JP2009070904A - Polishing composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing slurry preferably used for a CMP process, which can prevent the occurrence of dishing or erosion by having high polishing selectivity and high clear performance while maintaining a high polishing speed significant in the industrial field. <P>SOLUTION: The polishing composition is used which contains: a water-soluble resin (A) obtained by polymerizing 55-100 pts.wt. vinyl monomer containing amide group and 0-45 pts.wt. another vinyl monomer, an anti-corrosion agent, an auxiliary anti-corrosion agent, a complexing agent, an oxidizer and water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing composition and a method for producing an object to be polished using the polishing composition, and in particular, a polishing composition suitably used for chemical mechanical polishing (hereinafter referred to as CMP), and the polishing composition The present invention relates to a method for producing an object to be polished using a polishing composition.

  In recent years, in a wiring forming process, which is a process for manufacturing a semiconductor element, a groove for forming a wiring is dug on an insulating film formed on a semiconductor wafer, and a metal film for wiring is plated so as to cover the groove. A technique for embedding using a method or the like and forming a metal wiring by removing an excessive metal film is used. Here, CMP is used to remove the excessive metal film and planarize the surface of the semiconductor wafer. CMP is not just mechanical polishing using abrasive grains, but is a method of mechanically polishing the surface to be polished that has been modified by applying a chemical action, and the cooperation between the chemical action and the mechanical action. Because of the polishing by, controlled integration of chemical and mechanical action is important.

Conventionally, inorganic abrasive grains such as ceria, alumina, and silica have been used as abrasive grains used in CMP. However, these inorganic abrasive grains have high hardness, and there is a problem that scratches, dishing, erosion and the like occur when polishing soft metals such as copper.
Scratch refers to scratches caused by excessively locally polishing the surface to be polished due to abrasive grains that are too hard or aggregated with respect to the material to be polished. The scratch has a problem that the wiring of the semiconductor element is disconnected.
Dishing may occur due to distortion of the polishing pad during polishing, but the type and amount of pH adjusting agent, oxidizing agent and complexing agent for adjusting the liquid properties of the polishing composition and the surface to be polished This is likely to occur when the chemical properties of the surface to be polished do not match the mechanical polishing characteristics. The form of dishing is a concave shape generated by polishing the metal film at the center of the wiring part excessively than the surroundings.
Erosion refers to the generation of a concave shape larger than dishing that occurs in a portion where wiring patterns are dense. This occurs due to excessive polishing with abrasive grains that are too hard, and low polishing selectivity of the polishing composition for each object to be polished such as a metal film for wiring, an insulating film, and a barrier film existing on the surface to be polished. A polishing composition in which conventional inorganic abrasive grains play a major role in the polishing process has the advantage of a high polishing speed because of its mechanical polishing action, but has a high polishing selectivity for the object to be polished. There is a problem that erosion is likely to occur. Generally, in order to completely remove the metal film other than the wiring part on the entire surface of the semiconductor wafer to be polished, the polishing time is set according to the slowest part of the polishing rate. In such a region, excessive polishing (over polishing) is likely to occur, and erosion is likely to occur.
Dishing and erosion cause an increase and variation in wiring resistance, and further cause a short circuit between wirings formed in an upper layer.
On the other hand, if the polishing time is set too short in consideration of the occurrence of erosion, dishing, scratches, etc., a problem arises in that the metal film that should be removed remains other than the wiring portion and the clearness is poor. If the clearness is poor, the operation of the semiconductor element may become unstable. Therefore, it is necessary to surely remove the metal to be removed.
As described above, when scratching, dishing, erosion occurs, or when the clearness is poor, the reliability of the semiconductor element is significantly impaired, and the manufacturing yield is greatly reduced.

  Recently, in order to improve the performance of semiconductor elements, the 1/2 wiring width on the insulating film has been reduced from 90 nm to 65 nm and further to 45 nm. When the 1/2 wiring width is 45 nm, the thickness of the barrier layer becomes thinner than before. Therefore, there is a demand for a polishing composition and a polishing method that do not generate scratches, dishing, erosion, etc. Especially, erosion countermeasures are extremely important. It is expected that

In order to solve these problems, the abrasive composition is made of silica that is softer than alumina, and polishing is performed in a neutral to alkaline region where the metal to be polished forms a passive state and the metal ions to be polished are difficult to elute. Has been developed. However, even if the inorganic abrasive grains are changed from alumina to silica, the generation of scratches due to the abrasive grains themselves is suppressed, but the occurrence of scratches and erosion due to abrasive agglomerates and metal scraps to be polished has not been solved. .
Japanese Patent No. 3172008 (Patent Document 1) discloses a polishing method using, as abrasive grains, particles composed of organic polymer compounds or particles mainly composed of carbon selected from the group consisting of amorphous carbon and carbon black. Has been. However, Patent Document 1 has an object to completely remove abrasive grains remaining on the surface to be polished after polishing, and an invention that solves the problem by burning and removing abrasive grains made of organic polymer or carbon after polishing. However, since no oxidizing agent that oxidizes the surface of the metal to be polished is added, the chemical action does not work at all, and as a result, an industrially meaningful polishing rate is not obtained. .

Japanese Patent Application Laid-Open No. 2001-55559 (Patent Document 2) discloses an aqueous dispersion for chemical mechanical polishing containing organic particles having a functional group capable of reacting with a surface to be polished. Although improved, there has been no evaluation of dishing or erosion.
Japanese Patent Application Publication No. 2004-532521 (Patent Document 3) discloses a CMP polishing composition containing a water-soluble carboxylic acid polymer. However, when the metal corrosion region, that is, the metal to be polished is copper, it is on the acidic side. Therefore, there is a problem that a slit-shaped depression called a fang is easily formed by the copper corrosion reaction progressing at the interface portion between the copper layer and the barrier layer and the copper ions are eluted.
In Japanese Patent No. 3337464 (Patent Document 4) and Japanese Patent No. 3627598 (Patent Document 5), benzotriazole is used as a first protective film forming agent and polyacrylic is used as a second protective film forming agent or a water-soluble polymer. Although inventions using ammonium acid or polyacrylamide have been disclosed, the effect of suppressing etching is low in the neutral to alkaline region, and it cannot be expected to suppress the occurrence of dishing. In addition, the viscosity increases due to neutralization, and the fluidity of the polishing liquid decreases, which may reduce the polishing rate and the polishing quality. Moreover, since it does not substantially contain abrasive grains, an industrially meaningful polishing rate cannot be obtained, and there is a problem that the metal film cannot be completely removed and the clearness is poor.
Japanese Patent Laid-Open No. 2003-313541 (Patent Document 6) suppresses polishing of tantalum used as a material for a barrier layer by using resin particles having a lower modulus of elasticity than conventional inorganic abrasive grains, thereby reducing copper and tantalum. Although the invention has been disclosed to improve the polishing selectivity of copper, the polishing rate of copper is slower than conventional inorganic abrasive grains, so that a sufficient polishing selection ratio of copper and tantalum cannot be obtained, and erosion occurs. It is expected that it is difficult to completely suppress this.
JP-A-2001-144049 (Patent Document 7) discloses that by using a polishing liquid containing a water-soluble polymer, it is possible to suppress the occurrence of erosion. An industrially significant polishing rate has not been obtained.
Japanese Patent No. 3172008 JP 2001-55559 A JP-T-2004-532521 Japanese Patent No. 3337464 Japanese Patent No. 3627598 Japanese Patent Laid-Open No. 2003-313541 JP 2001-144049 A

  While maintaining an industrially significant polishing rate, a polishing composition having high polishing selectivity and high clearness, particularly in the process of manufacturing a semiconductor element, suppresses the occurrence of erosion even if excessive polishing is performed. A polishing composition suitably used for CMP is provided. Moreover, the manufacturing method of the to-be-polished object using this polishing composition is provided.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the polishing composition of the present invention is a water-soluble product obtained by polymerizing a vinyl monomer containing an amide group or copolymerizing a vinyl monomer containing an amide group and another vinyl monomer. A polishing composition comprising an adhesive resin (A) (hereinafter simply referred to as a water-soluble resin (A)), an anticorrosive agent, an anticorrosion aid, a complexing agent, an oxidizing agent, and water, The said subject can be solved by using this polishing composition.
As the anticorrosive, benzotriazole and its derivatives are preferably used.
From the viewpoint of reducing dishing, a water-soluble resin (B) obtained by polymerizing an aromatic carboxylic acid such as quinolinic acid, an aromatic amino acid such as phenylalanine, or a vinyl monomer containing a carboxyl group as an anticorrosive agent It is preferable that it contains at least one selected from the group consisting of water-soluble resin (B)).
As the complexing agent, carboxylic acids, amines, amino acids, ammonia and the like are preferably used, and as the oxidizing agent, hydrogen peroxide and the like can be preferably used from the viewpoint of suppressing a high polishing rate and dishing.
Moreover, it is preferable that a water-soluble resin (A) has a functional group which forms an anion from a viewpoint of improving the dispersibility to water. Examples of the functional group that preferably forms an anion include a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and among these, a carboxyl group is particularly preferable.
Further, from the viewpoint of obtaining a higher polishing rate, inorganic particles and / or organic particles may be contained.
Further, from the viewpoint of improving the uniformity of the polishing rate in the semiconductor wafer and / or from the viewpoint of suppressing clogging of the polishing composition in the supply line, an additive for suppressing foaming (hereinafter referred to as a foaming inhibitor). ) Is preferred. Examples of the foam inhibitor include polyethylene glycol type nonionic surfactants, polyether type nonionic surfactants, and emulsions of fatty acid esters.

  The polishing composition of the present invention exhibits a high polishing rate and has both high polishing selectivity and clearness even if it does not contain high-hardness inorganic abrasive grains or its concentration is low. In particular, the CMP in the wiring forming process, which is one process for manufacturing a semiconductor element, has a remarkable effect that the generation of erosion can be suppressed even if excessive polishing is performed.

The polishing composition of the present invention will be specifically described.
The polishing composition of the present invention has both a high polishing rate, high polishing selectivity, and high clearness. Referring to FIG. 1, the metal wiring layer 3 is formed in a thickness of 0.1 to 30 μm on the insulating layer 1 on which the metal wiring forming portion 4 is formed with the insulating portion therebetween. Here, the width of the metal wiring forming portion 4 is 9.0 μm, and the width of the insulating portion is 1.0 μm. The barrier metal layer 2 produced when excessive polishing is performed up to 1.5 × t time, where t is the polishing time necessary for polishing until the barrier metal layer 2 other than the metal wiring forming portion 4 is exposed under a certain polishing condition. The amount of erosion can be suppressed to 10 nm or less, preferably 8 nm or less, with the amount of dent being the amount of erosion.
When the metal wiring layer 3 contains at least one selected from copper, copper alloys, and oxides thereof, the effect of suppressing erosion is great. Further, the barrier metal layer 2 shown on the semiconductor wafer insulating film layer 1 is a thin layer made of at least one selected from tantalum, tantalum nitride, tantalum alloy, titanium, titanium nitride, titanium alloy, ruthenium, and ruthenium alloy, more preferably tantalum. In the case where is applied, a greater effect can be obtained.

Below, each component of the polishing composition of this invention is demonstrated.
(Water-soluble resin (A))
By containing the water-soluble resin containing an amide group, the polishing composition of the present invention has both a high polishing rate and high clearness, and can suppress erosion.
The monomer constituting the water-soluble resin (A) is 55 to 100 parts by weight, preferably 60 to 99 parts by weight of vinyl monomer containing an amide group with respect to 100 parts by weight of the total amount of the water-soluble resin (A). Part by weight, more preferably 70 to 99 parts by weight is included.
Examples of the vinyl monomer having an amide group include (meth) acrylamide, N-vinylacetamide, N-alkyl (meth) acrylamide, N, N′-dialkyl (meth) acrylamide, hydroxyalkyl (meth) acrylamide, and N-isopropyl. (Meth) acrylamide, methylenebis (meth) acrylamide, aminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and the like can be exemplified. Among these, (meth) acrylamide is particularly preferable because a high polishing rate can be obtained.
Here, (meth) acrylamide refers to either one or both of acrylamide and methacrylamide.
As the vinyl monomer having an amide group, only one type may be selected from those exemplified here, or a plurality of types of vinyl monomers may be mixed and used. Moreover, you may use the resin copolymerized as a mixture with the other vinyl monomer which does not contain an amide group.
Other vinyl monomers not containing an amide group include hydrophobic vinyl monomers such as styrene, alkyl (meth) acrylate, isobornyl (meth) acrylate and cyclohexyl (meth) acrylate, and cyano such as (meth) acrylonitrile. Group-containing vinyl monomers, carboxyl group-containing vinyl monomers such as (meth) acrylic acid, hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl (meth) acrylate, and glycidyl group-containing vinyl such as glycidyl (meth) acrylate Monomers, amino group-containing vinyl monomers such as N, N′-dimethylaminoethyl (meth) acrylate, and acetoacetoxy group-containing vinyl monomers such as acetoacetoxyethyl (meth) acrylate. A crosslinkable vinyl monomer may be used without departing from the gist of the present invention. Examples of such a crosslinkable vinyl monomer include methylenebis (meth) acrylamide, divinylbenzene, and polyethylene glycol chain-containing di (meta). ) Accelerate can be exemplified.
As for the vinyl monomer containing no amide group, only one type may be used, but there is no problem even if a plurality of types of vinyl monomers are used in combination.
Furthermore, having a functional group capable of forming an anion is one of preferred embodiments from the viewpoint of enhancing the solubility of the water-soluble resin (A) in water. In order to introduce a functional group capable of forming an anion into the water-soluble resin (A), a method in which a certain amount of a monomer having a functional group capable of forming an anion is copolymerized can be used. Examples of the monomer having a functional group capable of forming an anion include (meth) acrylic acid, itaconic acid, styrene sulfonic acid, crotonic acid, fumaric acid, maleic acid, methallyl sulfonic acid, and 2-methacryloxyethyl acid. A phosphate etc. can be illustrated.
The content of the monomer having a functional group capable of forming an anion is 0.5 to 30 parts by weight with respect to 100 parts by weight of the total weight of monomers used as a raw material for the water-soluble resin (A). More preferably, it is 1-20 weight part.
As the water-soluble resin (A), a copolymer of (meth) acrylamide and (meth) acrylic acid is preferable, and a copolymer of methacrylamide and methacrylic acid is particularly preferable.
From the viewpoint of obtaining a high polishing rate, the water-soluble resin (A) is preferably 0.5 to 20 parts by weight, more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the polishing composition.
The total weight of the resin component in the polishing composition is determined by, for example, centrifuging the polishing composition for 1 hour at 85,000 rpm and 20 ° C. using an ultracentrifuge such as CS100FX manufactured by Hitachi Koki Co., Ltd. And the supernatant, and the supernatant is further evaporated to dryness to determine the amount of water-soluble solids, and the concentration of the additive is separately determined by capillary electrophoresis or the like.
The average molecular weight of the water-soluble resin (A) is preferably 500,000 or less from the viewpoint of increasing the solubility, and more preferably 300,000 or less.

(Method for producing water-soluble resin (A))
Although the synthesis method of water-soluble resin (A) is not specifically limited, It can synthesize | combine suitably by superposing | polymerizing in the solvent which has water as the main component. In particular, aqueous solution polymerization can be suitably used.
Distilled water is charged into a flask equipped with a stirrer and a reflux condenser, and after replacing with an inert gas, a polymerization initiator is added, and the inside of the flask is stirred and contains a vinyl monomer or a mixture of vinyl monomers. The aqueous solution (A) can be synthesized by gradually dropping the aqueous solution to complete the polymerization.
The polymerization initiator is not particularly limited, but a water-soluble radical polymerization initiator is preferable, and a water-soluble azo type such as persulfate such as ammonium persulfate or 4,4′-azobis (4-cyanovaleric acid). A polymerization initiator is particularly preferred.
The polymerization temperature is not particularly limited, but can be preferably polymerized in the range of 30 to 95 ° C., more preferably in the range of 50 to 85 ° C. in consideration of the reaction time, conversion rate, and the like. .
Further, for the purpose of improving the stability of the reaction, a pH adjuster, EDTA which is a metal ion sealing agent, or a salt thereof may be added.
Further, a molecular weight modifier may be used at the time of polymerization, and examples thereof include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan, alcohols such as isopropanol, α-methylstyrene dimer, methallylsulfonic acid and the like.

(Anticorrosive)
The anticorrosive used in the polishing composition of the present invention is one that suppresses etching of the metal to be polished by forming a protective film on the surface of the metal to be polished. From the viewpoint of suppressing the occurrence of dishing, benzotriazole and / or benzotriazole derivatives can be preferably used, and benzotriazole is particularly preferably used.
From the viewpoint of suppressing a decrease in the polishing rate, the content of the anticorrosive is preferably 0.01 to 0.1 parts by weight with respect to 100 parts by weight of the polishing composition. If it is 0.1 parts by weight or more, it is difficult to obtain a high polishing rate that can be used industrially, while if it is 0.01 parts by weight or less, the occurrence of dishing may not be sufficiently suppressed.

(Anti-corrosion aid)
The anticorrosion aid in the present invention does not function as an anticorrosion agent alone because its metal anticorrosion ability is low, but improves the function of the anticorrosion agent in combination with an anticorrosion agent such as benzotriazole, and the anticorrosion agent alone Compared to the case where it is used, it is a compound that enables expression of a higher polishing rate while suppressing dishing. Specific examples include aromatic dicarboxylic acids such as quinolinic acid and quinaldic acid, aromatic amino acids such as tryptophan and phenylalanine, and metal ions such as ethylenediaminetetraacetic acid, diethylenetriaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, and cyclohexanediaminetetraacetic acid. Examples thereof include chelating compounds capable of conformation. These may function alone as anticorrosion aids, but may be used in combination.
(Water-soluble resin (B))
Further, as the anticorrosive auxiliary of the present invention, in addition to the above-described compounds, unsaturated monobasic acids such as (meth) acrylic acid and crotonic acid, unsaturated dibasic acids such as itaconic acid, fumaric acid and maleic acid, or A water-soluble resin (B) comprising these monoesters can also be used.
In particular, a water-soluble resin (B) that easily forms an anion containing at least one vinyl monomer selected from the group consisting of (meth) acrylic acid, crotonic acid, and itaconic acid can be suitably used. As the water-soluble resin (B) as an anticorrosion aid, a carboxyl group is included as an essential component as a functional group capable of forming an anion, and a sulfonic acid group and other copolymerizable vinyl monomers are polymerized. It is preferable that it can suppress the elution of the metal to be polished and suppress the occurrence of dishing. Examples of other copolymerizable vinyl monomers of the water-soluble resin (B) include esters of unsaturated monobasic acids such as (meth) acrylic acid and crotonic acid, allylsulfonic acid, Examples thereof include sulfonic acid-containing monomers such as methallyl sulfonic acid and sodium styrene sulfonate, and 2-methacryloxyethyl acid phosphate.
Although it does not specifically limit as a manufacturing method of water-soluble resin (B), It can manufacture using well-known polymerization methods, such as aqueous solution polymerization, emulsion polymerization, and dispersion polymerization. Moreover, homopolymers, such as commercially available polyacrylic acid, can also be used.
The composition of the monomer constituting the water-soluble resin (B) is 15 monomers having a functional group capable of forming an anion with respect to 100 parts by weight of all the monomers constituting the water-soluble resin (B). It is preferable that it is -100 weight part, More preferably, it is 20-100 weight part, The other vinyl monomer is 0-85 weight part, More preferably, it is 0-80 weight part.
(Amount of anticorrosion aid added)
The addition amount of the anticorrosion aid varies depending on the type and amount of the anticorrosive used, but is preferably in the range of 0.001 to 1.0 part by weight with respect to 100 parts by weight of the polishing composition. If the addition amount of the anti-corrosion aid is less than 0.001 part by weight, the anti-corrosion effect may be insufficient and the occurrence of dishing may not be suppressed. On the other hand, if the addition amount of the anticorrosive auxiliary exceeds 1.0 part by weight, the anticorrosive effect becomes too high, and the polishing rate and / or clearness may be lowered.

(Abrasive grains)
Abrasive grains may be further added to the polishing composition of the present invention from the viewpoint of improving the polishing rate. As the abrasive grains, inorganic abrasive grains such as colloidal silica, colloidal alumina, and ceria, organic abrasive grains such as acrylic resin particles, and / or composite abrasive grains composed of inorganic particles and organic particles can be used. Organic abrasive grains are preferable from the viewpoint of suppressing defects such as scratches and erosion because they have a lower hardness than inorganic abrasive grains and have a small mechanical action on the surface to be polished. When adding an inorganic abrasive grain, it is preferable to set it as 5 weight part or less with respect to 100 weight part of polishing compositions from a viewpoint of suppressing generation | occurrence | production of a scratch, erosion, etc.

(Complexing agent)
As the complexing agent used in the polishing composition of the present invention, acetic acid, oxalic acid, malonic acid, malic acid, tartaric acid, succinic acid, citric acid and other carboxylic acids, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, Examples thereof include amines such as triethylamine, amino acids such as glycine, aspartic acid and glutamic acid, ketones such as acetylacetone, ammonia and the like.
Of these, carboxylic acids, amines, amino acids, and ammonia are preferable, and oxalic acid, malonic acid, tartaric acid, and glycine are more preferable.
The addition amount of the complexing agent is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the polishing composition. More preferably, it is 1 to 5 parts by weight. If the amount is less than 0.1 parts by weight, the effect cannot be sufficiently exhibited and the intended polishing rate may not be achieved. On the other hand, when the amount is more than 10 parts by weight, the metal to be polished may excessively form a complex and elute to promote the occurrence of dishing.

(Oxidant)
Examples of the oxidizing agent used in the polishing composition of the present invention include hydrogen peroxide, ammonium persulfate, and potassium persulfate. Hydrogen peroxide is particularly preferably used.
The addition amount of the oxidizing agent is preferably in the range of 0.1 to 30 parts by weight, particularly preferably in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the polishing composition. When the addition amount of the oxidizing agent is less than 0.1 parts by weight, the chemical reaction between the metal to be polished and the water-soluble resin (A) does not proceed, and the target polishing rate may not be achieved. If the amount of the oxidizer added exceeds 30 parts by weight, an oxide film may be generated on the surface of the metal to be polished and passivated, and polishing may not proceed.

(PH of polishing composition)
The pH of the polishing composition of the present invention is preferably in the range of 2-11, more preferably in the range of 3-9. When the pH is less than 7, the corrosiveness of the polishing composition is high, and the load on the polishing apparatus is large. On the other hand, if the pH is higher than 11, when the semiconductor insulating film, which is the end point of polishing, and the metal to be polished form the same plane, the insulating film may be dissolved or partially decomposed.
(PH adjuster)
It does not specifically limit as a pH adjuster for adjusting pH of polishing composition of this invention, A conventionally well-known thing can be used. Particularly, a metal-free pH adjuster is preferably used, such as ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine and other amines, tetramethylammonium hydroxide, One or more pH adjusting agents selected from alkyl ammonium salts such as tetraethylammonium hydroxide can be particularly preferably used.
As the pH adjusting agent, the same substance as the complexing agent described above may be used for the two purposes of adjusting the pH of the polishing composition and forming a complex with the metal to be polished.

(Foaming inhibitor)
In order to suppress foaming, a foaming inhibitor may be added to the polishing composition of the present invention. As the foam inhibitor, a metal-free foam inhibitor can be preferably used, and examples thereof include polyethylene glycol type nonionic surfactants, polyether type nonionic surfactants, and emulsions of fatty acid esters. be able to. Of these, only one type may be used, or two or more types may be mixed and used.
(Other additives)
In addition to those described so far, an additive may be further added to the polishing composition of the present invention depending on the purpose. Examples of other additives include wetting agents, antistatic agents, preservatives, ultraviolet absorbers, light stabilizers, penetrants, fluidity improvers, and the like. Any additive may be added as long as it does not depart from the object of the present invention, but it is preferable to appropriately select an additive that does not contain a metal. These other additives may be added to the polishing composition of the present invention before, during or after polymerization of the water-soluble resin (A).

(Method for preparing polishing composition)
A method for preparing the polishing composition of the present invention will be described.
The polishing composition of the present invention comprises a water-soluble resin (A), an anticorrosive agent, an anticorrosion aid, a complexing agent, an oxidizing agent, and optionally abrasive grains and other additives, It can be prepared by dissolving or dispersing in. The method for preparing the polishing composition of the present invention is not particularly limited, but an aqueous solution of a complexing agent whose pH is adjusted and an aqueous solution of the water-soluble resin (A) are mixed, and the anticorrosive agent is further stirred while stirring. The aqueous solution and the aqueous solution of the anticorrosion aid are mixed, and then other additives are added as necessary, and the pH is adjusted again. When using abrasive grains, the aqueous solution of the complexing agent adjusted to pH and the aqueous solution of the water-soluble resin (A) are mixed with the slurry in which the abrasive grains are dispersed by adjusting the pH, and the slurry is stably dispersed. While confirming this, the aqueous solution of the anticorrosive agent and the aqueous solution of the anticorrosive agent are mixed, and then other additives are added as necessary, and the pH is adjusted again.
Finally, insoluble matters and aggregates are removed to obtain the polishing composition of the present invention.
In order to prevent unnecessary damage to the metal to be polished or the semiconductor wafer in the actual CMP process, it is preferable that no metal component is present in the polishing composition. In addition to the components constituting the polishing composition of the present invention, the water-soluble resin (A), the water-soluble resin (B), and / or the polymerization initiator and the molecular weight modifier used in the synthesis of the organic particles are also metals. It is preferable to use a substance that does not contain.
Examples of the polymerization initiator containing no metal include hydrogen peroxide, organic peroxides such as ammonium persulfate, cumene hydroxy peroxide, t-butyl hydroperoxide, and benzoyl peroxide, azobiscyanovaleric acid, 2,2′- Azobis (2-amidinopropane) dibasic acid salt and the like are preferably used.
The amount of the polymerization initiator used is generally 0.1 to 5 parts by weight with respect to 100 parts by weight of the monomer to be polymerized.

(Polishing method)
The polishing composition of the present invention is suitably used for CMP for polishing an excess wiring layer in a wiring formation process, which is one manufacturing process of a semiconductor element, but can also be used for polishing a hard disk substrate and other polishing. it can. In particular, it can be suitably used for polishing a relatively soft metal that easily forms a complex compound with a functional group such as an amide group such as copper, nickel, or zinc, or an organic acid.
The CMP will be specifically described. In a wiring forming process, which is one process for manufacturing a semiconductor element, a groove for forming a circuit is dug on a semiconductor wafer, and then a wiring forming metal layer is formed by plating or the like so as to fill the groove. Here, a polishing apparatus shown in FIG. 2 is used to polish the circuit forming surface of the semiconductor wafer on which the wiring forming metal layer is excessively formed by CMP. A polishing cloth (polishing pad) 22 is mounted on the turntable 21 of the polishing apparatus. The supply pipe 23 for supplying the polishing composition is disposed on the polishing pad 22 so that the polishing composition 27 can be dropped. The base holder 25 having the support shaft 24 on the upper surface is disposed so as to be able to move up and down and rotate in opposition to the upper side of the polishing pad 22.
The semiconductor wafer 26 as the object to be polished is fixed to the base holder 25 of such a polishing apparatus so that the surface to be polished faces the polishing cloth 22, and the polishing composition 27 is supplied from the supply pipe 23 and supported. Excess wiring is formed on the surface of the semiconductor wafer 26 by applying a desired load by causing the semiconductor wafer 26 to face the polishing pad 22 by the shaft 24 and rotating the base holder 25 and the turntable 21 in opposite directions. The metal layer is polished.
The surface of the semiconductor wafer 26 will be described assuming a silicon wafer. The surface of the silicon wafer is converted to silicon oxide by oxidation treatment, and the metal wiring forming portion 4 is dug out. On the semiconductor wafer underlayer 1 having such a structure, a barrier metal layer 2 using tantalum or the like is formed by sputtering or the like. A wiring metal seed layer is further formed on the surface of the barrier metal layer 2 by sputtering or the like, and a metal wiring layer 3 is formed thereon by electrolytic plating or the like. The surface shape of the metal wiring layer 3 is likely to have irregularities reflecting the surface shape of the underlayer 1. By polishing the excessively formed portion of the metal wiring layer 3 by CMP until the barrier metal layer other than the metal wiring forming portion 4 is exposed, a flat semiconductor wafer provided with the metal wiring layer 2 is formed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these examples. In the examples, all parts and% represent parts by weight and% by weight unless otherwise specified.

(Evaluation of polishing performance)
1. Calculation of polishing rate The polishing rate is calculated by cleaning the workpiece 1 with ultrapure water and ultrasonic cleaning, drying it, and measuring the film thickness before and after polishing by sheet resistance measurement using a 4-terminal probe. The average polishing rate was calculated from the amount of change and the polishing time. The polishing conditions are as shown below.
Polishing composition: The polishing composition of the present invention described in the following examples was used.
Object to be polished 1: 8 inch silicon wafer / thermal oxide film (500 nm) / tantalum film formed by sputtering (30 nm) / copper seed film formed by sputtering (150 nm) / copper film formed by plating (1500 nm)
Polishing object 2: Silicon wafer on which a wiring pattern was formed (SEMATECH # 854, film thickness: copper 1300 nm, underlayer: 30 nm
Polishing device: MAT-ARW-681M
Polishing cloth: IC-1000 / suba400, XY groove polishing load: 3.0 psi
Polishing time: 1 min.
Polishing composition supply amount: 200 cc / min.
Turntable rotation speed: 60rpm
Base rotation speed: 60rpm
2. Dishing measurement After polishing the object 2 under the above polishing conditions, the amount of depression in the wiring pattern portion in the region where the wiring width of the object 2 is 10 μm and the width of the insulating film between the wirings is 10 μm The dishing amount was measured using a meter.
3. Erosion measurement For the polished object 2 after polishing, in the region where the wiring pattern with a wiring width of 9 μm and an insulating film width between the wirings of 1 μm is repeated, the end of the wiring pattern portion using a palpation step meter And then the difference between the height of the tantalum film as the insulating layer at the end and the height of the tantalum film as the insulating layer located 100 μm from the end is eroded. It was. The polishing conditions are as described above, but the polishing time was set to 1.5 times the time required to finish polishing the wiring-forming metal in the portion where no groove was formed, so that excessive polishing occurred.
4). Evaluation of Clearness After polishing the workpiece 2 under the above polishing conditions, the tantalum layer, which is the barrier layer of the polished surface, was observed with a scanning electron microscope (x20,000 microscopically attached to the scanning electron microscope) An analyzer was used to measure whether or not copper as a circuit forming metal was present. The clearness was good when copper was not observed, and the clearness was poor when copper was observed.

(Synthesis of water-soluble resin (A))
A flask equipped with a stirrer and a reflux condenser was charged with 200 parts by weight of distilled water, replaced with nitrogen gas, and then heated to 75 ° C. Next, 2.0 parts by weight of ammonium persulfate was added, and then a mixture of the vinyl monomer of 200 parts by weight shown in Table 1 and 200 parts by weight of distilled water was continuously added dropwise over 2 hours while stirring the flask. Further, the polymerization reaction was completed by aging at the same temperature for 2 hours to obtain an aqueous solution containing the water-soluble resins (A-1), (A-2) and (A-3).

(Synthesis of water-soluble resin (B))
A method for synthesizing the water-soluble resin (B) will be described in the case of using the water-soluble resin (B) as an anticorrosion aid.
A flask equipped with a stirrer and a reflux condenser was charged with 360 parts by weight of distilled water, replaced with nitrogen gas, and then heated to 80 ° C. Next, after adding 2 parts by weight of ammonium persulfate, an emulsion comprising 65.0 parts by weight of ethyl acrylate, 35.0 parts by weight of methacrylic acid, 40.0 parts by weight of distilled water, and 0.1 parts by weight of ammonium lauryl sulfate is emulsified. The product and the inside of the flask were continuously added dropwise over 4 hours with stirring, and further aged at the same temperature for 4 hours to complete the polymerization. After cooling to room temperature, the pH was adjusted to 7 using 28% aqueous ammonia to obtain a water-soluble resin (B-1).

(Synthesis of organic particles)
A method for synthesizing organic particles will be described in the case where organic particles are included as abrasive grains.
A flask equipped with a stirrer and a reflux condenser was charged with 384 parts of distilled water and 1005 parts by weight of the water-soluble resin (A-1), replaced with nitrogen gas, and heated to 80 ° C. Subsequently, 2 parts by weight of ammonium persulfate was added, 30.0 parts by weight of styrene, 60.0 parts by weight of acrylonitrile, 5.0 parts by weight of methacrylic acid, 5.0 parts by weight of divinylbenzene, 40.0 parts by weight of distilled water, 0 parts by weight of ammonium lauryl sulfate. The emulsion consisting of 1 part by weight was continuously added dropwise over 4 hours while stirring the emulsion and the flask, and further aged for 4 hours to complete the polymerization to obtain organic particles (C-1). It was. The average particle diameter measured using an FPAR-1000 dynamic light scattering measurement apparatus manufactured by Otsuka Electronics Co., Ltd. was 162 nm.

(Preparation of Examples 1 to 10 and Comparative Examples 1 and 2)
An aqueous solution containing water-soluble resins (A-1), (A-2) and (A-3) is mixed dropwise with an aqueous complexing agent solution adjusted with ammonia using 1 mol / l aqueous ammonia. After adjusting the pH again, the concentration was adjusted using distilled water. Anti-corrosion agent, anti-corrosion aid, oxidizing agent and foaming inhibitor (0.2% by weight) were added immediately before polishing to prepare the polishing composition shown in Table 2. Benzotriazole was used as the anticorrosive, and water-soluble resin (B-1), polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) and cyclohexanediaminetetraacetic acid were used as the anticorrosive. Hydrogen peroxide was used as the oxidizing agent, and SN deformer 260 manufactured by San Nopco Co., Ltd. was used as the foaming inhibitor.
The polishing composition containing the organic particles (C-1) used in Example 10 was prepared using an aqueous solution of the water-soluble resin (A-1) containing the organic particles (C-1).
Table 3 shows the evaluation results of the polishing performance of each polishing composition.

FIG. 3 is a schematic diagram showing a cross-sectional structure of a surface to be polished used for evaluating the clearness of the present invention. It is a schematic diagram which shows the outline | summary of a grinding | polishing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer base layer 2 Barrier metal layer 3 Metal wiring layer 4 Metal wiring formation part 21 Turntable 22 Polishing cloth 23 Supply pipe 24 Support shaft 25 Base holder 26 Semiconductor wafer 27 Polishing composition

Claims (13)

  Water-soluble resin (A) obtained by polymerizing 55 to 100 parts by weight of vinyl monomer containing amide group and 0 to 45 parts by weight of other vinyl monomers, anticorrosive, anticorrosive, and complex Polishing composition characterized by including an agent, an oxidizing agent, and water.   The polishing composition according to claim 1, wherein the content of the water-soluble resin (A) is 0.5% by weight or more.   The polishing composition according to claim 1 or 2, wherein the vinyl monomer containing an amide group is acrylamide and / or methacrylamide.   The polishing composition according to claim 1, wherein the water-soluble resin (A) further has a functional group capable of forming an anion.   5. The polishing composition according to claim 4, wherein the functional group capable of forming an anion is at least one of a carboxyl group, a sulfonic acid group, and a phosphoric acid group.   The polishing composition according to claim 1, wherein the anticorrosive is a benzotriazole and / or a benzotriazole derivative.   A water-soluble resin obtained by polymerizing 15 to 100 parts by weight of a vinyl monomer containing an aromatic carboxylic acid, aromatic amino acid or carboxyl group and 0 to 85 parts by weight of another vinyl monomer. The polishing composition according to claim 1, comprising at least one selected from B).   8. The polishing composition according to claim 7, wherein the anticorrosion aid is at least one selected from quinolinic acid, quinaldic acid, tryptophan, phenylalanine, and cyclohexanediaminetetraacetic acid.   The polishing composition according to claim 7, wherein the water-soluble resin (B) contains acrylic acid and / or methacrylic acid.   The polishing composition according to claim 1, wherein the complexing agent is a carboxylic acid, an amino acid, ammonia, or a salt thereof.   The polishing composition according to claim 1, further comprising organic particles.   The polishing composition according to claim 1, further comprising an additive for suppressing foaming.   The additive for suppressing foaming includes at least one of a polyethylene glycol type nonionic surfactant, a polyether type nonionic surfactant, and an emulsion of a fatty acid ester. 12. The polishing composition according to 12.