfides and polymers, in particular polystyrene, poly(meth)acrylate, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polytetrafluoroethylene and polyamide.

Most preferably, the inorganic materials C are oxides C.

Particularly, the oxides C are selected from the group consisting of fumed silica, colloidal silica, fumed aluminum oxide, colloidal aluminum oxide, cerium oxide, titanium dioxide and zirconium dioxide, especially fumed silica, colloidal silica and fumed aluminum oxide.

The aqueous polishing agents of the polishing process of the invention and the polishing agents of the invention can contain broadly varying amounts of the solid, finely divided abrasives C. Therefore, the amounts can be excellently adjusted and adapted to the requirements of the individual case. Preferably, the polishing agents contain of from 1 to 15% by weight, most preferably 1 to 10% by weight and in particular 1 to 5% by weight, each value being based on the weight of the complete polishing agent concerned, of the solid, finely divided abrasives C. The aqueous polishing agents of the polishing process of the invention and the polishing agents of the invention can contain at least one additive D.

Preferably, the additive D is selected from the group of additives customarily used in the aqueous polishing agents for the CMP or the CMP slurries.

Most preferably, the additive D is selected from the group consisting of organic and inorganic acids and bases , pH buffering agents, surface active compounds and rheology modifiers. In particular, inorganic mineral acids are used. Particularly preferably nitric acid is used.

Preferably, the additives D which are selected from the group of acids, bases and pH buffering agents, are contained in the aqueous polishing agents of the polishing process of the invention and in the polishing agents of the invention in such amounts that a pH value of from 3 to 8, in particular 4 to 7 results.

The preparation of the aqueous polishing agents of the polishing process of the invention and of the polishing agents of the invention does not exhibit any particularities but can be carried out by dissolving or dispersing the above-described constituents A and B and optionally C and/or D (the aqueous polishing agents of the polishing process of the invention) or of A, B and C and optionally D (the polishing agent of the invention). For this purpose the customary and standard mixing processes and mixing apparatuses such as agitated vessels, in-line dissolvers, high shear impellers, ultrasonic mixers, homogenizer nozzles or counterflow mixers, can be used. Preferably, the aqueous polishing agents thus obtained are filtered through filters of the appropriate mesh aperture, in order to remove coarse-grained particles such as the agglomerates or aggregates of the solid, finely dispersed abrasives C.

Aqueous polishing agents of the polishing process of the invention and the polishing agents of the invention are used for the polishing, preferably the CMP of the most diverse patterned and unstructured, in particular patterned surfaces of materials.

Preferably, the patterned surfaces of materials concern metal patterns and metal- dielectric patterns. Most preferably, the metal patterns and the metal-dielectric patterns contain or consist of at least one, in particular one metallic material selected from the group consisting of the metals M as defined above and their alloys. In particular, copper is used as the metal M.

As the dielectrics the customarily used organic and inorganic dielectrics can be used. Examples of suitable dielectrics are known from the European patent application EP 1 306 415 A2, page 4, paragraph [0031], the disclosure of which is included by reference. In particular, silicon dioxide is used as the dielectric.

In particular, the metal-dielectric patterns concern copper-dielectric patterns used in the copper damascene process for the fabrication of wafers with IC.

As is known in the art, the metal-dielectric patterns, in particular the copper-dielectric patterns, can contain customarily used barrier layers. Examples of suitable barrier layers are also known from the European patent application EP 1 306 415 A2, page 4, paragraph [0032], the disclosure of which is included by reference.

The polishing process of the invention exhibits no particularities but can be carried out with the processes and the equipment customarily used for the CMP in the fabrication of wafers with IC.

As is known in the art, a typical equipment for the CMP consists of a rotating platen which is covered with a polishing pad. The wafer is mounted on a carrier or chuck with its upper side down facing the polishing pad. The carrier secures the wafer in the horizontal position. This particular arrangement of polishing and holding device is also known as the hard-platen design. The carrier may retain a carrier pad which lies between the retaining surface of the carrier and the surface of the wafer which is not being polished. This pad can operate as a cushion for the wafer.

Below the carrier, the larger diameter platen is also generally horizontally positioned and presents a surface parallel to that of the wafer to be polished. Its polishing pad contacts the wafer surface during the planarization process. During the polishing process the aqueous polishing agent of the polishing process of the invention or the polishing agent of the invention is applied onto the polishing pad as a continuous stream or in dropwise fashion.

Both the carrier and the platen are caused to rotate around their respective shafts extending perpendicular from the carrier and the platen. The rotating carrier shaft may remain fixed in position relative to the rotating platen or may oscillate horizontally relative to the platen. The direction of rotation of the carrier typically, though not necessarily, is the same as that of the platen. The speeds of rotation for the carrier and the platen are generally, though not necessarily, set at different values. 5

Customarily, the temperature of the platen is set at temperatures between 10 and 70⁰C.

For further details reference is made to the international patent application WO 10 2004/063301 A1 , the disclosure of which, in particular page 16, paragraph [0036] to page 18, paragraph [0040] in conjunction with the figure 1 , is included by reference.

By way of the polishing process of the invention and the polishing agent of the invention wafers with IC comprising copper damascene patterns can be obtained which 15 have an excellent functionality.

Examples and Comparative Examples

Example 1 20

The Bifunctionality a1 and a2 of D-glucosamine in CMP Slurries

1.1 The Passivating or Film Building Capability a1 of D-glucosamine in CMP Slurries

25 The passivating capability a1 of D-glucosamine was elucidated by determining the static etch rate (SER) of copper discs. The SER was determined with the following procedure. Copper discs were initially conditioned, washed, dried and then weighed before each experiment. The copper discs were conditioned by polishing for 30 seconds with a slurry comprising colloidal silica and ferric nitrate. The copper discs

30 were then held by a pair of Teflon covered tongs to reduce contamination and were then directly immersed in the stirred CMP slurries. The time of immersion was 5 minutes in each case. After the etching, the copper discs were cleaned with deionized water followed by an isopropyl alcohol rinse. Thereafter, the copper discs were dried with a steady stream of pressurized air, and the SER was calculated on the net weight-

35 loss and the surface area of the disc using the following calculation: SER = Weight-loss/[Density x (Circumferential Area + 2 x Area of Cross-section) x Time],

wherein Weight-loss = loss of weight in copper disc after dissolution; Density = density of copper;

Area of Cross-section = cross-section area of the disc; Circumferential Area = circumferential area of the disc; and Time = dissolution time.

The chemical composition of the CMP slurries and their SER appear in the Table 1.

Table 1 : Compositions of the CMP Slurries No. C1 (Comparison) and Nos. 1 to 4

(Examples) and their SER

CMP slurry constituents/% by weight pH SER/nm/min No. glycine H2O2 D-glucosamine

C1 0,5 150 1 0,5 0,25 110

0,5 0,5 85

0,5 0,75 50

0,5 1 1 35

The significant decrease in SER with the increase of the concentration of D- glucosamine demonstrated the passivation capability a1 of D-glucosamine.

1.2 The Complexing Capability a2 of D-glucosamine in CMP Slurries

The complexation capability of D-glucosamine was demonstrated by determining the material removal rates (MRR) of copper discs. Again, the copper discs were conditioned (as explained before), washed, dried and then weighed before each experiment. Thereafter, they were attached to a stainless steel carrier and then mounted on a single-side polishing machine (Struers Labopol-5 Grinding Table and

Struers LaboForce Arm, Westlake, Ohio). A polyurethane IC 1400 polishing pad was used for the experiments. The copper discs were polished for 5 minutes under a pressure of 41.37 kPa (6 psi) by supplying each of the CMP slurries at a rate of 120 ml/minute on the pad. The copper discs and the pad had a relative rotating speed of

150 rpm. The pad was conditioned with diamond grit conditioner to remove the products of the chemical reactions and to make the pad ready for the next run. After polishing, the discs were cleaned with a deionized water rinse followed by an isopropyl alcohol rinse. Thereafter, the discs were dried with a steady stream of pressurized air, and the MRR was calculated based on the net weight-loss in the polished surface area according to the calculation:

MRR = Weight-loss/(Density x Area of Cross-section x Time);

wherein

Weight-loss = loss of weight in copper disc after polish; Density = density of copper;

Area of Cross-section = cross-section area of the disc; and Time = polishing time.

The units of the MRR are generally measured in nanometer/minute (nm/min) or angstroms/minute (A/min).

The material composition of the CMP slurries used and their MRR can be found in the Table 2.

Table 2: Composition of the CMP Slurries Nos. C2 and C3 (Comparisons) and

Nos. 5 to 12 (Examples) and their MRR

CMP slurry constituent/% by weight pH MRR/nm/min

No. abrasive H2O2 D-glucosamine

aluminum oxide ^a)

C2 3 3 - 4 200

5 3 3 0,25 4 500

6 3 3 0,5 4 1750

7 3 3 0,75 4 2250

8 3 3 1 4 3450

silicon dioxide ^b»

C3 3 3 - < 50

9 3 3 0,25 150

10 3 3 0,5 350

1 1 3 3 0,75 900

12 3 3 1 1600

a) aluminum oxide Baikalox CR-30;

b) Aerosil® 130 of Degussa;

Thus, the increase in MRR with increments in amounts of D-glucosamine corroborated the complexation capabilities a2 of D-glucosamine in CMP slurries.

The complexation capability a2 of D-glucosamine was also elucidated by the relaxation times (T1 ) of D2O using a Bruker Avance 400NMR. To this end, 20 ppm and 40 ppm Cu²⁺ ions were added to each of the solutions Nos. C4 and C5 (Comparisons) and No. 13 (Example):

C4 D₂O;

C5 D2O + 1 % by weight of glycine; and

13 D2O + 1 % by weight of glycine + 1 % by weight of D-glucosamine.

Because of the addition of the Cu²⁺ ions the relaxation time (T1 ) of D2O decreased from 1 1.5 seconds (0 ppm; No. C4) to 3 seconds (20 ppm) to 2 seconds (40 ppm), which decrease indicated the complexation of the Cu²⁺ ions by D2O. In contrast to this, the solutions Nos. C5 and 13 exhibited a significantly lower decrease of the relaxation time (T1 ) of D₂O:

C5: 12 seconds (0 ppm) 6,5 seconds (20 ppm) 4 seconds (40 ppm); 13: 13 seconds (0 ppm) 6,5 seconds (20 ppm) 5 seconds (40 ppm).

This corroborated that the Cu²⁺-containing solutions Nos. C5 and 13 were free of the Cu²⁺-U2θ complexes due to the strong complexation capability a2 of glycine and glycine and D-glucosamine.

Moreover, the complexation capability a2 was also demonstrated using hydroxyl radical (•OH) trapping experiments on a UV-visible (UV-vis) diode array spectrophotometer. The catalytic role of the Cu²⁺-amino acid complexes in the decomposition of hydrogen peroxide to yield hydroxyl radicals was demonstrated. Hydroxyl radicals being much stronger oxidizing agents than hydrogen peroxide enhanced the MRR of copper during CMP in hydrogen peroxide based CMP slurries. The generation of hydroxyl radicals from hydrogen peroxide in the presence of Cu²⁺ ions and amino acids was monitored using p-nitrosodimethylaniline (PNDA) as the hydroxyl radical trapping agent. UV-vis spectroscopy was used to monitor the absorption intensity of PNDA in various hydrogen peroxide containing test solutions.

PNDA had a characteristic absorption peak at 440 nm. Its adduct with the hydroxyl radical had a much weaker absorption peak at the same wavelength. The absorption intensity was thus inversely related to the amount of hydroxyl radicals generated. Less PNDA intensity meant more hydroxyl radicals generated. The initial concentration of PNDA was fixed at 0.0415 mM. All the test solutions Nos. C6 to C9 (Comparisons) and Nos. 14 and 15 (Examples) were maintained at pH = 6.

The hydroxyl radical trapping experiments were conducted, and the pseudo-first-order rate constants and the initial hydroxyl radical concentrations in different peroxide containing solutions were calculated according to the equation:

k = k¹ [OH];

wherein k = Initial slope of the plot shown above; and k' = rate constant = 1.25 ± 0.2 x 10¹⁰/mol s at 21⁰C;

as described in detail in the article "Hydroxyl Radical Formation in H2θ2-Amino Acid Mixtures and Chemical Mechanical Polishing of Copper" published by M. Hariharaputhiran, J. Zhang, S. Ramajaran, J. J. Keleher, Yuzhuo Li, and S. V. Babu in the Journal of The Electrochemical Society, volume 147 (10), pages 3820-3826, 2000.

The relevant data can be found in the Table 3. They demonstrate that also in the case of D-glucosamine the Cu²⁺-amino acid complex generated hydroxyl radicals indicating the complexation capability a2 of D-glucosamine.

Table 3: Pseudo-First-order Rate Constant k and Initial Hydroxyl Radical

Concentration in Different Hydrogen Peroxide Containing Solutions

Solution

No. composition/% by weight k x 10³ 1/min (*OH) x 10¹⁴/M

T = 21⁰C T = 21⁰C

C6 PNDA 0.08 0.01

C7 PNDA + 3 H₂O₂ 1.78 0.3

C8 PNDA + 3 H₂O₂ + 2 D-glucosamine 1.48 0.2

14 PNDA + 3 H₂O₂ + 2 D-glucosamine

+ 100 ppm Cu²⁺ 8.4 1.2

15 PNDA + 3 H₂O₂ + 2 D-glucosamine

+ 200 ppm Cu²⁺ 1 1.3 1.55

C9 PNDA + 3 H₂O₂ + 1 glycine

+ 200 ppm Cu²⁺ 20.7 2.7

Example 2

The Polishing of 20.32 cm (8") Copper Blanket Wafers with CMP Slurries Containing D-glucosamine and Silica or Alumina Abrasives

CMP slurries containing 3% by weight of an alumina abrasive obtained from different vendors, 3% by weight of hydrogen peroxide and 0,5% by weight of D-glucosamine, each value being based on the complete weight of the concerned CMP slurry, or

varying amounts of a silica abrasive (Aerosil™ 130 from Degussa), varying amounts of hydrogen peroxide and varying amounts of D-glucosamine

were used to polished copper blanket wafers on a Westech 372M equipped with a Rodel IC 1000 with a Suba-IV K-groove pad. The polishing conditions were as follows:

Down force: 13.79 kPa (2 psi); Back pressure: 6.89 kPa (1 psi); Table/Carrier speed: 75/65 rpm; and - Flow rate: 200 ml/min.

After the polishing, the thickness of the polished copper blanket wafers was measured using a Prometrix RS 35, a four-point probe sheet resistant tool. Horizon, a noncontact optical profilometer was used to evaluate the surface quality of the polished copper blanket wafers.

The material compositions of the CMP slurries and the MRRs and the WIWNUs obtained therewith are shown in the Table 4. The data obtained clearly demonstrated D-glucosamine as a viable option for copper CMP.

Table 4: Composition of the CMP Slurries Nos. 16 to 24 and the MRRs and the

WIWNUs Obtained Therewith

CMP composition/% by weight pH MRR/A/min WIWNU/% slurry abrasive H2O2 D-glucos-

No. amine

aluminum oxide

16 3 EKC CU 150 3 0.5 4 3800 15 17 3 Baikalox CR-30 3 0.5 4.35 5910 9

18 Ferro SRS120 3 0.5 4.75 4170 9

Aerosil™ 130

19 3 3 1.5 5 13,750

20 3 3 1.5 6 11 ,800

21 3 3 1.5 7 10,400

22 3 3 1.25 6 6200 23 3 3 1.125 6 3450

24 2 4 1.125 7 2400

Example 3

The Polishing of 20.32 cm (8") Copper Patterned Wafers with CMP Slurries Containing D-glucosamine and Silica or Alumina Abrasives

Sematech 854 copper patterned wafers were polished on a Westech 372M equipped with a Rodel IC 1000 with a Suba-IV K-groove pad. The polishing conditions were as follows:

Down force: 13.79 kPa (2 psi); - Back pressure: 6.89 kPa (1 psi);

Table/Carrier speed: 75/65 rpm; and Flow rate: 200 ml/min.

After the polishing, the thickness of the polished copper blanket wafers was measured using a Prometrix RS 35, a four-point probe sheet resistant tool. The step heights were measured using an Ambios XP2 profilometer. The compositions of the CMP slurries were as follows: CMP slurry No. 25:

3% by weight of alumina (Baikalox CR-30), 3% by weight of hydrogen peroxide and 0.5 % by weight of D-glucosamine, each value being based on the complete weight of the CMP slurry, pH = 4.3.

CMP slurry No. 26:

3% by weight of Aerosil™ 130, 3% by weight of hydrogen peroxide and 1.25 percent by weight of D-glucosamine, each value being based on the complete weight of the CMP slurry, pH = 6.

The step heights obtained with the CMP slurry No. 25 are compiled in the Table 5. The step heights obtained with the CMP slurry No. 26 are compiled in the Table 6.

Table 5: Step Heights of Copper Patterned Test Wafers Obtained with the CMP Slurry No. 25

Polish Thick- Step Height 100_100 Step Height 50_50 Time/s ness/A Die 1 Die 2 Die 3 Die 1 Die 2 Die 3

0 10,500 5100 5000 4900 5100 5000 4900

60 4500 260 120 240 190 95 220

90 1200 n/a n/a n/a n/a n/a n/a

105 0 -270 -235 -150 -250 -350 -180

n/a not available Table 6: Step Heights of Copper Patterned Test Wafers Obtained with the CMP Slurry No. 26

Polish Die 1 Die 2 Die 3 Die 4 Die 5 Time/s Th./A S.H./A Th./A S.H./A Th./A S.H./A Th./A S.H./A Th./A S.H./A

0 10,8004160 10,800 5110 10,800 5000 10,8004980 10,800 5020

40 8400 2900 6300 1 100 6200 625 5600 n/a 5300 n/a

60 7500 2100 4900 n/a 4550 n/a 3950 n/a 3600 n/a

90 6200 1400 1550 n/a 1300 n/a 800 n/a 0 -575

110 5000 1 100 0 -455 0 -650 0 -980 0 -1650

n/a not available;

Th. Thickness;

S. H. Step Height;

The data obtained demonstrated D-glucosamine's capability a1 to passivate the copper surface to lessen the patterned defects such as dishing and erosion.

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in the light of the foregoing description. Accordingly, departures may be made from such details without departing from the spirit or scope of the general inventive concept.

Claims

What is claimed is:

1. A process for the polishing of patterned and unstructured surfaces of materials, wherein an aqueous polishing agent is used, which aqueous polishing agent comprises

(A) at least one bi- or multifunctional compound

M ♦+ Mⁿ⁺ + n e", wherein n = integer of from 1 to 4 and e" = electron;

and, at the same time,

(B) at least one oxidizing agent.

2. The process according to claim 1 , characterized in that the compound A is bifunctional.

3. The process according to the claim 1 , characterized in that the metal M is selected from the group consisting of Ag, Au, Bi, Cu, Ge, Ir, Os, Pd, Pt, Re, Rh, Ru, Tl and W.

4. The process according to claim 3, characterized in that the metal M is copper.

5. The process according to anyone of the claims 1 to 4, characterized in that the bi- or multifunctional compound A is selected from the group consisting of amino sugars and oligomers and polymers of amino sugars.

6. The process according to claim 5, characterized in that the bi- or multifunctional compound A is selected from the group consisting of D-glucosamine, D-galactosamine and chitosan.

7. The process according to claim 1 , characterized in that the aqueous polishing agent comprises at least one oxidizing agent B.

8. The process according to claim 7, characterized in that the oxidizing agent B is hydrogen peroxide.

9. The process according to claim 1 , characterized in that the aqueous polishing agent comprises at least one solid, finely divided abrasive C.

10. The process according to claim 9, characterized in that the solid, finely divided abrasive C has a particle size of from 1 to 300 nm.

1 1. The process according to claim 9 or 10, characterized in that the aqueous the solid finely divided abrasive C is selected from the group consisting of organic and inorganic materials which are inert under the conditions of the chemical mechanical polishing.

12. The process according to claim 11 , characterized in that the organic and inorganic materials C are selected from the group consisting of solid elements, in particular metals and carbon, borides, carbides, nitrides, phosphides, oxides, sulfides and polymers, in particular polystyrene, poly(meth)acrylate, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polytetrafluoroethylene and polyamide.

13. The process according to claim 12, characterized in that oxides are used as the inorganic materials C.

14. The process according to claim 13, characterized in that the oxides C are selected from the group consisting of fumed silica, colloidal silica, fumed aluminum oxide, colloidal aluminum oxide, cerium oxide, titanium dioxide and zirconium dioxide.

15. The process according to claim 1 , characterized in that the aqueous polishing agent contains at least one additive D.

16. The process according to claim 15, characterized in that the additive D is selected from the group consisting of organic and inorganic acids and bases, pH buffering agents, surface active compounds and rheology modifiers.

17. The process according to claim 16, characterized in that be aqueous polishing agent has a pH value of from 3 to 8.

18. The process according to claim 1 , characterized in that the aqueous polishing agent is used for the chemical mechanical polishing of patterned surfaces of materials.

19. The process according to claim 18, characterized in that the patterned surfaces are metal and metal-dielectric patterns.

20. The process according to claim 19, characterized in that the metal and the metal-dielectric patterns comprise or consist of at least one metallic material selected from the group consisting of the metals M as previously defined and of the alloys of the said metals M.

21. The process according to claim 20, characterized in that the metal M is copper.

22. The process according to claim 21 , characterized in that the aqueous polishing agents is used in the copper damascene process for the fabrication of wafers with integrated circuits.

23. An aqueous polishing agent, containing

(A) at least one bi- or multifunctional compound

M ♦+ Mⁿ⁺ + n e", wherein n = integer of from 1 to 4 and e" = electron;

and, at the same time,

(B) at least one oxidizing agent; and (C) at least one solid, finely divided abrasive.

24. The aqueous polishing agent according to claim 23, characterized in that the compound A is bifunctional.

25. The aqueous polishing agent according to the claim 24, characterized in that the metal M is selected from the group consisting of Ag, Au, Bi, Cu, Ge, Ir, Os, Pd, Pt, Re, Rh, Ru, Tl und W.

26. The aqueous polishing agent according to claim 25, characterized in that the metal M is copper.

27. The aqueous polishing agent according to anyone of the claims 23 to 26, characterized in that the bi- or multifunctional compound A is selected from the group consisting of amino sugars and oligomers and polymers of amino sugars.

28. The aqueous polishing agent according to claim 27, characterized in that the bi- or multifunctional compound A is selected from the group consisting of D-glucosamine, D-galactosamine and chitosan.

29. The aqueous polishing agent according to claim 23, characterized in that the aqueous polishing agent comprises at least one oxidizing agent B.

30. The aqueous polishing agent according to claim 29, characterized in that the oxidizing agent B is hydrogen peroxide.

31. The aqueous polishing agent according to claim 30, characterized in that the aqueous polishing agent comprises at least one solid, finely divided abrasive C.

32. The aqueous polishing agent according to claim 31 , characterized in that the solid, finely divided abrasive C has a particle size of from 1 to 300 nm.

34. The aqueous polishing agent according to claim 31 or 32, characterized in that the solid finely divided abrasive C is selected from the group consisting of organic and inorganic materials which are inert under the conditions of the chemical mechanical polishing.

35. The aqueous polishing agent according to claim 34, characterized in that the organic and inorganic materials C are selected from the group consisting of solid elements, in particular metals and carbon, borides, carbides, nitrides, phosphides, oxides, sulfides and polymers, in particular polystyrene, poly(meth)acrylate, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polytetrafluoroethylene and polyamide.

36. The aqueous polishing agent according to claim 35, characterized in that oxides are used as the inorganic materials C.

37. The aqueous polishing agent according to claim 36, characterized in that the oxides C are selected from the group consisting of fumed silica, colloidal silica, fumed aluminum oxide, colloidal aluminum oxide, cerium oxide, titanium dioxide and zirconium dioxide.

38. The aqueous polishing agent according to claim 23, characterized in that the aqueous polishing agent contains at least one additive D.

39. The aqueous polishing agent according to claim 38, characterized in that the additive D is selected from the group consisting of organic and inorganic acids and bases, pH buffering agents, surface active compounds and rheology modifiers.

40. The aqueous polishing agent according to claim 39, characterized in that be aqueous polishing agent has a pH value of from 3 to 8.

41. The aqueous polishing agent according to claim 23, characterized in that it contains of from 0.1 to 5% by weight, based on the weight of the complete aqueous polishing agent, of at least one bifunctional compound A.

42. The aqueous polishing agent according to claim 23 or 41 , characterized in that it contains of from 0.1 to 8% by weight, based on the weight of the complete aqueous polishing agent of at least one oxidizing agent B.

43. The aqueous polishing agent according to anyone of the claims 23, 41 or 42, characterized in that it contains of from 1 to 15% by weight, based on the weight of the complete aqueous polishing agent, of at least one solid, finely divided abrasive C.

44. The aqueous polishing agent according to claim 23, characterized in that it concerns a chemical mechanical polishing agent.

45. Wafers containing integrated circuits comprising copper damascene patterns chemically mechanically polished by the process according to claim 1.

46. Wafers containing integrated circuits comprising copper damascene patterns chemically mechanically polished with at least one aqueous polishing agent according to claim 23.