Polishing composition and polishing method

Abstract

The present invention provides a polishing composition that contains a cellulose derivative, the polishing composition being capable of maintaining low haze and having exceptional defect reduction properties. Provided is a polishing composition that contains a cellulose derivative and a basic compound. The weight-average molecular weight (Mw) of the cellulose derivative is less than 80,000.

Description

Polishing composition and polishing method

[0001] The present invention relates to a polishing composition and a polishing method. This application claims priority to Japanese Patent Application No. 2023-160704, filed on September 25, 2023, the entire contents of which are incorporated herein by reference.

[0002] Precision polishing using a polishing composition is performed on the surfaces of materials such as metals, semi-metals, non-metals, and their oxides. For example, the surface of a silicon wafer used as a component of a semiconductor device 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 (final polishing process). Patent Documents 1 and 2 are cited as technical documents related to polishing compositions primarily used for polishing semiconductor substrates such as silicon wafers.

[0003] Japanese Patent Application Publication No. 2021-95431 Japanese Patent Application Publication No. 2011-61089

[0004] Polishing compositions used for polishing semiconductor substrates such as silicon wafers and other substrates (e.g., polishing compositions used in a finish polishing process) are required to achieve a surface with low haze and few surface defects after polishing. Some such polishing compositions contain, in addition to water, a water-soluble polymer for the purposes of protecting the surface of the object to be polished and improving wettability. Among these, cellulose derivatives are cited as commonly used water-soluble polymers.

[0005] Cellulose derivatives are useful as components for improving surface quality in polishing compositions, but because they are made from natural cellulose, their quality tends to vary. Therefore, polishing compositions containing cellulose derivatives can cause micro-aggregations that lead to surface defects. Furthermore, general-purpose cellulose derivatives have relatively large molecular weights. For example, Patent Document 1 describes hydroxyethyl cellulose (HEC) with a weight-average molecular weight (Mw) of 250,000 as a conventional cellulose derivative. In polishing compositions containing such cellulose derivatives, surfactants are used to increase the dispersibility of the cellulose derivative, and aggregates are removed by filtration.

[0006] However, while cellulose derivatives having a relatively large molecular weight are advantageous in terms of protecting the surface to be polished, they tend to have poor liquid permeability through filters with small pore sizes, limiting the removal of aggregates, etc. For example, Patent Document 1 describes that the combined use of HEC with a Mw of 120,000 and a specific type of surfactant improves the filterability of the polishing composition and reduces defects.

[0007] Furthermore, Patent Document 2 describes a polishing composition containing an HEC hydrolysate with a Mw of 80,000, 330,000, 530,000, or 1,070,000, which is prepared by hydrolyzing HEC with a Mw of 300,000 to 3,000,000. Patent Document 2 also describes that by preferentially hydrolyzing the low-crystalline portion of HEC and selectively exposing the site that interacts with the silicon wafer on the molecular surface, good wettability with the silicon wafer surface is exhibited during polishing, and residues on the wafer surface that may cause silicon wafer surface defects are reduced during rinsing (paragraph 0011).

[0008] As described above, in the prior art, there have been occasional studies of HECs with molecular weights smaller than those of general-purpose HECs. However, in practical terms, HECs with Mw of 280,000 and 90,000 can achieve equivalent aggregation suppression and defect reduction by using a surfactant (see, for example, the comparison results of Comparative Examples 2 and 4 described below). Furthermore, due to the polishing effect based on molecular weight (improved polishing rate, reduced haze, etc.), studies of low-molecular-weight HECs have been limited to those with Mw of 80,000 or more, as described in Patent Document 2.

[0009] However, the required level of surface quality after polishing is increasing year by year, and also for surface defects, a higher level of defect reduction is required than before.If such a high level of defect reduction can be achieved by adding cellulose derivatives without relying on other additives such as surfactants, the degree of freedom in designing polishing compositions will be increased, which is desirable.Under such technical background, the present inventors have conducted extensive research, and as a result, by using a cellulose derivative in a low molecular weight range that has not been studied before, they have succeeded in obtaining a polishing composition that can maintain low haze and has excellent defect reduction properties, and have completed the present invention.That is, the present invention aims to provide a polishing composition that can maintain low haze and has excellent defect reduction properties in a composition containing cellulose derivatives, and a polishing method that uses this polishing composition.

[0010] According to the present specification, there is provided a polishing composition containing a cellulose derivative and a basic compound. The cellulose derivative has a weight average molecular weight (Mw) of less than 80,000. The polishing composition achieves excellent defect reduction while maintaining low haze.

[0011] In some embodiments, the weight-average molecular weight of the cellulose derivative is 4,000 or more and less than 80,000. The technology disclosed herein is preferably implemented by using a cellulose derivative having an Mw in the above range.

[0012] In some embodiments, the polishing composition further contains abrasive grains. A polishing composition containing abrasive grains is likely to achieve a good polishing rate. Furthermore, according to the technology disclosed herein, in embodiments containing abrasive grains, excellent defect reduction can be achieved. In particular, the abrasive grains are preferably colloidal silica having an average primary particle diameter of 20 nm or more and 50 nm or less. Although not particularly limited, colloidal silica having the above average primary particle diameter is suitable for a final polishing composition for semiconductor substrates such as silicon wafers.

[0013] The polishing composition disclosed herein can be preferably used for polishing a surface made of a silicon material. By polishing a surface made of a silicon material with the polishing composition, a high-quality surface made of a silicon material with significantly reduced defects can be achieved.

[0014] The polishing composition disclosed herein can be a concentrate. The polishing composition disclosed herein can be manufactured, distributed, and stored as a concentrate.

[0015] In some embodiments, a polishing method is provided, comprising the step of polishing a surface of a silicon material with the polishing composition described above. The polishing method can achieve a high-quality silicon material surface with significantly reduced defects.

[0016] The present specification also provides a rinse composition containing a cellulose derivative. The cellulose derivative has a weight average molecular weight (Mw) of less than 80,000. The rinse composition can be used, for example, in a rinse step after polishing.

[0017] 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.

[0018] <Cellulose Derivative (A)> The polishing composition disclosed herein contains a cellulose derivative (hereinafter also referred to as cellulose derivative (A)) having a weight-average molecular weight (Mw) of less than 80,000. Here, the term "cellulose derivative" refers to a cellulose in which some of the hydroxyl groups have been substituted with other substituents. Specifically, the cellulose derivative contains β-glucose units as the main repeating unit. The use of a cellulose derivative can achieve a low haze value. Furthermore, by using a cellulose derivative having an Mw of less than 80,000, excellent defect reduction can be achieved while maintaining a low haze value. Furthermore, polishing compositions containing a cellulose derivative with a small Mw exhibit good and efficient liquid permeability even through filters with small pore sizes. Therefore, for example, a small-pore filter can be used to sufficiently remove aggregates that cause defects. Furthermore, a polishing composition with good filter permeability can suppress filter clogging and improve filter life.

[0019] Specific examples of cellulose derivatives include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose. One type of cellulose derivative may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of improving the surface quality after polishing, hydroxyethyl cellulose (HEC) is preferably used as the cellulose derivative.

[0020] The Mw of the cellulose derivative (A) is less than 80,000 (specifically less than 80,000), and in some embodiments, from the viewpoint of defect reduction, it may be 70,000 or less, 60,000 or less, or 50,000 or less. In some preferred embodiments, the Mw of the cellulose derivative (A) is less than 50,000, more preferably 40,000 or less, even more preferably 30,000 or less, even more preferably 20,000 or less, and particularly preferably 10,000 or less (for example, less than 10,000, more specifically, for example, 9,000 or less). A polishing composition containing a cellulose derivative whose Mw is limited within the above range exhibits efficient liquid permeability even when a filter with a small pore size is used, and aggregates that cause defects are better removed, thereby achieving better defect reduction. The lower limit of the Mw of the cellulose derivative (A) is not particularly limited, and from the viewpoint of protecting the surface to be polished and improving polishing performance, in some embodiments, it may be 1,000 or more, 2,000 or more, 4,000 or more, 5,000 or more, or 6,000 or more. In other embodiments, the Mw of the cellulose derivative (A) may be 10,000 or more (e.g., more than 10,000), 15,000 or more, or 30,000 or more.

[0021] In this specification, the Mw of the cellulose derivative (A) can be a value based on gel permeation chromatography (GPC) (water-based, polyethylene oxide equivalent). A Tosoh HLC-8320GPC model may be used as the GPC measurement device. The measurement conditions are as follows. Similar methods are also used in the examples described below. [GPC measurement conditions] Sample concentration: 0.1 wt % Column: TSKgel GMPWXL Detector: differential refractometer Eluent: 0.1 mol / L NaNO ３ Aqueous solution Flow rate: 1.0 mL / min Measurement temperature: 40°C Sample injection volume: 200 μL

[0022] The cellulose derivative (A) may be synthesized by, for example, a known or conventional method, or may be obtained by lowering the molecular weight of a relatively high molecular weight cellulose derivative using an appropriate method and conditions selected from known or conventional molecular weight lowering treatment methods. It may be preferable to obtain the cellulose derivative by the above-mentioned molecular weight lowering. For example, a commercially available cellulose derivative may be subjected to one or more molecular weight lowering treatments selected from pressure decomposition, thermal decomposition, shear treatment, enzymatic decomposition, electrolysis, radiolysis, etc. under appropriate conditions (treatment time, etc.) to obtain a cellulose derivative (A) having the desired Mw.

[0023] <Basic Compound> The polishing composition disclosed herein contains a basic compound. In this specification, a basic compound refers to a compound that dissolves in water and increases the pH of the aqueous solution. By including a basic compound in the polishing composition, the object to be polished can be efficiently polished by its chemical polishing action (alkaline etching). Examples of basic compounds that can be used include nitrogen-containing organic or inorganic basic compounds, alkali metal hydroxides, alkaline earth metal hydroxides, quaternary phosphonium compounds, various carbonates and bicarbonates, etc. Examples of nitrogen-containing basic compounds include quaternary ammonium compounds, ammonia, amines (preferably water-soluble amines), etc. Such basic compounds can be used alone or in combination of two or more.

[0024] Among these basic compounds, at least one basic compound selected from, for example, alkali metal hydroxides, quaternary ammonium hydroxides, and ammonia can be preferably used. Among these, potassium hydroxide, tetraalkylammonium hydroxide (e.g., tetramethylammonium hydroxide), and ammonia are more preferred, and ammonia is particularly preferred.

[0025] <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 contained in the polishing composition. 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 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. The polishing composition disclosed herein may further contain an organic solvent (e.g., a lower alcohol or a lower ketone) that is uniformly miscible with water, as needed. Preferably, 90% by volume or more of the solvent contained in the polishing composition is water, and more preferably 95% by volume or more (e.g., 99 to 100% by volume) is water.

[0026] <Abrasive Grains> In some embodiments, the polishing composition preferably contains abrasive grains. The abrasive grains contribute to improving the polishing rate by mechanically polishing the surface of the object to be polished. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the purpose and mode of use 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; and carbonates such as calcium carbonate and barium carbonate. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles (here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid), polyacrylonitrile particles, etc. Such abrasive grains may be used alone or in combination of two or more types.

[0027] The abrasive grains are preferably inorganic particles, and among these, particles made of metal or semi-metal oxides are preferred, with silica particles being particularly preferred. In polishing compositions that can be used for polishing (e.g., finish polishing) objects having a silicon surface, such as silicon wafers, described below, it is particularly useful to employ silica particles as abrasive grains. 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.

[0028] Specific examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. Silica particles can be used alone or in combination of two or more types. Colloidal silica is particularly preferred because it is easy to obtain a polished surface with excellent surface quality after polishing. As colloidal silica, for example, colloidal silica produced by an ion exchange method using water glass (sodium silicate) as a raw material, or alkoxide-method colloidal silica (colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilane) can be preferably used. Colloidal silica can be used alone or in combination of two or more types.

[0029] The true specific gravity of the silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. The upper limit of the true specific gravity of silica is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less. The true specific gravity of the silica particles can be measured by a liquid substitution method using ethanol as a substitution liquid.

[0030] The average primary particle diameter of the abrasive grains (typically silica particles, preferably colloidal silica) is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, from the viewpoint of polishing rate, etc. From the viewpoint of obtaining a higher polishing effect (e.g., effects such as haze reduction and defect removal), in some embodiments, the average primary particle diameter is preferably 15 nm or more, more preferably 20 nm or more (e.g., more than 20 nm), even more preferably 25 nm or more, even more preferably 28 nm or more, particularly preferably 30 nm or more, and may even be 32 nm or more. Furthermore, from the viewpoint of scratch prevention, etc., the average primary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 45 nm or less. From the viewpoint of easily obtaining a surface with a lower haze, in some embodiments, the average primary particle diameter of the abrasive grains is preferably 43 nm or less, more preferably 40 nm or less (e.g., less than 40 nm), and may even be less than 38 nm.

[0031] In this specification, the average primary particle diameter is calculated from the specific surface area (BET value) measured by the BET method by the following formula: average primary particle diameter (nm) = 6000 / (true density (g / cm ３ ) × BET value (m ２ The specific surface area is the particle size (BET particle size) calculated by the formula: (1 / g / 2) / (2 / g). The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300."

[0032] The average secondary particle diameter of the abrasive grains (typically silica particles) 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 polishing rate, 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, 42 nm or more, or preferably 44 nm or more. Furthermore, 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 preferred embodiments, the average secondary particle diameter is 120 nm or less, more preferably 100 nm or less, and even more preferably 70 nm or less.

[0033] In this specification, the average secondary particle size refers to the particle size (volume average particle size) measured by dynamic light scattering. The average secondary particle size of the abrasive grains can be measured by dynamic light scattering using, for example, a product named "Nanotrac UPA-UT151" manufactured by Nikkiso Co., Ltd.

[0034] The shape (external shape) of the abrasive grains (typically silica particles) may be spherical or non-spherical. Specific examples of non-spherical particles include peanut-shaped (i.e., peanut shell-shaped), cocoon-shaped, confetti-shaped, and rugby ball-shaped. For example, silica particles in which most of the particles are peanut-shaped or cocoon-shaped can be preferably used.

[0035] Although not particularly limited, the average value of the long axis / short axis ratio (average aspect ratio) of the abrasive grains (typically silica particles) is, in principle, 1.0 or more, preferably 1.05 or more, more preferably 1.1 or more, and may be 1.2 or more. By increasing the average aspect ratio, a higher polishing rate can be achieved. Furthermore, from the viewpoint of reducing scratches, etc., the average aspect ratio of the abrasive grains (typically silica particles) is preferably 3.0 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and may be 1.4 or less.

[0036] The shape (external shape) and average aspect ratio of abrasive grains (typically silica particles) 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 (abrasive particles, typically silica particles) 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.

[0037] <Optional Water-Soluble Polymer> The polishing composition disclosed herein may contain, as an optional component, any water-soluble polymer other than the cellulose derivative (A) as long as it does not significantly impair the effects of the present invention.The type of the optional water-soluble polymer is not particularly limited, and any polymer having at least one functional group selected from a cationic group, an anionic group, and a nonionic group can be used.The optional water-soluble polymer may have a hydroxyl group, a carboxyl group, an acyl group, an acyloxy group, a sulfo group, an amide group, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, a polyoxyalkylene structure, etc.

[0038] Examples of the optional water-soluble polymer include cellulose derivatives having a Mw of 80,000 or more, starch derivatives, polymers containing oxyalkylene units such as copolymers of ethylene oxide (EO) and propylene oxide (PO), vinyl alcohol polymers, polymers containing nitrogen atoms such as polymers containing N-vinyl type monomer units, imine derivatives, and polymers containing N-(meth)acryloyl type monomer units, and polymers containing carboxylic acids (including anhydrides). Specific examples include pullulan, random copolymers and block copolymers of ethylene oxide (EO) and propylene oxide (PO), polyglycerin, polyvinyl alcohol (PVA), acetalized polyvinyl alcohol, butenediol polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfonate 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, and the like. Examples of the optional water-soluble polymer include olefin sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyvinylacetamide, polyacryloylmorpholine, polyhydroxyethylacrylamide, polyallylamine, glycidol-modified polyallylamine, methyldiallylamine-sulfur dioxide copolymer, polyvinyl caprolactam, polyvinylpiperidine, olefin-maleic acid (anhydride) copolymer, and styrene-maleic acid (anhydride) copolymer. From the viewpoint of improving polishing performance when used in a polishing composition, the optional water-soluble polymer is preferably a vinyl alcohol-based polymer or a polymer containing an N-(meth)acryloyl type monomer unit. The optional water-soluble polymer can be used alone or in combination of two or more. From the viewpoint of simplifying the composition, the polishing composition disclosed herein does not need to contain any optional water-soluble polymer other than the cellulose derivative (A).

[0039] The weight average molecular weight (Mw) of the water-soluble polymer is not particularly limited. For example, the Mw of the water-soluble polymer is about 200×10 ４ or less, and may be approximately 150×10 ４ From the viewpoint of cleaning properties, it is preferable that the thickness is about 100×10 ４ Less than 50 x 10 is also acceptable. ４ From the viewpoint of protecting the polishing surface, the Mw of the water-soluble polymer may be, for example, 0.5×10 ４ or more, and may be 0.7 × 10 ４ In some embodiments, the Mw is 1×10 ４ or more, and may be 2×10 ４ or more, for example, 5 × 10 ４ The Mw of the water-soluble polymer may be the weight-average molecular weight (water-based, polyethylene glycol equivalent) determined by GPC. The GPC measurement conditions may be the same as those for the cellulose derivative (A).

[0040] In an embodiment in which the polishing composition contains an optional water-soluble polymer, the content of the optional water-soluble polymer in the total water-soluble polymer contained in the polishing composition is suitably about 50% by weight or less (e.g., less than 50% by weight), and may be 30% by weight or less, less than 10% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can be preferably implemented in an embodiment in which the polishing composition does not substantially contain any optional water-soluble polymer.

[0041] <Surfactant> The polishing composition disclosed herein may contain a surfactant, or may be substantially free of a surfactant. In some embodiments, the polishing composition contains a surfactant. By adding a surfactant to the polishing composition, the dispersibility of the water-soluble polymer in the polishing composition can be improved, thereby improving filter permeability. Furthermore, a composition containing a surfactant can further improve the quality of the polished surface (reduced haze, reduced defects, etc.). Any of anionic, cationic, nonionic, and amphoteric surfactants can be used as the surfactant. Usually, anionic or nonionic surfactants can be preferably used. From the viewpoints of haze reduction, low foaming, and ease of pH adjustment, nonionic surfactants are more preferred. Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene derivatives (e.g., polyoxyalkylene adducts) such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyalkylene alkylglucosides, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; and copolymers of multiple types of oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). One surfactant may be used alone, or two or more may be used in combination.

[0042] Specific examples of nonionic surfactants include block copolymers of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymers, PEO (polyethylene oxide)-PPO (polypropylene oxide)-PEO type triblock copolymers, PPO-PEO-PPO type triblock copolymers, etc.), random copolymers of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene methyl glucoside, polyoxypropylene methyl glucoside, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, ethylenediaminetetrapolyoxyethylenepolyoxypropylene (poloxamine); and the like.Among these, preferred surfactants include block copolymers of EO and PO (particularly PEO-PPO-PEO type triblock copolymers), random copolymers of EO and PO, and polyoxyethylene alkyl ethers (e.g., polyoxyethylene decyl ether).As the polyoxyethylene alkyl ether, those having an EO addition mole number of about 1 to 10 (e.g., about 3 to 8) can be preferably used.

[0043] The molecular weight of the surfactant is, for example, less than 5,000, and is preferably 4,500 or less from the viewpoint of reducing aggregates of the cellulose derivative (A) or from the viewpoint of filterability and washability, and may be, for example, less than 4,000. Furthermore, from the viewpoint of surface activity, etc., the molecular weight of the surfactant is usually appropriate to be 200 or more, and from the viewpoint of haze reduction effect, etc., it is preferably 250 or more (e.g., 300 or more). A more preferred range of the molecular weight of the surfactant may vary depending on the type of the surfactant. For example, when a polyoxyethylene alkyl ether is used as the surfactant, its molecular weight is, for example, preferably less than 2,000, more preferably 1,900 or less (e.g., less than 1,800), even more preferably 1,500 or less, and may be 1,000 or less (e.g., 500 or less). Furthermore, when a block copolymer of EO and PO is used as the surfactant, its weight average molecular weight may be, for example, 500 or more, 1,000 or more, even 1,500 or more, 2,000 or more, or even 2,500 or more. The upper limit of the weight average molecular weight is, for example, less than 5,000, and preferably 4,500 or less, and may be, for example, less than 4,000, less than 3,800, or less than 3,500.

[0044] The molecular weight of the surfactant may be the molecular weight calculated from the chemical formula, or the weight average molecular weight (water-based, polyethylene glycol equivalent) determined by GPC. The GPC measurement conditions can be the same as those for the cellulose derivative (A). For example, in the case of polyoxyethylene alkyl ether, it is preferable to use the molecular weight calculated from the chemical formula, and in the case of a block copolymer of EO and PO, it is preferable to use the weight average molecular weight determined by GPC.

[0045] The polishing composition disclosed herein can be implemented in an embodiment that does not substantially contain a surfactant, or an embodiment in which the content of the surfactant is limited. Although not particularly limited, in the embodiment in which the polishing composition does not substantially contain a surfactant or an embodiment in which the content of the surfactant is limited, the content of the surfactant in the polishing composition may be less than about 50 parts by weight, less than 30 parts by weight, less than 10 parts by weight, less than 3 parts by weight, less than 1.5 parts by weight, or less than 1 part by weight, relative to 100 parts by weight of the cellulose derivative (A).

[0046] <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 the finish polishing step of silicon wafers), such as organic acids, organic acid salts, inorganic acids, inorganic acid salts, chelating agents, preservatives, and antifungal agents, within the range that does not significantly impair the effects of the present invention.

[0047] The organic acids and their salts, and the inorganic acids and their salts can be used alone or in combination of two or more. Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, itaconic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, glycolic acid, malonic acid, gluconic acid, alanine, glycine, lactic acid, organic sulfonic acids such as hydroxyethylidene diphosphate (HEDP) and methanesulfonic acid, and organic phosphonic acids such as nitrilotris(methylene phosphate) (NTMP) and phosphonobutanetricarboxylic acid (PBTC). Examples of organic acid salts include alkali metal salts (sodium salt, potassium salt, lithium salt, etc.) and ammonium salts of organic acids. Examples of inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, lithium salts, etc.) and ammonium salts of inorganic acids.

[0048] The chelating agent may be used alone or in combination of two or more. Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Suitable examples of the chelating agent include ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Examples of the preservatives and antifungal agents include isothiazolinone compounds, parahydroxybenzoic acid esters, phenoxyethanol, etc.

[0049] The polishing composition disclosed herein preferably does not substantially contain an oxidizing agent. If an oxidizing agent is contained in the polishing composition, when the polishing composition is supplied to a substrate (e.g., a silicon wafer), the surface of the substrate may be oxidized to form an oxide film, which may result in a decrease in the polishing rate. Specific examples of the oxidizing agent include hydrogen peroxide (H ２ O ２), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. In addition, "the polishing composition is substantially free of an oxidizing agent" means that the oxidizing agent is not contained at least intentionally. Therefore, a polishing composition that inevitably contains a trace amount of oxidizing agent due to raw materials, manufacturing method, etc. (for example, a polishing composition in which the molar concentration of the oxidizing agent in the polishing composition is 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) can be included in the concept of a polishing composition that is substantially free of an oxidizing agent as used herein.

[0050] <pH> The pH of the polishing composition disclosed herein is not particularly limited, and an appropriate pH can be adopted depending on the substrate, etc. In some embodiments, the pH of the polishing composition is suitably 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher. As the pH of the polishing composition increases, the polishing rate tends to improve. On the other hand, from the viewpoint of preventing dissolution of silica particles and suppressing a decrease in mechanical polishing action, the pH of the polishing composition is usually suitably 12.0 or lower, preferably 11.0 or lower, more preferably 10.8 or lower, and even more preferably 10.5 or lower.

[0051] In the technology disclosed herein, the pH of the polishing composition can be determined using a pH meter by performing three-point calibration using a standard buffer solution, placing a glass electrode in the composition to be measured, and measuring the value after stabilization for at least two minutes. For example, a glass electrode hydrogen ion concentration indicator (Model F-72) manufactured by Horiba, Ltd. can be used as the pH meter. The standard buffer solutions used were a phthalate pH buffer solution (pH: 4.01 (25°C)), a neutral phosphate pH buffer solution (pH: 6.86 (25°C), and a carbonate pH buffer solution (pH: 10.01 (25°C)).

[0052] <Polishing Liquid> The polishing composition disclosed herein is typically supplied to the surface of a substrate in the form of a polishing liquid containing the polishing composition, and is used to polish the substrate. The polishing liquid can be prepared, for example, by diluting any of the polishing compositions disclosed herein (typically with water). Alternatively, the polishing composition can be used as a polishing liquid as is. Another example of a polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

[0053] The content of the cellulose derivative (A) in the polishing liquid is not particularly limited, and can be, for example, 0.0001 wt% or more. From the viewpoint of haze reduction, etc., the preferred content is 0.0005 wt% or more, more preferably 0.001 wt% or more, even more preferably 0.002 wt% or more, for example, 0.005 wt% or more. From the viewpoint of polishing rate, etc., in some preferred embodiments, the content may be 0.2 wt% or less, more preferably 0.1 wt% or less, even more preferably 0.05 wt% or less, even more preferably 0.02 wt% or less, even more preferably 0.015 wt% or less, particularly preferably 0.012 wt% or less, or even 0.010 wt% or less (for example, less than 0.010 wt%).

[0054] In the embodiment where the polishing composition contains abrasive grains, the content of the cellulose derivative (A) in the polishing composition can also be determined by its relative relationship with the abrasive grains (typically silica particles).Although not particularly limited, the content of the cellulose derivative (A) relative to 100 parts by weight of abrasive grains can be, for example, 0.01 parts by weight or more, and is suitably 0.1 parts by weight or more.In some preferred embodiments, in order to better utilize the effects of using the cellulose derivative (A) (defect reduction and haze reduction), the content is 1 part by weight or more, more preferably 3 parts by weight or more, even more preferably 5 parts by weight or more, and may be 10 parts by weight or more, 15 parts by weight or more, or even 20 parts by weight or more.In addition, in some embodiments, the content of the cellulose derivative (A) relative to 100 parts by weight of abrasive grains is, for example, 30 parts by weight or less, suitably 20 parts by weight or less, preferably 15 parts by weight or less, more preferably 10 parts by weight or less (for example, less than 10 parts by weight), and may be 9 parts by weight or less, or may be 8 parts by weight or less. By limiting the content of the cellulose derivative (A), the polishing rate tends to be improved.

[0055] The content of the basic compound in the polishing liquid is not particularly limited. From the viewpoint of improving the polishing rate, etc., it is usually appropriate that the content be 0.00001 wt % or more, preferably 0.00005 wt % or more, more preferably 0.0001 wt % or more, particularly preferably 0.0003 wt % or more, and may be 0.0005 wt % or more, 0.001 wt % or more, or 0.005 wt % or more. Furthermore, from the viewpoint of improving surface quality (e.g., reducing haze), etc., the content is appropriate to be less than 0.1 wt %, preferably less than 0.05 wt %, and more preferably less than 0.03 wt % (e.g., less than 0.025 wt %). In some preferred embodiments, the content may be less than 0.01 wt % or less than 0.008 wt %.

[0056] In embodiments in which the polishing liquid contains abrasive grains (typically silica particles), the content of the abrasive grains in the polishing liquid is not particularly limited, and may be, for example, 0.001 wt % or more, preferably 0.05 wt % or more, and more preferably 0.10 wt % or more. By increasing the abrasive grain content, a higher polishing rate can be achieved. The content is suitably 10 wt % or less, preferably 7 wt % or less, more preferably 5 wt % or less, and even more preferably 2 wt % or less, and may be, for example, 1 wt % or less. In some embodiments, the content may be 0.75 wt % or less, 0.5 wt % or less (e.g., less than 0.5 wt %), 0.25 wt % or less (e.g., less than 0.25 wt %), or 0.2 wt % or less. Limiting the abrasive grain content within the above range facilitates maintaining surface quality.

[0057] In an embodiment in which the polishing liquid contains a surfactant, the content of the surfactant in the polishing liquid is not particularly limited. Typically, the content of the surfactant can be, for example, 0.00001 wt % or more, for example, from the viewpoint of improving the dispersibility and cleaning properties of the cellulose derivative (A). In some embodiments, from the viewpoint of reducing haze, the content may be 0.0002 wt % or more, 0.0003 wt % or more, or even 0.0005 wt % or more. In addition, from the viewpoint of polishing rate, the content may be 0.1 wt % or less, 0.01 wt % or less, or 0.005 wt % or less (e.g., 0.002 wt % or less). In an embodiment in which the polishing composition is substantially free of surfactant, or in an embodiment in which the content of surfactant is limited, the content of the surfactant in the polishing liquid may be less than 0.001 wt %, less than 0.0001 wt %, or less than 0.00001 wt %.

[0058] <Concentrate> The polishing composition disclosed herein may be in a concentrated form (i.e., in the form of a concentrated polishing liquid) before being supplied to a substrate. Such a concentrated polishing composition is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc. The concentration ratio is not particularly limited and can be, for example, about 2 to 100 times in volume terms, and typically about 5 to 50 times (e.g., about 10 to 40 times) is appropriate. Such a concentrated liquid can be diluted at a desired time to prepare a polishing liquid (working slurry), which can then be supplied to a substrate. The dilution can be performed, for example, by adding water to the concentrated liquid and mixing.

[0059] When the polishing composition (i.e., concentrate) is diluted and used for polishing, the content of the cellulose derivative (A) in the concentrate can be, for example, 3 wt% or less.From the viewpoint of the filterability and washability of the polishing composition, the content is usually preferably 1 wt% or less, more preferably 0.5 wt% or less, and may be 0.3 wt% or less.In addition, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content is usually appropriate to be 0.001 wt% or more, preferably 0.005 wt% or more, more preferably 0.01 wt% or more.

[0060] In some embodiments, the content of the basic compound in the concentrate can be, for example, less than 15 wt%. From the viewpoint of storage stability, etc., the content is usually preferably 0.7 wt% or less, more preferably 0.4 wt% or less, and may be 0.1 wt% or less, or may be 0.05 wt% or less. Furthermore, from the viewpoint of convenience during production, distribution, storage, etc., cost reduction, etc., the content of the basic compound in the concentrate can be, for example, 0.001 wt% or more, preferably 0.005 wt% or more, more preferably 0.01 wt% or more, and may be 0.02 wt% or more, or may be 0.05 wt% or more.

[0061] In an embodiment in which the concentrate contains abrasive grains (typically silica particles), the content of the abrasive grains in the concentrate can be, for example, 25% by weight or less. From the viewpoint of the dispersion stability and filterability of the polishing composition, the content is usually preferably 20% by weight or less, more preferably 15% by weight or less. In some preferred embodiments, the content of the abrasive grains may be 10% by weight or less, or may be 5% by weight or less (e.g., less than 5% by weight). Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content of the abrasive grains in the concentrate can be, for example, 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 0.7% by weight or more, and even more preferably 1% by weight or more.

[0062] In an embodiment in which the concentrate contains a surfactant, the surfactant content in the concentrate can be, for example, 0.25 wt % or less, preferably 0.15 wt % or less, more preferably 0.1 wt % or less, and may be 0.05 wt % or less, or may be 0.025 wt % or less. The surfactant content in the concentrate can be, for example, 0.0001 wt % or more, preferably 0.001 wt % or more, more preferably 0.005 wt % or more, and even more preferably 0.01 wt % or more. In an embodiment in which the polishing composition is substantially free of surfactant, or in which the surfactant content is limited, the surfactant content in the concentrate can be less than 0.01 wt %, less than 0.005 wt %, or less than 0.001 wt %.

[0063] <Preparation of Polishing Composition> The polishing composition used in the technology disclosed herein may be a single-component type or a multi-component type, including a two-component type. For example, the polishing composition may be configured so that a polishing liquid is prepared by mixing Part A, which contains at least abrasive grains among the components of the polishing composition, with Part B, which contains at least a portion of the remaining components, and mixing and diluting these at an appropriate timing as needed. Parts A and B may be filtered once or twice or more times, or may not be filtered.

[0064] The method for preparing the polishing composition is not particularly limited. For example, the components constituting the polishing composition may be mixed using a well-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 components may be mixed at once, or may be mixed in an appropriately set order. After mixing, one or more filtrations may be performed, or no filtration may be performed.

[0065] In some embodiments, the polishing composition is preferably used for polishing a substrate after being filtered through a filter. The structure of the filter is not particularly limited, and for example, a membrane filter including a layer composed of a porous membrane is preferably used. A filter having a filter fiber layer composed of filter fibers may also be used. An example of a filter having a filter fiber layer is a woven fabric filter (mesh filter). The media shape of the filter is not particularly limited, and a depth filter, a surface filter, a depth pleated filter obtained by pleating a depth filter, a pleated filter obtained by pleating a surface filter, etc. can be used. Among these, a pleated filter is preferred from the viewpoint of improving the filterability of the liquid to be filtered.

[0066] Although not particularly limited, in some embodiments, a filter having an average pore size of 0.15 μm or less as measured by a perm porometer is preferably used as the filter. Since the polishing composition disclosed herein has excellent filter liquid permeability, even when a filter having an average pore size of a predetermined value or less is used as described above, it can be efficiently filtered and aggregates that cause defects can be more effectively removed. In some preferred embodiments, the average pore size of the filter used may be 0.14 μm or less, more preferably 0.12 μm or less, even more preferably 0.10 μm or less, particularly preferably 0.08 μm or less, and may even be 0.06 μm or less. From the viewpoint of liquid permeability, etc., the lower limit of the average pore size may be, for example, 0.01 μm or more, or 0.03 μm or more.

[0067] Here, the average pore diameter of the filter in this specification is the pore diameter D50 value corresponding to an integrated value of 50% in the pore diameter distribution obtained by measurement based on the half-dry method in accordance with ASTM E1294-89. For example, it can be measured using a Perm Porometer (CFP-1200AXL) manufactured by PMI Corporation. The above measurement method is also used in the examples described below.

[0068] The filtration conditions (e.g., filtration differential pressure, filtration rate, and filtration volume) may be appropriately set based on common technical knowledge in this field, taking into consideration the target quality, production efficiency, and the like. The filtration method is not particularly limited, and known filtration methods such as natural filtration performed at normal pressure, suction filtration, pressure filtration, and centrifugal filtration may be appropriately employed. Furthermore, before or after the above-mentioned filter filtration, additional filtration treatments may be optionally performed, either preparatory or in multiple stages, depending on the purpose, such as removal of coarse particles or high-precision filtration.

[0069] <Applications> The polishing composition disclosed herein can be used to polish substrates of various materials and shapes. The substrate material can be, for example, a metal or semimetal such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or stainless steel, or an alloy thereof; a glassy material such as quartz glass, aluminosilicate glass, or glassy carbon; a ceramic material such as alumina, silica, sapphire, silicon nitride, tantalum nitride, or titanium carbide; a compound semiconductor substrate material such as silicon carbide, gallium nitride, or gallium arsenide; or a resin material such as polyimide resin. The substrate may be made of a combination of these materials. The shape of the substrate is not particularly limited. The polishing composition disclosed herein can be used to polish, for example, a flat substrate, such as a plate or polyhedron, or the edge of a substrate (e.g., wafer edge polishing).

[0070] The polishing composition disclosed herein can be particularly preferably used for polishing a surface made of a silicon material (typically, polishing a silicon wafer). Specific examples of silicon materials include silicon single crystal, amorphous silicon, and polysilicon. The polishing composition disclosed herein can be particularly preferably used for polishing a surface made of silicon single crystal (for example, polishing a silicon wafer).

[0071] The polishing composition disclosed herein can be preferably applied to a polishing process of a substrate (e.g., a silicon wafer). Before the polishing process using the polishing composition disclosed herein, the substrate may be subjected to a general treatment that can be applied to a substrate in a process upstream of the polishing process, such as lapping or etching.

[0072] The polishing composition disclosed herein is effective when used in the finishing step of a substrate (e.g., a silicon wafer) or in the polishing step immediately preceding it, and is particularly preferably used in the finishing polishing step. Here, the finishing polishing step refers to the final polishing step in the manufacturing process of the object (i.e., a step in which no further polishing is performed after that step). The polishing composition disclosed herein may also be used in a polishing step upstream of the finishing polishing (referring to a preliminary polishing step between the rough polishing step and the final polishing step, which typically includes at least a primary polishing step and may further include secondary, tertiary, etc. polishing steps), for example, a polishing step performed immediately preceding the finishing polishing.

[0073] The polishing composition disclosed herein is effective, for example, for polishing (typically finish polishing or polishing immediately before finish polishing) silicon wafers that have been prepared in an upstream process to have a surface roughness of 0.01 nm to 100 nm. Application to finish polishing is particularly preferred. The surface roughness Ra of the substrate can be measured, for example, using a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement Systems Inc.

[0074] <Polishing> The polishing composition disclosed herein can be used to polish a substrate, for example, in an embodiment including the following steps. A preferred embodiment of a method for polishing a silicon wafer as a substrate using the polishing composition disclosed herein is described below. That is, a polishing liquid containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include adjusting the concentration (e.g., diluting), adjusting the pH, or the like of the polishing composition to prepare the polishing liquid. Alternatively, the polishing composition may be used as the polishing liquid as is.

[0075] Next, the polishing liquid is supplied to the substrate, and polishing is performed by a conventional method. For example, when performing finish polishing of a silicon wafer, typically, a silicon wafer that has undergone a lapping process is set in a general polishing device, and a polishing liquid is supplied to the surface to be polished of the silicon wafer through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface to be polished of the silicon wafer, and the two are moved relatively (for example, rotated). Polishing of the substrate is completed through this polishing process.

[0076] The polishing pad used in the polishing step is not particularly limited. For example, a polishing pad of a foamed polyurethane type, a nonwoven fabric type, a suede type, or the like can be used. Each polishing pad may contain abrasive grains or may not contain abrasive grains. Usually, a polishing pad that does not contain abrasive grains is preferably used.

[0077] <Rinse> A substrate (e.g., a silicon wafer) polished with a polishing composition can be rinsed using a rinse solution containing the same components as the polishing composition, except that it does not contain abrasive grains. In other words, the technology disclosed herein may include a step (rinsing step) of rinsing a substrate (e.g., a silicon wafer) with a rinse solution containing the same components as the polishing composition, except that it does not contain abrasive grains. The rinsing step can reduce residues such as abrasive grains that cause defects and haze on the surface of the substrate (e.g., a silicon wafer). The rinsing step may be performed between polishing steps, or may be performed after the final polishing step and before the cleaning step described below. Such a rinse solution can typically be a rinsing composition containing a cellulose derivative with a Mw of less than 80,000 (e.g., a composition used to rinse silicon wafers). By using the rinsing composition containing the cellulose derivative with a Mw of less than 80,000, a substrate (e.g., a silicon wafer) polished with any of the polishing compositions disclosed herein can be suitably rinsed. The rinsing composition may have the same composition as the polishing composition described above except that it does not contain abrasive grains, and therefore, description thereof will not be repeated here.

[0078] <Cleaning> A substrate polished with the polishing composition disclosed herein is typically cleaned. Cleaning can be performed using an appropriate cleaning liquid. The cleaning liquid to be used is not particularly limited, and for example, SC-1 cleaning liquid (ammonium hydroxide (NH ４ OH) and hydrogen peroxide (H ２ O ２ ) and water (H ２ O), SC-2 cleaning solution (HCl and H ２ O ２ and H ２ Examples of cleaning solutions that can be used include an ozone water cleaning solution, a mixture of ozone water and ozone water, and a hydrofluoric acid cleaning solution. The temperature of the cleaning solution can be set to, for example, a range from room temperature (typically about 15°C to 25°C) to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning solution of about 50°C to 85°C can be preferably used.

[0079] As described above, the technology disclosed herein can include a method for manufacturing a polished object (e.g., a method for manufacturing a silicon wafer) that includes a polishing step by any of the polishing methods described above, and the provision of a polished object (e.g., a silicon wafer) manufactured by the method.

[0080] The matters disclosed by this specification include the following. [1] A polishing composition containing a cellulose derivative and a basic compound, wherein the cellulose derivative has a weight-average molecular weight of less than 80,000. [2] The polishing composition according to [1] above, wherein the cellulose derivative has a weight-average molecular weight of 4,000 or more and less than 80,000. [3] The polishing composition according to [1] or [2] above, further containing abrasive grains. [4] The polishing composition according to [3] above, wherein the abrasive grains are colloidal silica having an average primary particle diameter of 20 nm or more and 50 nm or less. [5] The polishing composition according to any of [1] to [4] above, which is used for polishing a surface made of a silicon material. [6] A concentrated solution of the polishing composition according to any of [1] to [5] above. [7] A polishing method comprising the step of polishing a surface made of a silicon material with the polishing composition according to any of [1] to [5] above. [8] A rinse composition containing a cellulose derivative, wherein the cellulose derivative has a weight-average molecular weight of less than 80,000.

[0081] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0082] Experiment 1 Preparation of Concentrated Polishing Composition (Examples 1 and 2 and Comparative Example 1) Abrasive grains, hydroxyethyl cellulose (HEC), ammonia, and deionized water were mixed to prepare concentrated polishing compositions according to each example. Colloidal silica with an average primary particle size of 35 nm was used as the abrasive grains. HEC with the Mw shown in Table 1 was used as the HEC.

[0083] <Filtration Treatment> The concentrated liquid of the polishing composition according to each example was filtered under the following filtration conditions: [Filtration Conditions] Suction pump: oil-free pump PSH028AA Filter holder: KP-47H 47 mm polysulfone holder Vacuum vessel: VT-500 Filtration differential pressure: 80 kPa Filter: filter with average pore size: 0.145 μm, filter diameter: 47 mm

[0084] <Preparation of Polishing Composition> The filtered concentrated polishing composition was diluted 20 times by volume with deionized water to obtain polishing compositions of each example with an abrasive concentration of 0.5%, an HEC concentration of 0.1%, and an ammonia concentration of 0.01%.

[0085] <Evaluation of Surface Quality of Polished Surface> (Polishing of Silicon Wafer) As a substrate, a commercially available silicon single crystal wafer (conductivity type: P-type, crystal orientation: <100>, COP (Crystal Originated Particle)-free) having a diameter of 300 mm, which had been lapped and etched, was pre-polished under the following polishing condition 1. The pre-polishing was carried out using a polishing solution containing 0.6% abrasive grains (colloidal silica having an average primary particle size of 35 nm) and 0.08% tetramethylammonium hydroxide (TMAH) in deionized water.

[0086] [Polishing condition 1] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 20 kPa Rotation speed of surface plate: 20 rpm Rotation speed of head (carrier): 20 rpm Polishing pad: Product name "SUBA400" manufactured by Nitta DuPont Supply rate of polishing liquid: 1.0 L / min Temperature of polishing liquid: 20°C Temperature of surface plate cooling water: 20°C Polishing time: 2 minutes

[0087] The polishing composition according to each example was used as a polishing liquid to polish the silicon wafer after the pre-polishing described above under the following polishing conditions 2, and then polished under the following polishing conditions 3.

[0088] [Polishing condition 2] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 16 kPa Rotation speed of surface plate: 52 rpm Rotation speed of head (carrier): 50 rpm Polishing pad: Product name "POLYPAS275NX" manufactured by Fujibo Ehime Co., Ltd. Supply rate of polishing liquid: 1.5 L / min Temperature of polishing liquid: 20°C Temperature of surface plate cooling water: 20°C Polishing time: 2 minutes

[0089] [Polishing condition 3] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 20 kPa Rotation speed of surface plate: 52 rpm Rotation speed of head (carrier): 50 rpm Polishing pad: Product name "POLYPAS275NX" manufactured by Fujibo Ehime Co., Ltd. Supply rate of polishing liquid: 1.5 L / min Temperature of polishing liquid: 20°C Temperature of surface plate cooling water: 20°C Polishing time: 2 minutes

[0090] NH maintained at 70°C ４ OH (29%): H ２ O ２ A first cleaning tank containing a cleaning solution of SiO 2 (31%):deionized water=2:5.3:48 (volume ratio), and a second cleaning tank containing ultrapure water at 25°C were prepared. The polished silicon wafer was immersed in the first cleaning tank for 6 minutes, then immersed in the second cleaning tank for 40 minutes, and then immersed again in the first cleaning tank for 6 minutes and in the second cleaning tank for 4 minutes, and then dried.

[0091] <Defect Measurement> The number of defects (total of LPDs and LPD-Ns) on the surfaces of the cleaned silicon wafers was measured in DC mode using a wafer inspection device, product name "Surfscan SP5," manufactured by KLA Tencor Corporation. The results obtained were converted into relative values, with the number of defects in Comparative Example 1 taken as 100%, and the obtained values ​​are shown in the corresponding columns in Table 1.

[0092] <Haze Measurement> The haze (ppm) of the silicon wafer surfaces after cleaning was measured in DW2O mode using a wafer inspection device, product name "Surfscan SP5," manufactured by KLA Tencor Corp. The results obtained were converted into relative values, with the haze value for Comparative Example 1 taken as 100%, and the obtained values ​​are shown in the corresponding columns in Table 1.

[0093] Experiment 2 Preparation of Concentrated Polishing Composition Examples 3 to 7 and Comparative Examples 2 to 4 Abrasive grains, HEC having the Mw shown in Table 2, ammonia, and deionized water were mixed to prepare a concentrated polishing composition according to each example. For Comparative Example 2, polyoxyethylene decyl ether (C10PEO5) was further mixed as a surfactant to prepare a concentrated polishing composition.

[0094] <Filtration Treatment> The concentrated liquid of the polishing composition according to each example was filtered under the same filtration conditions as in Experiment 1, except that a filter having the average pore size shown in Table 2 was used.

[0095] <Preparation of polishing composition> The concentrated solution of the polishing composition that has been filtered is diluted with deionized water to a volume ratio of 40 times, thereby obtaining polishing compositions according to each example, with an abrasive concentration of 0.12%, an HEC concentration of 0.009%, and an ammonia concentration of 0.005%. The concentration of surfactant in the polishing composition according to Comparative Example 2 is 0.0004%.

[0096] <Evaluation of Surface Quality of Polished Surface> (Polishing of Silicon Wafer) As a substrate, a commercially available silicon single crystal wafer (conductivity type: P-type, crystal orientation: <100>, COP (Crystal Originated Particle)-free) having a diameter of 300 mm, which had been lapped and etched, was pre-polished under the following polishing condition 1. The pre-polishing was carried out using a polishing solution containing 1.0% abrasive grains (colloidal silica having an average primary particle size of 35 nm) and 0.068% potassium hydroxide in deionized water.

[0097] [Polishing condition 1] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 12 kPa Rotation speed of surface plate: 52 rpm Rotation speed of head (carrier): 50 rpm Polishing pad: Product name "POLYPAS275NX" manufactured by Fujibo Ehime Co., Ltd. Supply rate of polishing liquid: 1.0 L / min Temperature of polishing liquid: 20°C Temperature of surface plate cooling water: 20°C Polishing time: 4 minutes

[0098] The polishing composition according to each example was used as a polishing liquid to polish the silicon wafer after the pre-polishing described above under the following polishing conditions 2, and then polished under the following polishing conditions 3.

[0099] [Polishing conditions 2 and 3] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 12 kPa Rotation speed of surface plate: 52 rpm Rotation speed of head (carrier): 50 rpm Polishing pad: Product name "POLYPAS275NX" manufactured by Fujibo Ehime Co., Ltd. Supply rate of polishing liquid: 2.0 L / min Temperature of polishing liquid: 20°C Temperature of surface plate cooling water: 20°C Polishing time: 4 minutes

[0100] The polished silicon wafer was removed from the polishing apparatus and washed with an ozone water cleaning solution (60 seconds), then washed with an SC-1 cleaning solution and a brush (110 seconds), and then washed with an ozone water cleaning solution (20 seconds) and a hydrofluoric acid cleaning solution (15 seconds) in one set, for a total of three sets of cleaning processes, and then washed with an ozone water cleaning solution (20 seconds).The silicon wafer was then dried.

[0101] <Measurement of Defects and Haze> Defects and haze were measured by the method described in Experiment 1. The results obtained were converted into relative values, with the number of defects and haze value for Comparative Example 3 taken as 100%, and the obtained values ​​are shown in the corresponding columns in Table 2. If the haze value is 110 or less, it is determined that a low haze value is maintained.

[0102] <Evaluation of Liquid Permeability (Common to Experiments 1 and 2)> The concentrated solution of the polishing composition according to each example was diluted with deionized water to a HEC concentration of 1.3%, to obtain an evaluation sample. Deionized water was also prepared as a reference. Each container containing the evaluation sample and the reference (deionized water) was stored in an air bath at 25°C. The filter used for the liquid permeability evaluation was washed with approximately 10 mL of deionized water. Next, under the filtration conditions of Experiment 1, the liquid permeation time was measured for 50 g of the reference and then 50 g of the evaluation sample. The liquid permeation index, which is the ratio of the liquid permeation time of the evaluation sample to the liquid permeation time of the reference (liquid permeation time ratio), was calculated. This operation was performed for each example, and the liquid permeation index for each example was obtained. The obtained results (liquid permeation index) were converted to a relative value, with the liquid permeation index for Comparative Example 2 being set to 100%, and the obtained values ​​are listed in the corresponding columns of Tables 1 and 2. When liquid did not pass through within the specified time, it was recorded as "not passed through."

[0103]

[0104]

[0105] As shown in Table 1, in Experiment 1, the polishing compositions of Examples 1 and 2, which contained an HEC with a Mw of less than 80,000, were able to reduce defects by 22% or more on a relative basis while reducing the haze value, compared to Comparative Example 1, which used an HEC with a Mw of 80,000 or more. Among these, Example 1, which used an HEC with a Mw of 20,000, achieved a more excellent defect reduction effect. The polishing compositions of Examples 1 and 2 also exhibited good filter permeability. In Experiment 2, as shown in Table 2, it was confirmed that the polishing compositions of Examples 3 to 7, which used an HEC with a Mw of less than 80,000, similarly to Experiment 1, had a superior defect reduction effect compared to Comparative Examples 3 and 4, which used HECs with a Mw of 90,000 and 280,000, respectively. A comparison of Comparative Examples 2 and 3 showed that the use of an HEC with a Mw of 280,000 in combination with a surfactant improved filter permeability and significantly reduced the number of defects, but still fell short of the defect reduction effect of Examples 3 to 7. Furthermore, the results of Examples 3 to 6, in which polishing compositions containing HEC with a Mw of 7,000 were filtered through filters with different pore sizes and evaluated, confirmed that polishing compositions containing low molecular weight HEC exhibit excellent liquid permeability even through filters with small average pore sizes, thereby further reducing defects.

[0106] 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 a cellulose derivative and a basic compound, the cellulose derivative having a weight average molecular weight of less than 80,000.

2. The polishing composition according to claim 1, wherein the weight average molecular weight of the cellulose derivative is 4,000 or more and less than 80,000.

3. The polishing composition according to claim 1 or 2, further comprising abrasive grains.

4. The polishing composition according to claim 3, wherein the abrasive grains are colloidal silica having an average primary particle diameter of 20 nm or more and 50 nm or less.

5. The polishing composition according to claim 1 or 2, which is used for 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.

8. A rinse composition comprising a cellulose derivative, the weight-average molecular weight of which is less than 80,000.

Images