Polishing composition

Abstract

The present invention provides a polishing composition which exhibits an improved polishing rate with respect to a non-altered surface, while maintaining or improving the polishing rate with respect to an altered surface. A polishing composition disclosed herein contains abrasive grains and a basic compound A. With respect to the basic compound A, the sum of the atomic weights of atoms constituting the cation or conjugate acid of the basic compound A is 40 or more, and the cation or conjugate acid of the basic compound A does not contain a carbon atom.

Description

polishing composition

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2023-131897, filed on August 14, 2023, the entire contents of which are incorporated herein by reference.

[0002] Conventionally, precision polishing using a polishing composition has been performed on the surfaces of materials such as metals, semi-metals, non-metals, and their oxides. For example, the surface of a silicon wafer, which is used as a component of a semiconductor product, is generally finished to a high-quality mirror surface through a lapping process and a polishing process. The polishing process includes, for example, a preliminary polishing process (preliminary polishing process) and a final polishing process (final polishing process). The preliminary polishing process includes, for example, a rough polishing process (primary polishing process) and an intermediate polishing process (secondary polishing process). Technical documents related to polishing compositions used in the polishing process include, for example, Patent Documents 1 and 2.

[0003] International Publication No. 2023 / 032714 International Publication No. 2019 / 065357

[0004] The surface to be polished with a polishing composition may be partially altered by artificial processing or exposure to the polishing composition, air, etc. during polishing. For example, a mark such as a barcode, number, or symbol (hard laser mark; hereinafter, sometimes referred to as "HLM") may be applied to the surface of a silicon wafer for purposes of identification, etc., by irradiating the front or back surface of the silicon wafer with laser light. Such laser light irradiation produces an altered layer on the silicon wafer surface around the HLM. The altered layer formed around the HLM is often more difficult to polish than the original silicon wafer surface, i.e., the unaltered silicon wafer surface. Furthermore, depending on the material constituting the surface to be polished, a natural oxide film may form on the surface to be polished. For example, a natural oxide film may form on the surface of a silicon wafer. Such a natural oxide film may be harder to polish than the unaltered surface to be polished.

[0005] The present inventors have found that, in order to obtain a higher quality surface or to further improve the polishing efficiency, it is preferable from the viewpoint of production that a polishing composition to be used for polishing such at least partially altered surfaces exhibits a high polishing rate for both unaltered and altered surfaces. It would be advantageous to obtain a polishing composition that exhibits an improved polishing rate for unaltered surfaces while maintaining or improving the polishing rate for altered surfaces.

[0006] The present invention has been made in consideration of these points, and aims to provide a polishing composition that exhibits an improved polishing rate for an unaltered surface to be polished (hereinafter also referred to as an "unaltered surface") while maintaining or improving the polishing rate for an altered surface to be polished (hereinafter also referred to as an "altered surface").

[0007] The inventors have found that by using abrasive grains and a specific basic compound, it is possible to achieve both a high polishing rate for an altered surface and a high polishing rate for an unaltered surface.

[0008] According to this specification, the polishing composition contains abrasive grains and a basic compound A. Here, the basic compound A is a basic compound in which the sum of the atomic weights of the atoms constituting the cation or conjugate acid of the basic compound A is 40 or more, and the cation or conjugate acid of the basic compound A does not contain a carbon atom. By using such a basic compound A, it is possible to improve the polishing rate for an unaltered surface while maintaining or improving the polishing rate for an altered surface.

[0009] In some embodiments, the basic compound A is a basic compound having a cation composed of a single atom. Here, the cation is a cation of an element whose atomic weight is 40 or more and which is selected from the group consisting of alkali metal elements, alkaline earth metal elements, transition elements of the fourth period of the periodic table, and typical elements of Group 12 or 13 of the fourth period of the periodic table. By using such a basic compound A, it is likely that the polishing rate for an unaltered surface can be further improved while maintaining or improving the polishing rate for an altered surface.

[0010] In some embodiments, the polishing composition contains silica particles as the abrasive. By using silica particles as the abrasive together with basic compound A, the effects of the present invention can be more suitably exhibited.

[0011] In some preferred embodiments, the polishing composition disclosed herein is used to polish a surface made of a silicon material. The polishing composition tends to exhibit an excellent polishing rate for both silicon materials and their altered surfaces. When such a polishing composition is used to polish a surface made of a silicon material, the polishing efficiency is likely to be improved. Furthermore, for example, when the polishing composition is used to polish a surface made of a silicon material to which an HLM has been applied, both the surface made of the unaltered silicon material and the raised portion of the HLM periphery, including the altered surface, can be suitably polished, thereby improving the elimination of the raised portion of the HLM periphery. In some embodiments, the polishing composition is used to pre-polish a surface made of a silicon material.

[0012] In some embodiments, the polishing composition can be a concentrate. The polishing composition disclosed herein can be manufactured, distributed, and stored as a concentrate.

[0013] In some embodiments, a polishing method is provided, comprising polishing a surface made of a silicon material with the polishing composition. The polishing method is likely to improve polishing efficiency. For example, the polishing method can be applied to polishing a surface made of a silicon material to which an HLM is attached, thereby improving the elimination of protrusions around the HLM.

[0014] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0015] <Abrasive Grains> The polishing composition disclosed herein contains abrasive grains. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the use mode of the polishing composition. 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; carbonates such as calcium carbonate and barium carbonate; and the like. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles, polyacrylonitrile particles, and the like. Here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid. The abrasive grains can be used alone or in combination of two or more types.

[0016] The abrasive grains are preferably inorganic particles, and in particular, particles made of metal or semi-metal oxides are preferred. Silica particles are a suitable example of abrasive grains that can be used in the technology disclosed herein. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which the abrasive grains are essentially made of silica particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and even 100% by weight) of the particles constituting the abrasive grains are silica particles.

[0017] The type of silica particles is not particularly limited and can be selected as appropriate. Silica particles may be used alone or in combination of two or more types. Examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. Colloidal silica is particularly preferred because it is less likely to scratch the surface of the object to be polished and can exhibit good polishing performance (such as the ability to reduce surface roughness). The type of colloidal silica is not particularly limited and can be selected as appropriate. Colloidal silica may be used alone or in combination of two or more types. Examples of preferred colloidal silica include colloidal silica prepared by ion exchange using water glass (sodium silicate) as a raw material, and alkoxide-processed colloidal silica. Here, alkoxide-processed colloidal silica refers to colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilane.

[0018] 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. Also, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In some preferred embodiments, at least a portion of the abrasive grains are contained in the polishing composition in the form of secondary particles.

[0019] The average primary particle diameter of the abrasive grains (e.g., silica particles) is not particularly limited, but from the viewpoint of maintaining the polishing rate while improving the ability to eliminate bumps, 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 even more preferably 30 nm or more. Abrasive grains having an average primary particle diameter of 40 nm or more may be used. In some embodiments, the average primary particle diameter may be, for example, greater than 40 nm, greater than 45 nm, or greater than 50 nm. Furthermore, from the viewpoint of preventing scratch generation, the average primary particle diameter of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, and particularly preferably 100 nm or less. In some embodiments, the average primary particle diameter may be 75 nm or less, or may be 60 nm or less.

[0020] In this specification, the average primary particle size of the abrasive grains is calculated from the specific surface area (BET value) measured by the BET method, as follows: average primary particle size (nm) = 6000 / (true density (g / cm ３ ) × BET value (m ２ For example, in the case of silica particles, the average primary particle diameter (nm) = 2727 / BET value (m ２ The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0021] The average secondary particle diameter of the abrasive grains is not particularly limited and can be appropriately selected, for example, from a range of about 15 nm to 300 nm. From the viewpoint of improving the ability to eliminate bumps, the average secondary particle diameter is preferably 30 nm or more, and more preferably 35 nm or more. In some embodiments, the average secondary particle diameter may be, for example, 40 nm or more, 45 nm or more, preferably 50 nm or more, even 60 nm or more, 65 nm or more (e.g., 70 nm or more), or even 75 nm or more. Furthermore, from the viewpoint of preventing the occurrence of scratches, the average secondary particle diameter is usually advantageously 250 nm or less, preferably 200 nm or less, and more preferably 150 nm or less. In some embodiments, the average secondary particle diameter may be 120 nm or less, or 110 nm or less.

[0022] In this specification, the average secondary particle size of abrasive grains refers to the particle size measured by dynamic light scattering, for example, using an Otsuka Electronics FPAR-1000 or an equivalent.

[0023] The shape (external shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical particles include peanut-shaped (i.e., the shape of a peanut shell), cocoon-shaped, confetti-shaped, and rugby ball-shaped.

[0024] The average aspect ratio of the abrasive grains is not particularly limited. In principle, the average aspect ratio of the abrasive grains is 1.0 or more, and can be 1.05 or more, 1.10 or more, or even 1.15 or more. Increasing the average aspect ratio tends to improve the polishing rate. In some embodiments, the average aspect ratio of the abrasive grains is greater than 1.2 (specifically, greater than 1.20), for example, 1.22 or more. Abrasive grains having an average aspect ratio greater than 1.2 are typical examples of the non-spherical abrasive grains. Furthermore, from the viewpoints of reducing scratches and improving polishing stability, the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less. In some embodiments, the average aspect ratio of the abrasive grains may be, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

[0025] The shape (outline) and average aspect ratio of the abrasive grains can be determined, for example, by electron microscope observation. A specific procedure for determining the average aspect ratio involves, for example, using a scanning electron microscope (SEM), drawing the smallest rectangle circumscribing each particle image for a predetermined number (e.g., 200) of abrasive grains whose individual particle shapes can be recognized. Then, for each rectangle drawn for each particle image, the long side length (long diameter value) is divided by the short side length (short diameter value) to calculate the long diameter / short diameter ratio (aspect ratio). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

[0026] The content of abrasive grains is not particularly limited and can be appropriately set depending on the purpose. The content of abrasive grains relative to the total weight of the polishing composition may be, for example, 0.01 wt % or more, 0.05 wt % or more, or 0.1 wt % or more. Increasing the content of abrasive grains tends to improve the polishing rate. In some embodiments, the content of abrasive grains may be 0.2 wt % or more, 0.5 wt % or more, or 0.6 wt % or more. In addition, from the viewpoint of preventing defects (e.g., scratch prevention) and suppressing residues, in some embodiments, the content of abrasive grains may be, for example, 10 wt % or less, 5 wt % or less, 3 wt % or less, 2 wt % or less, 1.5 wt % or less, or 1.2 wt % or less. These contents can be preferably applied, for example, to the content in the polishing liquid (working slurry) supplied to the polishing object.

[0027] In the case of a polishing composition that is diluted before use in polishing (i.e., a concentrated solution), the content of abrasive grains is usually 50% by weight or less, and more preferably 40% by weight or less, from the viewpoints of storage stability, filterability, etc. In addition, from the viewpoint of utilizing the advantages of forming a concentrated solution, the content of abrasive grains is preferably 1% by weight or more, and more preferably 5% by weight or more.

[0028] <Basic Compound A> The polishing composition disclosed herein contains a basic compound A. Here, basic compound A refers to a basic compound in which the sum of the atomic weights of the atoms constituting the cation or conjugate acid of basic compound A is 40 or more, and the cation or the conjugate acid does not contain a carbon atom. Herein, the term "basic compound" refers to a compound that, when added to a polishing composition, functions to increase the pH of the composition. The basic compound functions to chemically polish the surface to be polished and can contribute to improving the polishing rate. Among such basic compounds, the use of a basic compound A in which the sum of the atomic weights of the atoms constituting the cation or conjugate acid is relatively large, at 40 or more, and the cation or the conjugate acid does not contain a carbon atom, can easily achieve both a high polishing rate for a modified surface (e.g., an oxidized surface composed of silicon oxide; the same applies hereinafter) and a high polishing rate for an unmodified surface (e.g., a surface composed of an unmodified silicon material; the same applies hereinafter).

[0029] The reason why the use of basic compound A can easily achieve both a high polishing rate for a modified surface and a high polishing rate for an unmodified surface is not particularly limited, but can be understood as follows, for example. That is, a basic compound having a relatively large sum of atomic weights of atoms constituting the cations or conjugate acids tends to exhibit high alkalinity. Therefore, a basic compound having a relatively large sum of atomic weights of atoms constituting the cations or conjugate acids has a strong effect of chemically polishing the surface to be polished and is likely to contribute to improving the polishing rate. On the other hand, even if the sum of atomic weights of atoms constituting the cations or conjugate acids is relatively large, if the cations or conjugate acids contain carbon atoms, the basic compound tends to adhere to the surface to be polished due to its hydrophobic effect, and tends to protect the surface to be polished and inhibit chemical polishing. Such basic compounds may be disadvantageous from the perspective of the polishing rate (especially the polishing rate for a modified surface). Therefore, a basic compound having a relatively large sum of atomic weights of atoms constituting the cations or conjugate acids and a cation or conjugate acid that does not contain carbon atoms is likely to improve the polishing rate for the surface to be polished. Use of the basic compound makes it easy to achieve both a high polishing rate for the altered surface and a high polishing rate for the unaltered surface.

[0030] The cation or conjugate acid of the basic compound A is not particularly limited except that the sum of the atomic weights of the atoms constituting the cation or conjugate acid is 40 or more and that it does not contain any carbon atoms. The cation or conjugate acid of the basic compound A may be composed of one atom (monoatom) or two or more atoms. The upper limit of the sum of the atomic weights of the atoms constituting the cation or conjugate acid of the basic compound A is not particularly limited, but may be 200 or less, or 150 or less. The basic compound A can be used alone or in combination of two or more.

[0031] Examples of the basic compound A include hydroxides, carbonates, and hydrogencarbonates having the above-mentioned cations or conjugate acids. From the viewpoint of improving the polishing rate for both the altered surface and the unaltered surface, in some preferred embodiments, the basic compound A is a hydroxide having the above-mentioned cations or conjugate acids.

[0032] In some embodiments, the basic compound A is a basic compound Aa having a cation composed of a single atom. In such embodiments, the cation of the basic compound Aa is a cation of an element whose single atom constituting the cation has an atomic weight of 40 or more, and is typically an element whose atomic number is 20 or more. The upper limit of the atomic number of the atom constituting the cation of the basic compound Aa is not particularly limited, but may be 60 or less from the viewpoint of availability. Examples of the cation of such a basic compound Aa include Rb ＋ , Cs ＋ Cations of alkali metal elements (alkali metal cations), such as Ca ２＋ , Sr ２＋ , Ba ２＋ Cations of alkaline earth metal elements (alkaline earth metal cations), such as Fe ３＋ , Ni ２＋ , Cu ２＋ Cations of the fourth transition elements of the periodic table, such as Zn ２＋ Examples of the basic compound Aa include cations of typical elements of Group 12 or 13 of the fourth period of the periodic table, such as those mentioned above. Among these, from the viewpoint of improving the polishing rate for both altered and unaltered surfaces, alkali metal cations and alkaline earth metal cations are preferred, and alkali metal cations are more preferred. The basic compound Aa can be used singly or in combination of two or more.

[0033] Examples of the basic compound Aa include hydroxides, carbonates, hydrogencarbonates, etc. having the above cations. From the viewpoint of improving the polishing rate for both the altered surface and the unaltered surface, in some preferred embodiments, the basic compound Aa is a hydroxide having the above cation.

[0034] In some embodiments, the basic compound A is a basic compound Ab having a cation or conjugate acid composed of two or more atoms.

[0035] Preferred examples of the basic compound A include rubidium hydroxide, cesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, nickel(II) hydroxide, copper(II) hydroxide, iron(II) hydroxide, zinc hydroxide, rubidium carbonate, cesium carbonate, nickel(II) carbonate, copper(II) carbonate, iron(II) carbonate, zinc carbonate, etc. Among these, rubidium hydroxide, cesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide are preferred, and rubidium hydroxide and cesium hydroxide are particularly preferred.

[0036] The content of basic compound A relative to the total amount of the polishing composition (when two or more types of basic compound A are contained, the total content thereof) is preferably 0.005 wt % or more, more preferably 0.01 wt % or more, and even more preferably 0.05 wt % or more, from the viewpoint of the polishing rate for the altered surface and the unaltered surface. Increasing the content of basic compound A can also improve stability. The upper limit of the content of the basic compound A is suitably 5 wt % or less, and from the viewpoint of surface quality, etc., it is preferably 2 wt % or less, more preferably 1 wt % or less, even more preferably 0.5 wt % or less, and may be 0.4 wt % or less, 0.3 wt % or less, or 0.2 wt % or less (for example, less than 0.2 wt %). These contents can be preferably applied, for example, to the content in the polishing liquid (working slurry) supplied to the polishing object.

[0037] Furthermore, in the case of a polishing composition to be diluted and used for polishing (i.e., a concentrate), the content of basic compound A (when two or more types of basic compound A are contained, the total content thereof) is usually 10% by weight or less, and more preferably 5% by weight or less (e.g., 4% by weight or less), from the viewpoints of storage stability, filterability, etc. Furthermore, from the viewpoint of utilizing the advantages of forming a concentrate, the content of basic compound A is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 0.9% by weight or more (e.g., 1.5% by weight or more).

[0038] Abrasive grain content C in polishing composition Ｓ Content C of basic compound A relative to Ｔ(When two or more kinds of basic compounds A are contained, the total content thereof) weight ratio (C Ｔ / C Ｓ ) is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Ｔ / C Ｓ ) is suitably set to, for example, about 0.005 or more, and from the viewpoint of effectively exhibiting the effect of adding the basic compound A, it is preferably 0.01 or more, more preferably 0.02 or more, and may be, for example, 0.05 or more. Furthermore, from the viewpoint of mechanical polishing by abrasive grains, dispersion stability of the composition, etc., the above ratio (C Ｔ / C Ｓ ) is suitably, for example, approximately 1 or less, preferably 0.8 or less, more preferably 0.6 or less, and may be, for example, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less (e.g., less than 0.2).

[0039] The polishing composition disclosed herein may further contain another basic compound other than basic compound A, as long as the effects of the present invention are not significantly impaired. The other basic compound may be an organic basic compound or an inorganic basic compound other than basic compound A.

[0040] Examples of the organic basic compound include quaternary ammonium salts such as tetraalkylammonium salts. The anion in the ammonium salts is, for example, OH － , F － , Cl － ,Br － , I － , ClO ４ － , B.H. ４ － , HCO ３ －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 these, tetramethylammonium hydroxide (TMAH) is preferred. Other examples of organic basic compounds include quaternary phosphonium salts such as tetraalkylphosphonium salts. The anion in the phosphonium salts can be, for example, OH － , F － , Cl － ,Br － , I － , ClO ４ － , B.H. ４ － , HCO ３ － and the like. For example, halides and hydroxides of tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, etc. can be preferably used. Other examples of the organic basic compound 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 the like.

[0041] Examples of inorganic basic compounds other than basic compound A include ammonia; hydroxides of alkali metals with an atomic weight of less than 40, such as lithium, sodium, and potassium, or alkaline earth metals with an atomic weight of less than 40, such as magnesium; carbonates of alkali metals with an atomic weight of less than 40, such as lithium, sodium, and potassium, alkaline earth metals with an atomic weight of less than 40, such as magnesium, or ammonia; bicarbonates of alkali metals with an atomic weight of less than 40, such as lithium, sodium, and potassium, alkaline earth metals with an atomic weight of less than 40, such as magnesium, or ammonia; and the like. Specific examples of the hydroxides include lithium hydroxide, potassium hydroxide, and sodium hydroxide. Specific examples of the carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, lithium bicarbonate, lithium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate.

[0042] The polishing composition disclosed herein can be preferably implemented even in an embodiment that substantially does not contain any other basic compound than the basic compound A. Here, "the polishing composition substantially does not contain any other basic compound than the basic compound A" means that basic compounds other than the basic compound A are not blended at least intentionally, and for example, the content of basic compounds other than the basic compound A in the polishing composition is 1 × 10 －６ % by weight or less (preferably 5 x 10 －７ % by weight or less, more preferably 1×10 －７ % by weight or less, more preferably 5 × 10 －８ % by weight or less). The content of basic compounds other than basic compound A in the polishing composition may be 0% by weight. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

[0043] <Water> The polishing composition disclosed herein typically contains water. Ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used as the water. To minimize the inhibition of the functions of other components contained in the polishing composition, the water used preferably has a total transition metal ion content of, for example, 100 ppb or less. For example, the purity of the water can be increased by removing impurity ions using an ion exchange resin, removing foreign matter using a filter, distillation, or other procedures.

[0044] The polishing composition disclosed herein may further contain, as necessary, an organic solvent (such as a lower alcohol or a lower ketone) that is uniformly miscible with water. Usually, the solvent contained in the polishing composition preferably accounts for 90% by volume or more of water, and more preferably 95% by volume or more (e.g., 99 to 100% by volume) of water.

[0045] <Other Components> The polishing composition disclosed herein may further contain, as necessary, known additives that can be used in polishing compositions (e.g., polishing compositions used in polishing silicon wafers), such as water-soluble polymers, inorganic acid salts, organic acid salts, surfactants, chelating agents, preservatives, and antifungal agents, within the range that does not significantly impair the effects of the present invention.

[0046] Examples of the water-soluble polymer include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms, vinyl alcohol polymers, and polymers containing carboxylic acids (including anhydrides). Specific examples include hydroxyethyl cellulose, pullulan, random copolymers and block copolymers of ethylene oxide and propylene oxide, polyglycerin, polyvinyl alcohol, acetalized polyvinyl alcohol, butenediol polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinyl alcohol-polyvinylpyrrolidone graft copolymers, polyvinyl alcohol-polyvinylpyrrolidone random copolymers, polyvinyl alcohol-polyethylene oxide graft copolymers, polyvinyl alcohol-polyethylene oxide random copolymers, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyvinyl acetamide, polyacryloylmorpholine, polyhydroxyethylacrylamide, polyvinyl caprolactam, polyvinylpiperidine, olefin-maleic acid (anhydride) copolymer, and styrene-maleic acid (anhydride) copolymer. The water-soluble polymers can be used alone or in combination of two or more.

[0047] In some preferred embodiments, the polishing composition disclosed herein can be preferably implemented in an embodiment that is substantially free of a water-soluble polymer, i.e., an embodiment that does not contain a water-soluble polymer at least intentionally. Here, "the polishing composition is substantially free of a water-soluble polymer" means that a water-soluble polymer is not blended at least intentionally, and for example, the content of the water-soluble polymer in the polishing composition is 1 × 10 －６ % by weight or less (preferably 5 x 10 －７ % by weight or less, more preferably 1×10 －７ % by weight or less, more preferably 5 × 10 －８% by weight or less). The content of the water-soluble polymer in the polishing composition may be 0% by weight. These contents are preferably applied to the content in the polishing liquid (working slurry) supplied to the object to be polished, for example.

[0048] For example, inorganic acid salts include salts of hydrohalic acids (e.g., hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid), nitric acid, sulfuric acid, sulfurous acid, bisulfite, thiosulfuric acid, silicic acid, boric acid, phosphoric acid, etc. Furthermore, organic acid salts include salts of carboxylic acids (e.g., formic acid, acetic acid, propionic acid, benzoic acid, butyric acid, citric acid, tartaric acid, trifluoroacetic acid), organic sulfonic acids (e.g., methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid), sulfamic acid, organic phosphoric acids (e.g., ethyl phosphate), etc. The cations constituting the inorganic acid salts and organic acid salts are not particularly limited, and examples thereof include alkali metals (lithium, sodium, potassium, etc.), alkaline earth metals (calcium, strontium, barium, etc.), magnesium, ammonium, etc. In some embodiments, specific examples of sulfuric acid salts (sulfates) include lithium sulfate, sodium sulfate, potassium sulfate, ammonium sulfate, etc. Polishing using sulfates tends to effectively eliminate bumps. In this specification, the inorganic acid salts and organic acid salts do not include the basic compounds, and the organic acid salts do not include the chelating agents.

[0049] Examples of the surfactant are not particularly limited, and include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. ４ The use of a water-soluble organic compound (less than 100%) can improve the dispersion stability of the polishing composition. The weight-average molecular weight (Mw) of the surfactant can be determined by gel permeation chromatography (GPC) (water-based, polyethylene glycol equivalent) or calculated from the chemical formula. The surfactant may be used alone or in combination of two or more.

[0050] In some embodiments, the polishing composition has a composition in which the amount of surfactant used is limited. The content of surfactant in the polishing composition may be less than 0.3 wt %, less than 0.2 wt %, less than 0.1 wt %, less than 0.03 wt %, or less than 0.01 wt %. The technology disclosed herein can be preferably implemented in an embodiment in which the polishing composition is substantially free of surfactant, i.e., an embodiment in which surfactant is not at least intentionally added. These contents can be preferably applied, for example, to the content in the polishing liquid (working slurry) supplied to the object to be polished.

[0051] Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, 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. Of these, organic phosphonic acid chelating agents are more preferred. Among these, preferred are ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Particularly preferred chelating agents are ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid). The chelating agents can be used alone or in combination of two or more. The amount of chelating agent used can be set, for example, so that the content of the chelating agent in the working slurry is about 0.0001 to 1 wt %, about 0.001 to 0.5 wt %, or about 0.005 to 0.1 wt %, but is not limited thereto. The technology disclosed herein can be preferably implemented in an embodiment in which the polishing composition is substantially free of a chelating agent, i.e., an embodiment in which a chelating agent is not at least intentionally added.

[0052] Examples of the antiseptic and antifungal agent include isothiazolinone compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

[0053] The polishing composition disclosed herein preferably contains substantially no oxidizing agent. If an oxidizing agent is contained in the polishing composition, the supply of the composition may oxidize the substrate surface (e.g., the surface of a silicon wafer) and form an oxide film, which may result in a decrease in the polishing rate. Here, "substantially no oxidizing agent" in a polishing composition means that an oxidizing agent is not intentionally added, and it is acceptable for a trace amount of oxidizing agent to be unavoidably present due to raw materials, manufacturing method, etc. The term "trace amount" refers to a molar concentration of the oxidizing agent in the polishing composition of 0.001 mol / L or less (preferably 0.0005 mol / L or less, more preferably 0.0001 mol / L or less, even more preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less). In some preferred embodiments, the polishing composition does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably implemented in an embodiment that does not contain, for example, hydrogen peroxide, sodium persulfate, ammonium persulfate, or sodium dichloroisocyanurate.

[0054] <Polishing Composition> The polishing composition disclosed herein is supplied to an object to be polished in the form of a polishing liquid (working slurry) containing the polishing composition, for example, and used to polish the object to be polished. The polishing liquid may be prepared, for example, by diluting (e.g., with water) a concentrated solution of any of the polishing compositions disclosed herein. Alternatively, the polishing composition may be used as is as a polishing liquid. The concentration ratio of the concentrated solution may be, for example, about 2 to 140 times on a volume basis, and is usually about 5 to 80 times.

[0055] The pH of the polishing composition is, for example, 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, and even more preferably 9.5 or higher (e.g., 10.0 or higher). The technology disclosed herein is characterized by the use of a specific basic compound A. From this perspective, in some embodiments, the pH of the polishing composition is preferably 10.4 or higher. As the pH increases, the polishing rate for both the altered surface and the unaltered surface tends to improve. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (e.g., silica particles) and suppressing a decrease in the mechanical polishing action of the abrasive grains, the pH of the polishing composition is usually suitably 12.0 or lower, preferably 11.8 or lower, and more preferably 11.5 or lower.

[0056] The pH of the polishing composition can be determined by using a pH meter (e.g., a glass electrode hydrogen ion concentration indicator (model number F-23) manufactured by Horiba, Ltd.) and performing three-point calibration using 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)), then placing the glass electrode in the polishing composition and measuring the value after stabilization for at least two minutes.

[0057] The polishing composition disclosed herein may be a single-component type or a multi-component type, such as a two-component type. For example, the polishing composition may be configured so that a polishing liquid is prepared by mixing at least Part A containing abrasive grains with Part B containing the remaining components, and diluting the mixture at an appropriate time as needed.

[0058] 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 known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or may be mixed in an appropriately set order.

[0059] <Polishing> The polishing composition disclosed herein can be used to polish an object to be polished, for example, in an embodiment including the following steps. That is, a working slurry containing any of the polishing compositions disclosed herein is prepared. Next, the polishing composition is supplied to the object to be polished, and polished by a conventional method. For example, the object to be polished is placed in a general polishing device, and the polishing composition is supplied to the surface of the object to be polished (surface to be polished) through the polishing pad of the polishing device. For example, while continuously supplying the polishing composition, the polishing pad is pressed against the surface of the object to be polished, and the two are moved relative to each other (for example, rotated). Through this polishing process, polishing of the object to be polished is completed.

[0060] The polishing pad used in the polishing step is not particularly limited. For example, any of foamed polyurethane type, nonwoven fabric type, suede type, abrasive grain containing type, and abrasive grain non-containing type may be used. In addition, the polishing device may be a double-sided polishing device that polishes both sides of the object to be polished simultaneously, or a single-sided polishing device that polishes only one side of the object to be polished.

[0061] The polishing composition may be used in a manner that it is disposable after being used for polishing once (so-called "flow-through"), or may be recycled and used repeatedly. An example of a method for recycling a polishing composition is a method in which the used polishing composition discharged from a polishing machine is collected in a tank, and the collected polishing composition is supplied to the polishing machine again.

[0062] <Applications> The polishing composition disclosed herein is not particularly limited, but can preferably be used for the preliminary polishing of a surface made of a silicon material. The silicon material preferably contains at least one material selected from the group consisting of single crystal silicon, amorphous silicon, and polysilicon. The polishing composition is particularly suitable for polishing surfaces made of single crystal silicon (e.g., silicon wafers). Because the polishing composition exhibits a high removal rate on both altered and unaltered surfaces, it can also be preferably used for polishing surfaces to be polished, including surfaces bearing HLMs, which are prone to developing altered layers due to laser processing. The polishing composition disclosed herein is particularly preferably used in the preliminary polishing process, more specifically, in the rough polishing process (primary polishing process), which is the first polishing step in the polishing process, and the subsequent intermediate polishing process (secondary polishing process). Because a higher removal rate is often required in the preliminary polishing process, it is meaningful to use the polishing composition disclosed herein in the preliminary polishing process to achieve both a high removal rate and the elimination of protrusions around the HLM.

[0063] Prior to the polishing step using the polishing composition disclosed herein, the silicon wafer may be subjected to a general treatment applicable to silicon wafers, such as lapping, etching, or the application of the above-mentioned HLM. The silicon wafer has, for example, a surface made of silicon. Such a silicon wafer is preferably a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The polishing composition disclosed herein is also suitable for polishing silicon single crystal wafers with an HLM. The polishing composition disclosed herein can also be suitably used for polishing objects that do not have an HLM.

[0064] The matters disclosed by this specification include the following: [1] A polishing composition comprising abrasive grains and a basic compound A, wherein the sum of the atomic weights of the atoms constituting the cation or conjugate acid of the basic compound A is 40 or more, and the cation or conjugate acid of the basic compound A does not contain a carbon atom. [2] The polishing composition according to [1], wherein the basic compound A is a basic compound having a cation composed of a single atom, wherein the atomic weight of the atoms constituting the cation is 40 or more, and the cation is a cation of an element selected from the group consisting of alkali metal elements, alkaline earth metal elements, fourth period transition elements of the periodic table, and typical elements of Group 12 or 13 of Period 4 of the periodic table. [3] The polishing composition according to [1] or [2], wherein the abrasive grains are silica particles. [4] The polishing composition according to any of [1] to [3], which is used for polishing a surface made of a silicon material. [5] The polishing composition according to any one of [1] to [4] above, which is used for pre-polishing a surface made of a silicon material. [6] A concentrated solution of the polishing composition according to any one of [1] to [5] above. [7] A polishing method, comprising polishing a surface made of a silicon material with the polishing composition according to any one of [1] to [6] above.

[0065] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to those shown in these examples.

[0066] <Preparation of polishing composition> (Example 1) By mixing colloidal silica (average primary particle diameter: 55 nm) as abrasive grains, cesium hydroxide (CsOH) as a basic compound, and ion-exchanged water, a polishing composition containing 1 wt% of abrasive grains and 10 mM (10 mmol / L) of a basic compound was prepared. The pH of the obtained polishing composition was 10.5.

[0067] (Example 2 and Comparative Examples 1 to 7) Polishing compositions according to each example were prepared in the same manner as in Example 1, except that the type of basic compound was changed as shown in Table 1. In Table 1, "RbOH" represents rubidium hydroxide, "KOH" represents potassium hydroxide, "NaOH" represents sodium hydroxide, "LiOH" represents lithium hydroxide, and "NH ４ "OH" represents ammonium hydroxide, "TMAH" represents tetramethylammonium hydroxide, "TEAH" represents tetraethylammonium hydroxide, and "AEP" represents N-(2-aminoethyl)piperazine. Table 1 lists the pH of the polishing composition of each example, and the type of cation or conjugate acid, molecular weight, and whether or not the basic compound used in each example contains carbon atoms.

[0068] <Performance Evaluation> (Polishing of Unaltered Si Wafer) The polishing composition according to each example was used as a polishing liquid (working slurry) to polish the surface of a silicon wafer under the following conditions. The polishing liquid according to each example was left at room temperature for 24 hours or more after preparation. The object to be polished was a 60 mm x 60 mm silicon wafer (conductivity type: P-type, crystal orientation: <100>, resistivity 1 Ω cm or more but less than 100 Ω cm). (Polishing conditions) Polishing device: Single-sided polishing device manufactured by Engis Japan, model "EJ-380IN" Polishing pressure: 16 kPa Plate rotation speed: +50 rpm (counterclockwise rotation is positive (+); same below.) Head rotation speed: +50 rpm Polishing pad: Nitta DuPont, product name "SUBA800" Polishing liquid supply rate: 50 mL / min (flowing) Maintained temperature of polishing environment: 25°C Polishing removal rate: 4 μm

[0069] (Evaluation of Polishing Rate) Based on the weight difference of the silicon wafer before and after the polishing, the polishing rate R for the unaltered Si wafer in each example was calculated using the following formulas (1) to (3). Ｓｉ The polishing rate R in Comparative Example 1 was calculated. Ｓｉ The value converted into a relative value (relative polishing rate [%]) with the value being 100% is shown in Table 1 as "Relative Polishing Rate R Ｓｉ" column. Formula: ΔV = (W0 - W1) / d (1) Δx = ΔV / S (2) R Ｓｉ =Δx / t (3) ΔV: change in wafer volume before and after polishing W0: wafer weight before polishing W1: wafer weight after polishing d: specific gravity of silicon (= 2.33 g / cm ３ ) S: wafer surface area Δx: wafer thickness change before and after polishing t: polishing time

[0070] (Polishing of Silicon Oxide Layer (TEOS Layer)) The polishing composition according to each example was used as a polishing liquid (working slurry) to polish the surface of a silicon wafer (hereinafter also referred to as a "TEOS wafer") having a silicon oxide layer formed on its surface under the following conditions. The polishing liquid according to each example was used after being left at room temperature for 24 hours or more after preparation. The silicon oxide layer to be polished was a TEOS (Tetraethyl Orthosilicate) type silicon oxide layer (hereinafter also referred to as a "TEOS layer") produced using tetraethyl orthosilicate as a precursor. Specifically, the object to be polished was a silicon wafer (300 mm, blanket wafer, manufactured by Advantec Co., Ltd.) having a 1000 nm thick TEOS layer formed on its surface, cut into a size of 60 mm x 60 mm. (Polishing conditions) Polishing device: Single-sided polishing device manufactured by Engis Japan, model "EJ-380IN" Polishing pressure: 16 kPa Platen rotation speed: +50 rpm (counterclockwise rotation is positive (+); same below.) Head rotation speed: +50 rpm Polishing pad: Nitta DuPont, product name "SUBA800" Polishing liquid supply rate: 50 mL / min (flowing) Maintained temperature of polishing environment: 25°C Polishing time: 15 minutes

[0071] (Evaluation of Polishing Rate for TEOS Layer) Based on the difference in film thickness of the TEOS wafer before and after the polishing, the polishing rate R for the TEOS wafer in each example was calculated by the following formula: ＴＥＯＳThe film thickness before and after polishing was measured using an optical interference film thickness measuring device (manufactured by SCREEN Holdings Co., Ltd., model number: Lambda Ace VM-2030). ＴＥＯＳ is a relative value with the polishing rate R ＴＥＯＳ The value converted into the relative polishing rate R ＴＥＯＳ " column. Relative polishing rate R ＴＥＯＳ If the polishing rate is 80% or more, it is evaluated that the polishing rate for the TEOS wafer is maintained. ＴＥＯＳ = (X0-X1) / t X0: Film thickness before polishing X1: Film thickness after polishing t: Polishing time

[0072]

[0073] As shown in Table 1, the polishing compositions of Examples 1 and 2, which use basic compounds in which the sum of the atomic weights of the atoms constituting the cation or conjugate acid is 40 or more and the cation or conjugate acid does not contain a carbon atom, have a higher polishing rate R for a TEOS wafer (degraded surface) than the polishing compositions of Comparative Examples 1 to 4, which use basic compounds having a cation or conjugate acid in which the sum of the atomic weights of the constituent atoms is less than 40. ＴＥＯＳ While maintaining or improving the polishing rate R Ｓｉ It was confirmed that the polishing rate R for the TEOS wafer was clearly improved. ＴＥＯＳ It was confirmed that it was difficult to achieve both excellent polishing rates for both altered and unaltered surfaces.

[0074] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A polishing composition comprising abrasive grains and a basic compound A, wherein the sum of the atomic weights of the atoms constituting the cation or conjugate acid of the basic compound A is 40 or more, and the cation or conjugate acid of the basic compound A does not contain a carbon atom.

2. The polishing composition according to claim 1, wherein the basic compound A is a basic compound having a cation composed of a single atom, and the cation is a cation of an element selected from the group consisting of alkali metal elements, alkaline earth metal elements, transition elements of the 4th period of the periodic table, and typical elements of Group 12 or 13 of the 4th period of the periodic table, the atomic weight of the atom constituting the cation being 40 or more.

3. The polishing composition according to claim 1 or 2, which contains silica particles as the abrasive grains.

4. The polishing composition according to claim 1 or 2, which is used for polishing a surface made of a silicon material.

5. The polishing composition according to claim 1 or 2, which is used for pre-polishing a surface made of a silicon material.

6. A concentrated solution of the polishing composition according to claim 1 or 2.

7. A polishing method comprising polishing a surface made of a silicon material with the polishing composition according to claim 1 or 2.

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