Polishing Slurry

Abstract

The present invention provides a polishing slurry which remarkably inhibits the occurrence of scratch, dishing or erosion. According to the present invention, provided is a polishing slurry comprising organic particles (A), an oxidizing agent and a complexing agent, wherein said organic particles (A) are those obtained by coating a part of the surface of an organic particle (B) having functional groups capable of reacting with a metal to be polished on the surface with a resin (C) free from functional groups capable of reacting with a metal to be polished, and the organic particle (B) is preferably one containing a copolymer obtained by polymerization of a monomer composition comprising 1 to 50 weight % of one, two or more monomers selected from a monomer having a carboxyl group, a monomer having a hydroxyl group, a monomer having an amino group, a monomer having an acetoacetoxy group and a monomer having a glycidyl group, and 99 to 50 weight % of other monomers, with each percentage based on the total weight of the monomers.

Description

TECHNICAL FIELD

The present invention relates to a polishing slurry which is capable of polishing without damaging a surface of copper or the like for smoothing the surface in the formation of wiring comprising copper or the like used in the manufacture of semiconductor devices.

BACKGROUND ART

In late years, in a wiring process in the manufacture of semiconductor devices, as a technique for forming grooves for forming wiring on an insulation film and backfilling a metal film for wiring by the plating method, removing an excess metal film and smoothing an insulation film including metal wiring, CMP (Chemical and Mechanical Polishing) has been used. This is a method comprising mechanically polishing by a slurry with abrasive particles dispersed therein.

In the CMP technique, a slurry containing inorganic abrasive particles made of metal oxides such as ceria, alumina and the like or silica has conventionally been used. However, these inorganic abrasive particles have high hardness. When a metal film with low hardness such as copper or the like is polished, the inorganic abrasive particles-have therefore presented a big problem of creating abrasive damages on a metal surface called scratches or causing a phenomenon called erosion of formation in concave shapes by further polishing the metal film in the center of a dense area of wiring pattern including an insulation film of an under coat layer.

At present, in order to improve performance of semiconductors, the ½ width of wiring on the insulation film becomes much finer from 130 nm to 90 nm and even to 65 nm, and the surface of the insulation film to be polished is in a much complicated structure. If the width of wiring becomes much finer, abrasive damages on the metal surface due to scratches cause an open circuit, and dishing or erosion causes an increase in wiring resistance or deviation and a short circuit between wirings, thereby considerably deteriorating the reliability of semiconductor devices and drastically lowering the product yields.

This scratch is created by partial excess polishing generated by the hardness of abrasive particles or the existence of aggregated masses of abrasive particles.

Furthermore, erosion is created because of excess polishing by using hard abrasive particles, or a low polishing selectivity to an under coat layer such as an insulation film or a barrier layer for preventing diffusion of a metal.

In order to solve these problems, in case of inorganic abrasive particles, silica particles which are softer than alumina particles are used as abrasive particles, and a polishing solution which is made from neutral to alkaline without elution of a metal for polishing has been developed. For example, when silica is used as abrasive particles, scratches are reduced as compared to alumina, but when inorganic abrasive particles are used, occurrence of scratches or erosion cannot be prevented. So, the problems cannot be fundamentally solved.

Meanwhile, in late years, since the solid content in a polishing agent remains on the insulation film, the increasing total dielectric constant of the insulation film layer has been mentioned as a problem. An existing polishing agent composed of the alumina or silica as abrasive particles has the heat resistant property equivalent to that of the insulation film so that the solid content cannot be removed by thermal treatment but it can only be removed by using a washing solution. Since this removal by using a washing solution is a method for removing residual abrasive particles by slightly dissolving the insulation film, damage to the insulation film is great, which becomes a problem.

On the other hand, in U.S. Pat. No. 3,172,008, there has been disclosed a method employing particles of an organic polymer compound as abrasive particles. In the organic polymer used therein, since components free from functional groups such as a methacryl resin, a polystyrene resin and the like are used for abrasive particles, and the organic polymer does not contain an oxidizing agent for oxidizing the metal surface, a chemical action with a metal film to be polished never takes place. Thus, a polishing rate required for or sufficient for a wiring process in the manufacture of semiconductor devices is not obtained.

In order to solve the above problems regarding particles of the organic polymer compound, for example, in Japanese Patent Laid-open No. 2001-55559, there has been disclosed an aqueous dispersion for CMP containing organic particles having functional groups capable of reacting with a metal forming a surface to be polished. However, a phenomenon called dishing of formation in concave shapes by further polishing a metal film on wiring portion in the center is not solved. In order to prevent this, a technique using a protective-film forming agent such as benzotriazole or the like is disclosed in Japanese Patent Laid-open No. 1996-83780 and the like. However, since the protective-film forming agent such as benzotriazole or the like is highly effective, there is a drawback such that the polishing rate is remarkably lowered.

Patent Document 1: U.S. Pat. No. 3,172,008

Patent Document 2: Japanese Patent Laid-open No. 2001-55559

Patent Document 3: Japanese Patent Laid-open No. 1996-83780

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a polishing slurry containing specific organic particles which is remarkably inhibited in the occurrence of scratch, dishing or erosion.

In order to solve the above object, the present inventors have conducted an extensive study and as a result, have completed the present invention. That is, the present invention relates to a slurry comprising organic particles (A), wherein said organic particles (A) are those obtained by coating a part of the surface of an organic particle (B) having functional groups capable of reacting with a metal to be polished on the surface with a resin (C) free from functional groups capable of reacting with a metal to be polished.

The above polishing slurry comprising an oxidizing agent is a preferred embodiment because it promotes the reaction of the metal to be polished with the functional groups.

The organic particle (B) containing a copolymer obtained by polymerization of a monomer composition comprising 1 to 50 weight % of one, two or more monomers selected from a vinyl monomer having a carboxyl group, a vinyl monomer having a hydroxyl group, a vinyl monomer having an amino group, a vinyl monomer having an acetoacetoxy group and a vinyl monomer having a glycidyl group, and 99 to 50 weight % of other vinyl type monomers, with each percentage based on the total weight of the monomers is a preferred embodiment because it promotes the reaction with a metal to be polished.

Furthermore, the resin (C) containing a polymer of a styrene type monomer and/or a (meth)acrylic acid ester type monomer is a preferred embodiment because it controls the reaction with a metal to be polished.

Further, the above polishing slurry further comprising at least one complexing agent selected from carboxylic acids, amines, amino acids and ammonia, and having its pH in the range of 5 to 11 is a preferred embodiment from the viewpoint of the polishing rate.

Meanwhile, the oxidizing agent being hydrogen peroxide is a preferred embodiment from the viewpoint of the smoothness.

EFFECT OF THE INVENTION

The polishing slurry of the present invention is capable of polishing an excess metal film on a wiring pattern-formed insulation film with a high rate, capable of polishing without causing any damage or scratch due to polishing excess on the surface of a substance to be polished, and capable of polishing which produces high smoothness of the surface without any unevenness due to dishing, erosion or the like.

Further, since the polishing slurry of the present invention containing organic fine particles has a considerably lower decomposition temperature than that of the insulation film, it is possible to remove the residue of the polishing slurry without damaging the insulation film by thermal treatment or plasma treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a SEM image of organic particles obtained in Production Example 1.

FIG. 2 is a view illustrating a SEM image of organic particles obtained in Comparative Production Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail below.

(Organic Particles)

The organic particles (A) are those obtained by coating a part of the surface of an organic particle (B) having functional groups capable of reacting with a metal to be polished with a resin (C) free from functional groups capable of reacting with a metal to be polished.

In the present invention, “capable of reacting with a metal to be polished” means a capability of promoting a polishing rate of a metal to be polished by a chemically reactive action.

Examples of the functional group capable of reacting with a metal to be polished of the organic particle (B) include a carboxyl group, a hydroxyl group, am amine group, a ketone group, a glycidyl group and an acetoacetoxy group. Particularly preferably used is a carboxylic acid.

The organic particle (B) can be produced, for example, by polymerization of a monomer having functional groups capable of reacting with these metals to be polished and other vinyl type monomers capable of copolymerization with the monomer. In case of organic particles having a particularly preferable carboxyl group, it is preferable that an alkaline substance of not less than 0.3 mole equivalent is added on the basis of the carboxyl group in the obtained copolymer emulsion for dissociating the carboxyl group, to easily form a complex with a metal.

Examples of the carboxyl group-containing vinyl monomer used in the present invention include one, two or more kinds selected from unsaturated monobasic acids such as an acrylic acid, a methacrylic acid, a crotonic acid and the like; unsaturated dibasic acids such as an itaconic acid, a fumaric acid, a maleic acid and the like; or monoesters thereof. Particularly preferably used are an acrylic acid and a methacrylic acid.

Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl(meth)acrylate, 2-hdyroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate and the like.

Examples of the amino group-containing vinyl monomer include amino group-containing (meth)acrylate type monomers containing a tertiary amino group. Examples thereof include N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl-(meth)acrylate, N,N-t-butylaminoethyl(meth)acrylate, N,N-monomethylaminoethyl(meth)acrylate and the like.

Further, N-alkyl amino (meth)acrylamide containing a tertiary amino group is employed. Examples thereof include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylamide, N-isopropyl(meth)acrylamide and the like.

Examples of the acetoacetoxy group-containing vinyl monomer include acetoacetoxyethyl (meth)acrylate and the like. Examples of the glycidyl group-containing vinyl monomer include glycidyl(meth)acrylate and the like.

The amount of the monomer having functional groups capable of reacting with these metals to be polished is preferably from 1 to 50 weight parts, more preferably from 3 to 45 weight parts, and most preferably from 5 to 40 weight parts based on the total monomer components in the copolymer. When the amount is less than 1 weight part, the intended polishing rate might not be achieved. Further, when the amount exceeds 50 weight parts, water resistance and alkali resistance might be bad in some cases.

Examples of other vinyl type monomers capable of copolymerization with a monomer having functional groups capable of reacting with the aforementioned metal to be polished include styrene type monomers such as styrene, α-methylstyrene, vinyl toluene and the like; (meth)acrylic acid ester type monomers such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, isopropyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, n-hexyl(meth)acrylate, octyl(meth)acrylate, cyclohexyl(meth)acrylate, isobornyl(meth)acrylate and the like; vinyl esters such as vinyl acetate, vinyl propionate and the like; vinyl cyanides such as (meth)acrylonitrile and the like; and halogenated vinyl compounds such as vinyl chloride, vinylidene chloride and the like. Further, in addition to the carboxyl group-containing vinyl monomer as a functional group monomer, (meth)acrylamide or N-methylol(meth)acrylamide and the like are used as needed.

The amount of other vinyl type monomers to be used is preferably from 99 to 50 weight % and more preferably from 95 to 70 weight %.

Such organic particles may be those swelling by adding an alkaline substance or those without swelling. But, either of organic particles may be used. Further, “swelling” mentioned herein means the increasing average particle diameter of the primary particle by containing water or other water-soluble substances in the molecule without causing decomposition or cohesion.

In order to adjust the degree of swelling of organic particles by the addition of alkali, as needed, a crosslinking monomer can be copolymerized. The crosslinking monomer is a monomer containing 2 or more polymerizable unsaturated bonds in a molecule. Examples thereof include divinyl benzene, butadiene, ethylene glycol dimethacrylate, trimethylol propane trimethacrylate, ethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, diacrylate and the like. The amount of the crosslinking monomer to be used is preferably not more than 20 weight % and more preferably not more than 10 weight % in the total monomers. The crosslinking monomer is properly used depending on the kind of the unsaturated monomer having functional groups capable of reacting with a metal to be polished, its amount, the kind of the vinyl type copolymer and the like.

The resin (C) to be coated on the surface of the organic particle (B) is composed of a polymer free from functional groups capable of reacting with a metal to be polished, and preferably composed of a polymer of a styrene type monomer and/or a (meth) acrylic acid ester type monomer. Specific examples of the styrene type monomer and (meth)acrylic acid ester monomer include a monomer having functional groups capable of reacting with the aforementioned metal to be polished and other vinyl type monomers capable of copolymerization.

A method for the synthesis of the organic particles is not particularly limited, but the organic particles can be, for example, synthesized by multi-stage polymerization of emulsion polymerization. That is, there can be used a method comprising synthesizing the organic particle (B) having functional groups capable of reacting with a metal to be polished and then additionally synthesizing the polymer (C) free from functional groups capable of reacting with a metal to be polished, or, to the contrary, a method comprising synthesizing the polymer (C) free from functional groups capable of reacting with a metal to be polished and then additionally synthesizing the organic particle (B) having functional groups capable of reacting with a metal to be polished.

The amount of the monomer is adjusted such that a part of the surface of the organic particle (B) is coated with the resin (C). A part of the surface of the organic particles may be coated with the resin (C). Preferably 10% or more but less than 100% of the surface is coated, and more preferably 30% or more but less than 95% of the surface is coated. The coating ratio of the surface can be measured by SEM.

By coating the surface of the organic particle (B) with the resin (C), scratches or erosion can be inhibited.

The particle diameter at a state that the organic particles (B) are coated with the resin layer (C) is preferably from 10 to 5,000 nm and more preferably from 30 to 300 nm. Further, the molecular weight of the organic particles (B) is preferably from 10,000 to 5,000,000 and more preferably from 100,000 to 1,000,000. The molecular weight of the resin (C) is preferably from 1,000 to 1,000,000 and more preferably from 10,000 to 500,000.

The content of the organic particles in the polishing slurry is varied depending on the kind of the organic fine particle, but it is preferably from 0.1 to 20 weight %. When the content is less than 0.1 weight %, the effect of the organic fine particles cannot be fully exhibited so that the intended polishing rate cannot be achieved in some cases. Further, when the content is more than 20 weight %, the viscosity of the polishing slurry is high so that it becomes difficult to supply the polishing slurry at a predetermined rate upon polishing in some cases.

Since metal components, particularly impurity components such as sodium, potassium, iron, magnesium and the like contained in the polishing slurry have an influence on the stability of the polishing rate, it is required to inhibit such components to not more than 1 ppm by adding an oxidizing agent such as hydrogen peroxide or the like.

In order to obtain an aqueous dispersion of organic particles free from a metal, a monomer, a dispersing agent such as a surfactant and the like, a polymerization initiator and other additives, which are free from a metal can be used for its production.

Examples of the dispersing agent free from a metal include water-soluble polymers such as polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, (meth)acrylic acid (co)polymer, poly(meth)acrylamide (co)polymer, ethylene glycol and the like. Examples of the surfactant include an anionic surfactant, a non-ionic surfactant and a cationic surfactant. The anionic surfactant has an acidic group such as a sulfonic acid, a carboxylic acid or the like as a hydrophilic group, but those without containing metal salts such as Na, K or the like as its counter ion can be used. Generally used are ammonium salts. Examples thereof include ammonium salts such as dodecylbenzenesulfonic acid, lauryl sulfuric acid, alkyl diphenyl ether disulfonic acid, alkyl naphthalene sulfonic acid, dialkyl sulfosuccinic acid, stearic acid, oleic acid, dioctyl sulfosuccinate, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene alkyl phenyl ether sulfuric acid, dialkyl sulfosuccinic acid, stearic acid, oleic acid, tert-octylphenoxyethoxypolyethoxyethyl sulfuric acid and the like.

Furthermore, the greater part of the nonionic surfactants generally has an ethylene glycol chain as a hydrophilic group, and does not contain a metal. Examples thereof include polyoxyethylene lauryl ether, polyoxyethylene octylphenyl ether, polyoxyethylene oleylphenyl ether, polyoxyethylene nonylphenyl ether, oxyethylene-oxypropylene block copolymer, tert-octylphenoxyethylpolyethoxyethanol, nonylphenoxyethylpolyethoxyethanol and the like.

Meanwhile, examples of the cationic surfactant include lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, distearyl dimethyl ammonium chloride, alkyl benzyl dimethyl ammonium chloride, lauryl betaine, stearyl betaine, lauryl dimethyl amine oxide, lauryl carboxy methyl hydroxy ethyl imidazolinium betaine, coconut amine acetate, stearyl amine acetate, alkyl amine guanidine polyoxy ethanol, alkyl picolinium chloride and the like. These dispersing agents can be selected singly or in combination of 2 or more kinds.

Examples of the polymerization initiator free from a metal include azo compounds such as hydrogen peroxide, ammonium persulfate, azobiscyanovaleric acid,

• 2,2′-azobis(2-amidinopropane)dihydrochloride,
• 2,2′-azobis[2-(N-phenylamidino)propane]dihydrochloride,
• 2,2′-azobis{2-[N-(4-chlorophenyl)amidino]propane}dihydrochloride,
• 2,2′-azobis{2-[N-(4-hydroxyphenyl)amidino]propane}dihydrochloride, 2,2′-azobis[2-(N-benzylamidino)propane]dihydrochloride, 2,2′-azobis[2-(N-allylamidino)propane]dihydrochloride,
• 2,2′-azobis{2-[N-(2-hydroxyethyl)amidino]propane}dihydrochloride, azobisisobutyronitrile,
• 2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},
• 2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide}, 2,2′-azobis[2-methyl-N-[2-hydroxyethyl]propionamide],
• 2,2′-azobis(isobutyramide)dihydrate and the like; and organic peroxides such as cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxy benzoate, lauroyl peroxide and the like. One, two or more kinds thereof can be selected. As the initiator, preferably used are water-soluble initiators, and more preferably used are ammonium persulfate, azobiscyanovaleric acid and
• 2,2′-azobis(2-amidinopropane)dihydrochloride. The amount of the initiator to be used in general is from 0.1 to 5 weight %, based on the total weight of the monomer to be (co)polymerized.

Furthermore, when obtaining organic particles, mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan and the like; and allyl compounds such as allyl sulfonic acid, methallyl sulfonic acid, sodium salts thereof and the like can also be used as a molecular weight regulating agent, as needed.

Organic particles can be prepared by an emulsion polymerization method, a suspension polymerization method and a mechanical emulsification method which are known from the past. Examples of the emulsion polymerization method include a method for polymerization of various monomers to be fed at a time and a method for polymerization while continuously supplying monomers, in the presence of a dispersing agent and an initiator. The polymerization is usually carried out at a temperature of from 30 to 90 degree centigrade and an aqueous dispersion of organic particles is substantially obtained. The emulsion polymerization method is a more preferable polymerization method since organic particles with small particle diameters and excellent in the dispersion stability are obtained.

An acryl resin emulsion is most preferably used because it is excellent in the dispersability, and it does not generate separation (generation of supernatant and precipitation), or aggregated masses due to the lapse of time found in a polishing agent with organic fine particles such as methacryl resin, phenol resin, urea resin and the like, in addition to alumina, silica or emulsion as abrasive particles, and resulting in obtaining stable polishing rates at all times.

(Complexing Agent)

As a complexing agent, a water-soluble compound capable of forming a complex with a metal is preferable. Examples thereof include carboxylic acids such as acetic acid, oxalic acid, malic acid, tartaric acid, succinic acid, citric acid and the like; amines such as methylamine, dimethylamine, triethylamine, ethylamine, diethylamine, triethylamine and the like; amino acids such as glycine, asparatic acid, glutamic acid, cysteine and the like; ketones such as acetylacetone and the like; and nitrogen-containing cyclic compounds such as imidazole and the like. Preferably used are oxalic acid, malic acid and ethylamine.

The content of the complexing agent is varied depending on the kind of the complexing agent, but it is preferably in the range of 0.1 to 10 weight % in the polishing slurry. When the content is less than 0.1 weight %, the intended polishing rate might not be achieved in some cases because its effect is not fully exhibited. Further, when the content exceeds 10 weight %, dishing causing elution of a metal to be polished other than the target polishing might not be inhibited in some cases because formation of a complex with a metal to be polished is excessively progressed.

A metal to be polished forms a metal complex with a functional group and/or a complexing agent contained in organic fine particles, whereby good metal polishing is carried out. The metal complex may be composed of a ligand of organic fine particles and a ligand of a complexing agent, formation of a complex of organic fine particles and a metal may promote formation of a complex of a complexing agent and a metal, or formation of a complex of a complexing agent and a metal may promote formation of a complex of organic fine particles and a metal.

(Oxidizing Agent)

As an oxidizing agent, preferably used are potassium iodate and hydrogen peroxide, and more preferably used is hydrogen peroxide. The content of the oxidizing agent is preferably in the range of 0.1 to 15 weight % and particularly preferably in the range of 0.5 to 5 weight % in a polishing composition. When the content is less than 0.1 weight %, a chemical reaction of a metal with organic particles does not progress so that it is not possible to achieve the intended polishing rate in some cases. Further, when the content exceeds 15 weight %, an oxide film formed on a metal surface might be passivated for preventing the progress of polishing so that it is not possible to achieve the intended polishing rate in some cases.

(pH)

The pH of the polishing slurry of the present invention is preferably in the range of 5 to 11 and more preferably in the range of 7 to 10. When the pH of the polishing slurry is less than 5, elution of a metal cannot be inhibited so that dishing might occur in some cases. On the other hand, when the pH is above 11, an insulation film is dissolved or partially decomposed in some cases when a semiconductor insulation film and metal wiring are on the same surface, which is the final point in polishing a metal film.

Substances used for the pH adjustment of the polishing agent are not particularly limited. Examples of alkaline substances include amines such as ammonia, triethylamine, diethylamine, ethylamine, trimethylamine, dimethylamine, methylamine and the like; and inorganic substances such as NaOH, KOH and the like. Further, examples of acidic substances include inorganic substances such as hydrochloric acid, nitric acid and the like; and organic acids such as acetic acid, oxalic acid, citric acid and the like. The pH regulating agent may also be used as a complexing agent that can be a ligand of the aforementioned metals. Further, these substances may be used in combination of 2 or more kinds.

(Production Method of Polishing Slurry)

To produce the polishing slurry, for example, organic fine particles, a complexing agent, an oxidizing agent and water are mixed and then the pH of the mixture is adjusted to produce a slurry which is used as a polishing agent. This production method is not particularly limited, but it is preferable that an pH-adjusted aqueous solution of a complexing agent capable of forming a ligand with a metal is added to a pH-adjusted resin emulsion and the resulting mixture is well stirred and mixed. Then, an oxidizing agent is added thereto little by little, and further stirred and mixed.

After finally adjusting the pH and concentration of the mixture, insoluble substances and aggregated masses are removed therefrom by filtering using a filter paper to have a polishing agent.

(Additive)

Examples of the additive include nitrogen-containing heterocyclic ring compounds such as benzotriazole, quinaldic acid and the like; water-soluble polymers such as polyacrylic acid, polyvinyl alcohol, polyethylene glycol, glucose and the like; and substances such as a surfactant and the like. These additives may be added singly or in combination of 2 or more kinds. The amount to be added and the kind of the additives are not particularly limited as far as the object of the present invention can be achieved.

EXAMPLES

The present invention is now more specifically illustrated below with reference to Examples. Incidentally, in these Examples, part (s) and % refer to weight part (s) and weight % unless otherwise particularly mentioned.

A particle diameter of an organic particle in a polishing composition was measured by the following method.

(Particle Size Distribution Measurement Method using Principle of Laser Dynamic Light Scattering Method)

Measurement Device: MICROTRAC UPA Model: 9230 (a product of Leeds and Northrup)

Concentration Condition: crude sample solution

Measurement Time: 900 seconds

A polishing slurry was evaluated according to the following methods.

1. Evaluation of Polishing Rate

Polishing slurry: polishing composition of the present invention

Substance to be polished: 8-inch silicon wafer in which 5,000 Å of a thermal oxide film, 300 Å of a Ta film formed by the sputtering method, 1,500 Å of a seed copper film for plating formed by the CVD method, 15,000 Å of a copper film formed by the plating method are laminated on a substrate of the silicon wafer

Polishing device: Lapmaster LGD-15

Polishing pad: 340 mm IC-1000/suba400 grid

Polishing load: 2 psi

Polishing time: 1 min.

Slurry supplying rate: 15 cc/min

Table rotation speed: 60 rpm

Head rotation speed: 60 rpm

1) Calculation of Polishing Rate

A substance to be polished was subjected to ultra pure water washing and ultrasonic cleaning, and then dried. A film thickness was measured before and after polishing by measuring sheet resistance using a 4-point probe. An average polishing rate was calculated from the change in the film thickness and polishing time.

2) Surface Defects

The polished substance was washed with ultrapure water and dried, and then its surface was observed using a differential interference contrast microscope with a magnification of x2500. Incidentally, damage on the surface having a length of not less than 0.1 μm was determined as a scratch.

∘: 5 scratches or less

X: more than 5 scratches

2. Measurement of Amount of Dishing

A groove having a thickness of 5,000 Å and a width of 100 μm was formed on an oxide film on the silicon wafer by dry etching. Copper was embedded into this groove by the plating method to have a substance to be polished. Using the polishing composition of the present invention, the substance was polished under the above polishing conditions, and then a thickness of a concave in the center of the groove was measured by a cross-sectional SEM photograph. Incidentally, polishing was finished at the time when copper polishing of a part in which the groove was not formed was completed.

3. Measurement of Amount of Erosion

A plurality of grooves having a thickness of 5,000 Å and a width of 4.5 μm were formed at intervals of 0.5 μm on an oxide film on the silicon wafer by dry etching. Copper was embedded into these grooves by the plating method to have a substance to be polished. Using the polishing slurry of the present invention, the substance was polished under the above polishing conditions, and then the height difference between a groove in the center and grooves on both sides was measured by a cross-sectional SEM photograph. Polishing was finished at the time when copper polishing of a part in which the groove was not formed on both sides of the groove was completed.

4. Evaluation of Storage Stability

A polishing agent was allowed to stand for 6 hours at atmospheric pressure and room temperature. Then, the state of the polishing agent was visually observed.

∘: No supernatant or precipitate generated

X: Supernatant and precipitate generated

(Production Example of Organic Particles 1)

To separable flask equipped with a stirrer, a thermometer and a reflux condenser were fed 2,000 parts of water and 0.4 part of ammonium alkyl diphenyl ether disulfonate. The resulting mixture was stirred and heated to 70 degree centigrade while replacing with nitrogen. The internal temperature was kept at 70 degree centigrade and 5.2 parts of 10% azobiscyanovaleric acid aqueous solution neutralized with ammonia was added as a polymerization initiator. Separately, 216 parts of ethyl acrylate, 72 parts of methacrylic acid and 1.8 parts of n-dodecyl mercaptan were mixed and the mixture was added dropwise to the flask over 4 hours. After 30 minutes, 72 parts of styrene was added to the flask over 15 minutes and the resultant was kept at 70 degree centigrade for 4 hours.

The resulting emulsion had 13.5% of a solid content, an average particle diameter of 170.4 nm which was measured by light scattering, and pH of 5.0. The SEM image of the resulting organic particles is shown in Table 1.

(Production Example of Organic Particles 2)

To separable flask equipped with a stirrer, a thermometer and a reflux condenser were fed 547.3 parts of water and 0.3 part of ammonium alkyl diphenyl ether disulfonate. The resulting mixture was stirred and heated to 70 degree centigrade while replacing with nitrogen. The internal temperature was kept at 70 degree centigrade and 1.2 parts of ammonium persulfate was added as a polymerization initiator. Separately, 222.2 parts of methyl methacrylate, 59 parts of methacrylic acid and 15 parts of divinyl benzene were mixed to 120 parts of water and 0.25 part of ammonium alkyl diphenyl ether disulfonate to produce an emulsion of the monomers. This emulsion was added dropwise to the flask over 4 hours and then kept at 70 degree centigrade for 30 minutes. Subsequently, 60 parts of styrene, 23.7 parts of water and 0.05 part of ammonium alkyl diphenyl ether disulfonate were mixed. The resulting adjusted emulsion was added dropwise thereto over 15 minutes and kept at 70 degree centigrade for 4 hours.

The resulting emulsion had 32.6% of a solid content, an average particle diameter of 140 nm which was measured by light scattering, and pH of 2.9.

(Production Example of Organic Particles 3)

To separable flask equipped with a stirrer, a thermometer and a reflux condenser were fed 434.5 parts of water and 0.1 part of ammonium alkyl diphenyl ether disulfonate. The resulting mixture was stirred and heated to 70 degree centigrade while replacing with nitrogen. The internal temperature was kept at 70 degree centigrade, and 0.4 part of ammonium persulfate was added as a polymerization initiator and its dissolution was confirmed. Separately, 30 parts of methyl acrylate, 27.2 parts of butyl acrylate, 37.3 parts of acetoacetoxyethyl methacrylate and 5.5 parts of 2-hydroxyethyl methacrylate were mixed to 40 parts of water and 0.1 part of ammonium alkyl diphenyl ether disulfonate to produce an emulsion of the monomers. This emulsion was added dropwise to the flask over 4 hours. After 30 minutes, 10 parts of 2-ethylhexyl acrylate, 10 parts of butyl methacrylate, 8 parts of water and 0.02 part of ammonium alkyl diphenyl ether disulfonate were mixed. The resulting adjusted emulsion was added dropwise over 15 minutes and kept at 70 degree centigrade for 4 hours.

The resulting emulsion had 19.8% of a solid content, an average particle diameter of 183 nm which was measured by light scattering, and pH of 3.2.

Comparative Production Example 1 of Organic Particles

To separable flask equipped with a stirrer, a thermometer and a reflux condenser were fed 547.3 parts of water and 0.3 part of ammonium alkyl diphenyl ether disulfonate. The resulting mixture was stirred and heated to 70 degree centigrade while replacing with nitrogen. The internal temperature was kept at 70 degree centigrade, and 1.2 parts of ammonium persulfate was added as a polymerization initiator. Separately, 169.5 parts of styrene, 41 parts of methyl methacrylate, 85.6 parts of butyl acrylate and 60.5 parts of methacrylic acid were mixed to 142 parts of water and 0.3 part of ammonium alkyl diphenyl ether disulfonate to produce an emulsion of the monomers. This emulsion was added dropwise to the flask over 4 hours and thereafter it was kept at 70 degree centigrade for 4 hours.

The resulting emulsion had 34.2% of a solid content, an average particle diameter of 140.8 nm which was measured by light scattering, and pH of 2.4. A SEM image of the obtained organic particles is shown in FIG. 2.

Example 1

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia. This solution, the emulsion after pH adjustment in Production Example 1, pure water, 30% hydrogen peroxide and benzotriazole were well mixed so as to adjust an organic particle (solid content) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. The polishing results are shown in Table 1.

Example 2

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia. This solution, the emulsion after pH adjustment in Production Example 2, pure water, 30% hydrogen peroxide and benzotriazole were well mixed so as to adjust an organic particle (solid content) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. The polishing results are shown in Table 1.

Example 3

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia. This solution, the emulsion after pH adjustment in Production Example 3, pure water, 30% hydrogen peroxide and benzotriazole were well mixed so as to adjust an organic particle (solid content) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. The polishing results are shown in FIG. 1.

Example 4

The pH of a 10% glycine solution was adjusted to 7.5 using ammonia. This solution, the emulsion after pH adjustment in Production Example 1, pure water, 30% hydrogen peroxide and benzotriazole were well mixed so as to adjust an organic particle (solid content) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, glycine to be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. The polishing results are shown in Table 1.

Example 5

The pH of a 10% asparatic acid solution was adjusted to 7.6 using ammonia. This solution, the emulsion after pH adjustment in Production Example 1, pure water, 30% hydrogen peroxide and benzotriazole were well mixed so as to adjust an organic particle (solid content) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, asparatic acid to be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. The polishing results are shown in Table 1.

Comparative Example 1

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia. This solution, the emulsion after pH adjustment in Comparative Production Example 1, pure water, 30% hydrogen peroxide and benzotriazole were well mixed so as to adjust an organic particle (solid content) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. The polishing results are shown in Table 1.

Comparative Example 2

The operation and evaluation were carried out in the same manner as in Example 1, except that commercial colloidal silica (PL-1, a product of Fuso Chemical Co., Ltd.) was substituted for the organic particle in Example 1. The polishing results are shown in Table 1.

	TABLE 1
	Polishing
	Rate		Dishing	Erosion	Storage
	(Å/min)	Scratch	(Å)	(Å)	Stability
Example 1	3800	◯	400	220	◯
Example 2	3700	◯	400	240	◯
Example 3	3500	◯	380	210	◯
Example 4	3200	◯	370	200	◯
Example 5	3100	◯	350	190	◯
Comparative	4200	◯	2600	1200	◯
Example 1
Comparative	3900	X	3700	2200	X
Example 2

INDUSTRIAL APPLICABILITY

The polishing slurry of the present invention is capable of polishing an excess metal film on a wiring pattern-formed insulation film with a high rate, capable of polishing without causing any damage or scratch due to polishing excess on a surface of a substance to be polished, and capable of polishing which produces high smoothness of the surface without any unevenness due to dishing, erosion or the like.

Furthermore, since the polishing slurry of the present invention with a solid content composition containing organic fine particles has a considerably lower decomposition temperature than that of the insulation film, it can be subjected to thermal treatment and plasma treatment and it is possible to remove the residue of a polishing agent without damaging the insulation film. Therefore, its industrial applicability is very high.

Claims

1. A polishing slurry comprising organic particles (A), wherein said organic particles (A) are those obtained by coating a part of the surface of an organic particle (B) having functional groups capable of reacting with a metal to be polished on the surface with a resin (C) free from functional groups capable of reacting with a metal to be polished.

2. The polishing slurry according to claim 1, further comprising an oxidizing agent.

3. The polishing slurry according to claim 1, wherein said organic particle (B) contains a copolymer obtained by polymerization of a monomer composition comprising 1 to 50 weight % of one, two or more monomers selected from a monomer having a carboxylic acid group, a monomer having a hydroxyl group, a monomer having an amino group, a monomer having an acetoacetoxy group and a monomer having a glycidyl group, and 99 to 50 weight % of other monomers, with each percentage based on the total weight of the monomers.

4. The polishing slurry according to claim 1, wherein the resin (C) contains a polymer of a styrene type monomer and/or a (meth) acrylic acid ester type monomer.

5. The polishing slurry according to claim 2, wherein the polishing slurry further comprises at least one complexing agent selected from carboxylic acids, amines, amino acids and ammonia, and its pH is in the range of 5 to 11.

6. The polishing slurry according to claim 1, wherein the oxidizing agent is hydrogen peroxide.