JP2013110272A - Abrasive and method for polishing substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive and a polishing method which are capable of rapidly polishing a surface to be polished of an inorganic insulating film layer or the like while suppressing generation of polishing scratches.SOLUTION: The abrasive contains metal oxide particles and a medium. The metal oxide particles include metal oxide particles obtained by firing a metal oxide produced by heating a mixture containing a metal salt, a polymer compound, and a high boiling point organic solvent.

Description

  The present invention relates to an abrasive and a method for polishing a substrate.

  In the current ULSI semiconductor device manufacturing process, processing technology for high density and miniaturization has been researched and developed. CMP (Chemical Mechanical Polishing) technology, which is one of them, is used to flatten the surface of a substrate in the manufacturing process of a semiconductor element, in particular, flattening an interlayer insulating film, forming shallow trench elements, forming plugs and buried metal wiring, etc. It has become an indispensable technology when doing.

  Conventionally, a fumed silica-based abrasive as a chemical mechanical abrasive for planarizing an inorganic insulating film layer such as a silicon oxide film formed by a method such as plasma-CVD or low-pressure CVD in a manufacturing process of a semiconductor element (Abrasive grains) are generally studied. Fumed silica-based abrasives are produced by growing particles by a method such as thermal decomposition of tetrachlorosilicate and adjusting the pH. However, such an abrasive has a technical problem that the polishing rate is low.

  In generations after the design rule of 0.25 μm, shallow trench isolation is used for element isolation in an integrated circuit. In shallow trench isolation, CMP is used to remove an excess silicon oxide film formed on the substrate, and a stopper film having a low polishing rate is formed under the silicon oxide film in order to stop polishing. Silicon nitride or the like is used for the stopper film, and it is desirable that the polishing rate ratio between the silicon oxide film and the stopper film is large. The colloidal silica-based polishing material conventionally used in this process has a polishing rate ratio of the above-mentioned silicon oxide film and stopper film as small as about 3, and does not have a characteristic that can withstand practical use for shallow trench isolation. It was.

  On the other hand, cerium oxide abrasives are used as glass surface abrasives such as photomasks and lenses. Cerium oxide particles have a lower hardness than silica particles and alumina particles, and therefore are less likely to scratch the polished surface, and are useful for finish mirror polishing. Further, there are advantages that the polishing rate is high and the polishing rate ratio is large as compared with the silica abrasive. In recent years, CMP abrasives for semiconductors using high-purity cerium oxide particles have been used. For example, this technique is disclosed in Patent Document 1.

  It is known that cerium oxide particles are produced by firing and finely pulverizing cerium carbonate, cerium oxalate, cerium hydroxide, and the like as raw materials. For example, this technique is disclosed in Non-Patent Document 1.

  In recent years, a method for producing fine metal oxide particles by a polyol method in a liquid phase has also been studied. In this technique, a metal oxide is obtained through a hydrolysis / dehydration reaction by heating and refluxing a mixture containing a metal salt and a polyol, which is disclosed in Patent Documents 2 and 3, for example.

Japanese Patent Laid-Open No. 10-106994 JP 2008-115370 A JP 2008-11114 A

Ginya Adachi (edition) "Chemistry of rare earths"

  When the cerium oxide abrasive is applied to the polishing of the inorganic insulating film layer, it is considered that the processing proceeds by the chemical action of cerium oxide and the mechanical removal action by particles. When coarse particles are present in the abrasive, the mechanical removal action is concentrated locally, resulting in polishing flaws. On the other hand, if the particles are too fine, a desired polishing rate cannot be obtained. Thus, attempts have been made to select a cerium oxide secondary particle size that can achieve a desired polishing rate and minimize the occurrence of polishing flaws. As long as it is used, complete removal of coarse particles is difficult.

  On the other hand, it is said that fine particles can be produced by cerium oxide particle synthesis by a liquid phase method such as a polyol method. However, cerium oxide particles obtained by the liquid phase method have a problem that the primary particle size is small and a desired polishing rate cannot be obtained. In the future, as the number of semiconductor elements increases and the definition becomes higher, CMP polishing agents that use abrasives that suppress polishing scratches and that can be polished at high speeds will improve the yield and production efficiency of semiconductor elements. Desired.

  Accordingly, an object of the present invention is to provide an abrasive and a polishing method capable of polishing a surface to be polished such as an inorganic insulating film layer at a high speed while suppressing generation of polishing flaws.

The present invention is an abrasive containing metal oxide particles and a medium, wherein the metal oxide particles are produced by heating a mixture containing a metal salt, a polymer compound, and a high-boiling organic solvent. The present invention relates to an abrasive containing metal oxide particles obtained by firing an oxide.
As an embodiment of the abrasive of the present invention, for example, the coefficient of variation of the particle size of the metal oxide particles produced by heating the mixture is preferably 0.25 or less. As the high-boiling organic solvent, it is possible to use ethylene glycol or diethylene glycol, as the metal salt, it is possible to use nitrate or acetate, more specifically cerium nitrate or cerium acetate, As the polymer compound, a polymer compound having a weight average molecular weight of 2,000 to 1,000,000, such as polyvinyl pyrrolidone or hydroxypropyl cellulose, can be used. The metal salt is preferably used at a concentration of 0.05 mol / L or more, and the polymer compound is preferably used at a concentration of 30 to 150 g / L. By heating the mixture, metal oxide particles having an average particle diameter of preferably 10 to 300 nm when dispersed in a medium can be obtained.
Moreover, as embodiment of the abrasive | polishing agent of this invention, it is preferable that a calcination temperature is 200-1,200 degreeC, for example. The firing atmosphere can be nitrogen, helium, neon, argon, krypton, or xenon, and the metal oxide produced by heating the mixture can be dispersed and fired in the vehicle. It is. By firing, metal oxide particles having an average primary particle diameter of preferably 5 to 200 nm can be obtained, and metal oxide particles having an average particle diameter of preferably 10 to 300 nm when dispersed in a medium are obtained. Can be obtained.
The pH of the abrasive is preferably 3 to 9, and water can be used as a medium.

  Furthermore, the present invention relates to a method for polishing a substrate, characterized in that a predetermined substrate is polished with the above-described abrasive. As an embodiment of the substrate polishing method, by supplying the above-described abrasive to the polishing pad on the polishing surface plate, the surface to be polished of the semiconductor substrate on which the inorganic insulating film layer is formed and the polishing pad are moved relative to each other. A polishing method for a substrate to be polished is mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, the abrasive | polishing agent and polishing method which can grind | polish to-be-polished surfaces, such as an inorganic insulating film layer, at high speed, suppressing generation | occurrence | production of a damage | wound can be provided.

1 is an SEM photograph of the cerium oxide particles before firing obtained in Example 1. FIG. FIG. 2 is a SEM photograph of the cerium oxide particles after firing obtained in Example 6.

  The abrasive of the present invention is an abrasive containing metal oxide particles and a medium, and the metal oxide particles are produced by heating a mixture containing a metal salt, a polymer compound, and a high-boiling organic solvent. It is an abrasive | polishing agent containing the metal oxide particle obtained by baking the metal oxide to do.

  First, a method for obtaining a metal oxide (metal oxide before firing) will be described. A metal oxide is obtained by the heating process which heats the mixture containing a metal salt, a high molecular compound, and a high boiling point organic solvent.

  In general, it is known that a metal salt forms an oxide through a hydroxide when heated to a high temperature of 100 ° C. or higher under certain conditions. In the present invention, by heating the mixture, the primary particles of the metal oxide are precipitated in a high boiling point organic solvent in the presence of the polymer compound, and then aggregate to form spherical secondary particles. In the mixture, the polymer compound is preferably dissolved in a high-boiling organic solvent. At that time, the metal oxide acts as a catalyst on the surface of the secondary particle, and the polymer compound causes a crosslinking reaction to form a strong polymer layer, so that the secondary particle has a polymer layer on the surface. It becomes.

  As metal salts, inorganic acid salts such as sulfates, nitrates and hydrochlorides, and organic acid salts such as acetates can be used, and nitrates and acetates can be preferably used. Moreover, in order to facilitate reaction, the metal salt may be partially neutralized. Alternatively, an alkaline solution may be mixed with the mixture. As the alkali species or alkali solution of the partially neutralized salt, an aqueous alkali solution such as an aqueous ammonia solution, an aqueous potassium hydroxide solution, or an aqueous sodium hydroxide solution can be used. An aqueous ammonia solution is preferable.

  As the metal, cerium or zirconium can be preferably used. Cerium is particularly preferable. Accordingly, as the metal salt, for example, cerium nitrate, cerium acetate, cerium ammonium nitrate and the like can be used, and among them, cerium nitrate and cerium acetate are preferably used. From the viewpoint of favorably progressing the formation reaction of the metal oxide, the concentration of the metal salt (the number of moles of the metal salt added per unit high boiling point organic solvent) is preferably 0.05 mol / L or more. Further, from the viewpoint of stably forming fine particles, the concentration of the metal salt is preferably 2.0 mol / L or less.

  As the polymer compound, for example, water-soluble polymers such as polyvinylpyrrolidone, hydroxypropylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, and polyacrylamide are preferably used. Is done. Preferred are polyvinyl pyrrolidone and hydroxypropyl cellulose, and particularly preferred is polyvinyl pyrrolidone.

  The concentration of the polymer compound (the weight of the polymer compound added per unit high boiling point organic solvent) is sufficient when the metal oxide primary particles agglomerate to form secondary particles. 30 g / L or more is preferable, 40 g / L or more is more preferable, and 50 g / L or more is more preferable. The concentration of the polymer compound is preferably 150 g / L or less, more preferably 140 g / L or less, and 130 g is preferable in that primary particles are favorably formed without inhibiting metal oxide nucleation. / L or less is more preferable.

  The weight average molecular weight of the polymer compound is preferably 2,000 or more from the viewpoint that when a crosslinking reaction occurs on the surface of the aggregated secondary particles, a strong polymer layer is formed and the generation of coarse aggregated particles is suppressed. 3,000 or more is more preferable, and 4,000 or more is more preferable. Further, the weight average molecular weight of the polymer compound is 1,000,000 from the viewpoint that a strong polymer layer is formed on the surface of the primary particles of the metal oxide and secondary particles due to aggregation are hardly formed. The following is preferable, 500,000 or less is more preferable, and 200,000 or less is more preferable. The range of the weight average molecular weight is a preferable range since the particle diameter of the secondary particles of the metal oxide can be adjusted to be small by increasing the molecular weight of the polymer compound. The weight average molecular weight is a weight average molecular weight in terms of standard polyethylene glycol by gel permeation chromatography (GPC).

  The high boiling point organic solvent is an organic solvent having a high boiling point, for example, a solvent having a boiling point of 110 ° C. or higher, preferably 120 ° C. or higher, more preferably 130 ° C. or higher. There is no particular limitation on the upper limit of the boiling point. As the high-boiling organic solvent, it is preferable to use a solvent having a boiling point higher than the heating temperature when the mixture is heated. Specifically, polyhydric alcohol, that is, polyols can be preferably used. As the polyhydric alcohol, ethylene glycol, diethylene glycol, glycerin and the like can be used.

  When the mixture is heated, preferably heated to reflux, the temperature is preferably 110 ° C. or higher from the viewpoint that the formation of the metal oxide from the metal salt proceeds well. Further, the temperature is preferably 200 ° C. or lower in that the amount of the high-boiling organic solvent used is suppressed and the high-boiling organic solvent is easily removed from the mixture after the reaction. The reaction time can be, for example, 10 minutes to 120 minutes. The secondary particles of the metal oxide thus obtained by the liquid phase method have a spherical shape.

  The average particle diameter of the metal oxide particles (metal oxide before firing) dispersed in the medium is preferably 10 nm or more, more preferably 20 nm or more, and more preferably 40 nm or more from the viewpoint of obtaining a practical polishing rate after firing. Is more preferable. The average particle size of the metal oxide particles dispersed in the medium is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less, from the viewpoint that a sufficient effect of reducing polishing scratches can be obtained. In the present invention, the particle size distribution of the metal oxide particles can be determined by wet measurement using a laser diffraction method (for example, LA-950 manufactured by Horiba, Ltd.). The particle size means an average value of particle sizes in a volume-based particle size distribution. Since the secondary particles of the metal oxide have a polymer layer on the surface, the dispersion stability in the medium is good, and as a result, the metal oxide particles have a narrow particle size distribution.

  In general, particles having a small particle size tend to aggregate. However, in the present invention, secondary particles of metal oxide have good dispersion stability due to the effect of the polymer layer, resulting in monodisperse particles. Yes. The variation coefficient of the particle size of the monodisperse particles is ideally 0.0, and it can be said that the smaller the variation coefficient, the better the dispersibility. The coefficient of variation of the particle diameter of the metal oxide particles is preferably 0.25 or less, because the frequency with which coarse agglomerated particles are mixed into the particles in the abrasive is reduced and polishing scratches are less likely to occur. 20 or less is more preferable, and 0.15 or less is more preferable. The variation coefficient can be obtained as a value obtained by dividing the standard deviation in the particle size distribution by the average particle size.

  Next, a method for obtaining metal oxide particles (metal oxide particles after firing) will be described. The metal oxide particles are obtained by a firing step of firing the metal oxide obtained as described above.

  The primary particles of the metal oxide obtained by the liquid phase method as described above usually have a particle size of less than 5 nm and tend to have a low mechanical polishing ability. Furthermore, if the polymer layer formed on the surface of the secondary particles is too thick, the contact between the surface to be polished and the abrasive particles (metal oxide) is hindered, so that the polishing ability is further reduced. Accordingly, the present invention provides an excessive polymer layer formed on the surface of the secondary particle layer by growing the primary particles to a desired size by firing the metal oxide obtained by the liquid phase method. By removing this, the polishing ability is improved. Prior to firing, the metal oxide can be separated from the high-boiling organic solvent, the polymer compound, and the unreacted metal salt by an operation such as centrifugation. Further, after the separation, the metal oxide may be dried.

  The temperature in the firing step is preferably 200 ° C. or higher, more preferably 300 ° C. or higher, and even more preferably 400 ° C. or higher, from the viewpoint of growing primary particles and obtaining sufficient polishing ability. Further, the temperature is preferably 1,200 ° C. or less, more preferably 1,100 ° C. or less, more preferably 1,000, from the viewpoint of preventing excessive sintering between particles and suppressing the generation of abrasive scratches due to coarse particles. More preferably, it is not higher than ° C.

  The firing time is preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 5 hours or less from the viewpoint of preventing excessive sintering. The firing time is preferably 0.2 hours or more, more preferably 0.5 hours or more, and even more preferably 1 hour or more, from the viewpoint of growing crystals. Firing can be performed in air without controlling the atmosphere, or in an inert atmosphere. By firing, spherical secondary particles obtained by growing the primary particles of the metal oxide can be obtained.

  In order to suppress polishing scratches, it is desirable to maintain the monodispersity of the secondary particles of the metal oxide before firing, that is, the narrow particle size distribution, when firing the metal oxide. Although there is no restriction | limiting in particular as a method of suppressing the sintering between particle | grains, For example, considering that the frequency of sintering rises, so that it calcinates at high temperature, a sintering temperature is set.

  Moreover, in order to suppress sintering, it is preferable to bake in inert atmosphere, for example, presence of nitrogen, helium, neon, argon, krypton, xenon, etc. By firing in an inert atmosphere, it is possible to carbonize the polymer layer on the surface of the secondary particles of the metal oxide before firing and to suppress sintering between particles.

  Further, as a method for suppressing the sintering between the particles, the metal oxide may be dispersed in the vehicle and then fired. In the vehicle, secondary particles of metal oxide are present apart from each other, so that sintering during firing can be suppressed. A mixture of an organic solvent and a resin can be used for the vehicle, terpineol, terpineol, butyl carbitol, etc. are used as the organic solvent, and cellulose resins such as ethyl cellulose, acrylic resins, etc. are used as the resin. Can do. As a specific example, 10% by weight of ethyl cellulose dissolved in terpineol can be mentioned. The concentration of the metal oxide in the vehicle is preferably 70% by weight or less, more preferably 50% by weight or less, and still more preferably 30% by weight or less, from the viewpoint of preventing sintering between particles with respect to the weight of the vehicle. It is. Further, the concentration of the metal oxide in the vehicle is not particularly limited, but can be, for example, 5% by weight or more from the viewpoint of economy.

  After firing, the carbonized layer formed when the polymer layer is fired in an inert atmosphere may be removed. By removing the carbonized layer, the surface to be polished and the abrasive particles (metal oxide particles) come into contact with each other, and the polishing ability is considered to be improved. In order to remove the carbonized layer, for example, the metal oxide particles may be fired again in the presence of oxygen, specifically in air. The firing temperature is set to a temperature that prevents excessive increase of particles due to sintering. The firing temperature is preferably 700 ° C. or less, more preferably 600 ° C. or less, and even more preferably 500 ° C. or less from the viewpoint of avoiding sintering between particles. Further, the sintering temperature is preferably 200 ° C. or higher, more preferably 250 ° C. or higher, and further preferably 300 ° C. or higher from the viewpoint of obtaining the effect of removing the carbonized layer.

  By firing the metal oxide in this way, it is possible to grow primary particles while suppressing the generation of coarse particles. As a result, the mechanical polishing ability is improved and the polishing scratches are reduced. Can be achieved.

  The average primary particle diameter of the metal oxide particles (metal oxide particles after firing) is preferably 5 nm or more, more preferably 10 nm or more, and further preferably 20 nm or more from the viewpoint that a desired polishing rate can be obtained. preferable. In addition, the average primary particle size is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less, from the viewpoint of suppressing the generation of polishing flaws. The average particle size of the primary particle size of the metal oxide particles is a value determined by Rietveld analysis after measurement by XRD precision measurement (for example, RINT manufactured by Rigaku Corporation).

  Further, the average particle diameter of the metal oxide particles (metal oxide particles after firing) dispersed in the medium is preferably 10 nm or more, more preferably 20 nm or more, and 40 nm or more from the viewpoint of obtaining a desired polishing rate. Is more preferable. Further, the average particle diameter of the metal oxide particles is preferably 300 nm or less, more preferably 250 nm or less, and further preferably 200 nm or less from the viewpoint of suppressing the generation of polishing flaws. The average particle diameter of the metal oxide particles can be determined by measurement using a photon correlation method (for example, Zetasizer HS3000 manufactured by Malvern).

  D95 of the metal oxide particles (metal oxide particles after firing) dispersed in the medium is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less from the viewpoint of suppressing the occurrence of polishing flaws. . Further, D95 of the metal oxide particles is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 40 nm or more from the viewpoint of obtaining a desired polishing rate. D95 is a particle size distribution of metal oxide particles obtained by wet measurement using a laser diffraction method (for example, LA-950 manufactured by Horiba, Ltd.). In the obtained volume-based particle size distribution, metal oxide particles The particle size when the integrated value of 95% is 95%.

  In the present invention, the abrasive contains metal oxide particles (abrasive) and a medium, and the metal oxide particles are dispersed in the medium. The metal oxide particles are dispersed in a medium using a dispersant to prepare a slurry, and the slurry can be used as an abrasive as it is. Alternatively, the slurry is diluted with the medium or an additive is added. Can also be used. In addition, even if the slurry containing the metal oxide particles, the dispersant and the medium is diluted or an additive is added, the metal oxide particles dispersed in the medium are within the concentration range described below. The particle size distribution of the metal oxide particles does not vary, and the metal oxide particles exhibit the same average particle size, D95, before and after dilution / addition.

  As a medium for dispersing the fired metal oxide particles, an organic solvent selected from the following group in addition to water is suitable. Methanol, ethanol, 1-propanol, 2-propanol, 2-propyn-1-ol, allyl alcohol, ethylene cyanohydrin, 1-butanol, 2-butanol, (S)-(+)-2-butanol, 2-methyl- 1-propanol, t-butyl alcohol, perfluoro-t-butyl alcohol, t-pentyl alcohol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, glycerin, 2-ethyl-2- (hydroxymethyl) -1, Alcohols such as 3-propanediol and 1,2,6-hexanetriol; dioxane, trioxa , Tetrahydrofuran, diethylene glycol diethyl ether, 2-methoxyethanol, 2-ethoxyethanol, 2,2- (dimethoxy) ethanol, 2-isopropoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2 -Propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, tetraethylene glycol, dipropylene glycol, dipropylene Glycol monomethyl ether, dipropylene glycol monoe Ethers such as ether, tripropylene glycol monomethyl ether, polyethylene glycol, diacetone alcohol, 2-methoxyethyl acetate, 2-ethoxyethyl acetate and diethylene glycol monoethyl ether acetate; ketones such as acetone, methyl ethyl ketone, acetylacetone and cyclohexanone Among these, water, methanol, ethanol, 2-propanol, tetrahydrofuran, ethylene glycol, acetone, and methyl ethyl ketone are more preferable, and water is particularly preferable in that a high polishing rate can be obtained. As a method for dispersing the metal oxide particles obtained by firing in water, a homogenizer, an ultrasonic disperser, a ball mill, or the like can be used in addition to the dispersion treatment with a normal stirrer.

  The concentration of the metal oxide particles is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, from the viewpoint that a desired polishing rate can be obtained. More preferably 5 parts by weight or more. The concentration of the metal oxide particles is preferably 5 parts by weight or less, more preferably 2 parts by weight or less, and further preferably 1.5 parts by weight or less from the viewpoint of preventing aggregation of the metal oxide particles.

  Examples of the dispersant include a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, a water-soluble amphoteric dispersant, and the (co) polymerization component as an ammonium acrylate salt. A polymer dispersant containing is preferred. For example, polyacrylic acid ammonium, a copolymer of acrylic acid amide and ammonium acrylate, etc. are mentioned.

  In addition, at least one polymer dispersant containing an ammonium acrylate salt as a (co) polymerization component, a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, a water-soluble Two or more kinds of dispersants including at least one kind selected from amphoteric dispersants may be used in combination. Since it uses for grinding | polishing which concerns on manufacture of a semiconductor element, it is preferable to suppress the content rate of alkali metals, such as a sodium ion and a potassium ion, a halogen, and sulfur in a dispersing agent to 10 ppm or less. Examples of the water-soluble anionic dispersant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and a special polycarboxylic acid type polymer dispersant. Examples of the water-soluble nonionic dispersant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, Polyoxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, Polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polytetraoleate Xylethylene sorbite, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl methacrylate, alkyl alkanolamide Etc. Examples of the water-soluble cationic dispersant include polyvinyl pyrrolidone, coconut amine acetate, stearyl amine acetate and the like, and examples of the water-soluble amphoteric dispersant include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2 -Alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine and the like.

  The amount of the dispersant added is 0.1% with respect to 100 parts by weight of the metal oxide particles in terms of the dispersibility of the metal oxide particles in the abrasive and the prevention of settling, and the relationship between the polishing scratches and the amount of the dispersant added. 01 parts by weight or more is preferable, and 10 parts by weight or less is preferable with respect to 100 parts by weight of the metal oxide particles.

  The weight average molecular weight of the dispersant is preferably 100 or more, more preferably 1,000 or more, from the viewpoint of obtaining sufficient dispersion stability. Further, the molecular weight of the dispersant is preferably 50,000 or less, more preferably 10,000 or less, from the viewpoint of preventing the storage stability of the abrasive from being lowered due to an increase in viscosity. The weight average molecular weight is a standard polystyrene equivalent weight average molecular weight determined by gel permeation chromatography (GPC).

  In addition, the abrasive comprises vinyl alcohol, vinyl acetate, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, acrylonitrile, maleic acid, itaconic acid, vinyl pyrrolidone, vinyl caprolactam, acrylamide and methacrylamide as additives. A water-soluble polymer obtained by (co) polymerizing at least one monomer selected from the group can be used. More preferably, an anionic water-soluble polymer obtained by polymerizing acrylic acid, methacrylic acid, maleic acid and itaconic acid is used. Moreover, you may use another anionic water-soluble polymer for an abrasive | polishing agent. Examples thereof include alginic acid, pectic acid, carboxymethyl cellulose, polyaspartic acid, polyglutamic acid, polymalic acid, poly (p-styrenecarboxylic acid), polyvinyl sulfate, and polyglyoxylic acid.

  The amount of the water-soluble polymer used as an additive is preferably 0.001 part by weight or more, more preferably 0.01 part by weight or more with respect to 100 parts by weight of the metal oxide particles from the viewpoint of obtaining high planarization characteristics. preferable. In addition, the amount of the water-soluble polymer added is preferably 10 parts by weight or less, more preferably 1 part by weight or less, from the viewpoint of preventing a decrease in fluidity due to an increase in the viscosity of the abrasive.

  Different materials or the same material may be used for the dispersant and the additive. When the same substance is used, the total addition amount is 0.01 parts by weight or more with respect to 100 parts by weight of the metal oxide particles, and 10 parts by weight or less with respect to 100 parts by weight of the metal oxide particles. It is preferable to become.

  The weight average molecular weight of the water-soluble polymer used as an additive is preferably 100 or more, more preferably 1,000 or more, from the viewpoint that high planarization characteristics can be obtained. Further, the weight average molecular weight of the water-soluble polymer is preferably 5,000,000 or less, more preferably 1,000,000 or less, from the viewpoint of preventing the stability of the abrasive from decreasing due to an increase in viscosity. . The weight average molecular weight is a standard polystyrene equivalent weight average molecular weight determined by gel permeation chromatography (GPC).

  In order to adjust the abrasive to a predetermined pH, these additives can be adjusted in advance with an alkaline solution, or a complete or partially neutralized salt can be used. Alkaline aqueous solutions such as an aqueous ammonia solution, an aqueous potassium hydroxide solution, and an aqueous sodium hydroxide solution can be used as the alkali species of the alkaline solution or neutralized salt. An aqueous ammonia solution is preferable.

  The pH of the abrasive is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, from the viewpoint of exhibiting a chemical action force and obtaining a desired polishing rate. From the same point, 9 or less is preferable, 8 or less is more preferable, and 7 or less is more preferable. The pH of the abrasive can be adjusted with the above alkaline solution, preferably an aqueous ammonia solution.

  Further, carboxylate, phosphate, borate, and amine salt can be used as the pH stabilizer of the abrasive. Two or more pH stabilizers are used in combination, and the pKa value of at least one component of the pH stabilizer is within 1.0 unit of the pH of the abrasive, that is, the pKa is (abrasive pH-1) Those in the range of ~ (abrasive pH + 1) are preferably used. For example, when adjusting the pH of the abrasive to 5 to 6, phosphoric acid, acetic acid, propionic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, citric acid, etc. and salts thereof And ethylenediamine, pyridine, 2-aminopyridine, 3-aminopyridine, xanthosine, toluidine, picolinic acid, histidine, piperazine, 1-methylpiperazine, 2-bis (2-hydroxyethyl) amino-2- (hydroxymethyl)- 1,3-propanediol, uric acid and the like and salts thereof are preferably used.

  The abrasive of the present invention can be used in a method for polishing a predetermined substrate. Specifically, by supplying an abrasive to a polishing pad on a polishing surface plate, polishing is performed by relatively moving a surface to be polished of a substrate, which is a semiconductor wafer on which an inorganic insulating film is formed, and the polishing pad. Can be used in the method.

  As a predetermined substrate, a silicon oxide film layer or a silicon oxide film layer on a semiconductor substrate (for example, a Si substrate) such as a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, or a semiconductor substrate at a stage where a circuit element is formed. In addition, a substrate on which an inorganic insulating film layer such as a silicon nitride film layer is formed can be used. In one example, the silicon oxide film layer formed on such a semiconductor substrate is polished with the polishing agent of the present invention, thereby eliminating irregularities on the surface of the silicon oxide film layer and providing a smooth surface over the entire surface of the semiconductor substrate. And In the case of shallow trench isolation, polishing is performed up to the lower silicon nitride film layer while eliminating the unevenness of the silicon oxide film layer, leaving only the silicon oxide film layer embedded in the element isolation portion. At this time, if the polishing rate ratio with the silicon nitride serving as a stopper is large, the polishing process margin becomes large. Here, when the water-soluble polymer is added as an additive, the additive is selectively adsorbed on the silicon nitride film layer in a neutral pH range, and more effectively functions as a stopper film, thereby facilitating process management. .

  In addition, in order to use for shallow trench isolation, it is desirable that there are few scratches during polishing. Here, the abrasive using the metal oxide particles of the present invention as an abrasive (abrasive grain) suppresses the generation of polishing flaws because the concentration of coarse particles is kept small, and the target secondary particles Since many particles having a diameter are contained, the polishing rate can be increased.

Examples of a method for manufacturing the inorganic insulating film layer include a constant pressure CVD method and a plasma CVD method. In one example, the silicon oxide film layer formation by the constant pressure CVD method uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. It can be obtained by performing this SiH ₄ —O ₂ -based oxidation reaction at a low temperature of about 400 ° C. or less. When doping phosphorus: P in order to achieve surface flattening by high-temperature reflow, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive gas. The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, capacitive coupling type and inductive coupling type. The reaction as a gas, SiH ₄ as an Si source, an oxygen source as _{N 2} O was used was _SiH 4 -N ₂ O-based gas and _{TEOS-O 2} based gas using tetraethoxysilane (TEOS) in an Si source (TEOS- Plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa. As described above, the silicon oxide film layer may be doped with an element such as phosphorus or boron. Similarly, the silicon nitride film layer formation by the low pressure CVD method uses dichlorosilane: SiH ₂ Cl ₂ as a Si source and ammonia: NH ₃ as a nitrogen source. It can be obtained by performing this SiH ₂ Cl ₂ —NH ₃ oxidation reaction at a high temperature of 900 ° C. Examples of the plasma CVD method include SiH ₄ —NH ₃ gas using SiH ₄ as a Si source and NH ₃ as a nitrogen source. The substrate temperature is preferably 300 to 400 ° C.

As a polishing apparatus, a general polishing apparatus having a holder for holding a semiconductor substrate and a surface plate to which a polishing cloth (pad) is attached (a motor or the like whose rotation speed can be changed) is attached. 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. Further, it is preferable that the polishing cloth is subjected to groove processing so that an abrasive is collected. The polishing conditions are not limited, but the rotation speed of the surface plate and / or the semiconductor substrate is preferably a low rotation of 100 rpm or less so that the semiconductor does not jump out. The pressure applied to the polishing cloth of the semiconductor substrate having the film to be polished is preferably 10 to 100 kPa (100 to 1000 gf / cm ² ), and in order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern. Is more preferably ^{20 to} 50 kPa (200 to 500 gf / cm ² ). During polishing, the polishing agent is preferably continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, It is preferable that the surface of polishing cloth is always covered with the abrasive | polishing agent.

  It should be noted that the polishing agent of the present invention can be used for finish polishing by utilizing the feature that the surface of the film to be polished can be polished without scratches. That is, the first stage polishing is performed using a normal silica abrasive, cerium oxide abrasive, etc., and then the final polishing is performed using the abrasive of the present invention, for example, when performing shallow trench isolation. Polishing can be performed at high speed while suppressing the generation of scratches.

  The semiconductor substrate after the polishing is preferably washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. Thus, after forming shallow trench isolation on the semiconductor substrate, the silicon oxide film layer and the aluminum wiring are formed thereon, and the silicon oxide film layer formed thereon is planarized. A second-layer aluminum wiring is formed on the planarized silicon oxide film layer, and a silicon oxide film layer is formed again between the wirings and on the wiring by the above method, and then polished using the above-described polishing agent. As a result, unevenness on the surface of the insulating film layer is eliminated, and a smooth surface is obtained over the entire surface of the semiconductor substrate. By repeating this process a predetermined number of times, a desired number of semiconductor layers are manufactured.

  The abrasive of the present invention includes not only a silicon oxide film and a silicon nitride film formed on a semiconductor substrate, but also an inorganic insulating film such as a silicon oxide film, a glass, and a silicon nitride film formed on a wiring board having a predetermined wiring, Optical glass such as optical masks such as photomasks, lenses, and prisms, inorganic conductive films such as ITO, glass and crystalline materials, optical integrated circuits, optical switching elements, optical waveguides, end faces of optical fibers, scintillators, etc. It is used for polishing crystals, solid laser single crystals, blue laser or LED sapphire substrates, semiconductor single crystals such as SiC, GaP, and GaAS, glass substrates for magnetic disks, magnetic heads, and the like.

  In order to reduce polishing scratches caused by particles, it is desirable to reduce coarse particles contained in the abrasive. On the other hand, in order to obtain a desired polishing rate, it is desirable to use particles having appropriate primary particle size and secondary particle size. Embodiments of the present invention prepare a metal oxide having a small primary particle size, and then perform a baking treatment to suppress the generation of coarse particles, while maintaining a suitable primary particle size and secondary particle size. By obtaining product particles and using them as abrasives, it is possible to suppress the occurrence of polishing scratches on the surface to be polished and to polish at high speed.

  Hereinafter, embodiments of the present invention will be described in more detail by way of examples. The present invention is not limited to these examples.

[Example 1]
(Production of cerium oxide particles)
(Synthesis of cerium oxide particles)
For 30 mL of ethylene glycol, 7.8 g (0.6 mol / L) of cerium nitrate hexahydrate (manufactured by High Purity Chemical), 3.6 g of polyvinylpyrrolidone (PVP) having a weight average molecular weight of 4,400 in terms of PEG conversion by GPC (120 g / L) was added, and the mixture was heated to reflux at 165 ° C. for 90 minutes to obtain a suspension of cerium oxide particles.
The obtained suspension was centrifuged at 18,000 rpm for 30 minutes to separate ethylene glycol, PVP, unreacted cerium nitrate, and cerium oxide particles. A part of the cerium oxide particles was dried at 150 ° C. for 1 hour, and XRD precision measurement was performed using an X-ray diffractometer RINT manufactured by Rigaku Corporation. As measurement conditions, 2θ was 20 to 90 °, step width 0.05 °, time constant 5 seconds, current 20 mA, and voltage 40 kV. As a result of Rietveld analysis of the obtained data, the average particle size (crystallite size) of cerium oxide particles was 3 nm. The separated cerium oxide particles were washed with water and ethanol, washed with ethanol and then dried at 80 ° C. for 1 hour to obtain cerium oxide particles (FIG. 1). Part of the obtained cerium oxide particles was suspended in ion-exchanged water and dispersed with an ultrasonic homogenizer. Then, it filtered with the filter with a hole diameter of 1 micrometer. LA-950 manufactured by Horiba, Ltd. was used as a particle size distribution measuring apparatus by laser diffraction method, and the particle size distribution was measured with a refractive index of cerium oxide of 1.930 and a refractive index of water of 1.333. As a result, the average particle diameter of the cerium oxide particles was 89 nm, and the coefficient of variation, which is a value obtained by dividing the standard deviation by the average particle diameter, was 0.12. In addition, the above operation was repeated to obtain 100 g of cerium oxide particles.
(Calcination of cerium oxide particles)
In the firing furnace, 5 g of cerium oxide particles were fired. The atmosphere was not controlled, and was carried out in air at 1000 ° C. for 2 hours. As a result of measuring the primary particle diameter of the obtained cerium oxide particles by the same method as described above, it was 46 nm. Moreover, when SEM observation of the cerium oxide particle was performed, spherical secondary particles were confirmed, and a part of the secondary particles was sintered.

(Production of abrasive)
4 g of cerium oxide particles and 0.2 g of an ammonium polyacrylate aqueous solution (weight average molecular weight 10,000, 40 wt% aqueous solution) were mixed with 395 g of pure water. Then, ultrasonic dispersion was performed, and filtration was further performed with a 1 μm membrane filter to obtain an abrasive. A solid content obtained by sampling 5 g of the abrasive and drying at 150 ° C. for 1 hour was 0.6% by weight. When a sample obtained by diluting the abrasive 500 times with pure water was measured by a photon correlation method (dynamic light scattering method) using a Malvern Zetasizer HS3000 and the particle size of the cerium oxide particles was measured at 25 ° C. The diameter was 233 nm. Further, LA-950 manufactured by Horiba, Ltd. was used as a particle size distribution measuring apparatus by laser diffraction method, and the particle size distribution was measured with a refractive index of cerium oxide of 1.930 and a refractive index of water of 1.333. As a result, D95 was 645 nm. Further, the abrasive was sufficiently diluted with pure water, and the zeta potential was measured with a Zetasizer HS3000. The zeta potential was -53 mV.

(Polishing the insulating film layer)
The polishing characteristics of the obtained abrasive were evaluated using an 8-inch blanket wafer with a plasma TEOS (SiO ₂ ) film having a thickness of 1 μm. The wafer is set in a holder of a polishing apparatus (Mirra manufactured by Applied Materials) on which a suction pad for mounting a substrate is attached. On the other hand, a polishing pad IC-1000 made of Rodel's porous urethane resin is mounted on a φ480 mm polishing platen. (K groove) was pasted. The holder is placed on the pad with the insulating film face down, and the membrane, retainer ring, and inner tube pressure are 20.7 kPa (3 psi), 27.6 kPa (4 psi), and 20.7 kPa (3 psi) as processing loads, respectively. Set to. While dropping the above-mentioned abrasive on the surface plate at a rate of 50 mL / min, the surface plate and the wafer were operated at 98 rpm and 78 rpm, respectively, and the wafer with the plasma TEOS film was polished for 60 seconds. The polished wafer was thoroughly washed with pure water and then dried. Thereafter, the remaining film thickness of the insulating film was measured using an optical interference film thickness apparatus (Nanospec AFT-5100 manufactured by Nanometrics). The polishing rate was determined by dividing the amount of change in the remaining film thickness by the polishing time. As a result, the polishing rate was 260 nm / min. Further, the number of defects on the polished 8-inch blanket wafer with plasma TEOS (SiO ₂ ) film was measured. For the measurement, a defect observation apparatus ComPLUS manufactured by AMAT was used. The number of defects after cleaning the polished wafer with 0.1% hydrofluoric acid for 60 seconds was defined as the number of polishing flaws. As a result, it was 90 (relative value). The results are shown in Table 1.

[Example 2]
(Calcination of cerium oxide particles)
Cerium oxide particles were synthesized in the same manner as in Example 1 except that the firing temperature was 800 ° C. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
An abrasive was prepared in the same manner as in Example 1. The particle diameter, D95, and zeta potential of the cerium oxide particles were measured in the same manner as in Example 1.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were evaluated. The results of Example 2 are shown in Table 1.

[Example 3]
(Calcination of cerium oxide particles)
Cerium oxide particles were synthesized in the same manner as in Example 1 except that the firing temperature was 600 ° C. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
An abrasive was prepared in the same manner as in Example 1. The particle diameter, D95, and zeta potential of the cerium oxide particles were measured in the same manner as in Example 1.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were evaluated. The results of Example 3 are shown in Table 1.

[Example 4]
(Calcination of cerium oxide particles)
Cerium oxide particles were synthesized in the same manner as in Example 1 except that the firing temperature was 400 ° C. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
An abrasive was prepared in the same manner as in Example 1 except that no dispersant was added. The particle diameter, D95, and zeta potential of the cerium oxide particles were measured in the same manner as in Example 1.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were evaluated. The results of Example 4 are shown in Table 1.

[Comparative Example 1]
(Production of abrasive)
2 g of cerium oxide particles (particles before firing) synthesized in Example 1 were mixed with 198 g of pure water and subjected to ultrasonic dispersion to obtain an abrasive. The particle diameter, D95, and zeta potential of the cerium oxide particles were measured in the same manner as in Example 1.
(Polishing the insulating film layer)
The polishing rate for the plasma TEOS film was evaluated in the same manner as in Example 1. As a result, the polishing rate was 0 nm / min, and polishing did not proceed at all. The results of Comparative Example 1 are shown in Table 1.

[Comparative Example 2]
(Preparation of cerium oxide particles and abrasive)
By putting 40 g of cerium carbonate hydrate in an alumina container and firing in air at 800 ° C. for 2 hours, 20 g of yellowish white powder of cerium oxide was obtained. The fired powder particle size was 30 to 100 μm. Next, 20 kg of the sintered powder of cerium oxide was dry pulverized using a jet mill. 20 g of cerium oxide particles obtained by pulverization and 79.75 g of deionized water are mixed, and 0.25 g of a commercially available aqueous solution of ammonium polyacrylate (weight average molecular weight 8000, weight 40%) is added as a dispersant and stirred. Ultrasonic dispersion was performed. The ultrasonic frequency was 400 kHz and the dispersion time was 20 minutes. Then, it filtered with the filter with a hole diameter of 1 micrometer. Subsequently, the obtained cerium oxide dispersion (cerium oxide slurry) was diluted with deionized water so that the solid content concentration became 5% by weight. As a result of measuring the average particle size by the same method as in Example 1, it was 240 nm. A part of the cerium oxide dispersion was dried, and the primary particle size (crystallite size) was measured in the same manner as in Example 1. As a result, it was 90 nm. Prior to polishing, 160 g of pure water was added to 40 g of the cerium oxide dispersion to obtain an abrasive.
(Polishing the insulating film layer)
The polishing rate and polishing scratches on the plasma TEOS film were evaluated in the same manner as in Example 1. As a result, the polishing rate was 380 nm / min. The number of defects in Comparative Example 2 was set to 100 (relative value). The results of Comparative Example 2 are shown in Table 1.

Table 1 shows the results of Examples 1 to 4 and Comparative Examples 1 and 2.
As shown in Comparative Example 1, polishing with the unsintered cerium oxide particles hardly progressed. As shown in Comparative Example 2, the cerium oxide particles prepared through the firing step had a crystallite size as large as 90 nm and exhibited a high polishing rate.
Each of the polishing agents of Examples 1 to 4 had a higher polishing rate than the polishing agent of Comparative Example 1, and had fewer polishing flaws than the polishing agent of Comparative Example 2. As shown in Examples 1 to 3, the cerium oxide particles that were fired after being synthesized by the liquid phase method increased the crystallite size and the polishing rate as the firing temperature increased. In Example 4, a high polishing rate was exhibited even when firing at a relatively low temperature of 400 ° C. This is because an anionic dispersant was not used, and as a result, the zeta potential in the polishing agent showed a positive value, and electrostatic attraction was generated between the negatively charged SiO ₂ film as the surface to be polished. It was considered that the material was polished at high speed. When an attractive force acts between the abrasive particles and the surface to be polished, there is a tendency that it is difficult to remove the particles by washing after polishing. can do.

[Example 5]
(Calcination of cerium oxide particles)
In the firing furnace, the cerium oxide particles synthesized by the liquid phase method in Example 1 were fired. The atmosphere was not controlled and was carried out in air at 800 ° C. for 2 hours. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
10 g of cerium oxide particles and 0.5 g of an aqueous solution of ammonium polyacrylate (weight average molecular weight 10,000, 40 wt% aqueous solution) were mixed with 190 g of pure water. Thereafter, ultrasonic dispersion was performed, and filtration was further performed with a 1 μm membrane filter to obtain a cerium oxide dispersion (cerium oxide slurry). A solid content obtained by sampling 5 g of cerium oxide dispersion and drying at 150 ° C. for 1 hour was 1.25 wt%. A sample obtained by diluting a cerium oxide dispersion 500 times with pure water was measured using a Zetasizer HS3000 manufactured by Malvern at 25 ° C. in the same manner as in Example 1, and the average particle diameter was measured. Was 190 nm. Further, the particle size distribution was measured by the same method as in Example 1 using LA-950 manufactured by Horiba, Ltd. as a particle size distribution measuring apparatus by laser diffraction method. As a result, D95 was 610 nm. Prior to polishing, 13.3 g of a polycarboxylic acid aqueous solution (solid content concentration: 3% by weight) and 26.7 g of pure water were added to 160 g of the cerium oxide dispersion, and the pH was further adjusted with aqueous ammonia (25% by weight of ammonia). Was adjusted to 5.0 to obtain an abrasive.
(Polishing the insulating film layer)
When the insulating film was polished in the same manner as in Example 1, the polishing rate was 243 nm / min and the polishing scratches were 89 (relative value). The results of Example 5 are shown in Table 2.

[Example 6]
(Calcination of cerium oxide particles)
In the firing furnace, the cerium oxide particles synthesized by the liquid phase method in Example 1 were fired. Prior to firing, a vehicle in which 10 g of ethylcellulose was dissolved in 90 g of terpineol was prepared, and a dispersion in which 25 g of cerium oxide particles were dispersed in the vehicle was fired (FIG. 2). The atmosphere was not controlled and was carried out in air at 800 ° C. for 2 hours. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
A cerium oxide dispersion was prepared in the same manner as in Example 5. The solid content concentration of the cerium oxide dispersion was 2.00% by weight. In the same manner as in Example 5, the particle size and D95 were measured. Prior to polishing, 13.3 g of a polycarboxylic acid aqueous solution (solid content concentration 3% by weight) and 86.7 g of pure water are added to 100 g of the cerium oxide dispersion, and pH is further adjusted with aqueous ammonia (25% by weight of ammonia). Was adjusted to 5.0 to obtain an abrasive.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were measured. The results of Example 6 are shown in Table 2.

[Example 7]
(Calcination of cerium oxide particles)
The cerium oxide particles were fired in the same manner as in Example 6 except that the firing temperature was 850 ° C. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
A cerium oxide dispersion was prepared in the same manner as in Example 5. The solid content concentration of the cerium oxide dispersion was 2.80% by weight. In the same manner as in Example 5, the particle size and D95 were measured. Prior to polishing, 13.3 g of a polycarboxylic acid aqueous solution (solid content concentration 3% by weight) and 115.2 g of pure water were added as additives to 71.4 g of the cerium oxide dispersion, and ammonia water (25% by weight of ammonia) was further added. The pH was adjusted to 5.0 to obtain an abrasive.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were measured. The results of Example 7 are shown in Table 2.

[Example 8]
(Calcination of cerium oxide particles)
The cerium oxide particles were fired in the same manner as in Example 6 except that the firing temperature was 900 ° C. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
A cerium oxide dispersion was prepared in the same manner as in Example 5. The solid content concentration of the cerium oxide dispersion was 1.60% by weight. In the same manner as in Example 5, the particle size and D95 were measured. Prior to polishing, 13.3 g of a polycarboxylic acid aqueous solution (solid content concentration 3% by weight) and 61.7 g of pure water were added as additives to 125.0 g of the cerium oxide dispersion, and ammonia water (25% by weight of ammonia) was further added. The pH was adjusted to 5.0 to obtain an abrasive.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were measured. The results of Example 8 are shown in Table 2.

[Example 9]
(Calcination of cerium oxide particles)
In the firing furnace, the cerium oxide particles synthesized by the liquid phase method in Example 1 were fired. The atmosphere was an argon atmosphere, and the process was performed at 800 ° C. for 2 hours. Thereafter, the atmosphere was not controlled, and firing was performed in air at 500 ° C. for 2 hours to remove the carbonized layer on the surface of the cerium oxide particles. The primary particle diameter (crystallite size) of the cerium oxide particles was measured by the same method as in Example 1, and the cerium oxide particles were observed by SEM.
(Production of abrasive)
A cerium oxide dispersion was prepared in the same manner as in Example 5. The solid content concentration of the cerium oxide dispersion was 2.60% by weight. In the same manner as in Example 5, the particle size and D95 were measured. Prior to polishing, 13.3 g of a polycarboxylic acid aqueous solution (solid concentration 3% by weight) and 109.7 g of pure water were added as additives to 76.9 g of cerium oxide dispersion, and ammonia water (25% by weight of ammonia) was further added. The pH was adjusted to 5.0 to obtain an abrasive.
(Polishing the insulating film layer)
The insulating film was polished by the same method as in Example 1, and the polishing rate and polishing scratches were measured. The results of Example 9 are shown in Table 2.

[Comparative Example 3]
(Production of abrasive)
40 g of the cerium oxide dispersion prepared in Comparative Example 2 (solid content concentration 5% by weight), 13.3 g of a polycarboxylic acid aqueous solution (solid content concentration 3% by weight) as additives, and 146.7 g of pure water were mixed, and ammonia was further mixed. The pH was adjusted to 5.0 with water (25% by weight of ammonia) to obtain an abrasive.
(Polishing the insulating film layer)
The polishing rate and polishing scratches on the plasma TEOS film were evaluated in the same manner as in Example 1. As a result, the polishing rate was 270 nm / min. The number of defects in Comparative Example 3 was 100 (relative value). The results of Comparative Example 3 are shown in Table 2.

Table 2 shows the results of Examples 5 to 9 and Comparative Example 3.
In each of Examples 5 to 9, the polishing rate was high, and there were fewer polishing scratches than Comparative Example 3. In Example 5, since the cerium oxide particles were fired in the air, partial sintering occurred between the particles, and both the average particle diameter and D95 increased. On the other hand, as shown in Examples 6, 7 and 9, both the average particle size and D95 were small when the firing treatment was performed in the vehicle or in an argon atmosphere. That is, coarse particles were reduced by suppressing sintering between particles, and as a result, the number of polishing flaws was also reduced. In addition, since the primary particles grew while maintaining the narrow particle size distribution of the synthesized cerium oxide particles, the particles contained a large number of particles having a particle size suitable for polishing, and showed a polishing rate equivalent to that of Comparative Example 3. In addition, polishing scratches could be reduced. Furthermore, in Example 8, the firing temperature was increased to 900 ° C. However, since the firing treatment was performed in the vehicle, D95 could be suppressed to an increase of about 181 nm. In Example 8, although the polishing rate was higher than that in Comparative Example 3, polishing flaws could be reduced.

Claims (19)

A polishing agent containing metal oxide particles and a medium, wherein the metal oxide particles are produced by heating a mixture containing a metal salt, a polymer compound, and a high-boiling organic solvent. A polishing agent comprising metal oxide particles obtained as described above. The abrasive | polishing agent of Claim 1 whose coefficient of variation of the particle size of the particle | grains of the metal oxide produced | generated by heating a mixture is 0.25 or less. The abrasive | polishing agent of Claim 1 or 2 whose high boiling point organic solvent is ethylene glycol or diethylene glycol. The abrasive | polishing agent in any one of Claims 1-3 whose metal salt is nitrate or acetate. The abrasive | polishing agent in any one of Claims 1-4 whose metal salt is a cerium nitrate or a cerium acetate. The abrasive | polishing agent in any one of Claims 1-5 whose density | concentration of a metal salt is 0.05 mol / L or more. The abrasive | polishing agent in any one of Claims 1-6 whose high molecular compound is polyvinylpyrrolidone or a hydroxypropyl cellulose. The abrasive | polishing agent in any one of Claims 1-7 whose density | concentration of a high molecular compound is 30-150 g / L. The abrasive | polishing agent in any one of Claims 1-8 whose weight average molecular weights of a high molecular compound are 2,000-1,000,000. The abrasive | polishing agent in any one of Claims 1-9 whose average particle diameter of the particle | grains of the metal oxide produced | generated by heating a mixture is 10-300 nm. The abrasive | polishing agent in any one of Claims 1-10 whose baking temperature is 200-1,200 degreeC. The abrasive | polishing agent in any one of Claims 1-11 whose baking atmosphere is nitrogen, helium, neon, argon, krypton, or xenon. The abrasive | polishing agent in any one of Claims 1-12 which disperse | distributes the metal oxide produced | generated by heating a mixture in a vehicle, and bakes it. The abrasive | polishing agent in any one of Claims 1-13 whose average particle diameter of the primary particle of the metal oxide particle obtained by baking is 5-200 nm. The abrasive | polishing agent in any one of Claims 1-14 whose average particle diameter of the metal oxide particle obtained by baking disperse | distributed to the medium is 10-300 nm. The abrasive | polishing agent in any one of Claims 1-15 whose pH is 3-9. The abrasive | polishing agent in any one of Claims 1-16 whose medium is water. A method of polishing a substrate, comprising polishing a predetermined substrate with the abrasive according to claim 1. By supplying the polishing agent according to any one of claims 1 to 17 to a polishing pad on a polishing surface plate, the surface to be polished of the semiconductor substrate on which the inorganic insulating film layer is formed and the polishing pad are relatively moved. A method for polishing a substrate, comprising polishing.