JP6305674B2 - Polishing composition and method for producing semiconductor substrate - Google Patents

Description

  The present invention relates to a polishing composition and a method for producing a semiconductor substrate.

  As a polishing composition used for the purpose of polishing the surface of a silicon substrate, a polishing composition containing silicon dioxide particles as abrasive grains is known. For example, Patent Document 1 discloses a polishing composition containing two types of silica particles having different average primary particle diameters, a water-soluble polymer, and a basic compound. In the polishing composition of Patent Document 1, by incorporating two types of silica particles having different average primary particle diameters as abrasive grains, the polishing rate is improved and the surface roughness of the silicon substrate after polishing is reduced. Yes.

JP 2009-231486 A

  However, when the polishing composition of Patent Document 1 is used, there is a problem that scratches are easily generated on the polished surface of the silicon substrate. Further, the polishing composition of Patent Document 1 is insufficient from the viewpoint of reducing the haze level of the polished surface of the silicon substrate.

  An object of the present invention is to provide a polishing composition and a method for manufacturing a semiconductor substrate that can reduce scratches generated on the polishing surface of an object to be polished and can reduce the haze level of the polishing surface. is there.

In order to achieve the above object, the polishing composition of the present invention comprises an abrasive A having an average value of the major axis / minor axis ratio determined by using an electron microscope of 1.5 to 2.0 , and an electron The average value of the major axis / minor axis ratio determined using a microscope is 1.0 to 1.2, and the average value of the major axis of the abrasive grain A is 5 nm to 100 nm, The average value of the major axis of the abrasive grains B is 5 nm or more and 40 nm or less, and is used for polishing a silicon substrate.

Polishing composition Ken is preferably used in applications for final polishing of silicon substrate.
Moreover, the manufacturing method of the semiconductor substrate of this invention is characterized by including the grinding | polishing process of grind | polishing a silicon substrate using the said polishing composition.

  According to the polishing composition and the method for producing a semiconductor substrate of the present invention, it is possible to reduce scratches generated on the polishing surface of the object to be polished and to reduce the haze level of the polishing surface.

Hereinafter, an embodiment of the present invention will be described.
The polishing composition of the present embodiment contains abrasive grains, and preferably further contains a water-soluble polymer, a basic compound, a chelating agent, and a surfactant. The polishing composition is prepared by mixing each component such as abrasive grains with water.

  Polishing composition is used for the use which grind | polishes the surface of the silicon substrate as a grinding | polishing target object. The silicon substrate polishing step includes, for example, a rough polishing step (primary polishing / secondary polishing) for planarizing the surface of a silicon substrate sliced in a disk shape from a silicon single crystal ingot, and a rough polishing step A final polishing step of further removing the fine irregularities present on the surface of the silicon substrate to make a mirror surface, and the polishing composition is particularly preferably used for final polishing. The silicon substrate whose surface is polished with the polishing composition can be suitably used for manufacturing a semiconductor substrate.

(Abrasive grains)
The abrasive grains physically polish the surface of the silicon substrate by applying a physical action.
Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include particles made of a metal oxide such as silica, alumina, ceria, titania, and silicon nitride particles, silicon carbide particles, and boron nitride particles. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles.

  Of these specific examples, silica is preferred. Specific examples of the silica include silica particles selected from colloidal silica, fumed silica, and sol-gel silica. Among these silica particles, it is preferable to use silica particles selected from colloidal silica and fumed silica, particularly colloidal silica, from the viewpoint of reducing scratches generated on the polished surface of the silicon substrate. Of these, one kind may be used alone, or two or more kinds may be used in combination.

  The true specific gravity of silica is preferably 1.5 or more, more preferably 1.6 or more, and still more preferably 1.7 or more. Due to the increase in the true specific gravity of silica, a high polishing rate can be obtained when polishing a silicon substrate. The true specific gravity of silica is preferably 2.2 or less, more preferably 1.9 or less. The true specific gravity of the silica is calculated from the weight when the silica particles are dried and the weight when the silica particles are filled with ethanol having a known capacity.

  The content of abrasive grains in the polishing composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.3% by mass or more. By increasing the content of abrasive grains, a high polishing rate can be obtained when polishing a silicon substrate. The content of abrasive grains in the polishing composition is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, and most preferably 1% by mass or less. It is. By reducing the content of the abrasive grains, the stability of the polishing composition is improved.

  The abrasive grains are mainly abrasive grains A having an average value of the major axis / minor axis ratio of 1.5 or more and 3.0 or less, and an average value of the major axis / minor axis ratio of 1.0 or more and less than 1.5. It is composed of a certain abrasive grain B. In other words, the abrasive grains are contained in the polishing composition in a state where abrasive grains A and abrasive grains B having different average values of the major axis / minor axis ratio are mixed.

  In the polishing composition, by mixing the abrasive grains A and the abrasive grains B having different average values of the major axis / minor axis ratio, the other grains enter one of the grains to increase the abrasive density. It is done. By increasing the abrasive density in the polishing composition, a high polishing rate can be obtained when the silicon substrate is polished.

  The average value of the major axis / minor axis ratio is a value indicating the shape of the abrasive grains, and can be determined, for example, by photographic observation using an electron microscope. Specifically, the abrasive grains are observed using a scanning electron microscope, and a minimum rectangle circumscribing the particle image is drawn. For the rectangle drawn on the particle image, the value obtained by dividing the length of the long side (the value of the major axis) by the length of the short side (the value of the minor axis) is taken as the average value of the ratio of the major axis / minor axis calculate. Calculation of the average value of the major axis / minor axis ratio based on such image analysis processing can be performed using general image analysis software.

Hereinafter, the abrasive grains A and the abrasive grains B will be specifically described.
The abrasive grain A has an average value of the major axis / minor axis ratio of 1.5 or more, and preferably 1.7 or more. By increasing the average value of the major axis / minor axis ratio of the abrasive grains A, a high polishing rate can be obtained when the silicon substrate is polished. The average value of the major axis / minor axis ratio of the abrasive grain A is 3.0 or less, preferably 2.2 or less, more preferably 2.0 or less. By reducing the average value of the major axis / minor axis ratio of the abrasive grains A, scratches generated on the polished surface of the silicon substrate are reduced.

  The abrasive grain B has an average value of the major axis / minor axis ratio of 1.0 or more, preferably 1.05 or more. The abrasive grain B has an average value of the major axis / minor axis ratio of less than 1.5, preferably 1.2 or less. By setting the average value of the major axis / minor axis ratio of the abrasive grains B in the above range, the abrasive grain density in the polishing composition can be suitably increased. By reducing the average value of the major axis / minor axis ratio of the abrasive grains B, the haze level of the polished surface of the silicon substrate is reduced.

  The average value of the major axis of the abrasive grains A is 5 nm or more, preferably 30 nm or more, more preferably 45 nm or more. By increasing the average value of the major axis of the abrasive grains A, a high polishing rate can be obtained when the silicon substrate is polished. The average value of the major axis of the abrasive grains A is 100 nm or less, preferably 80 nm or less, and more preferably 75 nm or less. By reducing the average value of the major axis of the abrasive grains A, the haze level of the polished surface of the silicon substrate is reduced.

  The average value of the major axis of the abrasive grain B is 5 nm or more, preferably 20 nm or more. By increasing the average value of the major axis of the abrasive grains B, a high polishing rate can be obtained when the silicon substrate is polished. The average value of the major axis of the abrasive grain B is 45 nm or less, preferably 40 nm or less. By reducing the average value of the major axis of the abrasive grains B, the haze level of the polished surface of the silicon substrate is reduced.

  The average value of the major axis of the abrasive grains can be determined by photographic observation using an electron microscope. Specifically, a predetermined number (for example, 200) of abrasive grains A (or abrasive grains B) are observed using a scanning electron microscope, and a minimum rectangle circumscribing each particle image is drawn. And about the rectangle drawn with respect to the particle | grain image, the length (value of a major axis) of the long side is calculated | required, and the average value is calculated.

  The content ratio based on the mass of the abrasive grains A and the abrasive grains B is preferably in the range of 90:10 to 10:90, more preferably in the range of 80:20 to 20:80. By setting the content ratio of the abrasive grains A and the abrasive grains B in the above range, the abrasive density in the polishing composition can be suitably increased.

  The abrasive grains in which the abrasive grains A and the abrasive grains B are mixed have, for example, an average value of the major axis / minor axis ratio of 1.5 to 3.0 and an average value of the major axis of 5 nm to 100 nm. It can be obtained by blending abrasive grains and abrasive grains having an average value of major axis / minor axis ratio of 1.0 or more and less than 1.5 and an average value of major axis of 5 nm or more and 45 nm or less.

(water)
Water becomes a dispersion medium or solvent for other components. In order to avoid that the function of other components contained in the polishing composition is inhibited as much as possible, for example, the total content of transition metal ions is preferably 100 ppb or less. For example, the purity of water can be increased by operations such as removal of impurity ions using an ion exchange resin, removal of foreign matters by a filter, and distillation. Specifically, for example, ion exchange water, pure water, ultrapure water, distilled water or the like is preferably used.

(Water-soluble polymer)
A water-soluble polymer can be contained in the polishing composition. The water-soluble polymer improves the wettability of the polished surface of the silicon substrate during the surface treatment of the silicon substrate such as during polishing or rinsing. As the water-soluble polymer, those having at least one functional group selected from a cationic group, an anionic group and a nonionic group in the molecule can be used. Specific examples of the water-soluble polymer include those containing a hydroxyl group, carboxyl group, acyloxy group, sulfo group, quaternary nitrogen structure, heterocyclic structure, vinyl structure, polyoxyalkylene structure and the like in the molecule.

  Specific examples of the water-soluble polymer include cellulose derivatives, imine derivatives such as poly (N-acylalkyleneimine), polyvinyl alcohol, polyvinyl pyrrolidone, copolymers containing polyvinyl pyrrolidone as part of the structure, polyvinyl caprolactam, polyvinyl caprolactam. A polyoxyethylene, a polymer having a polyoxyalkylene structure, a polymer having a plurality of types such as diblock type, triblock type, random type, and alternating type, poly Examples include ether-modified silicone.

A water-soluble polymer may be used individually by 1 type, and may be used in combination of 2 or more type.
Among water-soluble polymers, a cellulose derivative, a polyvinyl pyrrolidone, or a polymer having a polyoxyalkylene structure is preferable from the viewpoints of improving wettability on a polished surface, reducing particles, and reducing surface roughness. Specific examples of the cellulose derivative include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose and the like. Among cellulose derivatives, hydroxyethyl cellulose is particularly preferable because it has a high ability to give wettability to the polished surface of a silicon substrate and has good detergency.

  The weight average molecular weight of the water-soluble polymer is preferably 1000 or more in terms of polyethylene oxide, more preferably 10,000 or more, still more preferably 100,000 or more, and most preferably 200,000 or more. As the weight average molecular weight of the water-soluble polymer increases, the wettability of the polished surface of the silicon substrate tends to increase. The water-soluble polymer preferably has a weight average molecular weight of 2000000 or less, more preferably 1500,000 or less, still more preferably 1000000 or less, and most preferably 500000 or less. A decrease in the weight average molecular weight of the water-soluble polymer tends to maintain the stability of the polishing composition.

  The content of the water-soluble polymer in the polishing composition is preferably 0.002% by mass or more, more preferably 0.004% by mass or more, and further preferably 0.006% by mass or more. By increasing the content of the water-soluble polymer in the polishing composition, the wettability of the polished surface tends to be further improved. The content of the water-soluble polymer in the polishing composition is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and still more preferably 0.1% by mass or less. . By reducing the content of the water-soluble polymer in the polishing composition, the stability of the polishing composition tends to be more maintained.

(Basic compound)
A basic compound can be contained in the polishing composition. The basic compound chemically polishes the polishing surface of the silicon substrate by applying a chemical action (chemical etching). Thereby, it becomes easy to improve the polishing rate at the time of polishing the silicon substrate.

  Specific examples of the basic compound include alkali metal hydroxides or salts, quaternary ammonium hydroxide or salts thereof, ammonia, amines, and the like. Examples of the alkali metal include potassium and sodium. Examples of the salt include carbonate, hydrogen carbonate, sulfate, acetate and the like. Examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, and tetrabutylammonium. Specific examples of the alkali metal hydroxide or salt include potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium acetate, potassium chloride and the like. Specific examples of the quaternary ammonium hydroxide or a salt thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. 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. These basic compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  Among the basic compounds, at least one selected from ammonia, ammonium salts, alkali metal hydroxides, alkali metal salts, and quaternary ammonium hydroxides is preferable. Among basic compounds, selected from ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate More preferred is at least one kind. Among the basic compounds, at least one selected from ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide is more preferable, and more preferably at least one of ammonia and tetramethylammonium hydroxide. Yes, most preferably ammonia.

  It is preferable that content of the basic compound in polishing composition is 0.001 mass% or more, More preferably, it is 0.002 mass% or more, More preferably, it is 0.003 mass% or more. When the content of the basic compound in the polishing composition is increased, a high polishing rate tends to be obtained when the silicon substrate is polished. The content of the basic compound in the polishing composition is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.2% by mass or less. Due to the decrease in the content of the basic compound in the polishing composition, the shape of the silicon substrate tends to be easily maintained.

  The pH of the polishing composition is preferably 8.0 or more, more preferably 8.5 or more, and still more preferably 9.0 or more. By increasing the pH of the polishing composition, a high polishing rate tends to be obtained when the silicon substrate is polished. It is preferable that pH of polishing composition is 12.5 or less, More preferably, it is 12.0 or less, More preferably, it is 11.5 or less. By reducing the pH of the polishing composition, the shape of the silicon substrate tends to be easily maintained.

(Chelating agent)
A chelating agent can be contained in the polishing composition. The chelating agent suppresses metal contamination of the silicon substrate by capturing metal impurity components in the polishing system to form a complex.

  Specific examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Specific examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriamine Examples include acetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Specific examples of the organic phosphonic acid chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylene Phosphonic 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- And methylphosphonosuccinic acid.

(Surfactant)
A surfactant can be contained in the polishing composition. The surfactant suppresses roughening of the polished surface of the silicon substrate. Thereby, it becomes easy to reduce the haze level of the polished surface. In particular, when a basic compound is included in the polishing composition, the polishing surface of the silicon substrate tends to be roughened by chemical polishing (chemical etching) with the basic compound. For this reason, the combined use of the basic compound and the surfactant is particularly effective.

  As the surfactant, those having a weight average molecular weight of less than 1000 are preferable, and examples thereof include anionic or nonionic surfactants. Among the surfactants, nonionic surfactants are preferably used. Since the nonionic surfactant has low foaming property, it is easy to handle at the time of preparation and use of the polishing composition. In addition, for example, pH adjustment is easier than when an ionic surfactant is used. Specific examples of the nonionic surfactant include oxyalkylene polymers such as polyethylene glycol and polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene Examples include polyoxyalkylene adducts such as ethylene glyceryl ether fatty acid esters and polyoxyethylene sorbitan fatty acid esters.

  Specifically, polyoxyethylene polyoxypropylene copolymer, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene Oxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl Ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene Nyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxy Ethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, monolaurate Polyoxyethylene sorbitan, polyoxyethylene sorbitan monopaltimate, Nosutearin Polyoxyethylene sorbitan monooleate polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan, polyoxyethylene sorbit tetraoleate, polyoxyethylene castor oil, polyoxyethylene hardened castor oil, and the like.

As the surfactant, one kind may be used alone, or two or more kinds may be used in combination.
(Other ingredients)
The polishing composition further contains known additives generally contained in the polishing composition as necessary, for example, organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, antifungal agents and the like. May be.

  Specific examples of organic acids include fatty acids such as formic acid, acetic acid and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, Organic sulfonic acid, organic phosphonic acid, etc. are mentioned. Specific examples of the organic acid salt include alkali metal salts such as sodium salts and potassium salts of organic acids described in the specific examples of organic acids, or ammonium salts.

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

Among organic acid salts and inorganic acid salts, ammonium salts are preferable from the viewpoint of suppressing metal contamination of the silicon substrate.
An organic acid and its salt, and an inorganic acid and its salt may be used individually by 1 type, and may be used in combination of 2 or more type.

Specific examples of the antiseptic and fungicide include isothiazoline compounds, paraoxybenzoates, phenoxyethanol and the like.
In the polishing step of polishing the surface of the silicon substrate using the polishing composition described above, while supplying the polishing composition to the surface of the silicon substrate, the polishing pad is pressed against the surface to rotate the silicon substrate and the polishing pad. Let At this time, the surface of the silicon substrate is polished by the physical action due to friction between the polishing pad and the silicon substrate surface and the physical action due to friction between the abrasive grains in the polishing composition and the silicon substrate surface. . In the case where the polishing composition contains a basic compound, the surface of the silicon substrate is polished by a chemical action by the basic compound in addition to the above physical action.

According to the embodiment described in detail above, the following effects are exhibited.
(1) The polishing composition has abrasive grains A having an average value of the major axis / minor axis ratio of 1.5 or more and 3.0 or less, and an average value of the major axis / minor axis ratio of 1.0 or more and less than 1.5. And abrasive grains B. The average value of the major axis of the abrasive grain A is 5 nm or more and 100 nm or less, and the average value of the major axis of the abrasive grain B is 5 nm or more and 45 nm or less. Thus, scratches generated on the polished surface of the silicon substrate after polishing using the polishing composition can be reduced, and the haze level of the polished surface can be reduced.

  (2) The polishing composition is used for polishing a silicon substrate, particularly for final polishing of a silicon substrate, so that the polishing surface has a low haze level and a high quality silicon substrate with little scratch on the polishing surface. Can be easily obtained.

  (3) The semiconductor substrate manufacturing method includes a polishing step of polishing the silicon substrate using the polishing composition described in the above section (1). As a result, a silicon substrate with a low haze level on the polished surface and a low scratch is formed on the polished surface, and a high-quality semiconductor substrate can be manufactured from the silicon substrate.

In addition, the said embodiment may be changed as follows.
-The polishing composition of the embodiment may be a one-part type or a multi-part type including a two-part type.

  -The polishing composition of the said embodiment may be in the state concentrated at the time of manufacture and sale. That is, the polishing composition of the above embodiment may be produced and sold in the form of a stock solution of the polishing composition.

  -The polishing composition of the said embodiment may be prepared by diluting the undiluted | stock solution of polishing composition with water. In this case, the dilution rate is preferably 2 times or more, more preferably 5 times or more, and further preferably 10 times or more. By increasing the dilution ratio, the transportation cost of the stock solution of the polishing composition can be reduced, and the storage location can be saved. The dilution ratio is preferably 100 times or less, more preferably 50 times or less, and further preferably 40 times or less. By reducing the dilution factor, the stability of the stock solution of the polishing composition is easily maintained.

  -Each component contained in the polishing composition of the embodiment may be filtered by a filter immediately before production. Further, the polishing composition of the above embodiment may be used after being filtered by a filter immediately before use. By performing the filtration treatment, coarse foreign matters in the polishing composition are removed, and the quality is improved.

  The material and structure of the filter used for the filtration process are not particularly limited. Examples of the filter material include cellulose, nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass. Examples of the filter structure include depth, pleats, membranes, and the like.

  -The polishing pad used in the polishing process using the polishing composition of the embodiment is not particularly limited. For example, any of non-woven fabric type, suede type, those containing abrasive grains, and those not containing abrasive grains may be used.

  In polishing the silicon substrate using the polishing composition of the above embodiment, the polishing composition once used for polishing may be collected and used again for polishing the silicon substrate. As a method of reusing the polishing composition, for example, a method of collecting the polishing composition discharged from the polishing apparatus in a tank and circulating it again into the polishing apparatus can be used. Reusing the polishing composition means that the environmental load can be reduced by reducing the amount of the polishing composition discharged as a waste liquid, and polishing the silicon substrate by reducing the amount of the polishing composition to be used. This is useful in that the manufacturing cost can be suppressed.

  When reusing a polishing composition, it is preferable to add a part or all of each component such as abrasive grains consumed or lost by polishing as a composition modifier. The composition adjusting agent may be added to each component individually, or may be added in a state where each component is mixed at an arbitrary ratio according to the size of the circulation tank, polishing conditions, and the like. By adding a composition adjusting agent to the polishing composition to be reused, the composition of the polishing composition is maintained, and the function of the polishing composition can be exhibited continuously.

  The polishing composition according to the embodiment includes abrasive grains A having a major axis / minor axis ratio of 1.5 or more and 3.0 or less, and abrasive grains having a major axis / minor axis ratio of 1.0 or more and less than 1.5. B may be included, the average value of the major axis of the abrasive grain A may be 5 nm or more and 100 nm or less, and the average value of the major axis of the abrasive grain B may be 5 nm or more and 45 nm or less.

  -The polishing composition of the said embodiment may be used for uses other than grind | polishing a silicon substrate. For example, it may be used to obtain a polished product such as a metal such as stainless steel, plastic, glass, and sapphire.

The embodiment will be described more specifically with reference to examples and comparative examples.
Compounding silica particles A and silica particles B as abrasive grains A and abrasive grains B, ammonia as a basic compound, hydroxyethyl cellulose having a weight average molecular weight of 250,000 as a water-soluble polymer, and ion-exchanged water, Polishing compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were prepared. As silica particle A and silica particle B, colloidal silica having an average value of the major axis / minor axis ratio of 1.5 or more and 3.0 or less, and an average value of the major axis / minor axis ratio of 1.0 or more and less than 1.5 Each of the colloidal silicas was blended.

  Tables 1 and 3 show the common composition of the polishing composition of each example, and the detailed configuration of silica particles A and B. The average value of the major axis of silica particle A and silica particle B shown in Table 3 is the average value of the major axis / minor axis ratio calculated based on photo observation using a scanning electron microscope “S-4700” manufactured by Hitachi, Ltd. is there.

  Next, the surface of the silicon substrate after preliminary polishing was polished under the conditions shown in Table 2 using the polishing composition of each example (corresponding to final polishing). A silicon substrate having a diameter of 300 mm, a conductivity type of P type, a crystal orientation of <100>, and a resistivity of 0.1 Ω · cm to 100 Ω · cm is a polishing slurry manufactured by Fujimi Incorporated (product) What was pre-polished using the name GLANZOX 1103) was used. While polishing rate was evaluated about the polishing composition of each example, the haze level and scratch of the grinding | polishing surface were evaluated about the silicon substrate after grinding | polishing.

(Polishing speed)
Calculate the polishing rate by measuring the difference in mass of the silicon substrate before and after polishing and dividing the obtained mass difference by the density, area and polishing time of the silicon substrate, and evaluate the polishing rate based on the calculated value did. The results are shown in the polishing rate column of Table 3. The evaluation criteria for the polishing rate are as follows.

Evaluation A: When the polishing rate is 0.04 μm / min or more.
Evaluation B: The polishing rate is 0.03 μm / min or more and less than 0.04 μm / min.
Evaluation C: When the polishing rate is 0.02 μm / min or more and less than 0.03 μm / min.

Evaluation D: When the polishing rate is less than 0.02 μm / min.
(Haze level)
The haze level of the polished surface is measured based on the measured value obtained by measuring the polished surface of the polished silicon substrate in the DWO mode of the wafer inspection device “Surfscan SP2” manufactured by KLA-Tencor. evaluated. The results are shown in the haze level column of Table 3. The evaluation criteria for the haze level are as follows.

Evaluation A: When the measured value is less than 0.090 ppm.
Evaluation B: When the measured value is 0.090 ppm or more and less than 0.095 ppm.
Evaluation C: When the measured value is 0.095 ppm or more and less than 0.100 ppm.

Evaluation D: When the measured value is 0.100 ppm or more.
(scratch)
Using a wafer inspection apparatus “Surfscan SP2” manufactured by KLA-Tencor Corporation, scratches present on the polished surface of the polished silicon substrate were evaluated. The results are shown in the scratch column of Table 3. The evaluation criteria for scratches are as follows.

Evaluation A: When no scratch is confirmed on the polished surface of the silicon substrate.
Evaluation C: When scratches are confirmed on the polished surface of the silicon substrate.

As shown in Table 3, in Examples 1 and 2, excellent results were obtained in all evaluations of polishing rate, haze level, and scratch. On the other hand, in Comparative Examples 1 to 4, one or more of the polishing rate, the haze level, and the scratch were evaluated.

  From these results, the average value of the major axis / minor axis ratio is 1.5 or more in the polishing composition from the viewpoint of reducing the haze level and scratch of the polishing surface while maintaining a suitable polishing rate. Silica particles A that are 0 or less and silica particles B that have an average value of the major axis / minor axis ratio of 1.0 or more and less than 1.5 are included, and the average value of the major axis of the silica particles A is 5 nm or more and 100 nm or less. In addition, it is suggested that the average value of the major axis of the silica particles B is 5 nm or more and 45 nm or less.

Next, a technical idea that can be grasped from the embodiment and examples will be described.
(A) Abrasive grain A having an average value of major axis / minor axis ratio of 1.5 or more and 3.0 or less, and abrasive grain B having an average value of major axis / minor axis ratio of 1.0 or more and less than 1.5 The polishing composition is characterized in that the average value of the major axis of the abrasive grain A is 5 nm or more and 100 nm or less, and the average value of the major axis of the abrasive grain B is 5 nm or more and 45 nm or less.

Claims (3)

The average value of the major axis / minor axis ratio obtained using an electron microscope is 1.5 to 2.0 and the average value of the major axis / minor axis ratio obtained using an electron microscope is 1.0. Containing abrasive grains B which is 1.2 or less,
The average value of the major axis of the abrasive grains A is 5 nm or more and 100 nm or less,
The average value of the major axis of the abrasive grains B is 5 nm or more and 40 nm or less,
A polishing composition, which is used for polishing a silicon substrate.   The polishing composition according to claim 1, which is used for final polishing of a silicon substrate.   A method for producing a semiconductor substrate, comprising a polishing step of polishing a silicon substrate using the polishing composition according to claim 1.