Grinding composition

Abstract

Provided is a polishing composition that can suppress a decrease in the polishing rate and reduce an edge roll-off amount after polishing, both at a high level. Provided is polishing composition for use in a preliminary polishing step for a silicon substrate. The polishing composition comprises an abrasive, a basic compound, a surfactant, a chelating agent, and water, and comprises, as the surfactant, a surfactant I having a repeating structure of an oxyalkylene unit.

Description

[Technical Field]

[0001] The present invention relates to a polishing composition, more specifically, to a polishing composition for pre-polishing silicon wafers. This application claims priority under Japanese Patent Application No. 2021-5835, filed on 18 January 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] The surface of silicon wafers used in the manufacture of semiconductor products is generally finished to a high-quality mirror surface through a lapping process (rough polishing process) and a polishing process (precision polishing process). The polishing process typically includes a preliminary polishing process and a finish polishing process. Patent documents 1 and 2 are technical documents relating to polishing compositions that can be used for polishing silicon wafers and the like. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2018 / 180479 [Patent Document 2] Japanese Patent Application Publication No. 2016-124943 [Overview of the project] [Problems that the invention aims to solve]

[0004] Generally, the pre-polishing process is positioned as a process that efficiently prepares the shape and general surface condition of a silicon wafer by removing the surface of the silicon wafer using a relatively easy-to-process polishing slurry. Such a pre-polishing process requires excellent polishing performance (specifically, a high polishing rate, etc.).

[0005] It is known that basic compounds are included in polishing compositions used to polish silicon wafers and the like in order to improve the polishing rate. However, with conventional methods that improve the polishing rate using basic compounds, the area near the edge of the silicon wafer is polished more excessively than the central part, which may lead to an undesirable reduction in the thickness of the outer edge after polishing (edge ​​roll-off). Patent documents 1 and 2 propose suppressing edge roll-off by using a specific type of water-soluble polymer, but there is a further need to achieve both a high polishing rate suitable for the pre-polishing process and a reduction in edge roll-off.

[0006] Therefore, the present invention aims to provide a polishing composition for the preliminary polishing process of silicon wafers that can achieve a high level of both suppression of the decrease in polishing rate and reduction of the amount of edge roll-off after polishing. [Means for solving the problem]

[0007] This specification provides a polishing composition for use in a preliminary polishing process for silicon wafers. This polishing composition comprises abrasive particles, a basic compound, a surfactant, a chelating agent, and water. The surfactant includes surfactant I having a repeating structure of oxyalkylene units. With this configuration, it is possible to reduce the amount of edge roll-off after polishing while suppressing a decrease in the polishing rate.

[0008] In one preferred embodiment of the polishing composition disclosed herein, the surfactant I is a polyoxyalkylene alkyl ether. By including a polyoxyalkylene alkyl ether as the surfactant, the amount of edge roll-off after polishing can be more effectively reduced.

[0009] In one preferred embodiment of the polishing composition disclosed herein, the ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant I is 50 or more. In this configuration, it is possible to more effectively reduce the amount of edge roll-off after polishing while maintaining the polishing rate.

[0010] In one preferred embodiment of the polishing composition disclosed herein, the ratio (A / S) of the weight concentration (A) of the abrasive grains to the weight concentration (S) of the surfactant I is less than 1000. In this configuration, it is possible to more effectively reduce the amount of edge roll-off after polishing while maintaining the polishing rate.

[0011] In one preferred embodiment of the polishing composition disclosed herein, the abrasive grains include silica particles. In embodiments using silica particles as abrasive grains, a reduction in the amount of edge roll-off after polishing can be achieved more effectively. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described below. Matters other than those specifically mentioned herein that are necessary for carrying out the present invention can be understood as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed herein and common technical knowledge in the art.

[0013] <Abrasive grains> The polishing compositions disclosed herein contain abrasive grains. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the manner in which the polishing composition is used. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include oxide particles such as 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 red iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles, and polyacrylonitrile particles. Here, (meth)acrylic acid refers comprehensively to acrylic acid and methacrylic acid. Abrasive grains can be used individually or in combination of two or more types.

[0014] As the abrasive grains mentioned above, inorganic particles are preferred, and among them, particles made of metal or metalloid oxides are preferred. A suitable example of abrasive grains that can be used in the technology disclosed herein is silica particles. The reason for this is as follows: In polishing silicon wafers, if silica particles made of the same elements and oxygen atoms as the object to be polished are used as abrasive grains, no residue of metals or metalloids other than silicon will be generated after polishing. Therefore, there is no risk of contamination of the silicon wafer surface or deterioration of the electrical properties of the silicon wafer due to the diffusion of metals or metalloids other than silicon into the object to be polished. Furthermore, because silicon and silica have similar hardness, polishing can be performed without causing excessive damage to the silicon wafer surface. Specific examples of silica particles include colloidal silica, fumed silica, and precipitated silica. Colloidal silica and fumed silica are preferred silica particles because they are less likely to cause scratches on the surface of the object to be polished and can achieve a surface with lower haze. Among these, colloidal silica is preferred.

[0015] In the technology disclosed herein, the abrasive grains contained in the polishing composition may be in the form of primary particles, or may be in the form of secondary particles in which a plurality of primary particles are aggregated. Further, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In a preferred embodiment, at least a part of the abrasive grains are contained in the polishing composition in the form of secondary particles.

[0016] The average primary particle diameter of the abrasive grains (typically silica particles) is not particularly limited, but from the viewpoint of the polishing rate and the like, it is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more. From the viewpoint of obtaining a higher polishing effect, the average primary particle diameter is preferably 25 nm or more, and more preferably 30 nm or more. Abrasive grains having an average primary particle diameter of 40 nm or more may be used. Further, from the viewpoint of reducing the amount of edge roll-off after polishing and the like, the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, for example 100 nm or less.

[0017] In this specification, the average primary particle diameter refers to the particle diameter (BET particle diameter) calculated by the formula of average primary particle diameter (nm) = 6000 / (true density (g / cm 3 ) × BET value (m 2 / g)). The specific surface area can be measured, for example, using a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0018] The average secondary particle diameter of the abrasive grains (for example, silica particles) is not particularly limited, but from the viewpoint of the polishing rate and the like, it is preferably 15 nm or more, more preferably 30 nm or more. From the viewpoint of obtaining a higher polishing effect, the average secondary particle diameter is preferably 50 nm or more. Further, from the viewpoint of reducing the amount of edge roll-off after polishing and the like, the average secondary particle diameter of the abrasive grains is suitably 300 nm or less, preferably 260 nm or less, and more preferably 220 nm or less.

[0019] In this specification, the average secondary particle diameter refers to the particle diameter (volume-average particle diameter) measured by dynamic light scattering. The average secondary particle diameter of abrasive grains can be measured, for example, using the "FPAR-1000" model or an equivalent product manufactured by Otsuka Electronics Co., Ltd.

[0020] The shape (outer form) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical abrasive grains include peanut-shaped (i.e., the shape of a peanut shell), cocoon-shaped, konpeito-shaped, and rugby ball-shaped grains.

[0021] While not particularly limited, the average aspect ratio of the major axis / minor axis ratio of the primary abrasive grains (average aspect ratio) is preferably 1.05 or higher, and more preferably 1.1 or higher. A higher polishing rate can be achieved by increasing the average aspect ratio of the abrasive grains. Furthermore, from the viewpoint of reducing scratches, the average aspect ratio of the abrasive grains is preferably 3.0 or lower, and more preferably 2.0 or lower. In some embodiments, the average aspect ratio of the abrasive grains may be, for example, 1.5 or lower, 1.4 or lower, or 1.3 or lower.

[0022] The shape (outer shape) and average aspect ratio of the abrasive grains can be determined, for example, by electron microscopy observation. A specific procedure for determining the average aspect ratio is to use a scanning electron microscope (SEM) to draw the smallest rectangle circumscribing each particle image for a predetermined number of abrasive grains (e.g., 200) whose individual particle shapes can be recognized. Then, for the rectangle drawn for each particle image, the ratio of the major axis to the minor axis is calculated by dividing the length of the major side (major axis value) by the length of the minor side (minor axis value). The average aspect ratio can be obtained by taking the arithmetic mean of the aspect ratios of the predetermined number of particles.

[0023] The abrasive content in the polishing composition is not particularly limited, but is typically 0.01% by weight or more, preferably 0.03% by weight or more, more preferably 0.05% by weight or more, and even more preferably 0.1% by weight or more. A higher polishing rate can be achieved by increasing the abrasive content. Also, from the viewpoint of reducing the amount of edge roll-off after polishing, the above content is usually appropriate to be 10% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less, 2% by weight or less, or 1.5% by weight or less (for example, 1.3% by weight or less), and even more preferably 1% by weight or less (less than 1% by weight), for example, 0.8% by weight or less or 0.5% by weight or less.

[0024] <Surfactants> The polishing compositions disclosed herein include a surfactant I having a repeating structure of oxyalkylene units (i.e., a polyoxyalkylene chain; hereinafter sometimes referred to as a "POA chain") as a surfactant.

[0025] Examples of the oxyalkylene units mentioned above include oxyethylene units, oxypropylene units, and oxybutylene units. Such oxyalkylene units may, but are not limited to, repeating units derived from their respective alkylene oxides. The oxyalkylene units contained in the POA chain of surfactant I may be of one type or two or more types. In a POA chain containing two or more types of oxyalkylene units, the content ratio of these oxyalkylene units is not particularly limited. Furthermore, in a POA chain containing two or more types of oxyalkylene units, these oxyalkylene units may be random copolymers of their respective alkylene oxides, block copolymers, alternating copolymers, or graft copolymers. Surfactant I may be used alone or in combination of two or more types.

[0026] Specific examples of surfactant I include polyoxyalkylene alkyl ethers (e.g., polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxybutylene alkyl ether); polyoxyalkylene alkenyl ethers (e.g., polyoxyethylene oleyl ether); polyoxyalkylene phenyl ethers (e.g., polyoxyethylene phenyl ether; polyoxyethylene styrene-derived phenyl ether; polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, and other polyoxyalkylene alkylphenyl ethers); polyoxyalkylene alkylamines (e.g., polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine); polyoxyalkylene fatty acid esters (e.g., polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monostearate, polyoxyethylene Monoesters and diesters of saturated or unsaturated fatty acids, such as oxyethylene monooleate, polyoxyethylene distearate, and polyoxyethylene dioleate; polyoxyethylene sorbitan fatty acid esters (e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate); fatty acid polyoxyalkylene sorbitans (e.g., polyoxyethylene sorbitan tetraoleate); block copolymers of ethylene oxide (EO) and propylene oxide (PO) (e.g., diblock copolymers, PEO (polyethylene oxide)-PPO (polypropylene oxide)-PEO type triblocks, PPO-PEO-PPO type triblock copolymers, etc.); random copolymers of EO and PO; and others such as polyoxyethylene glycol, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil. In some embodiments, polyoxyalkylene alkyl ethers can be preferably used as surfactant I.

[0027] The number of oxyalkylene units contained in surfactant I, i.e., the number of moles of alkylene oxide added, can be selected so that the effect of using surfactant I is appropriately exhibited. The upper limit of the number of moles of alkylene oxide added is not particularly limited, for example, 100 or less, 80 or less is appropriate, preferably 60 or less, more preferably 40 or less, even more preferably 30 or less from the viewpoint of suppressing a decrease in polishing rate, it may be 25 or less, or 18 or less (e.g., 14 or less). The lower limit of the number of moles of alkylene oxide added is not particularly limited, for example, 3 or more, 5 or more is appropriate, preferably 7 or more (e.g., 9 or more), it may be 10 or more, 12 or more, or 15 or more (e.g., 20 or more).

[0028] From the viewpoint of suitably exhibiting the effect of reducing the amount of edge roll-off while suppressing a decrease in the polishing rate, in some embodiments, surfactant I having a POA chain containing at least oxyethylene units can be preferably employed. The proportion of oxyethylene units (EOs) among the total number of oxyalkylene units contained in surfactant I may be, for example, 1% or more, preferably 5% or more, more preferably 10% or more, may be 20% or more, may be 30% or more, may be 45% or more, or may be 55% or more. 100% of the oxyalkylene units contained in surfactant I may be oxyethylene units. When surfactant I contains a combination of oxyethylene units and oxypropylene units, the ratio of the number of oxypropylene units (POs) to the number of oxyethylene units (EOs) (PO / EO) may be, for example, 5.0 or less, preferably 3.0 or less, and more preferably 2.0 or less. In some embodiments, the above ratio (PO / EO) may be, for example, 1.5 or less, may be 1.0 or less, or may be 0.8 or less. Furthermore, the above ratio (PO / EO) may be, for example, 0.1 or greater, 0.2 or greater, 0.4 or greater, 0.6 or greater, 0.9 or greater, or 1.3 or greater.

[0029] When using a polyoxyalkylene alkyl ether as surfactant I, the number of carbon atoms in the alkyl group of the alkyl ether is not particularly limited and can be selected so as to appropriately exhibit the effects of surfactant I. From the viewpoint of easily exhibiting surface activity, the number of carbon atoms in the alkyl group is suitable to be 3 or more, and preferably 5 or more. Also, from the viewpoint of surface protection of the object to be polished, the number of carbon atoms in the alkyl group is preferably 7 or more, more preferably 8 or more, and may also be 10 or more, or 12 or more. The number of carbon atoms in the alkyl group may be, for example, 27 or less, 25 or less, or 20 or less. From the viewpoint of solubility of surfactant I, in some embodiments, the number of carbon atoms in the alkyl group is preferably 18 or less, more preferably 16 or less, and even more preferably 14 or less. The alkyl group may be linear or branched. Specific examples of alkyl groups in the alkyl ethers mentioned above include, but are not limited to, propyl, butyl, pentyl, hexyl, octyl, 2-ethylhexyl, nonyl, decyl, isodecyl, lauryl, tridecyl, cetyl, stearyl, and isostearyl groups.

[0030] As the above polyoxyalkylene alkyl ether, it is preferable to use a polyoxyalkylene alkyl ether in which the primary carbon of the alkyl group is bonded to the polyoxyalkylene by an ether bond (hereinafter also referred to as "polyoxyalkylene primary alkyl ether") or a polyoxyalkylene alkyl ether in which the secondary carbon of the alkyl group is bonded to the polyoxyalkylene by an ether bond (hereinafter also referred to as "polyoxyalkylene secondary alkyl ether"). In the above polyoxyalkylene primary alkyl ether, the alkyl group may be linear or branched. In the above polyoxyalkylene secondary alkyl ether, the two alkyl groups bonded to the secondary carbon may be the same or different from each other. The two alkyl groups bonded to the secondary carbon may each be linear or branched independently.

[0031] In the polishing compositions disclosed herein, the weight-average molecular weight (Mw) of surfactant I is not particularly limited and can be appropriately selected within a range in which the effects of the present invention are appropriately exhibited. From the viewpoint of suppressing a decrease in polishing rate, etc., in some embodiments, the Mw of surfactant I is suitable to be less than 4000, preferably 3000 or less, more preferably 2500 or less, even more preferably 2000 or less, and may also be 1500 or less. Furthermore, from the viewpoint of surface activity, etc., the Mw of surfactant I is suitable to be 200 or more, and from the viewpoint of reducing edge roll-off after polishing, etc., it is preferably 300 or more (e.g., 350 or more). In some embodiments, the Mw of surfactant I may be 400 or more, 500 or more, 600 or more, or 800 or more (e.g., 1000 or more).

[0032] For surfactant I, the molecular weight (Mw) is determined from its chemical formula.

[0033] The content of surfactant I in the abrasive composition is not particularly limited as long as it does not significantly impair the effects of the present invention. For example, the content of surfactant I is 1.0 × 10 -6 It can be set to more than % by weight, and from the viewpoint of reducing edge roll-off, 5.0 × 10 -6 It is appropriate to set it to be % by weight or more, 1.0 × 10 -5 Weight% or more, 5.0×10 -5 More than % by weight, and even 1.0 × 10 -4 It is preferable that the amount be % by weight or more. Furthermore, the content of surfactant I can be, for example, 0.5% by weight or less, and from the viewpoint of maintaining the polishing rate, it is appropriate to be 0.25% by weight or less, preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and may even be 0.01% by weight or less. Note that if the polishing composition disclosed herein contains two or more types of surfactant I, the above content refers to the total content of those surfactants I. The above content of surfactant I can be preferably adopted in embodiments in which the polishing composition is used in the form of a polishing liquid.

[0034] The ratio (A / S) of the weight concentration of abrasive grains (A) to the weight concentration (S) of surfactant I in the polishing composition is not particularly limited as long as it does not significantly impede the effects of the techniques disclosed herein. The A / S ratio is typically 100 or more, preferably 200 or more, more preferably 300 or more, and even more preferably 400 or more. By increasing the A / S ratio, it is possible to preferably reduce edge roll-off after polishing while maintaining the polishing rate. The A / S ratio may also be, for example, 10000 or less, 7500 or less, 5000 or less, 3000 or less, 2000 or less, preferably 1500 or less (e.g., 1300 or less), more preferably 1000 or less (e.g., less than 1000), or 800 or less.

[0035] The polishing compositions disclosed herein may further contain one or more surfactants other than surfactant I as optional components, to the extent that they do not significantly impair the effects of the present invention. The optional surfactants other than surfactant I may be anionic, cationic, nonionic, or amphoteric. The Mw of the optional surfactant can be appropriately selected from the same range as surfactant I. The Mw of the optional surfactant is calculated based on its chemical formula, similar to the Mw of surfactant I. The content of the optional surfactant may be, for example, 20 parts by weight or less, less than 10 parts by weight, less than 3 parts by weight, less than 1 part by weight, or less than 0.3 parts by weight (for example, less than 0.1 parts by weight) per 100 parts by weight of abrasive grains. Preferably, the content of the optional surfactant is, for example, less than 1 time, less than 0.5 times, or less than 0.1 times the content of surfactant I by weight. The polishing compositions disclosed herein may preferably be implemented in a form that does not contain such optional surfactants.

[0036] <Basic compounds> The polishing composition disclosed herein contains a basic compound. Here, the basic compound refers to a compound having a function of increasing the pH of the polishing composition when added thereto. The basic compound may be an organic basic compound or an inorganic basic compound. The basic compound can be used alone or in combination of two or more kinds.

[0037] Examples of the organic basic compound include quaternary ammonium salts such as tetraalkylammonium salts. The anion in the above ammonium salt can be, for example, OH - 、F - 、Cl - 、Br - 、I - 、ClO4 - 、BH4 - 、HCO3 - and the like. For example, quaternary ammonium salts such as choline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetramethylammonium hydrogen carbonate can be preferably used. Among them, tetramethylammonium hydroxide is preferred. Other examples of the organic basic compound include quaternary phosphonium salts such as tetraalkylphosphonium salts. The anion in the above phosphonium salt can be, for example, OH - 、F - 、Cl - 、Br - 、I - 、ClO4 - 、BH4 - 、HCO3 - and the like. For example, halides, hydroxides, etc. such as tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, and tetrabutylphosphonium can be preferably used. Other examples of organic basic compounds include amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine; piperazines such as 1-(2-aminoethyl)piperazine and N-methylpiperazine; azoles such as imidazole and triazole; guanidine; and others.

[0038] Examples of inorganic basic compounds include ammonia; hydroxides of ammonia, alkali metals, or alkaline earth metals; carbonates of ammonia, alkali metals, or alkaline earth metals; bicarbonates of ammonia, alkali metals, or alkaline earth metals, etc. Specific examples of hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate.

[0039] Preferred basic compounds include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate. Among these, ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and potassium carbonate are particularly preferred. More preferred are tetramethylammonium hydroxide and potassium carbonate.

[0040] The content of basic compounds in an abrasive composition is usually appropriate to be 0.001% by weight or more. From the viewpoint of abrasive rate, the above content is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, and even more preferably 0.03% by weight or more. Furthermore, from the viewpoint of achieving a high degree of compatibility between abrasive rate and edge roll-off reduction, the content of basic compounds is usually appropriate to be 1% by weight or less, preferably 0.5% by weight or less, and more preferably 0.3% by weight or less. In an abrasive composition used as a polishing liquid as is, the above content may be, for example, 0.5% by weight or less, 0.2% by weight or less, or 0.1% by weight or less.

[0041] The ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant I in the polishing composition is not particularly limited as long as it does not significantly impede the effects of the techniques disclosed herein. The B / S ratio is typically 50 or more, preferably 70 or more, more preferably 90 or more, and may be 100 or more or 115 or more. Increasing the B / S ratio can preferably achieve the effect of reducing edge roll-off after polishing while maintaining the polishing rate. The B / S ratio can also be, for example, 300 or less, preferably 250 or less, more preferably 200 or less, and may be 170 or less or 140 or less.

[0042] <Chelating agent> The polishing compositions disclosed herein contain chelating agents. The chelating agents form complex ions with metal impurities that may be present in the polishing compositions and capture them. This helps to suppress contamination of the workpiece by metal impurities. The chelating agents can be used individually or in combination of two or more. Examples of chelating agents include aminocarboxylic acid chelating agents, organic phosphonic acid chelating agents, and organic sulfonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(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, and α-methylphosphonosuccinic acid. Examples of organic sulfonic acid chelating agents include ethylenediaminetetrakismethylenesulfonic acid. Of these, organic phosphonic acid-based chelating agents or organic sulfonic acid-based chelating agents are more preferred, and among these, ethylenediaminetetrakis(methylenephosphonic acid) is particularly preferred.

[0043] The content of the chelating agent in the abrasive composition is usually appropriate to be 0.0001% by weight or more. Preferably, the content is 0.0005% by weight or more, and more preferably 0.001% by weight or more. Furthermore, the content of the chelating agent is usually appropriate to be 0.05% by weight or less, preferably 0.01% by weight or less, more preferably 0.008% by weight or less, and even more preferably 0.005% by weight or less.

[0044] <Water> The polishing composition disclosed herein contains water. Preferably, the water used can be deionized water, pure water, ultrapure water, distilled water, etc. To minimize interference with the function of other components in the polishing composition, the water used preferably has a total content of transition metal ions of 100 ppb or less. For example, the purity of the water can be increased by operations such as removing impurity ions with an ion exchange resin, removing foreign matter with a filter, or distillation.

[0045] <Preparation of polishing composition> The method for producing the polishing composition disclosed herein is not particularly limited. For example, the components contained in the polishing composition may be mixed using a well-known mixing device such as a vane stirrer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all components may be mixed at once, or they may be mixed in an order set as appropriate.

[0046] The polishing compositions disclosed herein may be mono-component or multi-component, including two-component types. For example, the composition may be configured such that a mixture of liquid A, containing some of the components of the polishing composition, and liquid B, containing the remaining components, is used to polish an object to be polished.

[0047] <Polishing liquid> The polishing compositions disclosed herein are typically supplied to an object to be polished in the form of a polishing solution containing the polishing composition, and are used to polish the object in the form of a polishing solution. The polishing solution may be prepared, for example, by diluting one of the polishing compositions disclosed herein, where dilution is typically with water. Alternatively, the polishing composition may be used as is as a polishing solution. Another example of a polishing solution containing the polishing composition disclosed herein is a polishing solution obtained by adjusting the pH of the composition.

[0048] The pH of the polishing solution is preferably 8.0 or higher, for example 8.5 or higher, more preferably 9.0 or higher, even more preferably 9.5 or higher, and particularly preferably 10.0 or higher, for example 10.5 or higher. As the pH of the polishing solution increases, the polishing rate tends to improve. There is no particular upper limit to the pH of the polishing solution, but it is preferably 12.0 or lower, for example 11.8 or lower, and more preferably 11.5 or lower.

[0049] <Concentrate> The polishing compositions disclosed herein may be in a concentrated form before being supplied to the object to be polished. Such concentrated polishing compositions are advantageous in terms of convenience and cost reduction during manufacturing, distribution, and storage. The concentration ratio is not particularly limited, and may be, for example, about 2 to 80 times by volume, preferably about 5 to 60 times, but may also be about 15 to 40 times, or about 25 to 40 times.

[0050] Polishing compositions in the form of concentrated liquids can be used by diluting them at a desired time to prepare a polishing solution, and then supplying that solution to the object to be polished. Typically, this dilution can be performed by adding water to the concentrated liquid and mixing it. Furthermore, as will be described later, in the case of multi-component polishing compositions, some of the agents may be diluted and then mixed with the other agents to prepare a polishing solution, or multiple agents may be mixed and then the mixture may be diluted to prepare a polishing solution.

[0051] The abrasive content in the above-mentioned concentrated liquid can be, for example, 50% by weight or less. From the viewpoint of the stability and filterability of the polishing composition, the above content is usually preferably 45% by weight or less, and more preferably 40% by weight or less. Here, the stability of the polishing composition refers to, for example, the dispersion stability of the abrasive. Furthermore, from the viewpoint of convenience and cost reduction during manufacturing, distribution, storage, etc., the abrasive content can be, for example, 1.0% by weight or more, preferably 3.0% by weight or more, more preferably 5.0% by weight or more, and even more preferably 7.0% by weight or more.

[0052] The content of surfactant I in the above-mentioned concentrated solution may be, for example, 0.0001% by weight or more, preferably 0.001% by weight or more, more preferably 0.005% by weight or more, and even more preferably 0.01% by weight or more. Furthermore, the content of surfactant I is usually appropriate to be 1% by weight or less, preferably 0.5% by weight or less, may be 0.1% by weight or less, may be 0.05% by weight or less, and may be 0.03% by weight or less.

[0053] The content of the basic compound in the above concentrate is usually appropriate to be 0.03% by weight or more. Preferably, the content is 0.15% by weight or more, more preferably 0.3% by weight or more, and even more preferably 1% by weight or more. Furthermore, the content of the basic compound is usually appropriate to be 15% by weight or less, preferably 10% by weight or less, more preferably 6% by weight or less, and may also be 4% by weight or less, or 3% by weight or less.

[0054] The content of the chelating agent in the above-mentioned concentrated solution is usually appropriate to be 0.003% by weight or more. Preferably, the content is 0.005% by weight or more, more preferably 0.01% by weight or more, even more preferably 0.03% by weight or more, and particularly preferably 0.05% by weight or more. Furthermore, the content of the chelating agent is usually appropriate to be 1.5% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less, even more preferably 0.3% by weight or less, and particularly preferably 0.1% by weight or less.

[0055] <Application> The polishing compositions disclosed herein may preferably be used for polishing objects having a silicon surface. The techniques disclosed herein include, for example, polishing compositions comprising silica particles as abrasive grains, which may be particularly preferred for polishing objects being silicon. Typically, the polishing compositions comprise only silica particles as abrasive grains. The shape of the object to be polished is not particularly limited. The polishing compositions disclosed herein can be preferably applied to polishing objects having flat surfaces, such as plate-shaped or polyhedral objects, or to polishing the edges of such objects. For example, they can be preferably applied to polishing wafer edges.

[0056] <Polishing method> The polishing compositions disclosed herein are used as polishing compositions for pre-polishing single-crystal or polycrystalline silicon wafers in polishing operations. The silicon wafers typically have a surface made of silicon. Typical examples of the silicon wafers are silicon single-crystal wafers, such as silicon single-crystal wafers obtained by slicing a silicon single-crystal ingot. A preferred embodiment of a method for polishing an object using the polishing compositions disclosed herein will be described below. In other words, a polishing solution (slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing solution may involve adjusting the concentration of the polishing composition. Hereinafter, concentration adjustment may include dilution. Alternatively, the polishing composition may be used as is as a polishing solution. Furthermore, in the case of a multi-component polishing composition, preparing the polishing solution may involve mixing the agents, diluting one or more agents before mixing, diluting the mixture after mixing, and so on.

[0057] Next, the polishing solution is supplied to the object to be polished, and polishing is performed by conventional methods. For example, when performing the primary polishing process (first preliminary polishing process) of an object to be polished, the object that has undergone the lapping process is set in a general polishing device. In the primary polishing process, double-sided polishing is typically performed. Polishing solution is supplied to the surface of the object to be polished through the polishing pad of the polishing device. Typically, the polishing solution is supplied continuously, and the polishing pad is pressed against the surface of the object to be polished, causing the two to move relative to each other (e.g., by rotation). After that, if necessary, a further secondary polishing process (second preliminary polishing process) is performed, and finally, a finish polishing process is carried out to complete the polishing of the object. In the secondary polishing process, single-sided polishing is typically performed. The polishing pads used in the polishing process using the polishing compositions disclosed herein are not particularly limited. For example, nonwoven fabric type, suede type, polyurethane type, pads containing abrasive grains, pads without abrasive grains, etc., may be used.

[0058] This specification provides a method for manufacturing polished products, which includes a step of polishing an object to be polished using the polishing composition disclosed herein. The method for manufacturing polished products disclosed herein may further include a step of performing final polishing on the object to be polished after the polishing step using the polishing composition. Here, final polishing refers to the last polishing step in the manufacturing process of the target product, that is, a step in which no further polishing is performed after that step. The final polishing step may be performed using the polishing composition disclosed herein or using other polishing compositions. In a preferred embodiment, the polishing process using the above-mentioned polishing composition is a polishing process upstream of the final polishing. In particular, it can be preferably applied to a preliminary polishing process after the lapping process. For example, it can be preferably used in a double-sided polishing process (typically a primary polishing process) after the lapping process, or in the first single-sided polishing process (typically the first secondary polishing process) performed on a substrate that has undergone the double-sided polishing process. The double-sided polishing process and the first single-sided polishing process require a higher polishing rate than the final polishing process. Therefore, the polishing composition disclosed herein is suitable as a polishing composition used for polishing an object in at least one (preferably both) of the double-sided polishing process and the first single-sided polishing process.

[0059] The polishing composition may be used in a disposable manner after a single polishing application (so-called "flow-through" method), or it may be recycled and reused repeatedly. One example of a method for recycling the polishing composition is to collect the used polishing composition discharged from the polishing device into a tank and then supply the collected polishing composition back to the polishing device. When the polishing composition is recycled, the amount of used polishing composition treated as waste liquid is reduced compared to when it is used in a flow-through method, thereby reducing the environmental burden. In addition, costs can be reduced by reducing the amount of polishing composition used. When the polishing composition disclosed herein is recycled, new components, components that have decreased due to use, or components that are desirable to increase may be added to the polishing composition during use at any time. [Examples]

[0060] The following describes several embodiments of the present invention, but the present invention is not intended to be limited to those shown in these embodiments. In the following description, "%" refers to weight unless otherwise specified.

[0061] <Preparation of polishing composition> (Examples 1-8) A concentrated polishing composition was prepared by mixing abrasive grains, a surfactant, a basic compound, a chelating agent, and deionized water. Silica particles (average primary particle size 55 nm) were used as the abrasive grains. Surfactants A to H, which are polyoxyalkylene alkyl ethers having the structures shown in Table 1, were used as the surfactants. In Table 1, "EO number" indicates the number of moles of ethylene oxide added, "PO number" indicates the number of moles of propylene oxide added, "PO / EO ratio" indicates the ratio of the number of moles of propylene oxide added to the number of moles of ethylene oxide added, and "carbon number" indicates the number of carbon atoms in the alkyl group. In the "carbon chain" column, a linear chain is indicated when the primary carbon of the alkyl group is bonded to the polyoxyalkylene via an ether bond, and a branched chain is indicated when the secondary carbon of the alkyl group is bonded to the polyoxyalkylene via an ether bond. The molecular weights of surfactants A to H were as shown in the "molecular weight" column of Table 1. Tetramethylammonium hydroxide (hereinafter referred to as "TMAH") and potassium carbonate (hereinafter referred to as "K2CO3") were used as basic compounds. Ethylenediaminetetrakis(methylenephosphonic acid) (hereinafter referred to as "EDTPO") was used as a chelating agent. The abrasive content in the concentrated polishing composition was 8.0%, the surfactant content was 0.018%, the TMAH content was 1.6%, the K2CO3 content was 0.6%, and the EDTPO content was 0.04%.

[0062] (Comparative Example 1) Replace surfactant A with Mw1.7×10 4 Polyvinylpyrrolidone (hereinafter referred to as "PVP") was used. The PVP content in the concentrated polishing composition was 0.036%. The polishing composition according to this example was prepared in the same manner as in Example 1 in other respects. For convenience, the names and molecular weights of the polymers used are listed in the surfactant column.

[0063] <Evaluation of silicon polishing rate> For each example, a concentrated solution of the polishing composition was diluted 30 times with water and used as the polishing solution. Polishing tests were performed on silicon wafers, and the silicon polishing rate and edge roll-off amount were evaluated. The objects to be polished were 300 mm diameter silicon single crystal wafers (conduction type: P-type, crystal orientation: <100> A resistivity of 1 Ω·cm or more and less than 100 Ω·cm was used. The object to be polished was polished under the following conditions, and the average thickness before and after polishing was measured using a "NanoMetro 300-TT" manufactured by Kuroda Seiki Co., Ltd. Measurements were taken over the entire wafer, excluding a 1 mm area from the outer edge of the silicon wafer. The measurement pitch was 1 mm. The polishing rate was calculated from the difference in the average thickness before and after polishing and the polishing time. The obtained values ​​were converted to relative values ​​with the value of Comparative Example 1 set to 100%, and are shown in the "Polishing Rate" column of Table 1. If the "Polishing Rate" is 70% or higher, it is judged that the polishing rate has been maintained. [Polishing conditions] Polishing equipment: Double-sided polishing machine manufactured by Speedfam Co., Ltd., model "20B-5P-4D" Polishing pad: Nitta Haas Co., Ltd., product name "MH S-15A" Grinding load: 4935N Upper platen rotation speed: -21 revolutions / minute (clockwise rotation is considered positive rotation. The same applies below.) Lower platen rotation speed: +35 revolutions / minute Sun gear rotation speed: +16.2 revolutions / minute Internal gear rotation speed: +4.5 revolutions / minute Polishing allowance: 3 μm Polishing fluid supply rate: 4.5 L / min (flow-through application) Polishing solution temperature: 25℃

[0064] <Edge Roll-Off Amount Evaluation> The amount of edge roll-off at the outer edge of the polished silicon wafer was evaluated. The amount of edge roll-off was evaluated by measuring the shape displacement of the silicon wafer surface using the "NanoMetro 300-TT" manufactured by Kuroda Seiki Co., Ltd. Specifically, a relatively flat region 3.0 mm to 6.0 mm from the outer edge of the silicon wafer toward the center was designated as the reference region, and a straight line (reference line) approximating the shape displacement in this region was drawn using the least squares method. Next, the distance between the above reference line and the shape displacement of the silicon wafer at a position 1.0 mm from the outer edge was measured, and this was taken as the silicon wafer roll-off value. The obtained values ​​were converted to relative values ​​with the value of Comparative Example 1 set to 100%, and are shown in the "RoA" (Roll off Amount) column of Table 1. The smaller the "RoA" value, the more effectively the amount of edge roll-off was reduced.

[0065] [Table 1]

[0066] As shown in Table 1, it was confirmed that the polishing compositions of Examples 1 to 8, which contain surfactants A to H, provide a higher edge roll-off reduction effect while maintaining a suitable polishing rate. The results above show that by including a surfactant having a repeating oxyalkylene unit structure in addition to abrasive grains, basic compounds, chelating agents, and water, it is possible to effectively reduce the amount of edge roll-off after polishing while maintaining the polishing rate.

[0067] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above.

Claims

1. A polishing composition for use in the preliminary polishing process of silicon wafers, It consists of abrasive particles, a basic compound, a surfactant, a chelating agent, and water. The surfactant includes surfactant I having a repeating structure of oxyalkylene units. An abrasive composition wherein the weight-average molecular weight of the surfactant I is less than 4000.

2. A polishing composition for use in the preliminary polishing process of silicon wafers, It consists of abrasive particles, a basic compound, a surfactant, a chelating agent, and water. The surfactant includes surfactant I having a repeating structure of oxyalkylene units. An abrasive composition wherein the proportion of oxyethylene units to the total number of oxyalkylene units contained in the surfactant I is 10% or more.

3. The polishing composition according to claim 1 or 2, wherein the surfactant I is a polyoxyalkylene alkyl ether.

4. The polishing composition according to any one of claims 1 to 3, wherein the ratio (B / S) of the weight concentration (B) of the basic compound to the weight concentration (S) of the surfactant I is 50 or more.

5. The polishing composition according to any one of claims 1 to 4, wherein the ratio (A / S) of the weight concentration (A) of the abrasive grains to the weight concentration (S) of the surfactant I is less than 1000.

6. The polishing composition according to any one of claims 1 to 5, wherein the abrasive grains include silica particles.

7. A concentrated solution of the polishing composition according to any one of claims 1 to 6.

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