JP2009260236A - Abrasive powder, polishing method of substrate employing the same as well as solution and slurry employed for the polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive powder, capable of achieving both of reduction of polishing scratch and prominent polishing speed with sufficient high level in CMP (chemical mechanical polishing) technology for polishing a film formed on a substrate, and to provide a substrate polishing method employing the abrasive powder as well as a solution and slurry employed for the polishing method. <P>SOLUTION: The abrasive powder contains water, cerium oxide grain and additive, and the additive contains compound shown by a general formula (I) or a polymer having the compound as a monomeric unit. In this case, R<SP>1</SP>-R<SP>5</SP>in the general formula (I) show respectively and independently monovalent organic group or hydrogen atom which may have substituent while X<SP>1</SP>and X<SP>2</SP>show respectively and independently divalent organic group which may have substituent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abrasive, and more specifically, used in a step of flattening a substrate surface in a manufacturing process of a semiconductor element, particularly in a step of flattening a shallow trench isolation insulating film, a premetal insulating film, an interlayer insulating film, and the like. Related to the abrasive. The present invention also relates to a method for polishing a substrate using an abrasive, and a solution and slurry used therefor.

  In recent years, in the field of semiconductor element manufacturing processes, the importance of processing techniques for increasing the density and miniaturization of semiconductor elements has increased. One of them is CMP (Chemical Mechanical Polishing) technology for planarizing the surface of a semiconductor substrate, for example, forming shallow trench isolation, planarizing a premetal insulating film or an interlayer insulating film, and plugging. In addition, it is an indispensable technique for forming buried metal wiring.

  As an abrasive | polishing agent used in CMP technique, the fumed silica type thing is known, for example. The fumed silica-based abrasive is produced by grain growth by a method such as thermal decomposition of tetrachlorosilicate and adjusting the pH of the slurry in which the obtained particles are blended. Fumed silica abrasives are conventionally used for planarization of insulating films (for example, silicon oxide films) formed by methods such as CVD (Chemical Vapor Deposition) and spin coating. Has been.

  However, since the silica-based abrasive has a technical problem that the polishing rate is low, the use of a cerium oxide-based abrasive that can obtain a higher polishing rate than this is being studied. The cerium oxide-based abrasive is conventionally used for polishing glass surfaces such as photomasks and lenses. The following Patent Document 1 describes a technique for applying a cerium oxide-based abrasive to a semiconductor element manufacturing process. Patent Document 2 listed below describes a cerium oxide-based abrasive containing a predetermined organic compound having a hydrophilic group.

Japanese Patent Laid-Open No. 10-106994 Japanese Patent Application Laid-Open No. 08-022970

  By the way, with further progress of miniaturization of semiconductor elements, reduction of polishing scratches generated when polishing a substrate has been demanded. It is conceivable to cope with such a demand by using an abrasive containing abrasive grains having a small average particle diameter. However, when abrasive grains having a small average particle diameter are used, there is a problem that a sufficient polishing rate cannot be achieved and workability is lowered.

  The present invention has been made in view of the above circumstances, and in CMP technology for polishing a film to be polished formed on the surface of a substrate, polishing capable of achieving both a reduction in polishing scratches and a high polishing rate to a sufficiently high level. The purpose is to provide an agent. Another object of the present invention is to provide a method for polishing a substrate using the above-mentioned abrasive, and a solution and a slurry used in this polishing method.

一般式（Ｉ）中、Ｒ^１〜Ｒ^５は、それぞれ独立に、置換基を有していてもよい１価の有機基又は水素原子を示し、Ｘ^１及びＸ^２は、それぞれ独立に、置換基を有していてもよい２価の有機基を示す。 The present invention is an abrasive comprising water, cerium oxide particles and an additive, the additive comprising a compound represented by the following general formula (I) or a polymer having the compound as a monomer unit: Provide the agent.

In general formula (I), R ^{1 to} R ⁵ each independently represents a monovalent organic group or a hydrogen atom which may have a substituent, and X ¹ and X ² are each independently substituted. The divalent organic group which may have a group is shown.

  The compound represented by the general formula (I) or the polymer having this as a monomer unit has a betaine structure. A betaine structure is a compound that has positive and negative charges at non-adjacent positions in the same molecule, and no positively charged atoms are bonded to dissociable hydrogen atoms, and the molecule as a whole has no charge. Refers to the structure. Such a compound may have a cationic structure such as quaternary ammonium, sulfonium, phosphonium and the like.

  According to the abrasive of the present invention, the amide group and the carboxyl group of the compound represented by the general formula (I) or a polymer having this as a monomer unit (hereinafter referred to as “betaine structure compound”) are cerium oxide. It acts on the particles and / or the surface to be polished, and the polishing rate is improved as compared with conventional abrasives. Also, ionic quaternary ammonium and carboxyl groups provide improved dispersibility of cerium oxide particles in water. By improving the dispersibility of the cerium oxide particles, aggregation of the particles can be suppressed, and polishing scratches caused by secondary particles having a large particle size can be sufficiently reduced. In addition to this, it is possible to suppress the cerium oxide particles from adhering to the inside of the plastic container or the pipe.

  The abrasive of the present invention is suitable as an abrasive used in chemical mechanical polishing (CMP) technology. The “abrasive” as used in the present invention means a composition used for contacting and polishing a film to be polished formed on a substrate or the like.

  The abrasive of the present invention preferably has a pH of 3.0 or more and 7.0 or less. When the pH of the abrasive is within the above range, the polishing rate and the storage stability can be further improved. Further, from the viewpoint of high polishing rate and reduction of polishing scratches, the average particle diameter of the cerium oxide particles is preferably 1 nm or more and 400 nm or less.

  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 abrasive from the viewpoint of high polishing rate and reduction of polishing scratches.

  The content of the betaine structural compound is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the abrasive from the viewpoint of high polishing rate and reduction of polishing scratches.

  In the polishing agent of the present invention, the zeta potential of the cerium oxide particles is preferably +10 mV or more. When the zeta potential of the cerium oxide particles is +10 mV or more, the cerium oxide particles can be sufficiently dispersed in the liquid phase of the abrasive.

  The abrasive of the present invention preferably further contains at least one selected from carboxylic acids, amino acids and amphoteric surfactants. When the abrasive contains at least one of carboxylic acid and amino acid, the pH of the abrasive can be stabilized. Moreover, the grinding | polishing characteristic of an abrasive | polishing agent can be adjusted by mix | blending an amphoteric surfactant with an abrasive | polishing agent.

  The present invention is a method for polishing a substrate having a film to be polished formed on the surface, and while pressing the substrate against the polishing cloth so that the polishing cloth on the polishing platen and the film to be polished are in contact with each other, Provided is a substrate polishing method for polishing a film to be polished by relatively moving a substrate and a polishing surface plate while supplying the abrasive of the present invention between the film to be polished and a polishing cloth.

  Since the polishing method according to the present invention uses the above-described abrasive of the present invention to polish the film to be polished on the substrate, it is possible to achieve both a reduction in polishing scratches and an excellent polishing rate at a sufficiently high level.

  The present invention provides a solution used for the above polishing method and containing a betaine structure compound. The present invention also provides a slurry for use in the polishing method, the slurry containing a betaine structure compound. Hereinafter, these solutions or slurries are referred to as “additive-containing liquids”.

  In the polishing method of the present invention, a slurry containing cerium oxide particles (hereinafter referred to as “cerium oxide slurry”) may be used. By using a combination of the cerium oxide slurry and the additive-containing liquid, the polishing method according to the present invention can be suitably carried out. Moreover, there is an advantage that the polishing rate can be easily adjusted by adjusting the mixing ratio of the cerium oxide slurry and the additive-containing liquid.

  According to the present invention, in the CMP technique for polishing a film to be polished formed on the surface of a substrate, both reduction of polishing flaws and excellent polishing rate can be achieved at a sufficiently high level.

  Hereinafter, embodiments of the present invention will be described in detail. The abrasive | polishing agent which concerns on this embodiment contains the cerium oxide particle as an abrasive grain, an additive, and water. First, each component contained in the abrasive will be described.

(Cerium oxide particles)
There is no restriction | limiting in particular as a cerium oxide particle, Generally what can be obtained in a market can be used. For example, NanoTek (product name) manufactured by Nanophase Technologies, particles sold by Ferro Corporation, particles sold by Advanced Nano Products, particles sold by Rhodia, NanoPOP (product name) manufactured by Hitachi Maxell, etc. Can be mentioned.

  The cerium oxide particles preferably have an average particle size in the abrasive of 1 to 400 nm. The average particle diameter of the cerium oxide particles is more preferably 2 nm or more, and even more preferably 10 nm or more in that a good polishing rate can be easily obtained. Further, the average particle diameter of the cerium oxide particles is more preferably 300 nm or less, and even more preferably 250 nm or less, from the viewpoint of easily suppressing the occurrence of polishing flaws. As will be described later, when the abrasive is stored in two or more parts of a cerium oxide slurry containing cerium oxide particles and an additive-containing liquid, and these are mixed at the time of use, in the cerium oxide slurry The average particle size of the cerium oxide particles is preferably within the above range.

  Here, the average particle diameter of the cerium oxide particles in the abrasive (or in the cerium oxide slurry) means the value of D50 (median diameter of volume distribution, cumulative median value) measured with a laser diffraction particle size distribution meter. Specifically, about 100 μL of abrasive or cerium oxide slurry is collected and diluted with ion-exchanged water so that the particle content is about 0.005% by mass. The sample thus obtained is set in a laser diffraction particle size distribution meter (trade name: LA-920, manufactured by Horiba, Ltd.), and the value displayed as “D50” is read. In addition, when the average particle diameter of the sample having a particle content of around 0.005% by mass is measured by the laser diffraction particle size distribution analyzer (LA-920), the measured value of transmittance (H) by the distribution meter is 60 to 60. 70%.

  The content of the cerium oxide particles in the polishing liquid is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the total mass of the abrasive. When the content of the cerium oxide particles is less than 0.05 parts by mass, the polishing rate tends to be insufficient, and when the content exceeds 5 parts by mass, the cerium oxide particles tend to aggregate. The content of the cerium oxide particles is more preferably 0.1 to 2 parts by mass.

  The cerium oxide particles are preferably composed of two or more crystallites and have crystal grain boundaries. When such cerium oxide particles are used, the crystal grain boundary of the cerium oxide particles is broken by the stress during polishing, and polishing is performed while generating a new surface, so that high-speed polishing is possible. Such a technique is described in, for example, the republished patent WO99 / 31195. In addition, when the cerium oxide particles having a grain boundary and a compound represented by the general formula (I) described later or a polymer having the compound as a monomer unit are used in combination, the effect of the present invention is more sufficiently and surely achieved. To be played.

  The cerium oxide particles preferably have a crystallite diameter of 1 nm to 300 nm. The larger the crystallite diameter or the smaller the crystal distortion, that is, the better the crystallinity of the cerium oxide particles, the higher the speed of polishing, but the more easily the polishing scratches are generated.

  The amount of alkali metal and halogen contained in the cerium oxide particles is preferably 10 ppm or less based on the total mass of the cerium oxide particles. This is because cerium oxide particles containing a large amount of these components are not preferred for use in the process of manufacturing semiconductor devices.

  Cerium oxide is obtained by oxidizing a cerium compound of carbonate, nitrate, sulfate, or oxalate. Examples of the method for producing cerium oxide particles include firing or oxidation using hydrogen peroxide. When producing cerium oxide particles by firing, the firing temperature is preferably 350 to 900 ° C. Since the cerium oxide particles produced by the above method are usually in an aggregated state, it is preferable to mechanically pulverize the aggregate. As the pulverization method, dry pulverization using a jet mill or wet pulverization using a planetary bead mill is preferable. The description of the jet mill is described in “Chemical Industry Journal, Vol. 6 No. 5 (Japan Society for Chemical Engineering, pp. 527-532, 1980)”.

  Cerium oxide particles can also be prepared by a hydrothermal synthesis method. For example, a method of heating a precursor such as cerium hydroxide to 100 ° C. or higher in water can be mentioned.

(Additive)
The abrasive | polishing agent which concerns on this embodiment contains an additive. Here, the “additive” is a substance used for adjusting dispersibility, polishing characteristics, storage stability, etc. of the cerium oxide particles, and means components other than water and cerium oxide particles contained in the abrasive. .

一般式（Ｉ）中、Ｒ^１〜Ｒ^５は、それぞれ独立に、置換基を有していてもよい１価の有機基又は水素原子を示し、Ｘ^１及びＸ^２は、それぞれ独立に、置換基を有していてもよい２価の有機基を示す。 An abrasive | polishing agent contains the polymer (betaine structure compound) which has a compound represented by the following general formula (I) or the said compound as a monomer unit as an additive. The polishing rate can be improved by using such a compound as an additive.

In general formula (I), R ^{1 to} R ⁵ each independently represents a monovalent organic group or a hydrogen atom which may have a substituent, and X ¹ and X ² are each independently substituted. The divalent organic group which may have a group is shown.

In general formula (I), groups represented by R ^{1 to} R ⁵ are not particularly limited as long as they are chemically stable. Preferred examples include a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, Examples thereof include a phenyl group, a benzyl group, a chloro group, a difluoromethyl group, a trifluoromethyl group, and a cyano group. These groups may have a substituent. Among these, from the viewpoint of availability and solubility in water, a hydrogen atom or an alkyl group having 1 to 6 carbon atoms is more preferable, and a hydrogen or methyl group is more preferable.

In the general formula (I), the divalent organic groups represented by X ¹ and X ² are not particularly limited as long as they are chemically stable, but as a preferred example, an alkylene group having 1 to 6 carbon atoms. And a phenylene group. These groups may have a substituent. Among these, an alkylene group having 1 to 3 carbon atoms is more preferable from the viewpoint of availability and solubility in water.

  When using a polymer having a compound represented by the general formula (I) as a monomer unit, it may be a homopolymer obtained by polymerizing only the monomer represented by the general formula (I). A copolymer of the monomer represented by the general formula (I) and another monomer may be used. These polymers are obtained by a generally known polymerization technique (for example, radical polymerization of unsaturated compounds).

  The monomer used for copolymerization with the compound represented by formula (I) is preferably water-soluble. Preferred examples include vinyl alcohol, vinyl acetate, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, acrylonitrile, maleic acid, itaconic acid, vinylamine, vinylpyridine, allylamine, vinylpyrrolidone, vinylcaprolactam, vinyl methyl ether, Examples thereof include vinyl methyl oxazolidinone, vinyl formal, vinyl acetal, vinyl amine, vinyl isobutyl ether, acrylamide, and methacrylamide. These compounds may be used individually by 1 type, and may be used in combination of 2 or more types.

  The content of the betaine structure compound in the abrasive is preferably 0.01 parts by mass, more preferably 0.02 parts by mass with respect to 100 parts by mass of the total mass of the abrasive, 0 More preferably, it is 0.03 parts by mass. On the other hand, the upper limit of the content of the betaine structure compound is preferably 5 parts by mass, and more preferably 2 parts by mass. When the content of the betaine structure compound is less than 0.01 parts by mass, the polishing rate tends to be insufficient, and when it exceeds 5 parts by mass, the stability of the abrasive tends to be insufficient.

  The abrasive | polishing agent which concerns on this embodiment may further contain additives other than a betaine structure compound in order to adjust the dispersibility of a cerium oxide particle, polishing characteristics, and storage stability. For example, conventionally known additives can be appropriately used as long as the effects of the betaine structure compound are not impaired.

  Carboxylic acids and amino acids can be used to stabilize the pH, and amphoteric surfactants, anionic surfactants, nonionic surfactants, cationic surfactants, etc. can be used to adjust the polishing characteristics. Can be used. The total amount of these additives is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the total mass of the abrasive. If the total amount is less than 0.01 parts by mass, the effect of these additives tends to be insufficient, while if it exceeds 10 parts by mass, precipitates are likely to occur, making it difficult to disperse each component sufficiently uniformly. It is easy to become.

  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, glycine, Examples include alanine, β-alanine, methionine, cysteine, phenylalanine, leucine, valine, and isoleucine.

  The amphoteric surfactant is not particularly limited as long as it has solubility in water. For example, betaine, β-alanine betaine, lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxyl. And methyl-N-hydroxyethylimidazolinium betaine.

  The anionic surfactant is not particularly limited as long as it has solubility in water. For example, lauryl sulfate triethanolamine, lauryl ammonium sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, special polycarboxylic acid Type polymer dispersant and the like.

  The nonionic surfactant is not particularly limited as long as it has solubility in water. For example, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether , Polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivatives, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, poly Oxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene Vitan trioleate, polyoxyethylene sorbite tetraoleate, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2 -Hydroxyethyl methacrylate, alkyl alkanolamides and the like.

  The cationic surfactant is not particularly limited as long as it has solubility in water, and examples thereof include coconut amine acetate and stearyl amine acetate.

  Among the above surfactants, amphoteric surfactants are preferable from the viewpoint of improving dispersibility stability, and betaine and β-alanine betaine are more preferable.

  From the viewpoint of adjusting the polishing characteristics of the abrasive, a water-soluble polymer having a weight average molecular weight of 500 or more and less than 5 million may be added to the abrasive. If the weight average molecular weight of the water-soluble polymer is less than 500, the polishing characteristics cannot be sufficiently adjusted even if the water-soluble polymer is blended. It becomes expensive and difficult to handle. The weight average molecular weight of the water-soluble polymer is more preferably 1000 or more and less than 200,000.

  Specific examples of the water-soluble polymer include polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan, pullulan; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, polymaleic acid, polyitaconic acid, Polycarboxylic acids such as polyfumaric acid, poly (p-styrenecarboxylic acid), polyamic acid ammonium salt, polyamic acid sodium salt, polyglyoxylic acid and the like; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; polyethylene glycol Etc.

  It is preferable that content of the said water-soluble polymer of an abrasive | polishing agent is 0.01-5 mass parts with respect to 100 mass parts of total mass of an abrasive | polishing agent. If the content of the water-soluble polymer is less than 0.01 parts by mass, the effect of the water-soluble polymer tends to be insufficient, while if it exceeds 5 parts by mass, precipitates are likely to occur, and each component is sufficiently uniform. Difficult to disperse easily.

  According to the polishing agent of the present embodiment, it is possible to achieve both a reduction in polishing scratches and a high polishing rate at a sufficiently high level when polishing a semiconductor substrate by CMP technology. That is, the dispersibility of cerium oxide particles in water is improved by the ionic quaternary ammonium and carboxyl groups of the betaine structure compound contained in the additive. For this reason, aggregation of cerium oxide particles can be suppressed, and polishing scratches caused by secondary particles having a large particle diameter can be sufficiently reduced. In addition, the amide group and carboxyl group of the betaine structure compound act on the cerium oxide particles and / or the film to be polished, and a high polishing rate can be achieved.

(Abrasive preparation method)
The abrasive | polishing agent which concerns on this embodiment is obtained by stirring the liquid mixture of a cerium oxide particle, a betaine structure compound, and water, and disperse | distributing a cerium oxide particle in a liquid phase. If necessary, additives other than the betaine structure compound may be further added.

  As a method for dispersing the cerium oxide particles in the liquid phase, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the treatment with a normal stirrer. 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.

  The pH of the abrasive is preferably adjusted to a range of 3.0 or more and 7.0 or less from the viewpoint of storage stability of the abrasive and a high polishing rate. For pH adjustment, an acid component or an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH) can be used. In order to stabilize the pH, a buffer solution may be added to the abrasive. Examples of the buffer solution include an acetate buffer solution and a phthalate buffer solution.

  The pH of the abrasive can be measured using a pH meter (for example, Model pH81 manufactured by Yokogawa Electric Corporation). For example, after calibrating two pH meters using a phthalate pH buffer solution (pH 4.21) and a neutral phosphate pH buffer solution (pH 6.86) as standard buffers, the electrode of the pH meter is used as an abrasive. And measure the value after 2 minutes or more has stabilized. At this time, the temperature of the standard buffer solution and the abrasive is adjusted so as to be 25 ° C.

  In order to disperse cerium oxide particles (abrasive grains) sufficiently uniformly in the polishing liquid, the cerium oxide particles are preferably charged in the polishing agent. The zeta potential of the cerium oxide particles is preferably +10 mV or more, and more preferably in the range of +10 to +70 mV. For zeta potential measurement, for example, Zeta Sizer 3000HS (trade name) manufactured by Malvern can be used. In measuring the zeta potential, the abrasive is diluted with water so that the amount of scattered light of the abrasive is within the recommended range of the zeta sizer 3000HS.

  Since the polishing agent only needs to be mixed with the cerium oxide particles, the additive, and water at the stage of use, these components may be stored in separate containers during storage. For example, it is good also as a two-pack type abrasive | polishing agent which divides and preserve | saves into the cerium oxide slurry which contains a cerium oxide particle and water at least, and the additive containing liquid which contains an additive and water at least. Alternatively, a concentrated concentrate of an abrasive with a reduced water content may be prepared and used after diluting with water. Similarly, in the case of a two-component abrasive, a concentrated solution of a cerium oxide slurry and an additive-containing solution may be prepared, and these may be diluted with water for use.

(Substrate polishing method)
The polishing method according to the present embodiment polishes a semiconductor substrate having a surface to be polished formed on the surface in the process of manufacturing a semiconductor element, and planarizes the surface. Examples of the semiconductor substrate include a semiconductor substrate on which a shallow trench isolation pattern, a gate pattern, a wiring pattern, or the like is formed. Examples of the film to be polished include insulating films formed on these patterns, such as a silicon oxide film and a silicon nitride film. By polishing the insulating film formed on such a semiconductor substrate with the above-described abrasive, unevenness on the surface of the insulating film can be eliminated and the entire surface of the semiconductor substrate can be made smooth.

  In addition, as a method for further forming an insulating film on the surface of the semiconductor substrate, a CVD method represented by a low pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, etc., a spin coating method in which a liquid material is applied to a rotating substrate Etc.

The silicon oxide film formed by the low-pressure CVD method is formed, for example, by thermally reacting monosilane (SiH ₄ ) and oxygen (O ₂ ). The silicon nitride film formed by the low pressure CVD method is formed, for example, by thermally reacting dichlorosilane (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ). The silicon oxide film formed by the quasi-atmospheric pressure CVD method is formed, for example, by thermally reacting tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) and ozone (O ₃ ). The silicon oxide film formed by the plasma CVD method is formed, for example, by causing a plasma reaction between monosilane and nitrogen dioxide (N ₂ O). In addition, a silicon oxide film is formed by plasma reaction of tetraethoxysilane and oxygen. The silicon nitride film formed by the plasma CVD method is formed, for example, by reacting monosilane, ammonia, and nitrogen (N ₂ ) with plasma.

  The silicon oxide film formed by the spin coating method is formed, for example, by applying a liquid raw material containing inorganic polysilazane, inorganic siloxane, or the like on the substrate, and then heating and causing a thermosetting reaction.

  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 ° C. to 1000 ° C. as necessary. Further, the silicon oxide film may contain a trace amount of boron (B), phosphorus (P), carbon (C), and the like for improving the embedding property.

  The polishing method according to this embodiment can be carried out in the same manner as a conventionally known polishing method except that the above-described abrasive is used. For example, the semiconductor substrate is pressed against the polishing cloth so that the polishing cloth on the polishing platen comes into contact with the polishing film, and polishing is performed while supplying the above-described abrasive between the polishing film and the polishing cloth. Rotate the surface plate to polish the surface.

  As a polishing apparatus, a general apparatus having a holder capable of holding a substrate having a film to be polished such as a semiconductor substrate and a polishing surface plate to which a polishing cloth (pad) can be attached can be used. It is preferable to use a polishing apparatus that can change the number of rotations of the substrate holder and the polishing surface plate. An example of a commercially available polishing apparatus is a polishing apparatus (model number: EPO-111) manufactured by Ebara Corporation.

  Examples of the polishing cloth to be affixed to the polishing surface plate include general nonwoven fabrics, polyurethane foams, and porous fluororesins. It is preferable to use a polishing cloth that has been grooved so that the abrasive is accumulated, in that the characteristics of the polishing liquid can be utilized.

The rotation speed of the polishing surface plate is preferably 200 min ⁻¹ or less so that the semiconductor substrate does not jump out. The pressure (working load) for pressing the semiconductor substrate against the polishing surface plate is preferably 100 kPa or less. When the processing load exceeds 100 kPa, polishing scratches are likely to occur. While the semiconductor substrate is being polished, an abrasive is 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.

  When using a one-pack type abrasive (abrasive containing cerium oxide particles, additives and water), the abrasive can be supplied directly onto the polishing surface plate. When using a concentrated solution of an abrasive, the concentrated solution may be previously diluted with water and adjusted to a desired concentration. Alternatively, the concentrated solution and water may be sent through separate pipes, and these may be combined or mixed and supplied onto the polishing platen.

  When using a two-pack type abrasive | polishing agent, a cerium oxide slurry and an additive containing liquid can be sent by separate piping, and these can be combined or mixed and supplied on a polishing surface plate. When using the concentrated liquid of the cerium oxide slurry and the additive-containing liquid, these two liquids and water may be mixed and adjusted to a desired concentration. Alternatively, the concentrated solution of the cerium oxide slurry, the concentrated solution of the additive-containing solution, and water may be sent through separate pipes, and these may be combined or mixed and supplied onto the polishing platen. When using a two-component abrasive, the polishing rate can be adjusted by arbitrarily changing the mixing ratio of these two components.

  After the polishing, it is preferable to sufficiently wash the semiconductor substrate in running water to remove particles adhering to the substrate. For cleaning, dilute hydrofluoric acid or ammonia water may be used together with pure water. Further, a brush may be used to increase the cleaning efficiency. It is preferable to dry the water droplets adhered to the semiconductor substrate using a spin dryer or the like and then dry.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where an insulating film such as a silicon oxide film or a nitrogen silicon film is polished is exemplified, but the polishing agent of the present invention may be used for polishing a film other than the insulating film. Examples of such films include high dielectric constant films such as Hf-based, Ti-based, and Ta-based oxides; semiconductor films such as silicon, amorphous silicon, polysilicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors. Phase change film such as GeSbTe; inorganic conductive film such as ITO; polymer resin film such as polyimide, polybenzoxazole, acrylic, epoxy or phenol.

  Moreover, the abrasive | polishing agent of this invention is applicable not only to a film-form material but to various board | substrate materials, such as glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, or a plastic.

  Furthermore, the polishing agent and polishing method of the present invention are not limited to semiconductor device manufacturing processes, but include image display devices such as TFTs and organic ELs, photomasks, lenses, prisms, optical fibers, optical components such as single crystal scintillators, and optical switching. The present invention can also be applied in the process of manufacturing magnetic storage devices such as elements, optical elements such as optical waveguides, light emitting elements such as solid lasers and blue laser LEDs, magnetic disks, and magnetic heads.

<Synthesis of cerium oxide>
40 kg of cerium carbonate hydrate was put in an alumina container, which was fired in air at 830 ° C. for 2 hours to obtain 20 kg of yellowish white particles. It was confirmed by phase identification by X-ray diffraction that the particles were cerium oxide.

The cerium oxide particles obtained by firing had a particle size of 30 to 100 μm. The cerium oxide particles (15 kg) were dry pulverized using a jet mill. It was 9 m < ² > / g as a result of measuring the specific surface area of the cerium oxide particle after dry-grinding by BET method. In the following examples and comparative examples, the cerium oxide particles were used.

<Synthesis of Additive X>
100 mL of acetone and 15.6 g of N, N-dimethylaminopropyl acrylamide were mixed, and a mixture of 7.2 g of β-propiolactone and 50 mL of acetone was added on an ice bath. Subsequently, after stirring for 6 hours on an ice bath and 17 hours at room temperature, a white powder was collected by filtering the mixture. After washing with acetone, it was dried under vacuum to obtain 17.3 g of a compound represented by the following general formula (II). The yield was 76%. Hereinafter, this compound is referred to as “additive X”.

<Synthesis of Additive Y>
In a 500 mL separable flask equipped with a condenser, 5.0 g of the compound represented by the above general formula (II) and 94 g of water were placed and heated to 80 ° C. in a nitrogen stream. Thereafter, a mixture of 155 mg of ammonium persulfate and 1 g of water was added and reacted at 80 ° C. for 2 hours with stirring. After cooling to room temperature, an aqueous solution of a polymer of the compound represented by the general formula (II) was obtained. The weight average molecular weight of this polymer was measured by a static light scattering method. That is, by using Zetasizer Nano (trade name) manufactured by Malvern, the amount of scattered light having a concentration of 0.05 to 4 mg / mL was measured, and a Debye plot was performed. At this time, the refractive index concentration increment (dn / dC) was measured using a differential refractometer (trade name: DRM-3000, manufactured by Otsuka Electronics Co., Ltd.). Note that the measurement was carried out under the condition of 25 ° C. using water as a solvent. As a result, the weight average molecular weight Mw of the polymer was 36000. Hereinafter, this polymer is referred to as “additive Y”.

(Example 1)
12.5 g of cerium oxide particles, 236 g of deionized water, 1.25 g of additive X, and 120 μL of 1N nitric acid were mixed and subjected to ultrasonic dispersion while stirring. The mixed solution was filtered using a filter having a filtration accuracy of 1 μm. Thereafter, deionized water was added so that the content of the cerium oxide particles was 0.5% by mass to obtain an abrasive.

  In order to measure the average particle diameter (D50) of the cerium oxide particles in the abrasive, the abrasive was diluted with water so that the particle content was about 0.005% by mass to obtain a sample. Measurement was performed using a laser diffraction particle size distribution meter (trade name: LA-920, manufactured by Horiba, Ltd.). The refractive index was 1.93 and the transmittance was 68%. The results are shown in Table 1.

  In order to measure the zeta potential of the cerium oxide particles in the abrasive, a sample was obtained by diluting the abrasive with water so as to obtain an appropriate concentration. Zeta potential measurement was performed using a Zeta Sizer 3000HS (trade name, manufactured by Malvern). The results are shown in Table 1.

(Example 2)
50 g of cerium oxide particles, 442.5 g of deionized water, 2.5 g of L-tryptophan and 200 μL of 1N nitric acid were mixed and subjected to ultrasonic dispersion while stirring. The mixed solution was filtered using a filter having a filtration accuracy of 1 μm. Thereafter, deionized water was added so that the content of the cerium oxide particles was 1% by mass to obtain a concentrated cerium oxide slurry.

  250 g of concentrated cerium oxide slurry, 50 g of additive-containing liquid (containing 0.5 g of additive X and 49.5 g of water), and 200 g of water were mixed. Thereby, an abrasive having an additive X content of 0.1% by mass was obtained. The average particle size (D50) and zeta potential were measured in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
An abrasive as in Example 2 except that the concentrated solution of the cerium oxide slurry, the additive-containing liquid, and water were mixed so that the content of the additive X was 0.3% by mass. Got. The average particle size (D50) and zeta potential were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
Contains additive X in the same manner as in Example 2 except that the abrasive was prepared without using the additive-containing liquid, that is, 250 g of concentrated cerium oxide slurry was mixed with 250 g of water. Not obtained abrasive. The average particle size (D50) and zeta potential were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4
50 g of cerium oxide particles, 449 g of deionized water and 1.0 g of acetic acid were mixed and subjected to ultrasonic dispersion while stirring. The mixed solution was filtered using a filter having a filtration accuracy of 1 μm. Thereafter, deionized water was added so that the content of the cerium oxide particles was 1% by mass to obtain a concentrated cerium oxide slurry.

  250 g of concentrated cerium oxide slurry, 50 g of additive-containing liquid (containing 0.5 g of additive X and 49.5 g of water), and 200 g of water were mixed. Thereby, an abrasive having an additive X content of 0.1% by mass was obtained. The average particle size (D50) and zeta potential were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
The polishing agent was prepared without using an additive-containing liquid, that is, 250 g of concentrated cerium oxide slurry was mixed with 250 g of water, and the pH was adjusted to 4.76 by adding aqueous ammonia. Except having adjusted, it carried out similarly to Example 4, and obtained the abrasive | polishing agent which does not contain the additive X. The average particle size (D50) and zeta potential were measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
1 kg of cerium oxide particles, 23 g of a commercially available ammonium polyacrylate salt solution (40% by mass) and 8977 g of deionized water were mixed and subjected to ultrasonic dispersion while stirring. The mixed solution was filtered using a filter having a filtration accuracy of 1 μm. Thereafter, deionized water was added so that the content of the cerium oxide particles was 5% by mass to obtain a concentrated cerium oxide slurry.

  100 g of concentrated cerium oxide slurry was mixed with 900 g of water. 1N nitric acid was added to the mixture so that the pH was about 5 to obtain an abrasive (cerium oxide particle content: 0.5 mass%). The average particle size (D50) and zeta potential were measured in the same manner as in Example 1. The results are shown in Table 1.

<Abrasive evaluation test>
(Polish polishing speed)
As shown in FIGS. 1 and 2, a silicon nitride (SiN) film 2 having a thickness of 100 nm was formed on a silicon substrate 1 having a diameter of 200 mm, and a trench 3 was further formed. Next, as shown in FIG. 3, the trench 3 was filled with an insulating film 4 made of silicon oxide (SiO ₂ ) to produce an evaluation wafer. A plurality of such wafers were prepared.

  The initial film thickness of the insulating film 4 was 580 nm at the convex portion (corresponding to X in FIG. 3) and 610 nm at the concave portion (corresponding to Y in FIG. 3). The depth of the trench 3 (corresponding to Z in FIG. 3) was 460 nm. The size of the region where silicon nitride was formed was 100 μm wide and 100 μm long, and the interval between adjacent regions (the width of the trench 3) was 59 μm.

The abrasives prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were used, respectively, and chemical mechanical polishing of the evaluation wafer was performed as follows. First, the wafer was fixed to a substrate holder of a polishing apparatus (model number EPO-111, manufactured by Ebara Corporation). On the other hand, a polishing pad IC-1000 made of porous urethane resin (manufactured by Rodel, groove shape: perforate) was attached to a polishing surface plate having a diameter of 600 mm. The substrate holder was pressed against the polishing surface plate so that the surface of the insulating film 4 was in contact with the polishing pad. The processing load was set to 30 kPa. While dropping the abrasive onto the polishing pad at 200 mL / min, both the surface plate and the substrate holder were rotated at 50 min ⁻¹ to polish the wafer for 40 seconds. The polished evaluation wafer was thoroughly washed with pure water and then dried.

  Then, the remaining film thickness of the insulating film 4 of a recessed part and the remaining film thickness of the insulating film 4 of a convex part were measured using the optical interference type film thickness apparatus (Nanometrics company make, brand name: Nanospec AFT-5100), respectively. . Here, the convex portion polishing rate (unit: nm / min) was calculated by dividing the “reduction amount of the insulating film thickness of the convex portion (nm)” by the “polishing time (minute)”.

(Evaluation of the number of polishing scratches)
A plurality of silicon substrates having a diameter of 200 mm on which a silicon oxide film having a thickness of 1000 nm was formed on the entire surface was prepared. Each of the polishing agents prepared in Examples and Comparative Examples was used, and the silicon oxide film was polished in the same manner as in the case of obtaining the above-described convex portion polishing rate. The polished wafer was thoroughly washed with pure water, hydrofluoric acid, and ammonia water, and then dried. The number of polishing flaws was counted using a defect inspection apparatus using a scanning electron microscope.

(Evaluation of adhesion to polypropylene containers)
The abrasive | polishing agent prepared in Examples 1-4 and Comparative Examples 1-3 was accommodated in the polypropylene container, respectively. Whether or not cerium oxide particles or the like adhere to the inner surface of the polypropylene container was visually observed and evaluated.

  Table 1 shows the evaluation results of the abrasives prepared in Examples 1-4 and Comparative Examples 1-3. In addition, the relative number of polishing flaws in Table 1 is calculated based on the number of polishing flaws when the abrasive of Comparative Example 3 is used.

  As shown in Table 1, when the compound represented by the general formula (II) is contained in the abrasive, the polishing rate is improved and the polishing scratches are reduced.

It is a fragmentary top view which shows the silicon substrate in which the silicon nitride film and the trench were formed. It is the II-II sectional view taken on the line of the silicon substrate shown in FIG. It is sectional drawing which shows the silicon substrate after an insulating film embedding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Silicon nitride film, 3 ... Trench, 4 ... Insulating film (film to be polished).

Claims (10)

An abrasive containing water, cerium oxide particles and additives,
A polishing agent comprising a compound represented by the following general formula (I) or a polymer having the compound as a monomer unit.

[In General Formula (I), R ^{1 to} R ⁵ each independently represents a monovalent organic group which may have a substituent or a hydrogen atom, and X ¹ and X ² each independently represent The divalent organic group which may have a substituent is shown. ]   The abrasive | polishing agent of Claim 1 whose pH is 3.0 or more and 7.0 or less and whose average particle diameter of the said cerium oxide particle is 1 nm or more and 400 nm or less.   The abrasive according to claim 1 or 2, wherein the content 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 abrasive.   The content of the compound represented by the general formula (I) or the polymer having the compound as a monomer unit is 0.01 parts by mass or more with respect to 100 parts by mass of the abrasive. The abrasive | polishing agent as described in any one of 3.   The abrasive | polishing agent as described in any one of Claims 1-4 whose zeta potential of the said cerium oxide particle is + 10mV or more in the said abrasive | polishing agent.   The said additive is an abrasive | polishing agent as described in any one of Claims 1-5 which further contains at least 1 type chosen from carboxylic acid, an amino acid, and an amphoteric surfactant.   The abrasive according to any one of claims 1 to 6, which is for use in chemical mechanical polishing. A method for polishing a substrate having a film to be polished formed on a surface,
While pressing the said board | substrate against the said polishing cloth so that the polishing cloth on the polishing surface plate and the said to-be-polished film may contact | abut, the abrasive | polishing agent as described in any one of Claims 1-7 is said to be polished. A method for polishing a substrate, wherein the film to be polished is polished by relatively moving the substrate and the polishing platen while being supplied between the film and the polishing cloth.   The solution used for the grinding | polishing method of the board | substrate of Claim 8 containing the polymer which has the compound represented by the said general formula (I), or the said compound as a monomer unit.   The slurry used for the grinding | polishing method of the board | substrate of Claim 8 containing the polymer which has the compound represented by the said general formula (I), or the said compound as a monomer unit.

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