JP2010087457A - Cmp abrasive powder and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide CMP abrasive powder wherein a polishing speed and flatness of a polished film after polishing can be made sufficiently excellent with respect to CMP technique, and a polishing method in which the polished film is polished at a sufficiently excellent polishing speed using such CMP abrasive powder to make the flatness of the polished film after the polishing sufficiently excellent. <P>SOLUTION: Disclosed is the CMP abrasive powder containing cerium oxide grains, an additive, and water, wherein the zeta potential of the cerium oxide grains in the CMP abrasive powder is ≥+10 mV, and the additive contains a copolymer of vinylpyridine and an anionic monomer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a CMP abrasive and a polishing method using the same.

  The CMP (Chemical Mechanical Polishing) technique is a technique essential for forming shallow trench isolation, planarizing a premetal insulating film or an interlayer insulating film, forming a plug and a buried metal wiring, etc. in a semiconductor device manufacturing process. It has become.

As a CMP abrasive used in such a CMP technique, a fumed silica-based CMP abrasive is known. Further, a CMP abrasive using cerium oxide is disclosed as a CMP abrasive having improved polishing rate (see Patent Document 1). Furthermore, in order to control the polishing rate and improve the flatness of the polished film after polishing, a technique of adding an additive to the polishing agent using cerium oxide has been disclosed (see Patent Document 2).
Japanese Patent Laid-Open No. 10-106994 Japanese Patent Laid-Open No. 08-22970

  However, depending on the conventional CMP abrasive using cerium oxide, polishing scratches may occur during polishing, and the flatness of the film to be polished after polishing may not be sufficiently obtained. On the other hand, attempts have been made to improve the flatness by reducing the average particle diameter of the cerium oxide particles. However, in this case, although the flatness is improved, there is a problem that the polishing rate is lowered.

  Therefore, an object of the present invention is to provide a CMP polishing agent capable of sufficiently improving both the polishing rate and the flatness of a polished film after polishing in the CMP technique. Further, a CMP polishing method capable of polishing a film to be polished at a sufficiently good polishing rate using such a CMP polishing agent, and making the flatness of the film to be polished after polishing sufficiently good The purpose is to provide.

  The present invention is a CMP abrasive containing cerium oxide particles, an additive and water, wherein the zeta potential of the cerium oxide particles in the CMP abrasive is +10 mV or more, and the additive is vinyl pyridine and an anionic monolith. It is a CMP abrasive | polishing agent containing the copolymer with a monomer. By providing such a configuration, the CMP polishing slurry of the present invention can sufficiently improve both the polishing rate and the flatness of the film to be polished after polishing in the CMP technique.

  The average particle diameter of the cerium oxide particles is preferably 1 nm or more and 400 nm or less. When the average particle size is 1 nm or more, the polishing rate tends to be improved. When the average particle size is 400 nm or less, polishing scratches are less likely to occur during polishing, and good flatness of the film to be polished after polishing is obtained. It tends to be easier.

  The pH of the CMP abrasive is preferably 3.0 or more and 7.0 or less from the viewpoint of storage stability and polishing rate of the CMP abrasive.

  The content of the cerium oxide particles is preferably 0.05 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the CMP abrasive. When the content is 0.05 parts by mass or more, the polishing rate tends to be improved, and when the content is 5 parts by mass or less, the abrasive grains tend to hardly aggregate.

  The anionic monomer is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid and itaconic acid because the polishing rate is good.

  The content of the copolymer is preferably 0.001 part by mass or more with respect to 100 parts by mass of the CMP abrasive because the polishing rate becomes good.

  Further, the present invention is a CMP polishing method for polishing a film to be polished while supplying the CMP abrasive between the polishing cloth and the film to be polished formed on the substrate. According to the method of the present invention, the film to be polished can be polished at a sufficiently good polishing rate, and the flatness of the film to be polished after polishing can be made sufficiently good.

  According to the present invention, it is possible to provide a CMP polishing agent capable of sufficiently improving both the polishing rate and the flatness of a polished film after polishing in the CMP technique. Further, a CMP polishing method capable of polishing a film to be polished at a sufficiently good polishing rate using such a CMP polishing agent, and making the flatness of the film to be polished after polishing sufficiently good Can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to the following embodiments. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  The CMP abrasive | polishing agent which concerns on this embodiment contains a cerium oxide particle, an additive, and water.

(Cerium oxide particles)
The CMP abrasive according to this embodiment uses cerium oxide particles as abrasive particles (abrasive grains). There is no restriction | limiting in particular as cerium oxide, Generally what can be obtained in a market can be used. For example, “NanoTek” (trade name, manufactured by Nanophase Technologies), “NanoPOP” (trade name, manufactured by Hitachi Maxell, Inc.), those sold by Ferro Corporation, those sold by Advanced Nano Products, Rhodia The ones sold by the company can be mentioned.

  The zeta potential of the cerium oxide particles in the CMP abrasive is +10 mV or more. When the zeta potential is charged to a positive charge of +10 mV or higher, the dispersibility and the polishing rate of the CMP abrasive are improved. In order to further improve these properties, the zeta potential of the cerium oxide particles in the CMP abrasive is preferably in the range of +10 to +70 mV.

  The zeta potential can be measured using, for example, “Zeta Sizer 3000HS” (trade name, manufactured by Spectris Co., Ltd.). In this case, the CMP abrasive is diluted with water to measure the amount of scattered light recommended in “Zeta Sizer 3000HS”.

  Examples of a method for charging the cerium oxide particles to a positive charge in the CMP abrasive include a method in which the pH of the CMP abrasive is 8 or less. Furthermore, examples of a method for increasing the zeta potential of cerium oxide particles in the CMP abrasive include a method of reducing the pH of the abrasive to 7 or less, and a method of adding an amphoteric surfactant or a cationic surfactant.

  The average particle size of the cerium oxide particles is preferably 1 nm or more and 400 nm or less from the viewpoint of polishing rate and suppression of generation of polishing flaws. The average particle size is preferably 2 nm or more and more preferably 10 nm or more because a better polishing rate can be easily obtained. On the other hand, the average particle diameter is preferably 300 nm or less, and more preferably 250 nm or less, from the viewpoint of easily suppressing the occurrence of polishing flaws. In addition, as will be described later, when the CMP abrasive is stored and supplied in two or more liquids of a slurry containing abrasive grains and an additive liquid, the average grain size is in the state of slurry containing abrasive grains. It preferably has a diameter.

  In this embodiment, the “average particle diameter of cerium oxide particles” (hereinafter also referred to as “slurry particle diameter”) is a value of D50 measured by a laser diffraction particle size distribution meter (median diameter of volume distribution, cumulative). Median). Specifically, about 100 μL of CMP abrasive is weighed and the abrasive concentration is about 0.005% by mass (transmittance (H) when measured with a laser diffraction particle size distribution analyzer “LA-920” manufactured by Horiba, Ltd.) By diluting with ion-exchanged water so that the concentration becomes 60-70%), and the obtained diluted solution is put into the sample tank of “LA-920” and the value displayed as D50 is read. The slurry particle size can be measured.

  The content (concentration) of the cerium oxide particles is 0.05 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the CMP abrasive in terms of suppressing a decrease in polishing rate and aggregation of abrasive grains. Preferably, it is 0.1 to 2 parts by mass. When the content of the cerium oxide particles is less than 0.05 parts by mass, a sufficiently good polishing rate tends to be difficult to obtain. When the content is more than 5 parts by mass, the abrasive grains tend to aggregate.

  The cerium oxide particles are preferably composed of two or more crystallites surrounded by grain boundaries, and are preferably cerium oxide particles having crystal grain boundaries. By using such cerium oxide particles, the crystal grain boundaries are destroyed by the stress during polishing, and polishing is performed while generating a new surface, so that high-speed polishing is possible (Republished Patent No. 99/31195 pamphlet). Etc.). Further, the copolymer of vinyl pyridine and anionic monomer, which will be described later, exhibits particularly excellent effects when used in combination with cerium oxide particles having such crystal grain boundaries.

  The crystallite diameter of the cerium oxide particles is preferably 1 nm or more and 300 nm or less. When the crystallite diameter is less than 1 nm, crystal strain increases, and it is difficult to obtain a sufficiently good polishing rate. When the crystallite diameter is more than 300 nm, polishing flaws are likely to occur during polishing. There is a tendency that the flatness of the film to be polished is difficult to obtain. Here, the “crystallite diameter of cerium oxide particles” means the diameter of the crystallite when the cerium oxide particles are composed of two or more crystallites surrounded by a grain boundary. If not, it means the minimum diameter (primary particle diameter) of the cerium oxide particles.

  A cerium oxide powder (cerium oxide particle powder) is obtained by oxidizing a cerium compound such as carbonate, nitrate, sulfate, or oxalate by firing or a method using hydrogen peroxide or the like. When oxidizing by firing, the firing temperature is preferably 350 ° C. or higher and 900 ° C. or lower.

  Since the cerium oxide particle powder produced by the above method is in a state where the cerium oxide particles are aggregated, it is preferably mechanically pulverized. As the pulverization method, dry pulverization using a jet mill (see Chemical Industry Journal, Vol. 6 No. 5 (1980) pp. 527 to 532) or wet pulverization using a planetary bead mill is preferable.

  Moreover, a hydrothermal synthesis method can also be used as a method for producing the cerium oxide particle powder. Examples of the hydrothermal synthesis method include a method of heating a precursor such as cerium hydroxide to 100 ° C. or higher in water.

  The content of alkali metal and halogens in the cerium oxide particle powder is preferably suppressed to 10 ppm or less from the viewpoint of use in polishing for manufacturing a semiconductor element.

  As a method of dispersing such cerium oxide particle powder in water as a main dispersion medium, a method using a homogenizer, an ultrasonic disperser, a wet ball mill or the like in addition to a method of performing a dispersion treatment with a normal stirrer There is also. As the dispersion method and the particle size control method, for example, the method described in the complete collection of dispersion technologies (Information Organization, July 2005) can be used.

(Additive: Copolymer of vinyl pyridine and anionic monomer)
The CMP abrasive | polishing agent in this embodiment contains the copolymer (copolymer) of vinylpyridine and an anionic monomer component as an additive. Here, the “anionic monomer” means a monomer having an atom that can be negatively charged in water, particularly in water having a pH of 1 to 7.

  As such an anionic monomer, a monomer containing a sulfonic acid group, a hydroxyl group, a carboxyl group or the like is preferable from the viewpoint of polishing rate, and a monomer containing a carboxyl group is particularly preferable. As the anionic monomer containing a carboxyl group, acrylic acid, methacrylic acid, maleic acid, itaconic acid, and the like are preferable, and acrylic acid is most preferable.

  Copolymers of vinylpyridine and anionic monomers can be produced by various synthetic methods known to those skilled in the art. For example, it is produced by a method in which vinylpyridine and a carbon-carbon double bond portion of an anionic monomer are radically polymerized.

  As the polymer ratio of the copolymer of vinylpyridine and anionic monomer, from the viewpoint of improving the polishing rate, the ratio of vinylpyridine to anionic monomer (vinylpyridine: anionic monomer) is: The molar ratio of the monomers is preferably 99: 1 to 1:99, more preferably 99: 1 to 30:70, still more preferably 80:20 to 40:60, and 60:40 Most preferably, it is ˜40: 60.

  The used amount (content) of the copolymer of vinylpyridine and anionic monomer is 0.001 part by mass with respect to 100 parts by mass of the CMP abrasive in that an effect of improving the polishing rate is easily obtained. The above is preferable, 0.001 to 0.1 parts by mass is more preferable, and 0.01 to 0.05 parts by mass is most preferable.

  The weight average molecular weight of the copolymer of vinylpyridine and anionic monomer is not particularly limited as long as it can be dissolved in water, but is preferably 100 or more, more preferably 300 or more and less than 1 million, and 1000 or more and 10 Most preferred is less than 10,000. When the molecular weight is 100 or more, the polishing rate tends to be uniform, and when it is less than 1 million, the viscosity tends to be easy to handle without excessively increasing.

The weight average molecular weight of the copolymer can be measured using gel permeation chromatography (GPC). Specifically, for example, an HPLC pump (manufactured by Hitachi, Ltd., trade name “L-7100”) equipped with a differential refractometer (manufactured by Hitachi, Ltd., trade name “L-7100”) and a GPC column (Showa) It can be obtained as a polyethylene glycol equivalent value by connecting a product name “Shodex Asahipak GF-710HQ” manufactured by Denko Co., Ltd. and using “50 mM Na ₂ HPO ₄ aqueous solution + acetonitrile” (volume ratio 90:10) as a mobile phase. it can.

  Further, the additive used in the present embodiment may be a copolymer containing another kind of monomer in addition to vinylpyridine and an anionic monomer. In this case, the other type of monomer is not particularly limited as long as it is water-soluble, but a cationic monomer or a nonionic monomer can be used.

  Examples of the cationic monomer contained in the copolymer include vinylamine, allylamine, and monomers represented by the following general formulas (1) to (4). These can be used alone or in combination of two or more.

In the general formulas (1) to (4), R _{1 to} R ₅ each independently represent hydrogen or a monovalent organic group, and X represents a divalent organic group. The monovalent organic group is not particularly limited, and examples thereof include an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, a chloro group, a difluoromethyl group, a trifluoromethyl group, and a cyano group. These organic groups may have a substituent. Among these, from the viewpoints of availability and solubility in water, R _{1 to} R ₅ are preferably hydrogen or an alkyl group having 1 to 6 carbon atoms, and more preferably hydrogen or a methyl group.

  In the general formulas (1) to (4), the divalent organic group represented by X is not particularly limited, and examples thereof include an alkylene group having 1 to 6 carbon atoms and a phenylene group. These organic groups may have a substituent. Among these, from the viewpoint of availability and solubility in water, X is preferably an alkylene group having 1 to 3 carbon atoms.

  Examples of the nonionic monomer contained in the copolymer include vinyl alcohol, vinyl acetate, acrylic ester, methacrylic ester, acrylonitrile, vinyl pyrrolidone, vinyl caprolactam, vinyl methyl ether, vinyl methyl oxazolidinone, vinyl formal, vinyl Examples include acetal, vinyl isobutyl ether, acrylamide, methacrylamide, and monomers represented by the following general formulas (5) to (9). These can be used alone or in combination of two or more.

In the general formulas (5) to (9), R _{1 to} R ₃ each independently represent hydrogen or a monovalent organic group, and x represents an integer of 0 or more. The monovalent organic group is not particularly limited, and examples thereof include an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, a chloro group, a difluoromethyl group, a trifluoromethyl group, and a cyano group. These organic groups may have a substituent. Among these, from the viewpoint of availability and solubility in water, R _{1 to} R ₃ are preferably hydrogen or an alkyl group having 1 to 6 carbon atoms, and more preferably hydrogen or a methyl group.

  In the general formulas (5) to (9), x is an integer of 0 or more and is not particularly limited, but is preferably 0 to 100, more preferably 0 to 10, more preferably 1 from the viewpoint of polishing rate. Most preferred.

(Additive used in combination with a copolymer of vinylpyridine and anionic monomer)
The CMP abrasive according to the present embodiment is further separated in addition to the copolymer of vinyl pyridine and anionic monomer for the purpose of adjusting the dispersibility, polishing characteristics, storage stability, etc. of the cerium oxide particles. The additive may be included. As such an additive, a conventionally well-known thing can be included in the range which does not impair the effect of the copolymer containing the said anionic monomer. Examples of such additives include carboxylic acids and amino acids for obtaining the effect of stabilizing the pH, and surfactants for obtaining the effect of adjusting the polishing characteristics.

  The carboxylic acids are not particularly limited as long as they have solubility in water, and examples thereof include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and lactic acid.

  The amino acids are not particularly limited as long as they have solubility in water.For example, arginine, lysine, aspartic acid, glutamic acid, asparagine, glutamine, histidine, proline, tyrosine, tryptophan, serine, threonine, Examples include glycine, alanine, β-alanine, methionine, cysteine, phenylalanine, leucine, valine, and isoleucine. Among them, alanine, β-alanine, tryptophan, and the like are preferable in terms of polishing rate.

  The surfactant is not particularly limited as long as it has solubility in water. For example, amphoteric surfactants, anionic surfactants, nonionic surfactants, cationic surfactants An amphoteric surfactant is particularly preferable from the viewpoints of dispersibility and polishing rate.

  Examples of amphoteric surfactants include betaine, β-alanine betaine, lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, among others. Betaine, β-alanine betaine, and the like are preferable from the viewpoint of dispersibility.

  Examples of the anionic surfactant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and a special polycarboxylic acid type polymer dispersant.

  Nonionic surfactants include, for example, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octylphenyl ether, polyoxyethylene Oxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivatives, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, poly Oxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraoleic acid polio Siethylene sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl methacrylate, alkylalkanolamide Etc.

  Examples of the cationic surfactant include coconut amine acetate and stearylamine acetate.

  The amount of these additives is preferably such that the total amount of additives is 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the CMP abrasive. When the additive amount is 10 parts by mass or less, the abrasive grains tend not to settle.

  Further, the CMP abrasive according to this embodiment may contain a water-soluble polymer for the purpose of adjusting polishing characteristics. The water-soluble polymer is not particularly limited as long as it has solubility in water. For example, polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan, and pullulan; polyaspartic acid, polyglutamic acid , Polylysine, polymalic acid, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyamic acid ammonium salt, polyamic acid sodium salt, polyglyoxylic acid and other polycarboxylic acids and salts thereof; polyvinyl Examples include vinyl polymers such as alcohol, polyvinyl pyrrolidone, and polyacrolein; polyethylene glycol and the like. Among these, polyethylene glycol is preferable in terms of polishing characteristics.

  The weight average molecular weight of these water-soluble polymers is preferably 500 or more and less than 5 million, and more preferably 1000 or more and less than 200,000 in terms of adjusting polishing characteristics. When the molecular weight is 500 or more, the polishing property adjusting effect tends to increase, and when it is less than 5 million, it tends to be easy to handle.

  The blending amount of the water-soluble polymer is preferably 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the CMP abrasive. If the blending amount is 5 parts by mass or less, the abrasive tends to be difficult to settle.

(PH)
Although there is no restriction | limiting in particular as pH of CMP abrasive | polishing agent which concerns on this embodiment, In order to maintain the storage stability of abrasive | polishing agent and to obtain a favorable grinding | polishing rate, it may be 3.0 or more and 7.0 or less. preferable.

  The pH can be adjusted by adding an acid component or an alkali component such as ammonia, sodium hydroxide, or tetramethylammonium hydroxide (TMAH). A buffer solution may be added to stabilize the pH. Examples of such a buffer include acetate buffer and phthalate buffer.

  The pH can be measured with a pH meter (for example, “Model pH81” manufactured by Yokogawa Electric Corporation). Specifically, after calibrating the pH meter at two points using a phthalate pH buffer solution (pH 4.01) and a neutral phosphate pH buffer solution (pH 6.86) as a standard buffer solution, the pH meter electrode Is measured in a CMP abrasive and the value after 2 minutes has passed and stabilized. At this time, both the standard buffer solution and the CMP abrasive solution are measured at 25 ° C.

(Abrasive storage method)
The CMP abrasive according to this embodiment may be stored as a two-component CMP abrasive in which a cerium oxide slurry containing cerium oxide particles and water and an additive containing water and an additive are separated. You may preserve | save as a one-component CMP abrasive | polishing agent containing particle | grains, an additive, and water.

  In either case, it may be stored as a concentrated cerium oxide slurry with a reduced water content, a concentrated additive solution or a concentrated abrasive and diluted with water during polishing. When the cerium oxide slurry and the additive solution are stored as separate two-component abrasives, the polishing rate can be adjusted by arbitrarily changing the combination of these two components.

  When polishing with a two-pack type abrasive, the method of supplying the abrasive onto the polishing surface plate is, for example, by feeding the cerium oxide slurry and the additive liquid through separate pipes, and joining and mixing these pipes. There is a way to supply. In addition, concentrated cerium oxide slurry, concentrated additive solution and water are sent through separate pipes, and these are joined, mixed and supplied, or pre-mixed and supplied with cerium oxide slurry and additive solution, A method of mixing and supplying a concentrated cerium oxide slurry, a concentrated additive solution and water in advance can be used.

  When using a one-component CMP abrasive containing cerium oxide particles, additives, and water, as a method of supplying the abrasive onto the polishing surface plate, a method of supplying the abrasive directly by feeding, or a concentrated abrasive And a method of feeding them through separate pipes, and combining and mixing them, or a method of mixing and supplying a concentrated abrasive and water in advance, and the like.

(Polishing method)
As a CMP polishing method for polishing a film to be polished using the CMP abrasive according to this embodiment, a conventionally known method can be used. For example, the substrate having a film to be polished is pressed against a polishing surface plate to which a polishing cloth is attached so that the film to be polished and the polishing cloth are in contact with each other, and this embodiment is interposed between the film to be polished and the polishing cloth. There is a method of polishing a film to be polished by moving a substrate and / or a polishing surface plate while supplying the CMP abrasive according to the above.

  Examples of the substrate having a film to be polished include a substrate for manufacturing a semiconductor element, for example, a substrate having a film to be polished formed on a semiconductor substrate on which a shallow trench isolation pattern, a gate pattern, a wiring pattern, and the like are formed. Examples of the film to be polished formed on these patterns include insulating films such as a silicon oxide film and a silicon nitride film.

  By polishing the silicon oxide film or silicon nitride film formed on such a semiconductor substrate with the above-described CMP abrasive, the unevenness on the surface of the silicon oxide film layer is eliminated and the entire surface of the semiconductor substrate is made smooth. Can do.

  Hereinafter, the polishing method will be described by taking the case of a semiconductor substrate on which an insulating film is formed as an example. In the polishing method using the CMP abrasive of this embodiment, the polishing apparatus includes a substrate holder capable of holding a substrate having a film to be polished such as a semiconductor substrate, and a polishing constant capable of attaching a polishing cloth (polishing pad). A general polishing apparatus provided with a board can be used. The substrate holder and the polishing surface plate are each attached with a motor or the like whose rotational speed can be changed. For example, polishing apparatus manufactured by Ebara Corporation: model number “EPO-111” can be used.

  As an abrasive cloth, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used, and there is no restriction | limiting in particular. In addition, it is preferable that the polishing cloth is subjected to groove processing so that the CMP abrasive is accumulated at the time of polishing in view of the characteristics of the CMP abrasive according to the present embodiment.

  There is no limitation on the polishing conditions, but the rotation speed of the polishing surface plate is preferably 200 rotations / minute or less so that the semiconductor substrate does not pop out, and the pressure applied to the semiconductor substrate (processing load) It is preferable to set it as 100 kPa or less so that it may not occur. During polishing, a CMP abrasive is continuously supplied to the polishing cloth with a pump or the like. The supply amount is not limited, but it is preferable that the surface of the polishing pad is always covered with a CMP abrasive.

  After polishing, it is preferable to clean the semiconductor substrate thoroughly under running water to remove particles adhering to the substrate. For cleaning, dilute hydrofluoric acid or ammonia water may be used in combination with pure water, and a brush may be used in combination to increase cleaning efficiency. Moreover, after washing, it is preferable to dry after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.

  Examples of a method for manufacturing a film to be polished (insulating film) include a CVD method typified by a low pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, and a spin coating method in which a liquid material is applied to a rotating substrate. It is done.

When a silicon oxide film is formed by a low pressure CVD method, for example, a silicon oxide film can be obtained by thermally reacting monosilane (SiH ₄ ) and oxygen (O ₂ ). When a silicon nitride film is formed by a low pressure CVD method, for example, a silicon nitride film can be obtained by thermally reacting dichlorosilane (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ).

In the case of producing a silicon oxide film by the quasi-atmospheric pressure CVD method, for example, a silicon oxide film can be obtained by thermally reacting tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) and ozone (O ₃ ). When a silicon oxide film is formed by a plasma CVD method, for example, a silicon oxide film can be obtained by causing a plasma reaction between monosilane and nitrogen dioxide (N ₂ O). In addition, a silicon oxide film can be obtained in the same manner by causing a plasma reaction between tetraethoxysilane and oxygen.

In the case of forming a silicon nitride film by a plasma CVD method, for example, a silicon nitride film can be obtained by causing a plasma reaction of monosilane, ammonia, and nitrogen (N ₂ ). In the case of producing by a spin coating method, for example, a liquid raw material containing inorganic polysilazane, inorganic siloxane, or the like is applied onto a substrate and subjected to a thermosetting reaction in a furnace body or the like to obtain a silicon oxide film.

  In order to stabilize the film quality of an insulating film such as a silicon oxide film or a nitrogen silicon film obtained by the above method, heat treatment may be performed at a temperature of 200 to 1000 ° C. as necessary. In addition, the silicon oxide film obtained by the above method may contain a small amount of boron (B), phosphorus (P), carbon (C), or the like in order to improve the embedding property.

  The CMP abrasive | polishing agent and polishing method which concern on this embodiment are applicable also to films other than insulating films, such as a silicon oxide film and a nitrogen silicon film. For example, high dielectric constant films such as Hf, Ti, and Ta oxides; semiconductor films such as silicon, amorphous silicon, polysilicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors; phases such as GeSbTe The above polishing agent and polishing method can be applied to a change film; an inorganic conductive film such as ITO; a polymer resin film such as polyimide, polybenzoxazole, acrylic, epoxy, and phenol.

  The CMP abrasive and the polishing method can be applied not only to film-like materials but also to various substrate materials such as glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, and plastic.

  Further, the CMP polishing agent and polishing method are not limited to the manufacture of semiconductor elements, but include image display devices such as TFTs and organic ELs; optical parts such as photomasks, lenses, prisms, optical fibers, and single crystal scintillators; optical switching elements, It can also be used in the production of optical elements such as optical waveguides; light emitting elements such as solid lasers and blue laser LEDs; and magnetic storage devices such as magnetic disks and magnetic heads.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

(Additive A)
In a round bottom flask, 5.26 g (50 mmol) of 2-vinylpyridine and 20 mL of methanol were placed, and nitrogen gas was introduced. Next, the round bottom flask was placed in a 70 ° C. water bath, and while the solution in the flask was heated and stirred, a mixture of 328 mg of azobisisobutyronitrile and 20 mL of methanol, 3.62 g (50 mmol) of acrylic acid and methanol were mixed. 20 mL of the mixture was added to prepare a reaction solution. The obtained reaction solution was heated and stirred for 3.5 hours, then cooled to room temperature (25 ° C.), and added to 300 mL of diethyl ether to precipitate a copolymer of 2-vinylpyridine and acrylic acid. . This copolymer was further purified by reprecipitation to obtain 1.5 g of a pale yellow powder. The obtained pale yellow powder was a copolymer (hereinafter referred to as “additive”) having a molar ratio of 2-vinylpyridine to acrylic acid (hereinafter referred to as “2-vinylpyridine: acrylic acid”) of 50:50. A ”)). It was 1400 when the weight average molecular weight of the obtained additive A was measured by GPC.

(Additive B)
Additive B was obtained in the same manner as Additive A, except that the molar ratio of 2-vinylpyridine to acrylic acid was changed (2-vinylpyridine: acrylic acid = 80: 20).

(Cerium oxide particle powder)
40 kg of cerium carbonate hydrate was put in an alumina container and calcined in air at 830 ° C. for 2 hours to obtain 20 kg of a yellowish white calcined powder. As a result of phase identification by an X-ray diffraction method, this fired powder was confirmed to be a powder composed of cerium oxide particles (hereinafter referred to as “cerium oxide particle powder”). The particle diameter of the cerium oxide particles in the cerium oxide particle powder was 30 to 100 μm.

15 kg of the obtained cerium oxide particle powder was dry-ground using a jet mill. It was 9 m < ² > / g as a result of measuring the specific surface area of the said powder after dry-grinding by BET method. Further, when the cerium oxide particle powder was observed by SEM, it was an aggregate of a plurality of crystallites surrounded by grain boundaries, and the size of 20 randomly selected crystallites was in the range of 50 to 100 nm. It was.

(Concentrated cerium oxide slurry)
In the container, 15 kg of the cerium oxide particle powder, 84.98 kg of deionized water and 20 g of acetic acid were added and stirred for 10 minutes to obtain a cerium oxide mixed solution. The obtained cerium oxide mixed solution was fed to another container over 30 minutes. Meanwhile, ultrasonic irradiation was performed on the cerium oxide mixed solution at an ultrasonic frequency of 400 kHz in the pipe for feeding the liquid. 500 g ± 20 g of each cerium oxide mixed solution fed via ultrasonic irradiation was put into four 500 mL beakers. The cerium oxide mixed solution in each beaker was centrifuged for 2 minutes under the condition that the centrifugal force applied to the outer periphery was 500G. After centrifugation, the fraction that settled at the bottom of the beaker was collected and used as a concentrated cerium oxide slurry. The solid content concentration of the obtained concentrated cerium oxide slurry was measured and found to be 7.0% by mass. The average particle size of the concentrated cerium oxide slurry was measured using a laser diffraction particle size distribution analyzer (trade name “LA-920” manufactured by Horiba, Ltd.) with a refractive index of 1.93 and a transmittance of 68%. The value of was 113 nm.

Example 1
100 mg of the additive A, 100 mg of an acetic acid aqueous solution (1% by mass) and 464 g of water were mixed to prepare a mixed solution. To this mixed solution, 35.7 g of the above concentrated cerium oxide slurry (solid content concentration 7.0 mass%) is added, and 2.5 mass% aqueous ammonia is added until the pH becomes 5.11, mixed, and cerium oxide is mixed. A CMP abrasive having a concentration of 0.5% by mass and an additive A concentration of 0.02% by mass was obtained.

  The obtained abrasive was diluted to a concentration of about 0.005% by mass, and using a laser diffraction particle size distribution meter (manufactured by Horiba, Ltd., trade name “LA-920”), a refractive index of 1.93, When the average particle diameter (D50) of the cerium oxide particles in the abrasive was measured with a transmittance of 68%, the value of D50 was 118 nm.

  After diluting the abrasive to an appropriate concentration with water, the zeta potential of the cerium oxide particles in the abrasive was measured using a zeta potential measuring device (trade name “Zeta Sizer 3000HS” manufactured by Spectris Co., Ltd.). +29 mV.

(Examples 2 to 6)
As shown in Table 1, a CMP abrasive was prepared in the same manner as in Example 1 except that the type of additive, the concentration of the additive, or the pH of the abrasive was changed.

(Comparative Example 1)
A CMP abrasive was prepared in the same manner as in Example 1 except that no additive was used.

(Comparative Example 2)
1 kg of cerium oxide particles, 23 g of a commercially available aqueous solution of ammonium polyacrylate (40% by mass) and 8977 g of deionized water were mixed to obtain a mixed solution. The mixed solution was subjected to ultrasonic dispersion while stirring, then filtered through a 1 micron filter, and deionized water was added to obtain a concentrated cerium oxide slurry having 5% by mass of cerium oxide. 100 g of the obtained concentrated cerium oxide slurry, 5 g of an aqueous polyacrylic acid ammonium salt solution (40% by mass), and 900 g of water were mixed, 1N nitric acid was added until the pH reached 5, and a CMP abrasive (cerium oxide: 0 0.5 mass%, polyacrylic acid ammonium salt: 0.2 mass%).

(Evaluation wafer)
For evaluation of polishing characteristics, a commercially available wafer for CMP characteristics evaluation (“SEMATECH 864”, diameter 200 mm) was used. 1 is a partially enlarged end view of the evaluation wafer, FIG. 2 is a top view of the evaluation wafer, and FIG. 3 is a partially enlarged view of FIG. In this evaluation wafer, a silicon nitride (SiN) film 2 having a thickness of 150 nm is formed on a silicon substrate 3 by a CVD method, a groove having a depth of 470 nm (150 nm + 320 nm) is formed, and then HDP-CVD (high density plasma) is formed. The silicon oxide (SiO ₂ ) film 1 having a thickness of 610 nm is formed by chemical vapor deposition.

  As shown in FIG. 2, the wafer surface is divided into 61 areas (20 mm × 20 mm), and each area is further divided into 25 small areas (4 mm × 4 mm) (FIG. 3). Among these, except for two small areas, a linear uneven pattern is formed in each small area. The numerical values of 0 to 100% in FIG. 3 indicate the ratio (convex surface density) that the total area of the convex portions visible when the small regions are viewed in plan view in the small regions. 0% means that all are concave portions, and 100% is that all are convex portions, which means that no linear pattern is formed. 1 and 3, “L” indicates the line width (μm) of the convex portion, and “S” indicates the line width (μm) of the concave portion. In FIG. 2, “C” (Center), “M” (Middle), and “E” (Edge) indicate regions where the film thickness was measured.

(Polishing experiment)
The polishing experiment was performed using a polishing apparatus (model number “EPO-111” manufactured by Ebara Corporation) having a substrate holder and a polishing platen having a diameter of 600 mm. First, the evaluation wafer was fixed to a substrate holder, and a polishing cloth (polishing pad) “IC-1000” (Rodel model number, groove shape: perforate) made of porous urethane resin was attached to a polishing surface plate. Next, the evaluation wafer was pressed against the polishing cloth and the polishing surface plate with a processing load of 30 kPa so that the silicon oxide film 1 (insulating film or film to be polished) of the evaluation wafer was in contact with the polishing cloth. Then, the polishing surface plate and the substrate holder were each operated at 50 revolutions / minute while dropping the CMP abrasives prepared in the above Examples and Comparative Examples on the polishing cloth at a rate of 200 mL / minute. The wafer was polished for 40 seconds. The polished evaluation wafer was sufficiently washed with pure water and then dried.

After polishing, the SiO ₂ residual film thickness was measured for each region represented by C (Center), M (Middle), and E (Edge) of the evaluation wafer that had been cleaned and dried. In particular, in each region, L = 500 μm, S = 500 μm pattern (hereinafter referred to as “500/500”), L = 100 μm, S = 100 μm pattern (hereinafter referred to as “100/100”), L = 25 μm. , S = 25 μm pattern (hereinafter referred to as “25/25”) The residual SiO ₂ film thickness of each convex portion and concave portion was measured. For the measurement, an optical interference film thickness apparatus (manufactured by Nanometrics Japan Co., Ltd., trade name “Nanospec AFT-5100”) was used.

About each said pattern in each said area | region, the convex part grinding | polishing speed | rate was calculated | required by the following formula.
(formula)
Convex part polishing rate (nm / min) = (Reduction amount of convex part SiO ₂ film) (nm) / (Polishing time) (min)
Subsequently, the average convex part grinding | polishing rate in C, M, and E was calculated | required about 500/500, 100/100, and 25/25, respectively.

Furthermore, the average convex part grinding | polishing rate dispersion | variation was calculated | required by the following formula.
(formula)
Average convex polishing rate variation (%) = (standard deviation of average convex polishing rate of 500/500, 100/100, 25/25) / (average convex polishing of 500/500, 100/100, 25/25) Average speed)

  Table 1 shows the average convex portion polishing rate and its variation when the abrasives prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were used. In Table 1, additive A is a copolymer having a molar ratio of 2-vinylpyridine and acrylic acid of 50:50, and additive B is a copolymer having the molar ratio of 80:20. is there. Moreover, the quantity of an additive shows the content rate (mass%) of the additive with respect to the whole abrasive | polishing agent, and pH shows the pH of the whole abrasive | polishing agent.

  As shown in Table 1, when the abrasives of Examples 1 to 6 are used, the film to be polished can be uniformly polished at a higher speed than when the abrasives of Comparative Examples 1 and 2 are used. It became clear. That is, according to the polishing agent of the present invention, it has been clarified that both the polishing rate and the flatness of the polished film after polishing are sufficiently good in the CMP technique.

It is the elements on larger scale of the wafer for CMP characteristic evaluation in the example of the present invention. It is a top view of the wafer for CMP characteristic evaluation in the Example of this invention. FIG. 3 is a partially enlarged view of FIG. 2.

1 ... silicon oxide film _(SiO 2), 2 ... silicon nitride (SiN) film, 3 ... silicon substrate

Claims (7)

A CMP abrasive containing cerium oxide particles, additives and water,
The zeta potential of the cerium oxide particles in the CMP abrasive is +10 mV or more,
A CMP abrasive, wherein the additive comprises a copolymer of vinyl pyridine and an anionic monomer.   The CMP abrasive | polishing agent of Claim 1 whose average particle diameters of the said cerium oxide particle are 1 nm or more and 400 nm or less.   The CMP abrasive | polishing agent of Claim 1 or 2 whose pH is 3.0 or more and 7.0 or less.   The CMP abrasive | polishing agent as described in any one of Claims 1-3 whose content of the said cerium oxide particle is 0.05 to 5 mass parts with respect to 100 mass parts of the said CMP abrasive | polishing agents.   The CMP abrasive | polishing agent as described in any one of Claims 1-4 whose said anionic monomer is at least 1 sort (s) chosen from the group which consists of acrylic acid, methacrylic acid, maleic acid, and itaconic acid.   The CMP abrasive | polishing agent as described in any one of Claims 1-5 whose content of the said copolymer is 0.001 mass part or more with respect to 100 mass parts of said CMP abrasive | polishing agents.   A CMP polishing method for polishing the film to be polished while supplying the CMP abrasive according to any one of claims 1 to 6 between a polishing cloth and a film to be polished formed on a substrate.

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