TWI829675B - Grinding composition - Google Patents

Abstract

The present invention provides a polishing composition containing a polyvinyl alcohol-based polymer, which can suppress aggregation of the polyvinyl alcohol-based polymer contained in the composition and effectively reduce surface defects. The polishing composition provided by the present invention includes abrasive particles and water. The above-mentioned polishing composition further contains a polyvinyl alcohol-based polymer and a dispersant of the polyvinyl alcohol-based polymer. The above-mentioned dispersant contains ether bonds in the molecule. Furthermore, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersing agent is 0.01 or more and 10 or less.

Description

Grinding composition

The present invention relates to a polishing composition. This invention claims priority based on Japanese Patent Application No. 2018-69647 filed on March 30, 2018, and the entire content of which is incorporated into this specification by reference.

Precision polishing is performed using a polishing composition on the surface of materials such as metals, semimetals, nonmetals, and oxides thereof. For example, the surface of a silicon wafer used as a component of a semiconductor device generally undergoes a brushing step (rough polishing step) and a polishing step (precision polishing step) to achieve a high-quality mirror surface. The above-mentioned polishing step typically includes a preliminary polishing step (preliminary polishing step) and a finishing polishing step (final polishing step). Patent Document 1 can be cited as a technical document on a polishing composition mainly used for polishing semiconductor substrates such as silicon wafers. [Prior technical literature] [Patent Document]

Patent Document 1: Japanese Patent Application Publication No. 2010-34509

[Problem to be solved by the invention]

Polishing compositions used in finish polishing steps (particularly, finish polishing steps for semiconductor substrates such as silicon wafers and other substrates) are required to achieve a surface with low haze and few surface defects after polishing. Polishing compositions used for this purpose often contain, in addition to abrasive grains and water, water-soluble polymers for the purpose of improving protection of the surface of the object to be polished and improving wettability. For example, Patent Document 1 discloses a polishing composition for silicon wafers containing hydroxyethyl cellulose and polyvinyl alcohol (PVA) as water-soluble polymers.

By using polyvinyl alcohol-based polymers as water-soluble polymers, the wettability of the polished surface can be stably improved. However, as the level of requirements for surface quality after polishing increases, conventional polishing compositions using polyvinyl alcohol-based polymers tend to have insufficient effects on reducing surface defects.

The present invention was made in view of this point, and aims to provide a polishing composition that can effectively reduce surface defects even though it contains a polyvinyl alcohol-based polymer. [Means used to solve problems]

The present inventors considered that aggregation of the polyvinyl alcohol-based polymer contained in the polishing composition may be the main cause of the occurrence of the above-mentioned surface defects, discovered a polishing composition suitable for suppressing the aggregation, and completed the present invention. According to the present invention, a polishing composition containing abrasive grains and water is provided. The above-mentioned polishing composition further contains a polyvinyl alcohol-based polymer and a dispersant of the polyvinyl alcohol-based polymer. The above-mentioned dispersant contains ether bonds in the molecule. Furthermore, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersing agent is 0.01 or more and 10 or less. With this configuration, since the polyvinyl alcohol-based polymer and the dispersant of the polyvinyl alcohol-based polymer are contained in an appropriate mixing ratio, polyvinyl alcohol in the polishing composition can be appropriately suppressed by the action of the dispersant. Aggregation of vinyl alcohol polymers. By using a polishing composition containing a polyvinyl alcohol-based polymer in which such aggregation is suppressed, surface defects of the polished object can be appropriately reduced.

In addition, in this specification, the so-called "dispersant of polyvinyl alcohol-based polymer" refers to the preparation of a polishing composition that has improved polyvinyl alcohol-based polymer properties compared to a polishing composition that does not contain the dispersant. Agent (compound) with properties of polymer dispersion. Typically, a dispersant for a polyvinyl alcohol-based polymer is a compound that has the ability to improve the dispersion stability of the polyvinyl alcohol-based polymer in an aqueous solution. In this specification, unless otherwise mentioned, it is simply described as "dispersant", which means "dispersant for polyvinyl alcohol-based polymers". In addition, "surface defects" in this specification include LPD (Light Point Defects), which refers to foreign matter generally called particles. The occurrence of this surface defect can be evaluated by measuring the number of LPD detected by the wafer inspection apparatus used in Examples described below.

In a preferred aspect, the weight average molecular weight of the above-mentioned polyvinyl alcohol-based polymer is 3×10 ⁴ or more. The polyvinyl alcohol-based polymer with such a weight average molecular weight tends to aggregate easily, so the The present invention is meaningful when used in a polishing composition containing a polyvinyl alcohol-based polymer having the above weight average molecular weight.

In another preferred aspect of the polishing composition disclosed here, the weight average molecular weight of the dispersant is smaller than the weight average molecular weight of the polyvinyl alcohol polymer. With this configuration, aggregation of the polyvinyl alcohol-based polymer can be appropriately suppressed, and a polishing composition capable of reducing surface defects of the object to be polished can be realized.

In another preferred aspect of the polishing composition disclosed herein, the dispersant includes polyoxyethylene alkyl ether. By including this dispersant, the aggregation of the polyvinyl alcohol-based polymer can be more appropriately suppressed, and a polishing composition with a further enhanced effect of reducing surface defects can be realized.

In another preferred aspect of the polishing composition disclosed here, the weight average molecular weight of the dispersant is 1,500 or less. By including this dispersant, aggregation of the polyvinyl alcohol-based polymer can be appropriately suppressed, and a polishing composition with a further enhanced effect of reducing surface defects can be realized.

In another preferred aspect of the polishing composition disclosed here, the abrasive particles are silica particles. When using silicon oxide particles as abrasives, the polishing rate can be maintained and the surface defects of the object to be polished can be reduced more effectively.

A preferred aspect of the polishing composition disclosed here is used to polish a surface made of silicon. In the polishing composition disclosed here, when polishing the surface of a polishing object made of silicon, the polyvinyl alcohol-based polymer inhibits aggregation due to the action of the above-mentioned dispersant, thereby protecting the polishing object. The surface can appropriately reduce the surface defects.

Preferred embodiments of the present invention will be described below. In addition, in this specification, matters other than matters specifically mentioned and matters necessary for implementation of the present invention are design matters that can be grasped by the industry based on the prior art in the field. The present invention can be implemented based on the content disclosed in this specification and the technical common sense in this field.

>Abrasive grains> The polishing composition disclosed here contains abrasive grains. Abrasive grains are used to mechanically grind the surface of an object. The material, properties, etc. of the abrasive grains are not particularly limited, and can be appropriately selected according to the purpose of use, usage pattern, etc. of the polishing composition. Examples of abrasive particles include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silica particles, aluminum oxide particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide particles. Oxide particles such as 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, etc. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles ((meth)acrylic acid here means acrylic acid and methacrylic acid.), etc., Polyacrylonitrile particles, etc. Such abrasive grains may be used alone or in combination of two or more kinds.

The above-mentioned abrasive particles are preferably inorganic particles, particularly preferably particles composed of metal or semi-metal oxides, and particularly preferably silicon oxide particles. It is particularly meaningful to use silicon oxide particles as abrasive particles in a polishing composition that can be used for polishing (for example, finish polishing) of a polishing object having a surface made of silicon, such as a silicon wafer described later. The technology disclosed here can be effectively implemented, for example, in an aspect in which the abrasive grains are substantially composed of silicon oxide particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and may be 100% by weight) constituting the abrasive grain particles are silicon oxide particles.

Specific examples of silicon oxide particles include colloidal silica, fumed silica, precipitated silica, and the like. Silicon oxide particles can be used alone or in combination of two or more types. From the viewpoint of easily obtaining a polished surface with excellent surface quality after polishing, it is particularly preferable to use colloidal silicon oxide. As the colloidal silicon oxide, for example, colloidal silicon oxide produced by the ion exchange method using water glass (Na silicate) as a raw material, or colloidal silicon oxide produced by the alkoxide method (using alkane Colloidal silica produced by the hydrolysis and condensation reaction of oxysilane), etc. Colloidal silicon oxide can be used alone or in combination of two or more types.

The true specific gravity of the material constituting the abrasive grains (for example, silicon oxide constituting the silicon oxide particles) is preferably 1.5 or more, more preferably 1.6 or more, and further preferably 1.7 or more. The upper limit of the true specific gravity of the material constituting the abrasive grains (for example, silicon oxide) is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less. The true specific gravity of the material constituting the abrasive grains (for example, silicon oxide) can be measured using a liquid replacement method using ethanol as a replacement liquid.

The BET diameter of the abrasive particles (typically silicon oxide particles) is not particularly limited, but from the viewpoint of polishing efficiency, etc., it is preferably 5 nm or more, and more preferably 10 nm or more. From the viewpoint of obtaining better polishing effects (for example, effects of reducing haze, removing defects, etc.), the BET diameter is preferably 15 nm or more, and more preferably 20 nm or more (for example, more than 20 nm). In addition, from the viewpoint of preventing scratches and the like, the BET diameter of the abrasive grains is preferably 100 nm, more preferably 50 nm or less, and further more preferably 40 nm or less. From the viewpoint of easily obtaining a high-quality surface (for example, a surface with a low LPD number), the technology disclosed here is preferably suitable for polishing a surface that requires high quality after polishing. The abrasive particles used in the polishing composition preferably have a BET diameter of 35 nm or less (typically less than 35 nm, more preferably 32 nm or less, for example, less than 30 nm).

In addition, in this specification, the BET diameter refers to the specific surface area (BET value) measured by the BET method, BET diameter (nm) = 6000/(true density (g/cm ³ ) × BET value ( The particle size calculated by the formula m ² /g)). For example, in the case of silicon oxide particles, the BET diameter is calculated as BET diameter (nm) = 2727/BET value (m ² /g). The specific area can be measured, for example, using a surface area measuring device manufactured by MicroMetrics, brand name "Flow Sorb II 2300".

The shape (outer shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical particles include a peanut shape (that is, a peanut shape), a cocoon shape, a golden candy shape, a rugby ball shape, and the like. For example, abrasive grains in which most of the particles have a peanut shape or a cocoon shape can be preferably used.

Although not particularly limited, the average length/minor diameter ratio (average aspect ratio) of the abrasive grains is in principle 1.0 or more, preferably 1.05 or more, and further preferably 1.1 or more. By increasing the average aspect ratio, higher grinding efficiency can be achieved. In addition, the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less, from the viewpoint of reducing scratches and the like.

The shape (outer shape) and average aspect ratio of the abrasive grains can be grasped by, for example, electron microscope observation. Specific procedures for determining the average aspect ratio include, for example, using a scanning electron microscope (SEM) to draw the minimum image circumference of each particle for a given number (for example, 200) of abrasive particles that can identify individual particle shapes. Rectangle. Then, for the rectangle drawn by each particle image, the length of the long side (the value of the long axis) divided by the length of the short side (the value of the short axis) is calculated as the long diameter/short diameter ratio (aspect ratio) . By taking the arithmetic average of the aspect ratios of the above-mentioned predetermined number of particles, the average aspect ratio can be obtained.

>Polyvinyl alcohol-based polymer> The polishing composition disclosed here contains a polyvinyl alcohol-based polymer. Here, the polyvinyl alcohol-based polymer is a water-soluble organic compound (typically a water-soluble polymer) containing a vinyl alcohol unit as its repeating unit. Here, the vinyl alcohol unit (hereinafter also referred to as "VA unit") is a structural part represented by the following chemical formula: -CH ₂ -CH(OH)-;. The VA unit can be generated, for example, by hydrolyzing (saponification) vinyl acetate with a vinyl polymerized repeating unit (-CH ₂ -CH(OCOCH ₃ )-). By using a polishing composition containing a polyvinyl alcohol-based polymer, the wettability of the surface of the polishing object can be improved, and a surface with low haze and few surface defects after polishing can be easily achieved.

The polyvinyl alcohol-based polymer has a hydroxyl group (OH group) in the molecule. Therefore, polyvinyl alcohol-based polymers have the property of easily aggregating due to intramolecular or intermolecular hydrogen bonding. If part of the polyvinyl alcohol-based polymer contained in the polishing composition aggregates to reduce the dispersion stability of the composition, the surface defect reduction performance after polishing may be reduced. According to the technology disclosed here, by using a polyvinyl alcohol-based polymer in combination with a dispersant for the polyvinyl alcohol-based polymer described below, it is possible to achieve polishing that appropriately suppresses the aggregation of the polyvinyl alcohol-based polymer and improves the dispersion stability. Use composition.

The polyvinyl alcohol-based polymer may contain only VA units as repeating units, and may contain repeating units other than VA units (hereinafter also referred to as "non-VA units") in addition to VA units. In the case where the polyvinyl alcohol-based polymer contains a non-VA unit, the non-VA unit may be one selected from the group consisting of an oxyalkylene group, a carboxyl group, a sulfo group, an amine group, a hydroxyl group, a amide group, and an amide group. , nitrile group, ether group, ester group, and at least one structural repeating unit of their salts. Alternatively, the non-VA unit may have at least one structure selected from an oxyalkylene group, a carboxyl group, a sulfo group, an amine group, a hydroxyl group, a amide group, a amide group, a nitrile group, an ester group, and salts thereof. of repeating units. The polyethanol-based polymer may be a random copolymer containing VA units and non-VA units, or a block copolymer, a graft copolymer, etc. The polyvinyl alcohol-based polymer may contain only one type of non-VA unit as a non-VA unit, or may contain two or more types of non-VA units.

The ratio of the molar number of VA units to the molar number of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 5% or more, 10% or more, 20% or more, or is more than 30%. Although not particularly limited, in several aspects, the molar ratio of the VA unit may be more than 50%, may be more than 65%, may be more than 75%, may be more than 80%, It may also be 90% or more (for example, 95% or more or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100%" means that at least non-VA units are not intentionally included in the polyvinyl alcohol-based polymer. For example, a polishing composition containing polyvinyl alcohol (PVA) with a saponification degree of 98% or more (so-called fully saponified PVA) has high wettability to the surface of the polishing object and can easily achieve a surface with few surface defects after polishing. . In addition, since PVA with a high degree of saponification tends to aggregate more easily, it is meaningful to apply the present invention to PVA with a high degree of saponification (for example, PVA with a saponification degree of 98% or more). In other aspects, the ratio of the molar number of VA units to the molar number of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 95% or less, or 90% or less. It may be 80% or less, or it may be 70% or less.

The content of VA units (content based on weight) in the polyvinyl alcohol-based polymer may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight. More than % by weight. Although not particularly limited, in several aspects, the content of the above VA unit may be 50% by weight or more (for example, more than 50% by weight), 70% by weight or more, or more than 80% by weight (for example, more than 50% by weight). For example, 90% by weight or more, or 95% by weight or more, or 98% by weight or more). Substantially 100% by weight of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100% by weight" means that at least non-VA units are not intentionally included as repeating units constituting the polyvinyl alcohol-based polymer. In other aspects, the content of VA units in the polyvinyl alcohol-based polymer can be, for example, 95% by weight or less, or 90% by weight or less, or 80% by weight or less, or Can be 70% by weight.

The polyvinyl alcohol-based polymer may also contain multiple polymer chains with different contents of VA units in the same molecule. Here, the term "polymer chain" refers to a part (chain segment) constituting a part of a polymer in one molecule. For example, a polyvinyl alcohol-based polymer may include a polymer chain A containing more than 50% by weight of VA units and less than 50% by weight of VA units (i.e., less than 50% by weight of non-VA units) in the same molecule. More than % by weight) polymer chain B.

The polymer chain A may contain only VA units as repeating units, or may contain non-VA units in addition to VA units. The content of VA units in polymer chain A may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In several aspects, the content of VA units in polymer chain A can be more than 95% by weight or more than 98% by weight. Substantially 100% by weight of the repeating units constituting the polymer chain A may be VA units.

Polymer chain B may contain only non-VA units as repeating units, or may contain VA units in addition to non-VA units. The content of non-VA units in polymer chain B may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight. In several aspects, the content of non-VA units in polymer chain B can be more than 95% by weight or more than 98% by weight. Substantially 100% by weight of the repeating units constituting the polymer chain B may be non-VA units.

Examples of polyvinyl alcohol-based polymers containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The above-mentioned graft copolymer may be a graft copolymer having a structure in which polymer chain A (main chain) is grafted onto polymer chain B (side chain), or a polymer may be grafted onto polymer chain B (main chain). ) A graft copolymer with a structure of grafted polymer chain A (side chain). In one aspect, a polyvinyl alcohol-based polymer having a structure in which polymer chain A is grafted onto polymer chain B can be used.

Examples of the polymer chain B include a polymer chain in which a repeating unit derived from an N-vinyl type monomer is the main repeating unit and a polymer chain in which a repeating unit derived from an N-(meth)acrylyl type monomer is the main repeating unit. Units of polymer chains, etc. Furthermore, in this specification, the so-called main repeating unit refers to repeating units exceeding 50% by weight unless otherwise mentioned.

A good example of the polymer chain B is a polymer chain having an N-vinyl type monomer as the main repeating unit, that is, an N-vinyl-based polymer chain. The content of repeating units derived from N-vinyl monomers in the N-vinyl polymer chain is typically more than 50% by weight, and may be more than 70% by weight, or more than 85% by weight, or more. It can be more than 95% by weight. Substantially all of the polymer chain B may be repeating units derived from N-vinyl monomers.

Examples of N-vinyl type monomers include monomers having a nitrogen-containing heterocyclic ring (for example, a lactam ring) and N-vinyl chain amide. Specific examples of the N-vinyllactam type monomer include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N -Vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinone (N-vinyl-3,5-morpholinone). Specific examples of N-vinyl chain amide include N-vinyl acetamide, N-vinyl propionamide, N-vinyl butyamide, and the like. Polymer chain B may be, for example, N-vinyl in which more than 50% by weight (for example, more than 70% by weight, or more than 85% by weight, or more than 95% by weight) of its repeating units are N-vinylpyrrolidone units. Base polymer chain. Substantially all of the repeating units constituting the polymer chain B may be N-vinylpyrrolidone units.

Other examples of the polymer chain B include a polymer chain whose main repeating unit is a repeating unit derived from an N-(meth)acrylyl-type monomer, that is, an N-(meth)acrylyl-based Polymer chain. The content of the repeating unit derived from the N-(meth)acrylyl-based monomer in the N-(meth)acrylyl-based polymer chain is typically more than 50% by weight, and may be more than 70% by weight. The content may be 85% by weight or more, or the content may be 95% by weight or more. Substantially all of the polymer chain B may be repeating units derived from N-(meth)acrylyl-type monomers.

Examples of N-(meth)acrylyl-type monomers include chain amide having an N-(meth)acrylyl group and cyclic amide having an N-(meth)acrylyl group. Examples of chain amide having an N-(meth)acrylamide group include (meth)acrylamide; N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide N-alkyl (methyl) amide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-n-butyl (meth) acrylamide, etc. Acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N , N,N-dialkyl(meth)acrylamide such as N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, etc. Examples of the cyclic amide having an N-(meth)acrylyl group include N-(meth)acrylylmorpholine, N-(meth)acrylylpyrrolidine, and the like.

Other examples of the polymer chain B include a polymer chain containing an oxyalkylene (oxyalkylene) unit as a main repeating unit, that is, an oxyalkylene-based polymer chain. The content of the oxyalkylene units in the oxyalkane-based polymer chain is typically more than 50% by weight, may be more than 70% by weight, may be more than 85% by weight, may be more than 95% by weight. Substantially all of the repeating units contained in the polymer chain B may be oxyalkane units.

Examples of the oxyalkylene unit include an oxyethyl unit, an oxypropyl unit, an oxybutyl unit, and the like. Such oxyalkylene units may be repeating units respectively derived from corresponding alkylene oxides. The number of oxyalkylene units contained in the oxyalkane-based polymer chain may be one type or two or more types. For example, an oxyalkylene-based polymer chain including an oxyethylene unit and an oxypropylene unit may be combined. In an oxyalkylene polymer chain containing two or more kinds of oxyalkylene units, these oxyalkylene units can be random copolymers of corresponding alkylene oxides, or block copolymers, Graft copolymers, etc.

Other examples of the polymer chain B include a polymer chain containing, as a main repeating unit, an alkyl vinyl ether unit, a structural unit obtained by acetalizing polyvinyl alcohol and an aldehyde, or the like. Among these, preferred ones are selected from a vinyl ether unit (alkyl vinyl ether unit) having an alkyl group having a carbon number of 1 to 10, and a monocarboxylic acid having a carbon number of 1 to 7. A group consisting of acid vinyl ester units (monocarboxylic acid vinyl ester units) and structural units obtained by acetalizing polyvinyl alcohol and an aldehyde having an alkyl group with a carbon number of 1 to 7 .

Examples of the vinyl ether unit having an alkyl group having a carbon number of 1 to 10 include a propyl vinyl ether unit, a butyl vinyl ether unit, a 2-ethylhexyl vinyl ether unit, and the like. Examples of the vinyl ester unit derived from a monocarboxylic acid having 1 to 7 carbon atoms include a vinyl propionate unit, a vinyl butyrate unit, a vinyl valerate unit, a vinyl hexanoate unit, and the like.

The polyvinyl alcohol-based polymer used in the polishing composition disclosed here may be PVA that is not modified (non-denatured PVA) or modified PVA that is a copolymer containing VA units and non-VA units. Non-denatured PVA and denatured PVA can also be used in combination. The polyvinyl alcohol-based polymer used in the polishing composition disclosed here preferably does not contain ether bonds.

According to the technology disclosed here, even when non-denatured PVA is used as the polyvinyl alcohol-based polymer, it is possible to obtain a polishing composition that can well suppress aggregation of the non-denatured PVA. Therefore, it is more meaningful to apply the present invention to a polishing composition containing non-denatured PVA. For example, when denatured PVA and non-denatured PVA are used together as the polyvinyl alcohol-based polymer, the content of the denatured PVA is preferably less than 50% by weight, more preferably less than 30% by weight, based on the total amount of the polyvinyl alcohol-based polymer. It is more preferably 10% by weight or less, 5% by weight or less, or 1% by weight or less. In several aspects of the polishing composition disclosed here, polyvinyl alcohol (PVA) containing only non-denatured PVA can be favorably used as the polyvinyl alcohol-based polymer.

The weight average molecular weight (Mw) of the polyvinyl alcohol-based polymer used in the polishing composition disclosed here is not particularly limited. The Mw of the polyvinyl alcohol-based polymer is usually 2×10 ³ or more, may be 5×10 ³ or more, or may be 1×10 ⁴ or more. As the Mw of the polyvinyl alcohol-based polymer increases, the surface wettability after grinding tends to increase. In addition, when the Mw of the polyvinyl alcohol-based polymer becomes high, the dispersion stability of the polyvinyl alcohol-based polymer tends to decrease, so the applicable significance of the present invention becomes larger. From this point of view, the Mw of the polyvinyl alcohol-based polymer of the polishing composition disclosed here is preferably 3×10 ⁴ or more, more preferably 4×10 ⁴ or more, and still more preferably 5×10 ⁴ or more, especially Preferably, it is 6×10 ⁴ or more (for example, 6.5×10 ⁴ or more).

The upper limit of Mw of the polyvinyl alcohol-based polymer used in the polishing composition disclosed here is not particularly limited. The Mw of the polyvinyl alcohol-based polymer is usually 100×10 ⁴ or less, preferably 30×10 ⁴ or less, and may be 20×10 ⁴ or less (for example, 15×10 ⁴ or less). From the viewpoint of coexistence of polishing rate and surface protection of the object to be polished, the Mw of the polyvinyl alcohol-based polymer may be 10×10 ⁴ or less or 8×10 ⁴ or less.

In addition, in this specification, the weight average molecular weight (Mw) of the polyvinyl alcohol-based polymer, dispersant, water-soluble polymer and surfactant can be based on the value based on aqueous gel permeation chromatography (GPC) (aqueous gel permeation chromatography). , polyethylene oxide conversion). As a GPC measurement device, model name "HLC-8320GPC" manufactured by Tosoh Corporation can be used. The measurement conditions may be as follows. The same method can also be used for the embodiments described later. [GPC measurement conditions] Sample concentration: 0.1% by weight Column: TSKgel GMPW _XL Detector: Differential refractometer Eluate: 100 mM sodium nitrate aqueous solution/acetonitrile=10~8/0~2 Flow rate: 1 mL/min Measurement temperature :40℃ Sample injection volume: 200 μL

>Dispersants for polyvinyl alcohol-based polymers> The polishing composition disclosed here contains a dispersant of a polyvinyl alcohol-based polymer (hereinafter also simply referred to as a “dispersant”). According to the technology disclosed herein, the dispersant system described above has at least one ether linkage in the molecule. According to the polishing composition containing the dispersant and the polyvinyl alcohol-based polymer together, it is possible to realize a polishing composition that suppresses the aggregation of the polyvinyl alcohol-based polymer and improves the dispersion stability. When implementing the technology disclosed here, the mechanism by which a dispersant containing ether bonds in the molecule contributes to suppressing the aggregation of polyvinyl alcohol-based polymers does not need to be elucidated, but it is considered that the dispersant contains Hydrogen bonds are generated between the ether-bonded oxygen atoms of the dispersant and the hydroxyl groups of the polyvinyl alcohol-based polymer, thereby hindering the hydrogen bonding between the hydroxyl groups of the polyvinyl alcohol-based polymer. However, the explanation is not limited to this mechanism.

As long as the dispersant contained in the polishing composition disclosed here contains an ether bond in the molecule, various compounds can be used in an appropriate content without particular limitation. The dispersant contained in the polishing composition disclosed here may be a compound having one ether bond in the molecule, or a polyether having two or more ether bonds in the molecule. In addition, the above-mentioned dispersing agent may be a polymer compound or may not be a polymer compound. When the dispersant is a polymer compound, the ether linkage may be included in the main chain of the polymer, may be included in the side chain, or may be included in both the main chain and the side chain. In addition, when the above-mentioned dispersing agent is not a polymer compound, the dispersing agent may be a compound generally known as a surfactant. The above-mentioned dispersants may be used singly or in combination of two or more. The above-mentioned dispersants are preferably water-soluble.

Examples of compounds having one ether bond in the molecule include diethyl ether, tetrahydrofuran, and the like. From the viewpoint of having appropriate dispersibility in the aqueous polishing composition and improving the dispersion stability of the polyvinyl alcohol-based polymer, the dispersant is preferably a polyether having two or more ether bonds in the molecule.

For example, examples of dispersants that can be used favorably include polyethers having an ether bond in the main chain. Examples of polyethers having ether bonds in the main chain include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and poly1,4-butylene glycol; polyoxyethylene alkyl ethers; , polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethyl fatty acid ester, polyoxyethyl glyceryl ether fatty acid ester, polyoxyethyl sorbitan fat Polyoxyalkylene derivatives of acid esters (for example, polyoxyalkylene adducts); copolymers of multiple types of oxyalkylene groups (for example, diblock copolymers, triblock copolymers, Random copolymers, interactive copolymers), etc. Alternatively, other examples include cellulose derivatives, starch derivatives, and the like.

Specific examples include block copolymers (diblock copolymers) of ethylene oxide (EO) and propylene oxide (PO), PEO (polyethylene oxide)-PPO (polypropylene oxide)- Oxyalkylene copolymers such as PEO triblock copolymers, PPO-PEO-PPO triblock copolymers, etc.), random copolymers of EO and PO; oxyalkylene copolymers such as polyethylene glycol, etc. Polymer; polyoxyethylene propyl ether, polyoxy ethyl butyl ether, polyoxy ethyl amyl ether, polyoxy ethyl hexyl ether, polyoxy ethyl octyl ether, polyoxy ethyl ether Ethyl 2-ethylhexyl ether, polyoxyethylidene nonyl ether, polyoxyethylene ethyl decyl ether, polyoxyethylene ethyl isodecyl ether, polyoxyethylene ethyl tridecyl ether, polyoxyethylene Polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene ethyl stearyl ether, polyoxyethylene ethyl isostearyl ether, polyoxyethylene oleyl ether, etc. Oxyethylidene alkyl ether; polyoxyethylidene phenyl ether, polyoxyethylidene octyl phenyl ether, polyoxyethylidene nonyl phenyl ether, polyoxyethylidene dodecyl phenyl ether Polyoxyethylidene alkylphenyl ethers such as ethers; polyoxyethylidene styrenated phenyl ether, polyoxyethylidene laurylamine, polyoxyethylidene stearylamine, polyoxyethylidene laurylamine Oleylamine, polyoxyethylidene monolaurate, polyoxyethylidene monostearate, polyoxyethylidene distearate, polyoxyethylidene monooleate, polyoxyethylidene monooleate Dioleate, polyoxyethyl sorbitan monolaurate, polyoxyethyl sorbitan monopalmitate, polyoxyethyl sorbitan monostearate, polyoxyethylene monooleate Ethyl sorbitan ester, trioleic acid polyoxyethylidene sorbitan ester, tetraoleic acid polyoxyethylidene sorbitan ester, polyoxyethylene ethyl castor oil, polyoxyethylidene hardened castor oil Oxyalkylene derivatives of others.

Or, as other specific examples, hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, Cellulose derivatives such as ethyl hydroxyethyl cellulose and carboxymethyl cellulose; starch derivatives such as alpha starch, polytriglucose (pullulan), carboxymethyl starch, cyclodextrin, etc.

In addition, as another dispersant that can be used favorably, a polyether having an ether bond in a side chain can be exemplified. Examples of the polyether having an ether bond in the side chain include polyacryloyl morpholine (PACMO).

Among them, examples of dispersants that can be favorably used in the polishing composition disclosed here include polyoxyethylene alkyl ether, HEC, and PACMO. Among them, polyoxyethylene alkyl ether is preferred.

The number of carbon atoms in the alkyl group of the polyoxyethylene alkyl ether that can be used here is not particularly limited. For example, the number of carbon atoms in the alkyl group is preferably 5 or more, more preferably 6 or more, and still more preferably 7 or more. For example, the number of carbon atoms in the alkyl group is preferably 12 or less, more preferably 11 or less, still more preferably 10 or less, and particularly preferably 9 or less. The number of carbon atoms of the alkyl group may be, for example, 8. In addition, the molar number of ethylene oxide added to the polyoxyethylene alkyl ether is not particularly limited, but it is preferably 4 or more, more preferably 5 or more, and still more preferably 6 or more. It is preferably 10 or less, more preferably 9 or less, still more preferably 8 or less, and particularly preferably 7 or less. From the viewpoint of reducing surface defects after polishing, a polyoxyethylene having an ethylene oxide addition mole number of 4 to 10 (for example, 6) can be suitably used as a dispersant used in the polishing composition disclosed here. Ethyl ethyl octyl ether.

In the polishing composition disclosed here, from the viewpoint of favorably improving the dispersion stability of the polyvinyl alcohol-based polymer, the content ratio of the polyvinyl alcohol-based polymer and the dispersant contained in the polishing composition is preferably Designed to appropriate scope. For example, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant in the polishing composition is preferably 0.01 or more and 10 or less, more preferably 0.02 or more and 5 or less (for example, 0.04 or more and below 4).

For example, in the case where the dispersing agent is a polyoxyethylene derivative containing polyoxyethylene alkyl ether or the like, the content of the polyvinyl alcohol-based polymer in the polishing composition is relative to the content of the dispersing agent. The molar ratio is preferably 1 or less, more preferably 0.5 or less, and still more preferably 0.1 or less (for example, 0.07 or less). Furthermore, in this aspect, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant is usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more, still more preferably 0.04 or more. . Containing the polyvinyl alcohol-based polymer and the dispersant in this blending ratio can appropriately suppress the aggregation of the polyvinyl alcohol-based polymer and easily realize a polishing composition that can reduce surface defects after polishing.

For example, when the dispersing agent is a water-soluble polymer (typically HEC or PACMO) containing repeating units with ether bonds, the content of the polyvinyl alcohol-based polymer in the polishing composition is relative to the dispersing agent. The molar ratio of the content is preferably 15 or less, more preferably 10 or less, and still more preferably 5 or less (for example, 4 or less). In addition, in this aspect, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant is usually 0.1 or more, preferably 0.3 or more, more preferably 0.5 or more, and still more preferably 1 above. Containing the polyvinyl alcohol-based polymer and the dispersant in this blending ratio can appropriately suppress the aggregation of the polyvinyl alcohol-based polymer and easily realize a polishing composition that can reduce surface defects after polishing.

The weight average molecular weight (Mw) of the dispersant is not particularly limited. The Mw of the dispersant is usually 100 or more, preferably 200 or more, more preferably 300 or more. In addition, the Mw of the dispersant is usually 100×10 ⁴ or less, preferably 70×10 ⁴ or less, more preferably 50×10 ⁴ or less.

For example, when the dispersant is a polyoxyalkylene derivative such as polyoxyethylene alkyl ether, the Mw of the dispersant is preferably 3,000 or less, more preferably 1,500 or less, still more preferably 700 or less, and particularly preferably is less than 500. In addition, when the dispersing agent is a polyoxyalkylene derivative, the Mw of the dispersing agent is preferably 100 or more, more preferably 200 or more, and still more preferably 300 or more. According to a polishing composition containing a dispersant having an Mw in this range, surface defects after polishing can be significantly reduced.

When the dispersant is a water-soluble polymer containing repeating units with ether bonds (typically HEC or PACMO), the Mw of the dispersant may be 1×10 ⁴ or more, or 5×10 ⁴ or more, or It is 10×10 ⁴ or more, and it can also be 20×10 ⁴ or more. In addition, the Mw of the dispersant may be 100×10 ⁴ or less, 50×10 ⁴ or less, 45×10 ⁴ or less, or 40×10 ⁴ or less.

In a preferred embodiment, the Mw of the dispersant is smaller than the Mw of the polyvinyl alcohol polymer. According to the polishing composition containing the dispersant having this Mw, the polishing surface can be appropriately protected and surface defects after polishing can be significantly reduced.

As a dispersant that can be used in the polishing composition disclosed here, a compound with an Mw of less than 1×10 ⁴ and a compound with an Mw of 1×10 ⁴ or more may be used in combination. For example, as the above-mentioned dispersant, a polyoxyalkylene derivative such as polyoxyethylene alkyl ether and a water-soluble polymer containing a repeating unit having an ether bond (typically HEC or PACMO) may be used in combination. . The dispersant that can be used in the polishing composition disclosed here preferably contains polyoxyalkylene derivatives such as polyoxyethylene alkyl ether. When the above-mentioned polyoxyalkylene derivative and the above-mentioned water-soluble polymer are used together as a dispersant, the content of the water-soluble polymer is preferably greater than 50% by weight, more preferably 70% by weight or more, based on the entire dispersant. More preferably, it is 80 weight% or more, 85 weight% or more, or 90 weight% or more.

As a dispersant that can be used in the polishing composition disclosed here, a compound having an Mw of less than 1×10 ⁴ can be used alone. For example, an embodiment may be implemented in which only polyoxyalkylene derivatives such as polyoxyethylene alkyl ether are used as the dispersing agent.

>Water-soluble polymer> The polishing composition disclosed here may optionally further contain a water-soluble polymer other than the above-mentioned polyvinyl alcohol-based polymer and dispersant within a range that does not significantly hinder the effects of the present invention. The above-mentioned water-soluble polymer may have at least one functional group selected from a cationic group, anionic group and a nonionic group in the molecule. The above-mentioned water-soluble polymer may have, for example, a hydroxyl group, a carboxyl group, a sulfo group, a primary amide structure, a heterocyclic structure, a vinyl structure, etc. in the molecule. From the viewpoint of reducing aggregates and improving cleanability, nonionic polymers can be suitably used as the water-soluble polymers.

Examples of the water-soluble polymer include polymers containing nitrogen atoms. As the polymer containing a nitrogen atom, either a polymer containing a nitrogen atom in the main chain or a polymer having a nitrogen atom in a side chain functional group (side group) can be used. Examples of polymers containing nitrogen atoms in the main chain include single polymers and copolymers of N-acylalkyleneimine type monomers. Specific examples of the N-acylethyleneimine type monomer include N-acetylethyleneimine, N-propylethyleneimine, and the like. Examples of the polymer having a nitrogen atom in a side group include a polymer containing an N-vinyl type monomer unit. For example, single polymers and copolymers of N-vinyl pyrrolidone can be used.

The polishing composition disclosed here can be implemented in an aspect that does not substantially contain water-soluble polymers other than polyvinyl alcohol-based polymers and dispersants.

>Surfactant> The polishing composition disclosed here may optionally contain a surfactant other than the above-mentioned dispersant within a range that does not significantly hinder the effects of the present invention. As the surfactant, any of anionic, cationic, nonionic, and amphoteric surfactants can be used. The polishing composition disclosed here can be implemented in an aspect that does not substantially contain a surfactant other than a dispersant.

>Water> As water in the polishing composition disclosed here, ion-exchange water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used. In order to avoid hindering the functions of other components contained in the polishing composition as much as possible, the water used is preferably such that the total content of transition metal ions is 100 ppb or less. The purity of water can be improved by, for example, using ion exchange resin to remove impurity ions, using filters to remove foreign matter, distillation, etc.

>Basic compounds> The polishing composition disclosed here contains a basic compound. In this specification, an alkaline compound refers to a compound that has the function of raising the pH of an aqueous solution when dissolved in water. As the basic compound, organic or inorganic basic compounds containing nitrogen, alkali metal hydroxides, alkaline earth metal hydroxides, various carbonates, bicarbonates, etc. can be used. Examples of the basic compound containing nitrogen include quaternary ammonium compounds, quaternary phosphonium compounds, ammonia, amines (preferably water-soluble amines), and the like. Such basic compounds may be used singly or in combination of two or more.

Specific examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, and the like. Specific examples of carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, and the like. Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-amino Ethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethyltetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-amine Azoles such as 1-(2-aminoethyl) piperazine, N-methyl piperazine, guanidine, imidazole, and triazole, etc. Specific examples of the quaternary phosphonium compound include quaternary phosphonium hydroxide such as tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide.

As the quaternary ammonium compound, quaternary ammonium salts (typically strong bases) such as tetraalkylammonium salts and hydroxyalkyltrialkylammonium salts can be preferably used. The anionic component in the quaternary ammonium salt may be, for example, OH ^- , F ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , BH ₄ ^- . Among them, a preferred example is a quaternary ammonium salt whose anion is OH ^- , that is, quaternary ammonium hydroxide. Specific examples of quaternary ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide and tetrapentylammonium hydroxide. Tetraalkylammonium hydroxide such as hexylammonium, hydroxyalkyltrialkylammonium hydroxide such as 2-hydroxyethyltrimethylammonium hydroxide (also called choline), etc.

Among these basic compounds, for example, at least one basic compound selected from the group consisting of alkali metal hydroxides, quaternary ammonium hydroxide, and ammonia can be preferably used. Among them, tetraalkylammonium hydroxide (for example, tetramethylammonium hydroxide) and ammonia are more preferred, and ammonia is particularly preferred.

>Other ingredients> In addition, the polishing composition disclosed here may optionally further contain a chelating agent, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt, a preservative, Conventional additives that can be used in polishing slurries (typically polishing slurries that can be used in the polishing step of silicon wafers) such as antifungal agents can be used.

It is preferred that the polishing composition disclosed here contains substantially no oxidizing agent. If the polishing composition contains an oxidizing agent, supplying the composition may cause the surface of the silicon substrate to be oxidized and produce an oxide film, which may reduce the polishing rate. Here, the term "polishing composition substantially does not contain an oxidizing agent" means that at least an oxidizing agent is not intentionally blended, and a trace amount of an oxidizing agent inevitably contained from raw materials, manufacturing methods, etc. is allowed. The above-mentioned trace amount means that the molar concentration of the oxidant in the polishing composition is 0.0005 mol/L or less (preferably 0.0001 mol/L or less, more preferably 0.00001 mol/L or less, particularly preferably 0.000001 mol). ear/L or less). A preferred aspect of the polishing composition can be implemented in an aspect that does not contain any of hydrogen peroxide, sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate, for example.

>pH> The pH of the polishing composition disclosed here is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, still more preferably 9.3 or higher, for example, 9.5 or higher. As the pH of the polishing composition becomes higher, the polishing rate tends to increase. On the other hand, from the viewpoint of suppressing the dissolution of abrasive grains (such as silicon oxide particles) and the reduction in mechanical polishing effect, the pH of the polishing composition is preferably 12.0 or less, preferably 11.0 or less, and 10.8 or less. Better, and below 10.5 is even better.

For pH, you can use a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model F-23) manufactured by Horiba Manufacturing Co., Ltd.) and a standard buffer solution (phthalic acid pH buffer solution pH: 4.01 (25°C), medium After performing a 3-point calibration (phosphate pH buffer solution pH: 6.86 (25°C), carbonate pH buffer solution pH: 10.01 (25°C)), place the glass electrode into the composition to be measured, measure and grasp the elapsed time for 2 minutes. value after stabilization.

>Use> The polishing composition of the technology disclosed here can be suitably used for polishing objects having various materials and shapes. The material of the grinding object may be, for example, metals or semi-metals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, or alloys thereof; quartz glass, aluminosilicate glass, glassy Glassy substances such as carbon; ceramic materials such as alumina, silicon oxide, sapphire, silicon nitride, tantalum nitride, titanium carbide, etc.; compound semiconductor substrate materials such as silicon carbide, gallium nitride, gallium arsenide, etc.; polycrystalline Resin materials such as amine resin, etc. It may also be a grinding object made of a plurality of materials among these.

The polishing composition of the technology disclosed here can be used particularly well for polishing a surface made of silicon (typically, polishing a silicon wafer). A typical example of the silicon wafer referred to here is a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by cutting a silicon single crystal ingot.

The polishing composition disclosed here can be well applied to the polishing step of a polishing object (for example, a silicon wafer). Before subjecting the object to polishing to the polishing step using the polishing composition disclosed herein, the object to be polished in a step upstream of the polishing step may also be subjected to general treatments such as brushing and etching.

The polishing composition disclosed herein can be advantageously used, for example, for polishing an object to be polished (for example, a silicon wafer) whose surface roughness is adjusted to a surface state of 0.1 nm to 100 nm through an upstream step. The surface roughness Ra of the polishing target material can be measured using, for example, a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement System Inc. It is effective when used for final polishing (finishing polishing) or for polishing before it, and it is particularly suitable for use in final polishing. Here, the so-called final polishing refers to the final polishing step in the manufacturing process of the target object (that is, no further polishing step will be performed after this step).

>Grinding composition> The polishing composition disclosed here is typically supplied to an object to be polished in the form of a polishing liquid containing the polishing composition, and is used for polishing the object to be polished. The above-mentioned polishing liquid can be prepared, for example, by diluting any of the polishing compositions disclosed herein (typically, diluting with water). Alternatively, the polishing composition may be used as it is as a polishing liquid. That is, the concept of the polishing composition in the technology disclosed here includes a polishing liquid (working slurry) that is supplied to an object to be polished and used for grinding the object, and a concentrated liquid that is diluted and used as a polishing liquid (i.e., Both sides of the original solution of the grinding fluid). Other examples of the polishing liquid containing the polishing composition disclosed here include a polishing liquid prepared by adjusting the pH of the composition.

(Slurry) The content of abrasive grains in the polishing liquid is not particularly limited, but is typically 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.10% by weight or more, for example, 0.15% by weight or more. By increasing the content of abrasive grains, higher grinding speeds can be achieved. From the viewpoint of the dispersion stability of the particles in the polishing composition, the above content is usually 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, and even more preferably 2% by weight or less. % or less, for example, 1 wt% or less, or 0.7 wt% or less. In a preferred aspect, the above content may be 0.5% by weight or less or less than 0.2% by weight.

The concentration of the polyvinyl alcohol-based polymer in the polishing liquid is not particularly limited, but may be, for example, 0.0001% by weight or more. From the viewpoint of reducing haze, the concentration is preferably 0.0005% by weight or more, more preferably 0.001% by weight or more, for example, 0.003% by weight or more, or 0.005% by weight or more. In addition, from the viewpoint of polishing speed and the like, the concentration of the polyvinyl alcohol-based polymer is generally preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and may be 0.05% by weight or less (for example, 0.01% by weight) % or less), or 0.008% by weight or less.

The concentration of the dispersant in the polishing liquid is not particularly limited, and may be, for example, 0.0001% by weight, preferably 0.0003% by weight or more. In addition, the concentration of the dispersant in the polishing liquid is generally preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and may also be 0.05% by weight or less. In a preferred aspect, the concentration of the dispersant in the polishing liquid may be 0.0001 wt% or more and 0.002 wt% or less, or may be 0.0002 wt% or more and 0.001 wt% or less. In addition, in another preferred aspect, the concentration of the dispersant in the polishing liquid may be 0.005% by weight or more and less than 0.03% by weight.

When the polishing composition disclosed here contains an alkaline compound, the concentration of the alkaline compound in the polishing liquid is not particularly limited. From the viewpoint of increasing the polishing speed, etc., generally, the concentration is preferably 0.001% by weight or more of the polishing liquid, and more preferably 0.003% by weight (for example, 0.005% by weight or more). In addition, from the viewpoint of reducing haze, etc., the above-mentioned concentration is preferably less than 0.3% by weight or less, preferably less than 0.1% by weight, and more preferably less than 0.05% by weight (for example, less than 0.03% by weight) .

(Concentrate) The polishing composition disclosed here may be in a concentrated form before being supplied to the object to be polished (that is, the concentrated liquid form of the polishing liquid may also be regarded as the original liquid of the polishing liquid.). Such a concentrated form of the polishing composition is advantageous from the viewpoints of convenience in manufacturing, distribution, storage, etc., cost reduction, and the like. The concentration ratio is not particularly limited, but may be, for example, about 2 to 100 times in volume terms, and usually about 5 to 50 times (for example, about 10 to 40 times) is more appropriate.

Such a concentrated liquid can be diluted at a desired timing to prepare a polishing liquid (working slurry), and the polishing liquid can be supplied to the object to be polished. The above-mentioned dilution can be performed, for example, by adding water to the above-mentioned concentrated liquid and mixing it.

The content of the abrasive particles in the concentrated liquid may be, for example, 50% by weight or less. From the viewpoint of the handleability of the concentrated liquid (for example, the dispersion stability of the abrasive grains, filterability, etc.), the content of the abrasive grains in the concentrated liquid is preferably 45% by weight or less, more preferably 40% by weight. %the following. In addition, from the viewpoint of convenience in manufacturing, distribution, storage, etc., cost reduction, etc., the content of the abrasive grains may be, for example, 0.5% by weight or more, preferably 1% by weight or more, and more preferably 3% by weight. above.

(Preparation of polishing composition) The polishing composition used in the technology disclosed here may be in a single-dose form or may be in a multi-dose form including a two-dose form. For example, part A including at least abrasive grains among the components of the polishing composition can be mixed with part B including at least a part of the remaining components, and the polishing liquid can be prepared by mixing and diluting the components at an appropriate timing if necessary. composition.

The preparation method of the polishing composition is not particularly limited. For example, a conventional mixing device such as a wing mixer, an ultrasonic disperser, or a homogenizer can be used to mix the components constituting the polishing composition. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once or in an appropriately set order.

>Grinding> The polishing composition disclosed here can be used for polishing an object to be polished, for example, in an aspect including the following operations. Hereinafter, a preferred aspect of a method of polishing a polishing object (for example, a silicon wafer) using the polishing composition disclosed herein will be described. That is, a polishing liquid containing any of the polishing compositions disclosed herein is prepared. Preparing the above-mentioned polishing liquid may include operations such as adding and adjusting the concentration of the polishing composition (for example, diluting), adjusting the pH, etc., to prepare the polishing liquid. Alternatively, the polishing composition may be used as it is as a polishing liquid.

Next, the polishing liquid is supplied to the object to be polished, and the object is polished in a normal manner. For example, when completing polishing of a silicon wafer, the silicon wafer that has undergone the polishing step is typically mounted on a general polishing device, and the polishing pad of the polishing device supplies polishing fluid to the surface to be polished of the silicon wafer. . Typically, while the above-mentioned polishing liquid is continuously supplied, the polishing pad is pressed against the polishing target surface of the silicon wafer and the two are relatively moved (for example, rotated). Through this grinding step, the grinding object is completely grinded.

The polishing pad used in the above-mentioned polishing step is not particularly limited. For example, foamed polyurethane type, nonwoven type, leather type, etc. polishing pads can be used. Each polishing pad may contain abrasive particles or may not contain abrasive particles. Generally, polishing pads that do not contain abrasive particles work well.

The object to be polished using the polishing composition disclosed here is typically cleaned. Cleaning can be done using an appropriate cleaning fluid. The cleaning liquid used is not particularly limited, and can be used. For example, in the field of semiconductors and other fields, a general SC-1 cleaning liquid (ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ) and water) can be used. (Mixture of H ₂ O)), SC-2 cleaning solution (Mixture of HCl, H ₂ O ₂ and H ₂ O), etc. The temperature of the cleaning liquid may be, for example, in a range from room temperature or above (typically about 15°C to 25°C) to about 90°C. From the perspective of improving the cleaning effect, a cleaning fluid of about 50°C to 85°C can be used optimally.

Several embodiments of the present invention will be described below, but the present invention is not intended to be limited to the embodiments. Furthermore, "parts" and "%" in the following explanations are based on weight unless otherwise mentioned. In addition, PVA described below is a saponified product of polyvinyl acetate.

>Evaluation of dispersion stability> The dispersion stability of aqueous solutions containing the dispersants used in the following examples or water-soluble polymers other than the dispersants was evaluated as follows. First, a test liquid for dispersion stability evaluation was prepared as follows.

(Example 1A) Polyvinyl alcohol (PVA), a dispersant and water were mixed to prepare an aqueous solution containing 0.1% PVA and the remainder consisting of water, to prepare a test liquid according to Example 1A. As PVA, use one with an Mw of 7×10 ⁴ and a saponification degree of 98% or more. As a dispersant, polyoxyethylene octyl ether with an ethylene oxide addition mole number of 6 (hereinafter also represented by "C8PEO6") was used.

(Example 2A) In addition to using polyacrylamide morpholine (PACMO) with Mw of 39×10 ⁴ as the dispersant instead of C8PEO6, an aqueous solution containing the same components used in Example 1A at the same concentration was prepared as Example 2A. Test fluid.

(Example 3A) The test liquid of Example 3A was prepared in the same manner as in Example 1A, except that hydroxyethyl cellulose (HEC) with Mw of 26×10 ⁴ was used instead of C8PEO6 as the dispersant. The concentration of PVA in the test solution of Example 3A was 0.10%.

(Example 4A) Except not using a dispersant, an aqueous solution containing the same components used in Example 3A at the same concentration was prepared as the test solution of Example 4A.

(Example 5A) The test liquid of Example 5A was prepared in the same manner as in Example 1A, except that polyvinylpyrrolidone (PVP) with an Mw of 1.7×10 ⁴ was used instead of C8PEO6. The concentration of PVA in the test solution of Example 5A was 0.10%, and the concentration of PVP was 0.05%.

(Example 6A) Except that PVA was not used, an aqueous solution containing the same components used in Example 5A at the same concentration was prepared as the test solution of Example 6A.

In each of the test examples of Examples 1A to 3A, the molar ratio of the content of PVA to the content of the dispersant having an ether bond is as shown in this column of Table 1.

Next, 20 ml of each test solution of Examples 1A to 6A was taken, put into a lidded container with a capacity of 80 ml, and shaken at a shaking intensity of 300 spm in an environment of 23°C. While the container is being shaken, the presence or absence of precipitates in the container is visually confirmed every 12 hours. The dispersion stability of each test liquid was evaluated in the following three stages. In the shaking test under the above test conditions, those that did not produce precipitates even if shaken for 72 hours or more were evaluated as good (○), and those that were shaken for 24 hours or more and less than 72 hours were evaluated as good (○). The vibration that produces precipitates is evaluated as acceptable (△), and the vibration that produces precipitates for less than 24 hours is evaluated as poor (╳). The evaluation results are shown in the column of dispersion stability in Table 1.

[Table 1]

As shown in Table 1, the test solutions of Examples 1A to 3A, which contain a dispersant with an ether bond in the molecule, can significantly improve the solution quality compared to the test solutions of Examples 4A to 5A, which do not contain a dispersant. Dispersion stability. In addition, since the test liquid of Example 6A, which does not contain PVA, showed good dispersion stability, this indicates that the main cause of damage to the dispersion stability of the test liquid is aggregation from PVA. In addition, the PVA used in the test liquid of Example 4A was replaced with PVA having a molecular weight of 1.1×10 ⁴ and a saponification degree of 98% or more. The test liquid was prepared in the same manner and the dispersion stability was evaluated in the same manner. As a result, the The evaluation of the dispersion stability of the test liquid was acceptable (Δ). From this, it can be seen that the dispersion stability of the test liquid of Example 4A is lower than this test liquid. This shows that the test liquid containing PVA with a high molecular weight tends to easily cause aggregation of PVA.

>Preliminary grinding steps> Next, the contents of the preliminary polishing step applicable to the following examples will be shown. (preliminary grinding step) Prepare a front-stage polishing composition containing 0.9% abrasive grains and 0.1% alkaline compound, with the remainder consisting of water. Colloidal silica with a BET diameter of 35 nm was used as abrasive particles. Potassium hydroxide (KOH) is used as the alkaline compound. This pre-stage polishing composition was used as a polishing liquid (working slurry), and the silicon wafer to be polished was polished under the following pre-stage polishing conditions. As the silicon wafer, a commercially available silicon single crystal wafer with a diameter of 300 mm that has been ground and etched was used (conduction type: P type, crystal orientation: >100>, resistivity: 1Ω‧cm or more and less than 100Ω‧ cm, no COP).

[Preliminary grinding conditions] Grinding device: Blade grinder manufactured by Okamoto Machinery Manufacturing Co., Ltd., model "PNX-332B" Grinding load: 20 kPa Fixed plate speed: 20 rpm Drive plate rotation number: 20 rpm Polishing pad: Made by FUJIBO Ehime Co., Ltd., product name "FP55" Grinding fluid supply rate: 1 liter/min Grinding fluid temperature: 20℃ Fixing plate cooling water temperature: 20℃ Grinding time: 2 minutes

>Preparation of polishing composition and completion of polishing> (Example 1B) Prepare a polishing composition containing abrasive grains, polyvinyl alcohol (PVA), a dispersant, and an alkaline compound, with the remainder consisting of water, to prepare a polishing composition as in Example 1B Grinding compositions. As the abrasive grains, colloidal silica with a BET diameter of 25 nm was used. As PVA, use one with an Mw of 7×10 ⁴ and a saponification degree of 98% or more. As a dispersant, polyoxyethylene octyl ether (C8PEO6) with an ethylene oxide addition mole number of 6 was used. Ammonia is used as the alkaline compound. The concentration of each component in the polishing composition of Example 1B was 3.3% for the abrasive grains, 0.11% for the PVA, and 0.21% for the basic compound. This polishing composition was diluted 20 times with deionized water (DIW) and used as a polishing slurry (working slurry). The silicon wafer that had completed the above-mentioned preliminary polishing step was polished under the following completion polishing conditions.

[Finishing grinding conditions] Grinding device: Leaf grinder manufactured by Okamoto Machinery Co., Ltd., model "PNX-332B" Grinding load: 15 kPa Fixed plate speed: 30 rpm Drive plate rotation number: 30 rpm Polishing pad: Polishing pad manufactured by FUJIBO Ehime Co., Ltd., brand name "POLYPAS27NX" Grinding fluid supply rate: 2 liters/min Grinding fluid temperature: 20℃ Fixing plate cooling water temperature: 20℃ Grinding time: 4 minutes

Remove the ground silicon wafer from the grinding device and use a cleaning solution of NH ₄ OH (29%): H ₂ O ₂ (31%): deionized water (DIW) = 2:5.3:48 (volume ratio) Cleaning (SC-1 Cleaning). More specifically, a cleaning tank equipped with an ultrasonic oscillator with a frequency of 720 kHz is prepared, the above-mentioned cleaning liquid is stored in the cleaning tank, kept at 70°C, the polished silicon wafer is immersed in the cleaning tank for 6 minutes, and then ultrasonic is used. Rinse with pure water. After repeating this step twice, the silicon wafer is dried.

(Example 2B) A polishing composition of Example 2B was prepared by using PACMO with an Mw of 39×10 ⁴ as a dispersant instead of C8PEO6 and containing the same components as in Example 1B at the same concentration. Except using this polishing composition, the same operation as in Example 1B was carried out to complete the polishing, cleaning and drying of the silicon wafer that completed the preceding polishing step.

(Example 3B) The polishing composition of Example 3B was prepared in the same manner as in Example 1B, except that HEC with Mw of 26×10 ⁴ was used instead of C8PEO6 as the dispersant. The concentration of each component in the polishing composition of Example 3B was 3.3% for the abrasive grains, 0.10% for the PVA, and 0.23% for the basic compound. Except using this polishing composition, the same operation as in Example 1B was carried out to complete the polishing, cleaning and drying of the silicon wafer that completed the preceding polishing step.

(Example 4B) The polishing composition of Example 4B was prepared in the same manner as Example 1B except that a dispersant was not used. The concentration of each component in the polishing composition of Example 4B was 3.3% for the abrasive grains, 0.10% for the PVA, and 0.21% for the basic compound. Except using this polishing composition, the same operation as in Example 1B was carried out to complete the polishing, cleaning and drying of the silicon wafer that completed the preceding polishing step.

(Example 5B) The polishing composition of Example 5B was prepared in the same manner as in Example 1B, except that PVP with Mw1.7×10 ⁴ was used instead of C8PEO6. The concentration of each component in the polishing composition of Example 5B is 3.3% for abrasive grains, 0.10% for PVA, 0.05% for PVP, and 0.21% for an alkaline compound. Except using this polishing composition, the same operation as in Example 1B was carried out to complete the polishing, cleaning and drying of the silicon wafer that completed the preceding polishing step.

(Example 6B) The polishing composition of Example 6B was prepared by including the same components as Example 5B at the same concentration except that PVA was not used. Except using this polishing composition, the same operation as in Example 1B was carried out to complete the polishing, cleaning and drying of the silicon wafer that completed the preceding polishing step.

In each polishing composition of Examples 1B to 3B, the molar ratio of the content of PVA to the content of the dispersant having an ether bond is as shown in this column of Table 2.

>Evaluation of surface defects> The silicon wafers obtained in each of the above examples were evaluated as follows. (Measurement of LPD number) A wafer inspection device (manufactured by KLA Tencor, trade name "SURFSCAN SP2 xp") was used to measure the number of LPDs larger than 32 nm existing on the surface (polished surface) of the silicon wafer. The number of measured LPDs is expressed in the corresponding columns of Table 2 in the following three stages. The smaller the number of LPDs, the greater the surface defects that reduce the polished surface. ◎: 100 or less ○: 101 or more and less than 1,000 ╳: 1001 or more

[Table 2]

As shown in Table 2, the polishing compositions of Examples 1B to 3B that contain PVA and a dispersant having an ether bond in the molecule, compared with the polishing compositions of Examples 4B to 5B that do not contain a dispersant, LPD The number is significantly reduced and the surface defects of the grinding surface are reduced. In particular, the polishing composition of Example 1B using C8PEO6 as the dispersant significantly reduced surface defects.

Although specific examples of the present invention have been described in detail above, these are only examples and do not limit the scope of the application. The technology described in the patent application scope includes various modifications and changes of the specific examples illustrated above.

without.

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Claims (6)

A polishing composition comprising abrasive grains and water, further comprising: a polyvinyl alcohol-based polymer and a dispersant for the polyvinyl alcohol-based polymer, wherein the dispersant includes a polyoxyethylene alkyl group ether, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant is 0.01 or more and 0.1 or less, wherein the above-mentioned polishing composition is supplied to the object to be polished in the form of a polishing liquid, and in the above-mentioned polishing liquid The content of the above-mentioned abrasive grains is not less than 0.01% by weight and not more than 10% by weight, the content of the above-mentioned polyvinyl alcohol-based polymer in the above-mentioned polishing liquid is not less than 0.0001% by weight and not more than 0.2% by weight, and the above-mentioned dispersant in the above-mentioned polishing liquid is The content of the above-mentioned polishing composition is from 0.0001 to 0.2% by weight, and the content of the above-mentioned basic compound in the above-mentioned polishing liquid is from 0.001 to 0.3% by weight. For example, in the polishing composition of claim 1, the weight average molecular weight of the polyvinyl alcohol-based polymer is 3×10 ⁴ or more. For example, in the polishing composition of claim 1 or 2, the weight average molecular weight of the dispersant is smaller than the weight average molecular weight of the polyvinyl alcohol polymer. For example, in the polishing composition of claim 1 or 2, the weight average molecular weight of the above-mentioned dispersant is 1500 or less. For example, in the polishing composition of claim 1 or 2, the abrasive particles are silicon oxide particles. For example, the polishing composition of Item 1 or 2 of the patent application is used to polish the surface made of silicon.