JPWO2018216733A1 - Polishing composition and polishing method using the same - Google Patents

Abstract

The present invention provides a polishing composition that is thickened while maintaining properties such as dispersibility of abrasive grains, polishing rate, and reduction of haze. The present invention contains abrasive grains, a basic compound, a water-soluble polymer A having a function of protecting the surface of an object to be polished, a water-soluble polymer B having a thickening effect, and water, and The weight average molecular weight of the water-soluble polymer B is 50,000 or more, the abrasive grain adsorption parameter 1 of the water-soluble polymer B obtained from the standard test 1 is 40% or less, and the water-soluble polymer obtained from the standard test 2 is used. A polishing composition in which the substrate adsorption parameter 2 of the organic polymer B is 20% or less.

Description

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

  Metals or semiconductors such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, and stainless steel, or alloys thereof; compound semiconductor wafer materials such as silicon carbide, gallium nitride, and gallium arsenide; Polished as required and applied in various fields.

  In particular, various researches have been made on a technique for polishing a silicon wafer in order to manufacture a mirror wafer having a highly flat mirror surface with high quality without scratches or impurities in order to manufacture a semiconductor element such as an integrated circuit.

  In polishing, a polishing composition containing abrasive grains (for example, colloidal particles such as colloidal silica) is used in order to finish the wafer surface into a highly accurate mirror surface and to reduce haze. For example, in JP-A-2004-128070 (corresponding to US Patent Application Publication No. 2004/0127047), silicon dioxide, an alkali compound, a water-soluble polymer compound such as hydroxyethyl cellulose, and water are contained, and Silicon is colloidal silica in which the average primary particle diameter obtained from the specific surface area measured by the BET method and the average secondary particle diameter measured by the laser scattering method are within a specific range, or the average primary particle diameter and the average secondary particle diameter. A polishing composition that is fumed silica having a secondary particle size within a specific range has been proposed.

  In JP 2011-61089 A, an abrasive, hydroxyethyl cellulose, and a basic compound are contained, and the hydroxyethyl cellulose is obtained by hydrolyzing hydroxyethyl cellulose having a weight average molecular weight of 300,000 to 3,000,000. A polishing liquid composition which is prepared hydroxyethyl cellulose has been proposed.

  Recently, for polishing compositions applied to polishing silicon wafers, etc., while increasing the dispersibility of abrasive grains, polishing rate, and performance such as reduction of haze, increase the viscosity to increase processing uniformity of the wafer surface. New demands for them are increasing. However, the current situation is that there is not enough knowledge to meet this new demand.

  The present invention has been made in view of such circumstances, and provides a thickened polishing composition while maintaining performance such as dispersibility of abrasive grains, polishing rate, and reduction of haze. The purpose is to The present invention also aims to provide a polishing method using such a polishing composition.

  The above problems include abrasive grains, a basic compound, a water-soluble polymer A having a function of protecting the surface of an object to be polished, a water-soluble polymer B having a thickening effect, and water, The weight average molecular weight of the water-soluble polymer B is 50,000 or more, the abrasive particle adsorption parameter 1 of the water-soluble polymer B obtained from the standard test 1 is 40% or less, and the water-soluble polymer obtained from the standard test 2 is used. This is solved by a polishing composition in which the substrate adsorption parameter 2 of the functional polymer B is 20% or less.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. Unless otherwise specified, operations and measurements of physical properties are performed under the conditions of room temperature (range of 20 ° C. to 25 ° C.) / Relative humidity of 40% RH to 50% RH.

[Polishing composition]
One form of the present invention comprises abrasive grains, a basic compound, a water-soluble polymer A having a function of protecting the surface of an object to be polished, a water-soluble polymer B having a thickening effect, and water. Including, the weight average molecular weight of the water-soluble polymer B is 50,000 or more, the abrasive adsorption parameter 1 of the water-soluble polymer B obtained from standard test 1 is 40% or less, obtained from standard test 2 The polishing composition has a substrate adsorption parameter 2 of the water-soluble polymer B of 20% or less.

  The present inventors conducted studies to increase the viscosity of a polishing composition while maintaining the properties such as dispersibility of abrasive grains, polishing rate, and reduction of haze. In the process, water-solubility such as hydroxyethyl cellulose contained in the polishing composition described in JP-A-2004-128070 (corresponding to US Patent Application Publication No. 2004/0127047) and JP-A-2011-61089. When a study was conducted to simply increase the addition amount of the polymer, thickening was achieved for the time being, but the dispersibility of the abrasive grains, the polishing rate, and the performance originally required for the polishing composition such as reduction of haze, etc. We found that it would decrease.

  The present inventors conducted further studies based on the results of such studies. As a result, surprisingly, the water-soluble polymer A having a function of protecting the surface of the object to be polished, the weight average molecular weight of 50,000 or more, and the abrasive adsorption parameter 1 obtained from the standard test 1 were 40%. The dispersibility of the abrasive grains, the polishing rate, and the haze of the water-soluble polymer B having the thickening action, which is the following and the substrate adsorption parameter 2 obtained from the standard test 2 is 20% or less. It was found that a thickened polishing composition can be obtained while maintaining performances such as reduction of viscosity.

  The mechanism of action by which the above effects are obtained by the polishing composition of the present invention is unknown, but it is considered as follows. That is, the water-soluble polymer A contained in the polishing composition according to the present invention has a function of protecting the surface of the object to be polished. Since such a water-soluble polymer A forms a water-soluble polymer film on the surface of the object to be polished, the haze of the object to be polished can be reduced. Further, since the water-soluble polymer B contained in the polishing composition according to the present invention has a weight average molecular weight of 50,000 or more, it has an action of increasing the viscosity of the polishing composition. Further, since the water-soluble polymer B has the abrasive adsorption parameter 1 obtained by the standard test 1 and the substrate adsorption parameter 2 obtained by the standard test 2 of not more than a specific value, it may be excessively adsorbed to the abrasive grains. Without, it is possible to maintain good dispersibility of the abrasive grains in the polishing composition, and also without excessive adsorption to the surface of the object to be polished, it is possible to maintain a good polishing rate by the polishing composition. it can. The polishing composition according to the present invention in which the water-soluble polymer A and the water-soluble polymer B are used together increases the dispersibility of the abrasive grains, the polishing rate, and the haze while maintaining performance. Thickening is achieved.

  The above mechanism is based on speculation, and its correctness does not affect the technical scope of the present application.

  Hereinafter, each component contained in the polishing composition according to the present invention will be described in detail.

<Abrasive grains>
The polishing composition according to one aspect of the present invention essentially contains abrasive grains. The abrasive grains serve to mechanically polish the surface of the object to be polished.

  The material and properties of the abrasive grains are not particularly limited, and can be appropriately selected depending on the purpose of use and the mode of use of the polishing composition. Examples of the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and oxide particles such as red iron oxide particles; Examples thereof include nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate. Specific examples of the organic particles include polymethylmethacrylate (PMMA) particles, poly (meth) acrylic acid particles, and polyacrylonitrile particles. The term “(meth) acrylic acid” as used herein means a generic term for acrylic acid and methacrylic acid. The abrasive grains may be used alone or in combination of two or more.

  As the abrasive grains, inorganic particles are preferable, and particles made of metal or semimetal oxides are particularly preferable. Silica particles are mentioned as particularly preferable abrasive grains. Examples of silica particles include colloidal silica, fumed silica, and precipitated silica.

  Among the silica particles, colloidal silica and fumed silica are preferable, and colloidal silica is particularly preferable. When colloidal silica or fumed silica is used, particularly when colloidal silica is used, scratches generated on the surface of the silicon wafer in the polishing step are reduced.

  Here, the surface of a silicon wafer, which is a preferable object to be polished, is generally finished into a high quality mirror surface through a lapping step and a polishing step. The polishing step is usually composed of a plurality of polishing steps including a preliminary polishing step (preliminary polishing step) and a final polishing step (final polishing step). For example, a polishing composition having a high processing force (polishing force) is used in the step of roughly polishing a silicon wafer (eg, a preliminary polishing step), and a polishing force is used in a more delicate polishing step (eg, a final polishing step). There is a tendency that polishing compositions having a low viscosity are used. As described above, since the polishing composition used has different polishing characteristics required for each polishing step, the content of each component contained in the polishing composition also depends on the polishing composition used in the polishing composition. Different ones may be employed depending on the stage of the process.

  As described above, even in the abrasive grains contained in the polishing composition, the content and the particle size thereof are different from each other depending on the stage of the polishing step in which the polishing composition is used. sell.

  The increase in the content of the abrasive grains improves the polishing rate for the surface of the object to be polished. On the other hand, the reduction in the content of the abrasive grains tends to improve the dispersion stability of the polishing composition and reduce the residue of the abrasive grains on the polished surface.

  The content of the abrasive grains in the polishing composition used in the preliminary polishing step is not particularly limited, but is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, and 0 It is more preferably at least 1 mass%, particularly preferably at least 0.2 mass%. The content of abrasive grains in the polishing composition used in the preliminary polishing step is preferably 10% by mass or less, more preferably 5% by mass or less, and 1% by mass or less. More preferably, it is most preferably 0.8% by mass or less.

  The content of the abrasive grains in the polishing composition used in the final polishing step is not particularly limited, but is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, and 0 It is particularly preferably at least 1% by mass. The content of abrasive grains in the polishing composition used in the final polishing step is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less. Even more preferably, it is most preferably 0.5% by mass or less.

  In addition, the increase in the particle size of the abrasive grains facilitates mechanical polishing of the surface of the object to be polished, and improves the polishing rate. On the other hand, haze is likely to be reduced due to the decrease in the particle size of the abrasive grains.

  The average primary particle diameter of the abrasive grains in the polishing composition used in the preliminary polishing step is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, further preferably 20 nm or more, and 30 nm. It is even more preferable that the above is satisfied. The average primary particle diameter of the abrasive grains used in the preliminary polishing step is preferably 100 nm or less, more preferably 80 nm or less, and further preferably 60 nm or less.

  The average primary particle diameter of the abrasive grains in the polishing composition used in the final polishing step is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, and further preferably 20 nm or more. The average primary particle diameter of the abrasive grains in the polishing composition used in the final polishing step is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less.

  The average secondary particle size of the abrasive grains in the polishing composition used in the preliminary polishing step is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, and 40 nm or more. Is more preferable. The average secondary particle diameter of the abrasive grains in the polishing composition used in the preliminary polishing step is preferably 250 nm or less, more preferably 180 nm or less, and even more preferably 150 nm or less.

  The average secondary particle diameter of the abrasive grains in the polishing composition used in the final polishing step is preferably 10 nm or more, more preferably 20 nm or more, further preferably 30 nm or more, and 40 nm or more. Is particularly preferable. The average secondary particle diameter of the abrasive grains in the polishing composition used in the final polishing step is preferably 100 nm or less, more preferably 90 nm or less, and even more preferably 80 nm or less.

  Generally, in a polishing composition containing a water-soluble polymer and abrasive grains, aggregates of abrasive grains mediated by the water-soluble polymer are likely to be formed. Therefore, in a polishing composition containing a water-soluble polymer and abrasive grains, as compared with a polishing composition containing no water-soluble polymer, the average particle size of the particles present in the polishing composition tends to be large. is there. In the present specification, "particles present in the polishing composition" is used as a term including not only aggregates of abrasive grains mediated by a water-soluble polymer but also abrasive grains not forming aggregates. To be

  The average secondary particle diameter of the particles present in the polishing composition used in the preliminary polishing step is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 40 nm or more. The average secondary particle diameter of the particles present in the polishing composition used in the preliminary polishing step is preferably 250 nm or less, more preferably 180 nm or less, and further preferably 150 nm or less. .

  The average secondary particle size of the particles present in the polishing composition used in the final polishing step is preferably 10 nm or more, more preferably 20 nm or more, further preferably 30 nm or more, and 40 nm or more. Is particularly preferable. The average secondary particle diameter of the particles present in the polishing composition used in the final polishing step is preferably 100 nm or less, more preferably 90 nm or less, and further preferably 80 nm or less. .

  The value of the average primary particle diameter of the abrasive grains is calculated, for example, from the specific surface area measured by the BET method. The specific surface area of the abrasive grains can be measured using, for example, "Flow SorbII 2300" manufactured by Micromeritics. Further, the average secondary particle diameter of the particles present in the abrasive grains and the polishing composition is measured, for example, by a dynamic light scattering method, for example, "Nanotrack (registered trademark) UPA-UT151" manufactured by Nikkiso Co., Ltd. Can be used to measure.

<Basic compound>
The polishing composition according to one aspect of the present invention essentially contains a basic compound. Here, the basic compound means a compound having a function of increasing the pH of the polishing composition by being added thereto. The basic compound has a function of chemically polishing the surface of an object to be polished by etching, and a function of improving dispersion stability of abrasive grains. Further, the basic compound can be used as a pH adjuster.

  Specific examples of the basic compound include hydroxides or salts of Group 2 elements or alkali metals, quaternary ammonium compounds, ammonia or salts thereof, amines and the like.

  In the hydroxide or salt of Group 2 element or alkali metal, the Group 2 element is not particularly limited, but an alkaline earth metal can be preferably used, and examples thereof include calcium. In addition, examples of the alkali metal include potassium and sodium. Examples of the salt include carbonate, hydrogen carbonate, sulfate, acetate and the like. Examples of the hydroxides or salts of Group 2 elements or alkali metals include calcium hydroxide, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium acetate, potassium chloride, sodium hydroxide, sodium hydrogen carbonate, And sodium carbonate and the like.

  Examples of the quaternary ammonium compound include hydroxides such as tetramethylammonium, tetraethylammonium and tetrabutylammonium, salts such as chlorides, carbonates, hydrogencarbonates, sulfates and phosphates. Specific examples include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and other tetraalkylammonium hydroxides; tetramethylammonium carbonate, tetraethylammonium carbonate, tetrabutylammonium carbonate and other tetraalkylammonium carbonates; chloride Examples thereof include tetraalkylammonium chloride, such as tetramethylammonium, tetraethylammonium chloride, and tetrabutylammonium chloride.

  Other ammonium salts include ammonium carbonate and ammonium hydrogen carbonate.

  Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine. , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine and the like.

  Here, as the basic compound, a preferable compound can be selected according to its expected function.

  Here, as the basic compound in the polishing composition used in the preliminary polishing step, it is preferable to use a quaternary ammonium hydroxide compound such as tetramethylammonium hydroxide or ammonia from the viewpoint of improving the polishing rate. Further, as the basic compound in the polishing composition used in the preliminary polishing step, from the viewpoint of improving the polishing rate, it is preferable to include a carbonate or a hydrogen carbonate, and the like, potassium carbonate, potassium hydrogen carbonate, ammonium carbonate, It is preferable to include ammonium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, or the like. From the viewpoint of easy handling, the quaternary ammonium hydroxide compound and ammonia are more preferable, and ammonia is the most preferable.

  Further, the basic compound in the polishing composition used in the final polishing step does not contain an alkaline earth metal, an alkali metal, or a transition metal from the viewpoint that it does not remain attached to the object to be polished after polishing. Is preferred. Therefore, the basic compound is preferably, for example, a quaternary ammonium hydroxide compound, an amine, or ammonia. From the viewpoint of easy handling, the quaternary ammonium hydroxide compound and ammonia are more preferable, and the ammonia Is most preferred.

  The content of the basic compound in the polishing composition (when two or more kinds are used, the total amount thereof) is preferably 0.001 mass% or more, and more preferably 0.003 mass% or more. By increasing the content of the basic compound, it becomes easy to obtain a high polishing rate. On the other hand, the content of the basic compound in the polishing composition (when two or more kinds are used, the total amount thereof) is preferably 0.2% by mass or less, and 0.1% by mass or less. More preferable. By reducing the content of the basic compound, haze is easily reduced.

  In addition, it is advisable to reduce the content of the basic compound stepwise as the final polishing step is approached. A preferred embodiment is a form in which the content of the basic compound in the preliminary polishing composition is the largest, and the content is in the range of 2 times or more and 20 times or less the content of the basic compound in the finish polishing composition. Preferably there is.

<Water-soluble polymer A>
The polishing composition according to one aspect of the present invention essentially contains a water-soluble polymer A having a function of protecting the surface of an object to be polished. Since the water-soluble polymer A forms a water-soluble polymer film on the surface of the object to be polished, the haze of the object to be polished can be reduced.

  As the water-soluble polymer A, those having at least one functional group selected from a cation group, an anion group and a nonion group in the molecule can be used. Specific examples of the water-soluble polymer A include those containing a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, a polyoxyalkylene structure, and the like in the molecule. A nonionic water-soluble polymer can be preferably used from the viewpoints of reducing aggregates and improving detergency. Suitable examples include polymers containing oxyalkylene units, polymers containing nitrogen atoms (nitrogen-containing water-soluble polymers), polyvinyl alcohol, cellulose derivatives, starch derivatives and the like.

  The water-soluble polymer A is more preferably at least one selected from the group consisting of a polymer containing an oxyalkylene unit, a polymer containing a nitrogen atom, polyvinyl alcohol, and a cellulose derivative, and a polymer containing a nitrogen atom. And at least one selected from the group consisting of cellulose derivatives.

  Examples of the polymer containing an oxyalkylene unit include polyethylene oxide (PEO), a block copolymer of ethylene oxide (EO) and propylene oxide (PO), and a random copolymer of EO and PO. The block copolymer of EO and PO may be a diblock body, a triblock body or the like containing a polyethylene oxide (PEO) block and a polypropylene oxide (PPO) block. The triblock body includes a PEO-PPO-PEO type triblock body and a PPO-PEO-PPO type triblock body. Usually, a PEO-PPO-PEO type triblock body is more preferable. In a block copolymer or a random copolymer of EO and PO, the molar ratio of EO and PO (EO / PO) constituting the copolymer is from the viewpoint of solubility in water and detergency. It is preferably larger than 1, more preferably 2 or more, and further preferably 3 or more (for example, 5 or more).

  The polymer containing a nitrogen atom is not particularly limited as long as it has one or more nitrogen atoms in the monomer unit or one or more nitrogen atoms in a part of the side chain. Examples of the monomer used for forming the polymer containing a nitrogen atom include amine, imine, amide, imide, carbodiimide, hydrazide, urethane and the like, and the structures thereof are linear, cyclic, primary, secondary, It may be any of the third grade. Further, it may be a nitrogen-containing water-soluble polymer having a salt structure in which a nitrogen atom is part of a cation. Further, both a polymer containing a nitrogen atom in the main chain and a polymer having a nitrogen atom in a side chain functional group (pendant group) can be used. Examples of the nitrogen-containing water-soluble polymer having a salt structure include quaternary ammonium salts. Examples of the nitrogen-containing water-soluble polymer include polycondensation polyamides such as water-soluble nylon, polycondensation polyesters such as water-soluble polyesters, polyaddition polyamines, polyaddition polyimines, and polyaddition (meth) acrylamides. , A water-soluble polymer having a nitrogen atom in at least a part of its alkyl main chain, a water-soluble polymer having a nitrogen atom in at least a part of its side chain, and the like. The water-soluble polymer having a nitrogen atom in the side chain also includes a water-soluble polymer having a quaternary nitrogen in the side chain. Specific examples of the polyaddition type nitrogen-containing water-soluble polymer include polyvinyl imidazole, polyvinyl carbazole, polyvinyl pyrrolidone, poly N-vinyl formamide, polyvinyl caprolactam, polyvinyl piperidine and the like. Further, the nitrogen-containing water-soluble polymer may be one partially having a hydrophilic structure such as a vinyl alcohol structure, a methacrylic acid structure, a vinyl sulfonic acid structure, a vinyl alcohol carboxylic acid ester structure, or an oxyalkylene structure. Good. Further, it may be a polymer having a plurality of types of structures such as these diblock type, triblock type, random type and alternating type. The nitrogen-containing water-soluble polymer may be any one having a cation in a part or all of the molecule, one having an anion, one having both an anion and a cation, one having a nonion, and the like. Examples of the polymer containing a nitrogen atom in the main chain include homopolymers and copolymers of N-acylalkyleneimine type monomers. Specific examples of the N-acylalkyleneimine type monomer include N-acetylethyleneimine and N-propionylethyleneimine. Examples of the polymer having a nitrogen atom in the pendant group include homopolymers and copolymers of N- (meth) acryloyl type monomers, homopolymers and copolymers of N-alkoxyalkyl (meth) acrylamide type monomers, N- Homopolymers and copolymers of hydroxyalkyl (meth) acrylamide type monomers, homopolymers and copolymers of N-alkyl (meth) acrylamide type monomers, homopolymers of N-dialkyl (meth) acrylamide type monomers, and Examples thereof include copolymers, homopolymers and copolymers of N-vinyl type monomers. Here, "(meth) acryloyl" means a generic term for acryloyl and methacryloyl. Specific examples of the N- (meth) acryloyl-type monomer include N- (meth) acryloylmorpholine and N- (meth) acryloylpiperidine. Specific examples of the N-alkoxyalkyl (meth) acrylamide type monomer include N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide and the like. Specific examples of N-hydroxyalkyl (meth) acrylamide type monomers include N- (2-hydroxyethyl) (meth) acrylamide, N- (1,1-dimethyl-2-hydroxyethyl) (meth) acrylamide and the like. To be Specific examples of N-alkyl (meth) acrylamide type monomers include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide and the like. . Specific examples of the N-dialkyl (meth) acrylamide type monomer include N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide and the like. Specific examples of the N-vinyl type monomer include N-vinylpyrrolidone and the like. In the present specification, the term "copolymer", unless otherwise specified, means a comprehensive reference to various copolymers such as random copolymers, alternating copolymers, block copolymers, and graft copolymers. is there.

  The saponification degree of polyvinyl alcohol is not particularly limited. As the polyvinyl alcohol, cationized polyvinyl alcohol having a cationic group such as a quaternary ammonium structure may be used. Examples of the cationized polyvinyl alcohol include those derived from a monomer having a cationic group such as diallyldialkylammonium salt and N- (meth) acryloylaminoalkyl-N, N, N-trialkylammonium salt.

  The "cellulose derivative" refers to a cellulose in which a part of hydroxyl groups is substituted with another different substituent. Examples of the cellulose derivative include cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, and pullulan.

  Examples of the starch derivative include pregelatinized starch, pullulan, cyclodextrin and the like. Of these, pullulan is preferred.

  The water-soluble polymer A may be used alone or in combination of two or more.

  Among the above-mentioned water-soluble polymers A, it is preferable that the water-soluble polymers A contain a cellulose derivative from the viewpoint of easily reducing the haze of the object to be polished. When a cellulose derivative is used as the water-soluble polymer A, a water-soluble polymer film is more likely to be formed on the surface of the object to be polished (particularly a silicon wafer), as compared with the case where another water-soluble polymer is used, and haze of The reduction effect is further improved. Further, among the cellulose derivatives, hydroxyethyl cellulose is particularly preferable from the viewpoint that a water-soluble polymer film is easily formed on the surface of the object to be polished and the haze reducing effect is high.

  The weight average molecular weight of the water-soluble polymer A is preferably 2,000,000 or less, and preferably 1,500,000 or less in terms of polyethylene oxide, from the viewpoint of improving the polishing rate and reducing haze. More preferably, it is still more preferably 1,000,000 or less. The weight average molecular weight of the water-soluble polymer A in the polishing composition is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 30,000 or more. When the weight average molecular weight of the water-soluble polymer A is within the above range, the dispersion stability of the polishing composition and the cleaning performance of the silicon wafer when the object to be polished is a silicon wafer (silicon substrate) Is also preferable. As the weight average molecular weight of the water-soluble polymer A, a value measured by the GPC method (water-based, converted to polyethylene oxide) can be adopted.

  The content of the water-soluble polymer A contained in the polishing composition may be different depending on the stage of the polishing step in which the polishing composition is used.

  By increasing the content of the water-soluble polymer A, the formation of the water-soluble polymer film on the surface of the object to be polished is promoted and the haze can be reduced. On the other hand, the reduction of the content of the water-soluble polymer A improves the polishing rate.

The content of the water-soluble polymer A in the polishing composition used in the preliminary polishing step (when two or more kinds are used, the total amount thereof) improves the wettability of the polishing surface and further reduces the haze. From the viewpoint, it is preferably 1 × 10 ⁻⁶ mass% or more, more preferably 5 × 10 ⁻⁵ mass% or more, and further preferably 1 × 10 ⁻⁴ mass% or more. On the other hand, from the viewpoint of improving the polishing rate, it is preferably 0.5 mass% or less, more preferably 0.1 mass% or less, further preferably 0.05 mass% or less, and 0 It is even more preferably 0.01% by mass or less, and particularly preferably 0.005% by mass or less.

The content of the water-soluble polymer A in the polishing composition used in the finish polishing step (the total amount when two or more kinds are used) improves the wettability of the polishing surface and further reduces the haze. From the viewpoint, it is preferably 1 × 10 ⁻⁴ mass% or more, more preferably 1 × 10 ⁻³ mass% or more, and further preferably 2 × 10 ⁻³ mass% or more. On the other hand, from the viewpoint of improving the polishing rate, it is preferably 0.5 mass% or less, more preferably 0.1 mass% or less, further preferably 0.05 mass% or less, and 0 It is particularly preferable that the content is 0.01% by mass or less.

  Among the above, particularly when a cellulose derivative (for example, hydroxyethyl cellulose) is used as the water-soluble polymer A in the polishing composition, it may be used in combination with polyvinylpyrrolidone.

<Water-soluble polymer B>
The polishing composition according to one aspect of the present invention essentially contains a water-soluble polymer B having a thickening action. Since the water-soluble polymer B according to the present invention has a weight average molecular weight of 50,000 or more, it has an action of increasing the viscosity of the polishing composition. Further, since the water-soluble polymer B has an abrasive grain adsorption parameter 1 obtained by the standard test 1 of 40% or less, it is not excessively adsorbed to the abrasive grains, and the abrasive grains are dispersed in the polishing composition. The goodness can be maintained. Further, since the water-soluble polymer B has a substrate adsorption parameter 2 obtained by the standard test 2 of 20% or less, it is not excessively adsorbed on the surface of the object to be polished and has a good polishing rate by the polishing composition. Can be maintained at. The polishing composition according to the present invention in which the water-soluble polymer A and the water-soluble polymer B are used in combination increases the dispersibility of the abrasive grains, the polishing rate, and the performance such as reduction of haze. Thickening is achieved.

  The weight average molecular weight of the water-soluble polymer B is 50,000 or more. When the weight average molecular weight of the water-soluble polymer B is less than 50,000, the effect of increasing the viscosity of the polishing composition while maintaining the performance such as the dispersibility of abrasive grains cannot be obtained. The weight average molecular weight of the water-soluble polymer B is preferably 100,000 or more, more preferably 200,000 or more. Further, the weight average molecular weight of the water-soluble polymer B is preferably 7,000,000 or less, more preferably 5,000,000 or less, from the viewpoint of storage stability of the polishing composition. It is more preferably 3,000,000 or less, and particularly preferably 1,500,000 or less.

  As the weight average molecular weight of the water-soluble polymer B, a value measured by the GPC method (water-based, converted to polyethylene oxide) can be adopted.

  The water-soluble polymer B has an abrasive grain adsorption parameter 1 obtained by standard test 1 of 40% or less. Here, "abrasive grain adsorption parameter 1" represents the ease with which the water-soluble polymer B is adsorbed to the abrasive grains, and since the abrasive grain adsorption parameter 1 is 40% or less, it is highly water-soluble. Adsorption of the molecule B to the abrasive grains hardly occurs, and the dispersibility of the abrasive grains in the polishing composition is improved. When the abrasive grain adsorption parameter 1 exceeds 40%, the water-soluble polymer B is more likely to be adsorbed to the abrasive grains, and the dispersibility of the abrasive grains in the polishing composition is lowered. The abrasive grain adsorption parameter 1 is preferably 40% or less, more preferably 20% or less, and further preferably 5% or less. The lower limit of the abrasive grain adsorption parameter 1 is usually 0%.

  Abrasive grain adsorption parameter 1 can be calculated by the following formula 1 by performing standard test 1 by the method shown below.

Standard Test 1: Calculation of Abrasive Grain Adsorption Parameter 1 The following standard solution is prepared, and this standard solution is centrifuged under the following centrifugation conditions to collect the supernatant.

<< Composition of standard solution >>
Aqueous dispersion in which the concentration of abrasive grains is 0.46% by mass, the concentration of ammonia is 0.009% by mass, and the concentration of water-soluble polymer B is 0.017% by mass << Centrifugation Conditions >>
Centrifuge: manufactured by Beckman Coulter, Inc., Avanti (registered trademark) HP-30I
Rotation speed: 20000 rpm
Centrifuge time: 30 min
The total organic carbon concentration (TOC) of the standard liquid and the supernatant liquid was measured using the following measuring device, and the standard liquid measurement value was set to C1, the supernatant liquid measurement value was set to C2, and the abrasive particles were adsorbed by the following formula 1. Calculate parameter 1:
TOC measuring device: TOC-5000A manufactured by Shimadzu Corporation.

  In addition, the water-soluble polymer B has a substrate adsorption parameter 2 obtained by standard test 2 of 20% or less. Here, "substrate adsorption parameter 2" represents the ease of adsorption of the water-soluble polymer B to the object to be polished, and when the substrate adsorption parameter 2 is 20% or less, the water-soluble polymer is B is less likely to be adsorbed to the object to be polished, and the polishing rate of the polishing composition is improved. When the substrate adsorption parameter 2 exceeds 20%, the water-soluble polymer B is more likely to be adsorbed on the object to be polished, and the polishing rate by the polishing composition is lowered. The substrate adsorption parameter 2 is preferably 20% or less, and more preferably 15% or less. The lower limit of the substrate adsorption parameter 2 is usually 0%.

  The substrate adsorption parameter 2 can be calculated by the following equation 2 by performing the standard test 2 by the method shown below.

-Standard test 2: Calculation of substrate adsorption parameter 2 Prepare the following two standard solutions:
Reference standard solution: Aqueous solution containing 1.3% by mass of ammonia Standard solution for evaluation: Aqueous solution containing 1.3% by mass of ammonia and 0.18% by mass of water-soluble polymer B.

  The single crystal silicon substrate pretreated by the method of <Silicon wafer pretreatment> described in the examples is cut into a chip type of 60 mm × 30 mm to prepare an evaluation substrate. The weight of this evaluation substrate is W0. Further, the evaluation substrate is immersed in an approximately 5 mass% HF (hydrogen fluoride) aqueous solution for 30 seconds (removal of natural oxide film), and then rinsed with deionized water. The evaluation substrate thus treated with the oxide film is immersed in the evaluation standard solution at 25 ° C. for 12 hours, rinsed with deionized water, dried and weighed. This weight is W1. The etching rate (ER) is calculated from the weight difference (W0-W1) before and after immersion and the specific gravity of silicon. Separately, by the same method as above, the etching rate obtained using the reference standard solution is set to α, and the substrate adsorption parameter 2 is calculated by the following equation 2.

  Specific examples of the water-soluble polymer B having the above-mentioned properties include polyacrylic acid and salts thereof. As the water-soluble polymer B, one kind may be used alone, or two or more kinds may be used in combination.

  Among them, it is more preferable that the water-soluble polymer B contains polyacrylic acid from the viewpoint of storage stability of the polishing composition.

  The content of the water-soluble polymer B contained in the polishing composition may be different depending on the stage of the polishing step in which the polishing composition is used.

  By increasing the content of the water-soluble polymer B, the viscosity can be increased. On the other hand, by reducing the content of the water-soluble polymer B, the storage stability of the polishing composition can be improved.

The content of the water-soluble polymer B in the polishing composition used in the preliminary polishing step is not particularly limited, but is preferably 1 × 10 ⁻⁶ mass% or more, and 5 × 10 ⁻⁵ mass% or more. It is more preferable that the content is 0.0001% by mass or more. Further, the content of the water-soluble polymer B in the polishing composition used in the preliminary polishing step is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and The content is more preferably 0.05% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably 0.005% by mass or less.

The content of the water-soluble polymer B in the polishing composition used in the final polishing step is not particularly limited, but is preferably 1 × 10 ⁻⁶ mass% or more, and 5 × 10 ⁻⁵ mass% or more. It is more preferable that the content is 0.0001% by mass or more. The content of the water-soluble polymer B in the polishing composition used in the final polishing step is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and The content is more preferably 0.05% by mass or less, still more preferably 0.01% by mass or less, and particularly preferably 0.005% by mass or less.

<Water>
The polishing composition according to one aspect of the present invention essentially contains water. Water functions as a solvent for dissolving other components or a dispersion medium for dispersing the other components.

  From the viewpoint of inhibiting contamination of the object to be polished and the action of other components, water containing as little impurities as possible is preferable. For example, water having a total content of transition metal ions of 100 mass ppb or less is preferable. Here, the purity of water can be increased by operations such as removal of impurity ions using an ion exchange resin, removal of foreign matter by a filter, and distillation. Specifically, as the water, for example, it is preferable to use ion exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like.

<Other ingredients>
The polishing composition according to one aspect of the present invention may contain other components, if necessary, in addition to the abrasive grains, the basic compound, the water-soluble polymer A, the water-soluble polymer B, and water. On the other hand, however, the polishing composition according to the present invention preferably contains substantially no oxidizing agent. When the polishing composition contains an oxidizing agent, the composition is supplied to the object to be polished (for example, a silicon wafer), whereby the surface of the object to be polished is oxidized to form an oxide film, This can reduce the polishing rate. Specific examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. In addition, that the polishing composition is substantially free of an oxidizing agent means that the oxidizing agent is not included at least intentionally. Therefore, a small amount (for example, the molar concentration of the oxidizing agent in the polishing composition is 0.0005 mol / L or less, preferably 0.0001 mol or less, more preferably 0.00001 mol / L or less, particularly preferably 0.000001 mol / L or less) is inevitably contained in the polishing composition is included in the concept of the polishing composition that does not substantially contain the oxidizing agent. Can be done.

  Other components that can be contained in the polishing composition include, for example, chelating agents, preservatives / antifungal agents, surfactants, and other known additives (for example, organic acids, organic acid salts, inorganic acids, inorganic acids). Salt, etc.) and the like, but are not limited thereto.

(Chelating agent)
The polishing composition according to one aspect of the present invention may contain a chelating agent. The chelating agent is an object to be polished by forming a complex by capturing a metal impurity originally contained in the polishing composition or a metal object generated from the object to be polished or the polishing apparatus during polishing or mixed from the outside to form a complex. Suppressing the retention of metallic impurities on objects. In particular, when the object to be polished is a semiconductor, metal contamination of the semiconductor is prevented by suppressing residual metal impurities, and deterioration of semiconductor quality is suppressed.

  Examples of chelating agents include aminocarboxylic acid type chelating agents and organic phosphonic acid type chelating agents.

  Specific examples of the aminocarboxylic acid-based chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, and diethylenetriaminepentane Examples thereof include acetic acid, sodium diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and sodiumtriethylenetetraminehexaacetic acid.

  Specific examples of the organic phosphonic acid type chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylene). Phosphonic acid), triethylenetetramine hexa (methylenephosphonic acid), ethane-1,1, -diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane- 1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2 , 3,4-tricarboxylic acid, α-methylphosphonosuccinic acid And the like.

  These chelating agents may be used alone or in combination of two or more.

  Among the chelating agents, organic phosphonic acid chelates are preferable, and ethylenediaminetetrakis (methylenephosphonic acid) is more preferable.

  The content of the chelating agent in the polishing composition (when two or more kinds are used, the total amount thereof) is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, and 0.1. More preferably, it is 001% by mass or more. By increasing the content of the chelating agent, the effect of suppressing the metal impurities remaining on the object to be polished is enhanced. Further, the content of the chelating agent in the polishing composition (when two or more kinds are used, the total amount thereof) is preferably less than 0.5% by mass, more preferably less than 0.3% by mass, It is more preferably less than 0.1% by mass, and most preferably less than 0.05% by mass. By reducing the content of the chelating agent, the storage stability of the polishing composition is further maintained.

(Antiseptic / antifungal agent)
The polishing composition according to one aspect of the present invention may further contain an antiseptic / antifungal agent.

  Examples of the preservatives and fungicides include isothiazoline-based preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters. , And phenoxyethanol.

  These preservatives and fungicides may be used alone or in combination of two or more.

(Surfactant)
The polishing composition according to one aspect of the present invention may include a surfactant. The surfactant may be any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  Examples of the anionic surfactant include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfuric acid ester, alkyl sulfuric acid ester, polyoxyethylene alkyl sulfuric acid, alkyl sulfuric acid, alkylbenzene sulfonic acid, alkyl phosphoric acid ester, polyoxyethylene alkyl. Examples thereof include phosphoric acid ester, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, and salts thereof.

  Examples of the cationic surfactant include alkyl trimethyl ammonium salt, alkyl dimethyl ammonium salt, alkyl benzyl dimethyl ammonium salt, and alkyl amine salt.

  Examples of amphoteric surfactants include alkyl betaines and alkyl amine oxides.

  Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, and alkyl alkanolamides. Specific examples of the nonionic surfactant include a block copolymer of ethylene oxide (EO) and propylene oxide (PO) (diblock body, PEO (polyethylene oxide) -PPO (polypropylene oxide) -PEO type triblock body). , PPO-PEO-PPO triblock, etc.), random copolymer of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether. , Polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, poly Xyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, Polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene lauryl amine, polyoxyethylene stearyl amine, polyoxyethylene oleyl amine, polyoxyethylene monolauric acid ester, polyoxyethylene mono Stearic acid ester, polyoxyethylene distearic acid ester, Oxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, trioleate poly Examples thereof include oxyethylene sorbitan, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil. Among them, preferred surfactants include block copolymers of EO and PO (particularly PEO-PPO-PEO type triblock products), random copolymers of EO and PO, and polyoxyethylene alkyl ethers (for example, Polyoxyethylene decyl ether). Such a surfactant may be added for the purpose of reducing haze and improving detergency.

  The weight average molecular weight of the surfactant in the polishing composition is not particularly limited, but from the viewpoint of improving the polishing rate, it is preferably 200 or more, more preferably 250 or more, and preferably 300 or more. More preferable. The increase in the weight average molecular weight of the surfactant improves the polishing rate.

  The weight average molecular weight of the surfactant is preferably less than 10,000 and more preferably 9500 or less from the viewpoint of reducing haze.

  One of these surfactants may be used alone, or two or more thereof may be used in combination.

(Other known additives)
The polishing composition may further contain a known additive generally contained in the polishing composition, such as an organic acid, an organic acid salt, an inorganic acid or an inorganic acid salt, if necessary.

  Examples of organic acids include monocarboxylic acids such as formic acid, acetic acid, propionic acid, acrylic acid and methacrylic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, oxalic acid, tartaric acid, malic acid, maleic acid and fumaric acid. , Dicarboxylic acids such as succinic acid, polycarboxylic acids such as citric acid, organic sulfonic acids, and organic phosphonic acids. Examples of the organic acid salts include alkali metal salts such as sodium salts and potassium salts of organic acids, ammonium salts, and the like.

  Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, carbonic acid and the like. Examples of the inorganic acid salt include alkali metal salts such as sodium salts and potassium salts of inorganic acids, or ammonium salts.

  The organic acid and its salt, and the inorganic acid and its salt may be used alone or in combination of two or more kinds.

  The content of the organic acid and its salt, and the inorganic acid and its salt (the total amount when two or more kinds are used) in the polishing composition is preferably 0.00005% by mass or more, and 0.0001% by mass. The above content is more preferable, and the content is more preferably 0.0005 mass% or more. Further, the content of the organic acid and its salt, and the inorganic acid and its salt (the total amount when two or more kinds are used) in the polishing composition is preferably less than 0.5% by mass, and 0.3 It is more preferably less than 0.1% by mass, even more preferably less than 0.1% by mass, and most preferably less than 0.05% by mass.

[Form of polishing composition, etc.]
The polishing composition according to the present invention may be a one-component type or a multi-component type composed of two or more agents. Further, the polishing composition described above may be used for polishing as it is, or diluted by adding water to a concentrated solution of the polishing composition, or in the case of a multi-component polishing composition, water. And an aqueous solution containing a part of the constituents may be added to dilute and prepare for polishing. For example, the polishing composition can be prepared by storing and / or transporting the concentrated solution of the polishing composition and then diluting it at the time of use. That is, the concept of the polishing composition in the technology disclosed herein includes a polishing liquid (working slurry) which is supplied to a polishing object and used for polishing the polishing object, and a diluted polishing solution. Both a concentrated solution (stock solution of polishing solution) is included.

  The concentrated form of the polishing composition is advantageous from the viewpoints of convenience, cost reduction, and the like during production, distribution, storage, and the like. The concentration ratio can be, for example, about 2 times or more and 100 times or less in terms of volume, and is preferably about 5 times or more and 50 times or less. The concentration ratio of the polishing composition according to a more preferable aspect is 10 times or more and 40 times or less.

  The polishing composition according to the present invention is preferably alkaline, and its pH is preferably 8 or higher, more preferably 9 or higher, and even more preferably 9.5 or higher. When the pH of the polishing composition increases, the polishing rate tends to improve. On the other hand, the pH is preferably 12 or less, more preferably 11 or less, and further preferably 10.8 or less. When the pH of the polishing composition decreases, the accuracy of the surface tends to improve.

  From the above, the pH of the polishing composition according to the present invention is preferably in the range of 8 or more and 12 or less, more preferably in the range of 9 or more and 11 or less, and in the range of 9.5 or more and 10.8 or less. Is particularly preferable. Particularly, when the object to be polished is a silicon wafer, the pH of the polishing composition is preferably in the above range.

  When the polishing composition is reused, it may be adjusted so that the pH is within the above range, if necessary. For adjusting the pH, a known pH adjuster may be used, or the above basic compound may be used. The pH value of the polishing composition can be confirmed with a pH meter. The detailed measuring method will be described in Examples.

[Object to be polished]
The object to be polished by using the polishing composition according to one embodiment of the present invention is not particularly limited and can be applied to the polishing of objects to be polished having various materials and shapes. Examples of materials to be polished include silicon materials, metals such as aluminum, nickel, tungsten, steel, tantalum, titanium, and stainless steel, or semimetals, or alloys thereof; quartz glass, aluminosilicate glass, glass-like Glassy substances such as carbon; ceramic materials such as alumina, silica, sapphire, silicon nitride, tantalum nitride, titanium carbide; compound semiconductor substrate materials such as silicon carbide, gallium nitride, gallium arsenide; resin materials such as polyimide resin; etc. Is mentioned. Further, the object to be polished may be composed of a plurality of materials among the above materials.

  Among these, a silicon material is preferable because the effect of the polishing composition according to the present invention can be more remarkably obtained. That is, the polishing composition according to one aspect of the present invention is preferably used for polishing a silicon material.

  The silicon material preferably contains at least one material selected from the group consisting of silicon single crystal, amorphous silicon and polysilicon. As the silicon material, silicon single crystal or polysilicon is more preferable, and silicon single crystal is particularly preferable, from the viewpoint that the effect of the present invention can be more remarkably obtained. That is, the object to be polished is preferably a single crystal silicon substrate.

  Further, the shape of the object to be polished is not particularly limited. The polishing composition according to the present invention can be preferably applied to polishing an object to be polished having a flat surface such as a plate shape or a polyhedron shape.

[Polishing method]
As another aspect of the present invention, there is provided a polishing method including polishing an object to be polished using the above polishing composition. The polishing composition according to the present invention is particularly suitable for use in the finish polishing step because it has an excellent effect of reducing haze. That is, the polishing method according to the present invention is preferably used in the finish polishing step. Therefore, according to the present invention, there is also provided a method for manufacturing an abrasive article (for example, a method for manufacturing a silicon wafer) including a final polishing step using the polishing composition. The final polishing step refers to the final polishing step in the manufacturing process of the target object (that is, the step in which further polishing is not performed after that step). The polishing composition according to the present invention is also used in a polishing step upstream of the final polishing step (refers to a step between the rough polishing step and the final polishing step), for example, a polishing step performed immediately before the final polishing step. It may be used.

  The polishing composition according to the present invention is particularly preferably used for polishing a single crystal silicon substrate, as described above. In particular, the polishing composition according to the present invention is suitable as a polishing composition used in the final polishing step of a single crystal silicon substrate. More specifically, the polishing composition according to the present invention is used for polishing a single crystal silicon substrate whose surface roughness is adjusted to a surface state of 0.01 nm or more and 100 nm or less by a step upstream from a finish polishing step. It is suitable when applied.

  As a polishing apparatus, a holder for holding a substrate or the like having an object to be polished, a motor capable of changing the number of revolutions, and the like are attached, and a general polishing plate having a polishing pad (polishing cloth) can be attached. A polishing machine can be used.

  As the polishing pad, general non-woven fabric type, polyurethane type, suede type and the like can be used without particular limitation. It is preferable that the polishing pad is grooved so that the polishing composition is retained therein.

  The polishing conditions are appropriately set depending on the stage of the polishing process in which the polishing composition is used.

  In the preliminary polishing step, the rotation speed of the surface plate is preferably about 10 rpm or more and 100 rpm or less, more preferably about 20 rpm or more and 50 rpm or less. At this time, the upper rotary platen and the lower rotary platen may have different rotation speeds, but they are usually set to the same relative speed with respect to the wafer. In the finish polishing step, a single-side polishing machine can be preferably used, and the rotation speed of the surface plate is preferably 10 rpm or more and 100 rpm or less, more preferably 20 rpm or more and 50 rpm or less, and 25 rpm or more and 50 rpm or less. It is more preferable that the degree is approximately. With such a rotation speed, the haze level on the surface of the object to be polished can be significantly reduced.

  The object to be polished is usually pressed by a platen. The pressure at this time can be appropriately selected, but in the preliminary polishing step, it is preferably about 5 kPa or more and 30 kPa or less, more preferably about 10 kPa or more and 25 kPa or less. Further, in the case of the finish polishing step, it is preferably about 5 kPa or more and 30 kPa or less, more preferably about 10 kPa or more and 20 kPa or less. With such a pressure, the haze level on the surface of the object to be polished can be significantly reduced.

  The supply rate of the polishing composition can be appropriately selected according to the size of the platen, but in view of economy, in the case of the preliminary polishing step, it is usually about 0.1 L / min or more and 5 L / min or less. Is preferable, and more preferably about 0.2 L / min or more and about 2 L / min or less. Further, in the case of the finish polishing step, it is usually preferably 0.1 L / min or more and 5 L / min or less, and more preferably 0.2 L / min or more and 2 L / min or less. With such a supply rate, the surface of the object to be polished can be efficiently polished, and the haze level of the surface of the object to be polished can be significantly reduced.

  The holding temperature of the polishing composition in the polishing apparatus is not particularly limited, but from the viewpoint of stability of the polishing rate and reduction of haze level, it is usually preferably 15 ° C or higher and 40 ° C or lower, and 18 ° C or higher and 25 ° C or lower The following degree is more preferable.

  Regarding the above-mentioned polishing conditions (setting of the polishing apparatus), only one example has been described, and it may be out of the above range or the setting can be changed appropriately. Those skilled in the art can appropriately set such conditions.

  Furthermore, it is preferable to carry out washing and drying after polishing. The method and conditions for these operations are not particularly limited, and known ones are appropriately adopted. For example, SC-1 cleaning is preferably performed as the step of cleaning the object to be polished. "SC-1 cleaning" is a cleaning method performed using, for example, a mixed liquid of ammonia and hydrogen peroxide solution (for example, 40 ° C or higher and 80 ° C or lower). Particles on the surface of the silicon wafer can be removed by performing SC-1 cleaning and, for example, thinly etching the surface of the silicon wafer.

  The present invention will be described in more detail with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.

[Examples 1 to 5 and Comparative Examples 1 to 7]
(1) Preparation of Polishing Composition Examples 1 to 5 and Comparative Example 1 having a pH of 10.4 by mixing the following materials in deionized water so as to have the compositions shown in Table 2 below. Each of the polishing compositions Nos. 7 to 7 was prepared (mixing temperature: about 20 ° C., mixing time: about 5 minutes). The pH of the polishing composition (liquid temperature: 20 ° C.) was confirmed with a pH meter (trade name: LAQUA (registered trademark) manufactured by Horiba, Ltd.). At this time, standard buffer solutions (phthalate pH buffer solution pH: 4.01 (25 ° C), neutral phosphate pH buffer solution pH: 6.86 (25 ° C), carbonate pH buffer solution pH: 10. 01 (25 ° C)), the glass electrode was inserted into the polishing composition, and after 2 minutes or more, the value was measured after it was stabilized.

-Abrasive grains (colloidal silica, average primary particle size: 35 nm, average secondary particle size: 60 nm)
・ Basic compound (ammonia water (29% by mass))
・ Water-soluble polymer A
HEC: hydroxyethyl cellulose (weight average molecular weight: 500,000)
・ Water-soluble polymer B
PAA: polyacrylic acid (weight average molecular weight: 1,100,000, 100,000, 200,000)
HEC: hydroxyethyl cellulose (weight average molecular weight: 500,000)
PEO-PPO-PEO: PEO-PPO-PEO type triblock body
(Weight average molecular weight: 9,000)
PEO-PPO Random: Random copolymer of EO and PO
(Weight average molecular weight: 1,000,000)
PVA: Polyvinyl alcohol (weight average molecular weight: 100,000)
・ Chelating agent EDTPO: ethylenediaminetetrakis (methylenephosphonic acid)
-Organic acid salt (triammonium citrate).

  Further, the average primary particle diameter of the abrasive grains is a value measured by using a surface area measuring device (trade name: Flow Sorb II 2300 manufactured by Micromeritics Co., Ltd.).

(2) Evaluation <Silicon wafer pretreatment>
A single crystal silicon substrate (diameter: 200 mm or 300 mm, p-type, crystal orientation <100>, COP free) was polished under the condition 1 using the standard slurry I prepared with the composition shown in the following Table 1, and further the following Table 1 Polishing was performed under the condition 2 using the standard slurry II prepared with the composition shown in.

≪Pretreatment condition≫
(Condition 1)
Polishing machine: Single-wafer polishing machine PNX-332B (manufactured by Okamoto Machine Tool Co., Ltd.)
Polishing pad: POLYPAS (registered trademark) FP55 (nonwoven fabric type, thickness about 2 mm, density about 0.3 g / cm ³ , compression rate about 7%, compression elastic modulus about 90%, hardness about 50 °, manufactured by Fuji Bow Ehime Co., Ltd. )
Polishing load: 20kPa
Platen rotation rate: 20 rpm
Head (carrier) rotation speed: 20 rpm
Supply rate of polishing composition: 1 L / min
Polishing time: 2.5min
Surface plate cooling water temperature: 20 ° C
Holding temperature of the polishing composition: 20 ° C.

(Condition 2)
Polishing machine: Single-wafer polishing machine PNX-332B (manufactured by Okamoto Machine Tool Co., Ltd.)
Polishing pad: POLYPAS (registered trademark) 27NX (suede type, thickness about 1.5 mm, density about 0.4 g / cm ³ , compression rate about 20%, compression elastic modulus about 90%, hardness about 40 °, average aperture diameter) Approximately 45 μm, Porosity approximately 25%, made by Fujibo Ehime Co., Ltd.)
Polishing load: 15kPa
Platen rotation rate: 30 rpm
Head (carrier) rotation speed: 30 rpm
Supply rate of polishing composition: 2 L / min
Polishing time: 2.5min
Surface plate cooling water temperature: 20 ° C
Holding temperature of the polishing composition: 20 ° C.

≪Washing and drying≫
A cleaning liquid (NH ₄ OH (29 mass%): H ₂ O ₂ (31 mass%): deionized water (DIW) = 1: 3: 30 (volume ratio)) was further added to the polished single crystal silicon substrate. Washed with (SC-1 wash). More specifically, two cleaning tanks are prepared, the cleaning solution is stored in each of the first and second cleaning tanks and kept at 60 ° C., and the silicon wafer after polishing is used as the first cleaning tank. After 6 minutes, after passing through a rinse tank equipped with an ultrasonic oscillator of ultrapure water having a frequency of 950 kHz, it was immersed in the second cleaning tank for 6 minutes while the ultrasonic oscillator was operating. Then, IPA vapor drying was performed.

  As described above, the silicon wafer was pretreated by polishing, cleaning and drying.

<Standard test 1: Calculation of abrasive grain adsorption parameter 1>
The following standard solution was prepared, and the standard solution was centrifuged under the following centrifugation conditions to collect the supernatant.

<< Composition of standard solution >>
Aqueous dispersion in which the concentration of abrasive grains is 0.46% by mass, the concentration of ammonia is 0.009% by mass, and the concentration of water-soluble polymer B is 0.017% by mass << Centrifugation Conditions >>
Centrifuge: manufactured by Beckman Coulter, Inc., Avanti (registered trademark) HP-30I
Rotation speed: 20000 rpm
Centrifuge time: 30 min
The total organic carbon concentration (TOC) of the standard liquid and the supernatant liquid was measured using the following measuring device, and the standard liquid measurement value was set to C1, the supernatant liquid measurement value was set to C2, and the abrasive particles were adsorbed by the following formula 1. Parameter 1 was calculated:
TOC measuring device: TOC-5000A manufactured by Shimadzu Corporation.

<Standard test 2: Calculation of substrate adsorption parameter 2>
Two standard solutions were prepared:
Reference standard solution: aqueous solution containing 1.3% by mass of ammonia Standard solution for evaluation: containing 1.3% by mass of ammonia and 0.18% by mass of water-soluble polymer B Aqueous solution.

  The single crystal silicon substrate pretreated by the method of <Silicon wafer pretreatment> was cut into a 60 mm x 30 mm chip die to prepare an evaluation substrate. The weight of this evaluation substrate was W0. Further, the evaluation substrate was immersed in an approximately 5 mass% HF (hydrogen fluoride) aqueous solution for 30 seconds (removal of natural oxide film), and then rinsed with deionized water. The substrate for evaluation thus treated with an oxide film was immersed in a standard solution for evaluation at 25 ° C. for 12 hours, rinsed with deionized water, dried and weighed. This weight was defined as W1. The etching rate (ER) was calculated from the weight difference (W0-W1) before and after immersion and the specific gravity of silicon. Separately, by the same method as described above, the etching rate obtained using the reference standard solution was set to α, and the substrate adsorption parameter 2 was calculated by the following equation 2.

<D ₉₀ >
The D ₉₀ (particle size at which the cumulative mass from the small particle size side of the cumulative particle size distribution on the volume basis is 90%) of the particles present in the polishing compositions of Examples and Comparative Examples was measured by UPA manufactured by Nikkiso Co., Ltd. -Measured using UT151 (unit: μm). When D ₉₀ is small, the dispersibility of the abrasive grains is excellent.

<Polishing rate (RR)>
The weight W2 of the single crystal silicon substrate pretreated by the above method of <silicon wafer pretreatment> was measured. After the measurement, it was immersed in an approximately 3% by mass HF (hydrogen fluoride) aqueous solution and rinsed with deionized water. Then, the polishing compositions of Examples and Comparative Examples were used to perform polishing under the following Condition 3. After polishing, SC-1 cleaning and spin drying as described above were performed to measure the weight W3. The polishing rate (RR, unit: nm / min) was calculated from the weight difference (W2-W3) before and after polishing and the specific gravity of silicon.

(Condition 3)
Polishing machine: Single-wafer polishing machine PNX-322 (manufactured by Okamoto Machine Tool Co., Ltd.)
Polishing pad: POLYPAS (registered trademark) 27NX (suede type, thickness about 1.5 mm, density about 0.4 g / cm ³ , compression rate about 20%, compression elastic modulus about 90%, hardness about 40 °, average aperture diameter) Approximately 45 μm, Porosity approximately 25%, made by Fujibo Ehime Co., Ltd.)
Polishing load: 15kPa
Platen rotation rate: 30 rpm
Head (carrier) rotation speed: 30 rpm
Supply rate of polishing composition: 0.4 L / min
Polishing time: 5 min
Surface plate cooling water temperature: 20 ° C
Holding temperature of the polishing composition: 20 ° C.

<Haze>
The single crystal silicon substrate pretreated as described above was polished under the above condition 1 using the above standard slurry I, and further under the above condition 2 using the polishing compositions of the examples and comparative examples. After that, SC-1 cleaning and IPA vapor drying were performed, and the haze (DWO mode) of the substrate was measured using “Surfscan SP2” manufactured by KLA-Tencor Corporation.

<Viscosity>
The viscosities of 40-fold concentrated liquids of the polishing compositions of Examples and Comparative Examples at 25 ° C. were measured by a capillary kinematic viscometer, Canon Fenceke, manufactured by Shibata Scientific Co., Ltd. (unit: mPa · s).

  The evaluation results of the polishing compositions of Examples and Comparative Examples are shown in Table 3 below.

From the above results, the polishing compositions of Examples 1 to 5 maintain good dispersibility of abrasive grains (D ₉₀ ), polishing rate, and haze, as compared with the polishing compositions of Comparative Examples. However, it was found that it is possible to increase the viscosity.

The polishing composition of Comparative Example 1 had good D ₉₀ , polishing rate, and haze, but could not be thickened because it did not contain the water-soluble polymer B. In Comparative Example 2, the D ₉₀ , polishing rate, and viscosity were good, but the haze was worsened because there was no water-soluble polymer A. In the polishing compositions of Comparative Examples 3 and 5, the abrasive grain adsorption parameter 1 and the substrate adsorption parameter 2 of the water-soluble polymer B were too high, D ₉₀ became large, and the polishing rate was lowered. In the polishing composition of Comparative Example 4, the abrasive particle adsorption parameter 1 and the substrate adsorption parameter 2 of the water-soluble polymer B were too high, and the molecular weight was small, so that the thickening effect could not be sufficiently obtained. In the polishing composition of Comparative Example 6, the abrasive particle adsorption parameter 1 of the water-soluble polymer B was low, but the substrate adsorption parameter 2 was too high, and the haze deteriorated. In the polishing composition of Comparative Example 7, since the water-soluble polymer B had a small molecular weight, the dispersibility (D ₉₀ ) of the abrasive grains deteriorated when an attempt was made to obtain a sufficient thickening effect.

  The present application is based on Japanese Patent Application No. 2017-104877 filed on May 26, 2017, the disclosure content of which is incorporated by reference in its entirety.

Claims (9)

An abrasive grain, a basic compound, a water-soluble polymer A having a function of protecting the surface of an object to be polished, a water-soluble polymer B having a thickening effect, and water,
The weight average molecular weight of the water-soluble polymer B is 50,000 or more,
Abrasive grain adsorption parameter 1 of the water-soluble polymer B obtained from standard test 1 is 40% or less,
A polishing composition in which the substrate adsorption parameter 2 of the water-soluble polymer B obtained from standard test 2 is 20% or less.   The polishing composition according to claim 1, wherein the water-soluble polymer B contains polyacrylic acid.   The polishing composition according to claim 1, wherein the water-soluble polymer A contains a cellulose derivative.   The polishing composition according to claim 1, which is substantially free of an oxidizing agent.   The polishing composition according to claim 1, further comprising a chelating agent.   The polishing composition according to claim 1, comprising at least one of an organic acid and an organic acid salt.   The polishing composition according to claim 1, wherein the polishing composition has a pH in the range of 8 or more and 12 or less.   The polishing composition according to claim 1, wherein the polishing object is a single crystal silicon substrate.   A polishing method comprising polishing an object to be polished with the polishing composition according to claim 1.