WO2019187969A1 - Polishing composition - Google Patents

Abstract

Provided is a polishing composition that, although including a polyvinyl alcohol-based polymer, has suppressed aggregation of the polyvinyl alcohol-based polymer in the composition and can effectively reduce surface defects. This polishing composition includes abrasive grains and water. The polishing composition also includes the polyvinyl alcohol-based polymer and a dispersant for the polyvinyl alcohol-based polymer. The dispersant includes an ether bond in the molecules thereof. The molar ratio of the polyvinyl alcohol-based polymer content relative to the dispersant content is 0.01–10.

Description

Polishing composition

The present invention relates to a polishing composition. This application claims priority based on Japanese Patent Application No. 2018-69647 filed on Mar. 30, 2018, the entire contents of which are incorporated herein by reference.

Precision polishing using a polishing composition is performed on material surfaces such as metal, metalloid, nonmetal, and oxides thereof. For example, the surface of a silicon wafer used as a component of a semiconductor device or the like is generally finished into 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 (preliminary polishing process) and a final polishing process (final polishing process). Patent document 1 is mentioned as technical literature regarding the polishing composition mainly used for the use which grinds semiconductor substrates, such as a silicon wafer.

Japanese Patent Application Publication No. 2010-34509

A polishing composition used in a finishing polishing process (particularly, a polishing polishing process for a semiconductor substrate such as a silicon wafer or other substrate) is required to have a performance that realizes a surface having low haze and less surface defects after polishing. Many polishing compositions for such applications contain a water-soluble polymer for the purpose of protecting the surface of a polishing object and improving wettability in addition to abrasive grains and water. For example, Patent Document 1 discloses a polishing composition for silicon wafers containing hydroxyethyl cellulose or polyvinyl alcohol (PVA) as a water-soluble polymer.

By using a polyvinyl alcohol-based polymer as the water-soluble polymer, the wettability of the surface after polishing can be stably improved. However, with the advancement of the required level for the surface quality after polishing, the conventional polishing composition using the polyvinyl alcohol polymer tends to be insufficient in reducing the surface defects.

This invention is made | formed in view of this point, and it aims at providing the polishing composition which can reduce a surface defect effectively, although it is a polishing composition containing a polyvinyl alcohol-type polymer. .

The present inventors have thought that aggregation of the polyvinyl alcohol polymer contained in the polishing composition may be a factor causing the surface defects, and have found a polishing composition suitable for suppressing such aggregation. The present invention has been completed.
According to the present invention, a polishing composition comprising abrasive grains and water is provided. The polishing composition further includes a polyvinyl alcohol polymer and a dispersant for the polyvinyl alcohol polymer. The dispersant includes an ether bond in the molecule. The molar ratio of the content of the polyvinyl alcohol polymer to the content of the dispersant is 0.01 or more and 10 or less. According to this configuration, since the polyvinyl alcohol polymer and the polyvinyl alcohol polymer dispersant are contained in an appropriate mixing ratio, the aggregation of the polyvinyl alcohol polymer in the polishing composition causes the action of the dispersant. Is appropriately suppressed. Thus, according to the polishing composition containing the polyvinyl alcohol-based polymer in which aggregation is suppressed, surface defects of the polished object after polishing are appropriately reduced.

In this specification, the term “polyvinyl alcohol polymer dispersant” means that the dispersibility of the polyvinyl alcohol polymer is improved by adding it to the polishing composition as compared with the polishing composition not containing the dispersant. It refers to an agent (compound) having the performance of Typically, the dispersant for the polyvinyl alcohol polymer is a compound having the ability to improve the dispersion stability of the polyvinyl alcohol polymer in an aqueous solution. In the present specification, unless otherwise specified, what is simply described as “dispersant” means “a dispersant for a polyvinyl alcohol polymer”. In addition, the “surface defect” in the present specification includes LPD (Light Point Defectives) which means a foreign substance generally called a particle. The occurrence of such surface defects can be evaluated by measuring the number of LPDs detected by a wafer inspection apparatus used in examples described later.

In a preferred embodiment, the polyvinyl alcohol-based polymer has a weight average molecular weight of 3 × 10 ⁴ or more. Since a polyvinyl alcohol polymer having such a weight average molecular weight tends to aggregate more easily, it is meaningful to apply the present invention to a polishing composition containing a polyvinyl alcohol polymer having the above weight average molecular weight.

In another preferred embodiment of the polishing composition disclosed herein, the weight average molecular weight of the dispersant is smaller than the weight average molecular weight of the polyvinyl alcohol polymer. According to such a configuration, it is possible to realize a polishing composition capable of appropriately suppressing aggregation of the polyvinyl alcohol-based polymer and reducing surface defects of the object to be polished.

In another preferred embodiment of the polishing composition disclosed herein, the dispersant contains polyoxyethylene alkyl ether. According to the configuration containing such a dispersant, it is possible to realize a polishing composition in which aggregation of the polyvinyl alcohol-based polymer is more appropriately suppressed and surface defect reduction properties are further improved.

In another preferred embodiment of the polishing composition disclosed herein, the dispersant has a weight average molecular weight of 1500 or less. According to the configuration containing such a dispersant, it is possible to realize a polishing composition in which aggregation of the polyvinyl alcohol-based polymer is more appropriately suppressed and surface defect reduction properties are further improved.

In another preferred embodiment of the polishing composition disclosed herein, the abrasive grains are silica particles. In the polishing using silica particles as the abrasive grains, the surface defect defects can be effectively reduced while maintaining the polishing rate.

The polishing composition according to a preferred embodiment disclosed herein is used for polishing a surface made of silicon. In the polishing composition disclosed herein, the surface of the polishing object is protected by the action of the polyvinyl alcohol polymer in which aggregation is suppressed by the action of the dispersant in polishing where the polishing object is a surface made of silicon. Thus, defects on the surface can be appropriately reduced.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Abrasive grains>
The polishing composition disclosed herein contains abrasive grains. The abrasive grains serve to mechanically polish 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 of use and usage of the polishing composition. Examples of the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include 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, oxide particles such as bengara particles; Examples thereof include 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. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid). And polyacrylonitrile particles. Such abrasive grains may be used singly or in combination of two or more.

As the abrasive grains, inorganic particles are preferable, and particles made of metal or metalloid oxide are preferable, and silica particles are particularly preferable. In a polishing composition that can be used for polishing (for example, finish polishing) of an object to be polished having a surface made of silicon, such as a silicon wafer described later, it is particularly meaningful to employ silica particles as abrasive grains. The technique disclosed here can be preferably implemented, for example, in a mode in which the abrasive grains are substantially composed of silica particles. Here, “substantially” means 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, or 100% by weight) of the particles constituting the abrasive grains. It means silica particles.

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

The true specific gravity of the abrasive constituent material (for example, 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 the abrasive grain constituent material (for example, silica) is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less. As the true specific gravity of the abrasive grain constituent material (for example, silica), a measured value by a liquid replacement method using ethanol as a replacement liquid can be adopted.

The BET diameter of the abrasive grains (typically silica particles) is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more from the viewpoint of polishing efficiency and the like. From the viewpoint of obtaining a higher polishing effect (for example, effects such as haze reduction and defect removal), the BET diameter is preferably 15 nm or more, and more preferably 20 nm or more (for example, more than 20 nm). Further, from the viewpoint of preventing scratches, the BET diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and further preferably 40 nm or less. The technique disclosed herein is preferably applied to polishing in which a high-quality surface is required after polishing because a high-quality surface (for example, a surface having a small number of LPDs) is easily obtained. As the abrasive used in such a polishing composition, an abrasive having 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) is preferable.

In this specification, the BET diameter refers to the BET diameter (nm) = 6000 / (true density (g / cm ³ ) × BET value (m ² / g) from the specific surface area (BET value) measured by the BET method. )) The particle diameter calculated by the formula. For example, in the case of silica particles, the BET diameter can be calculated from the BET diameter (nm) = 2727 / BET value (m ² / g). The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritex Corporation, a trade name “Flow Sorb II 2300”.

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

Although not particularly limited, the average value of the major axis / minor axis ratio (average aspect ratio) of the abrasive grains is theoretically 1.0 or more, preferably 1.05 or more, more preferably 1.1 or more. It is. By increasing the average aspect ratio, higher polishing efficiency can be realized. 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.

The shape (outer shape) and average aspect ratio of the abrasive grains can be grasped by, for example, observation with an electron microscope. As a specific procedure for grasping the average aspect ratio, for example, a predetermined number (for example, 200) of abrasive particles capable of recognizing the shape of independent particles using a scanning electron microscope (SEM) is used. Draw the smallest rectangle that circumscribes the image. For the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (major axis value) by the length of the short side (minor axis value) is the major axis / minor axis ratio (aspect ratio). ). An average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the predetermined number of particles.

<Polyvinyl alcohol polymer>
The polishing composition disclosed herein contains a polyvinyl alcohol polymer. Here, the polyvinyl alcohol 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 portion represented by the following chemical formula: —CH ₂ —CH (OH) —. The VA unit can be produced, for example, by hydrolyzing (saponifying) a repeating unit (—CH ₂ —CH (OCOCH ₃ ) —) having a structure in which vinyl acetate is vinyl polymerized. According to the polishing composition containing a polyvinyl alcohol polymer, the wettability of the surface of the polishing object is improved, and a surface having low haze and few surface defects is easily realized after polishing.

The polyvinyl alcohol polymer has a hydroxy group (OH group) in the molecule. For this reason, a polyvinyl alcohol-type polymer has a property which is easy to aggregate by the effect | action of the hydrogen bond in a molecule | numerator or between molecules. When a part of the polyvinyl alcohol-based polymer contained in the polishing composition aggregates and the dispersion stability of the composition decreases, the ability to reduce surface defects after polishing may decrease. According to the technology disclosed herein, the use of a polyvinyl alcohol polymer and a polyvinyl alcohol polymer dispersant described later in combination effectively suppresses aggregation of the polyvinyl alcohol polymer and improves the dispersion stability. Compositions can be realized.

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 an embodiment in which the polyvinyl alcohol-based polymer includes a non-VA unit, the non-VA unit includes an oxyalkylene group, a carboxy group, a sulfo group, an amino group, a hydroxyl group, an amide group, an imide group, a nitrile group, an ether group, an ester group, and these It may be a repeating unit having at least one structure selected from the salts of Alternatively, the non-VA unit is a repeating unit having at least one structure selected from oxyalkylene groups, carboxy groups, sulfo groups, amino groups, hydroxyl groups, amide groups, imide groups, nitrile groups, ester groups, and salts thereof. It can be. The polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, or may be a block copolymer or a graft copolymer. The polyvinyl alcohol-based polymer may include only one type of non-VA unit as the non-VA unit, or may include two or more types of non-VA units.

The ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. . Although not particularly limited, in some embodiments, the ratio of the number of moles of the VA unit may be 50% or more, 65% or more, 75% or more, 80% or more, It may be 90% or more (for example, 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol polymer may be VA units. Here, “substantially 100%” means that at least intentionally, the polyvinyl alcohol polymer does not contain a non-VA unit. For example, according to a polishing composition containing polyvinyl alcohol (PVA) (so-called fully saponified PVA) having a saponification degree of 98% or more, the surface of the object to be polished has high wettability, and the surface having few surface defects after polishing is obtained. Easy to realize. Moreover, since PVA with a high saponification tendency tends to aggregate more easily, it is meaningful to apply this invention to PVA with a high saponification degree (for example, PVA with a saponification degree 98% or more). In some other embodiments, the ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 95% or less, may be 90% or less, and may be 80% or less. It may be 70% or less.

The content of VA units (content based on weight) in the polyvinyl alcohol polymer may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight or more. Although not particularly limited, in some embodiments, the content of the VA unit may be 50% by weight or more (eg, more than 50% by weight), 70% by weight or more, and 80% by weight or more ( For example, it may be 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 intentionally, a non-VA unit is not included as a repeating unit constituting the polyvinyl alcohol-based polymer. In some other embodiments, the content of VA units in the polyvinyl alcohol-based polymer may be, for example, 95% by weight or less, 90% by weight or less, 80% by weight or less, or 70% by weight or less. .

The polyvinyl alcohol-based polymer may contain a plurality of polymer chains having different VA unit contents in the same molecule. Here, the polymer chain refers to a part (segment) that constitutes a part of a polymer of one molecule. For example, the polyvinyl alcohol-based polymer has a polymer chain A having a VA unit content of more than 50% by weight and a VA unit content of less than 50% by weight (that is, a non-VA unit content of more than 50% by weight). ) The polymer chain B may be contained in the same molecule.

The polymer chain A may contain only VA units as repeating units, and may contain non-VA units in addition to VA units. The content of the VA unit in the 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 some embodiments, the content of VA units in the polymer chain A may be 95% by weight or more, or 98% by weight or more. Substantially 100% by weight of the repeating units constituting the polymer chain A may be VA units.

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

Examples of the polyvinyl alcohol polymer containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The graft copolymer may be a graft copolymer having a structure in which a polymer chain B (side chain) is grafted to a polymer chain A (main chain), and the polymer chain B (main chain) is polymer chain A (side). It may be a graft copolymer having a structure in which the chain) is grafted. In one embodiment, a polyvinyl alcohol polymer having a structure in which a polymer chain B is grafted to a polymer chain A can be used.

Examples of the polymer chain B include a polymer chain having a repeating unit derived from an N-vinyl type monomer as a main repeating unit, and a polymer having a repeating unit derived from an N- (meth) acryloyl type monomer as a main repeating unit. A chain. In the present specification, the main repeating unit means a repeating unit contained in an amount exceeding 50% by weight unless otherwise specified.

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

Examples of the N-vinyl type monomer include a monomer having a nitrogen-containing heterocyclic ring (for example, a lactam ring) and an N-vinyl chain amide. Specific examples of N-vinyl lactam type monomers include N-vinyl pyrrolidone, N-vinyl piperidone, N-vinyl morpholinone, N-vinyl caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl- 3,5-morpholinedione and the like can be mentioned. Specific examples of the N-vinyl chain amide include N-vinylacetamide, N-vinylpropionic acid amide, N-vinylbutyric acid amide and the like. The polymer chain B is, for example, an N-vinyl polymer chain in which more than 50% by weight (for example, 70% by weight or more, 85% by weight or more, or 95% by weight or more) of the repeating unit is an N-vinylpyrrolidone unit. obtain. Substantially all of the repeating units constituting the polymer chain B may be N-vinylpyrrolidone units.

Another example of the polymer chain B includes a polymer chain having a repeating unit derived from an N- (meth) acryloyl type monomer as a main repeating unit, that is, an N- (meth) acryloyl polymer chain. The content of repeating units derived from the N- (meth) acryloyl type monomer in the N- (meth) acryloyl-based polymer chain is typically more than 50% by weight and may be 70% by weight or more. % By weight or 95% by weight or more may be used. Repeating units derived from N- (meth) acryloyl type monomers may be sufficient as the polymer chain B.

Examples of the N- (meth) acryloyl type monomer include a chain amide having an N- (meth) acryloyl group and a cyclic amide having an N- (meth) acryloyl group. Examples of chain amides having an N- (meth) acryloyl group include (meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl ( N-alkyl (meth) acrylamides such as (meth) acrylamide and Nn-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meta) ) Acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide such as N, N-di (n-butyl) (meth) acrylamide; Examples of the cyclic amide having an N- (meth) acryloyl group include N- (meth) acryloylmorpholine and N- (meth) acryloylpyrrolidine.

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

Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxybutylene units, and the like. Each such oxyalkylene unit can be a repeating unit derived from the corresponding alkylene oxide. The oxyalkylene unit contained in the oxyalkylene polymer chain may be one kind or two or more kinds. For example, it may be an oxyalkylene polymer chain containing a combination of oxyethylene units and oxypropylene units. In the oxyalkylene polymer chain containing two or more types of oxyalkylene units, these oxyalkylene units may be a random copolymer of a corresponding alkylene oxide, and may be a block copolymer or a graft copolymer. Also good.

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, and the like. Among these, vinyl ether units (alkyl vinyl ether units) having an alkyl group having 1 to 10 carbon atoms, vinyl ester units derived from monocarboxylic acids having 1 to 7 carbon atoms (monocarboxylic acid vinyl ester units), And it is preferable when it selects from the group which consists of a structural unit obtained by acetalizing polyvinyl alcohol and the aldehyde which has a C1-C7 alkyl group.

Examples of vinyl ether units having an alkyl group having 1 to 10 carbon atoms include propyl vinyl ether units, butyl vinyl ether units, 2-ethylhexyl vinyl ether units and the like. Examples of vinyl ester units derived from monocarboxylic acids having 1 to 7 carbon atoms include vinyl propanoate units, vinyl butanoate units, vinyl pentanoate units, vinyl hexanoate units, and the like.

The polyvinyl alcohol polymer used in the polishing composition disclosed herein may be unmodified PVA (non-modified PVA), and is a modified PVA that is a copolymer containing VA units and non-VA units. It may be. A combination of non-modified PVA and modified PVA may be used. The polyvinyl alcohol polymer used in the polishing composition disclosed herein preferably does not contain an ether bond.

According to the technique disclosed herein, even when non-modified PVA is used as the polyvinyl alcohol polymer, a polishing composition in which aggregation of the non-modified PVA is suitably suppressed can be obtained. For this reason, it is more meaningful to apply the present invention to a polishing composition containing non-modified PVA. For example, in the case where a modified PVA and a non-modified PVA are used in combination as a polyvinyl alcohol-based polymer, the content of the modified PVA is preferably less than 50% by weight, more preferably based on the total amount of the polyvinyl alcohol-based polymer. It is 30% by weight or less, more preferably 10% by weight or less, 5% by weight or less, or 1% by weight or less. In some embodiments of the polishing composition disclosed herein, polyvinyl alcohol (PVA) containing only non-modified PVA can be preferably used as the polyvinyl alcohol-based polymer.

The weight average molecular weight (Mw) of the polyvinyl alcohol polymer used in the polishing composition disclosed herein is not particularly limited. The Mw of the polyvinyl alcohol polymer is usually 2 × 10 ³ or more, may be 5 × 10 ³ or more, and may be 1 × 10 ⁴ or more. As the Mw of the polyvinyl alcohol polymer increases, the wettability of the surface after polishing tends to increase. Further, since the dispersion stability of the polyvinyl alcohol polymer tends to decrease as the Mw of the polyvinyl alcohol polymer increases, the significance of application of the present invention increases. From this viewpoint, the Mw of the polyvinyl alcohol polymer used in the polishing composition disclosed herein is preferably 3 × 10 ⁴ or more, more preferably 4 × 10 ⁴ or more, and further preferably 5 × 10 ⁴ or more, particularly preferably 6 × 10 ⁴ or more (for example, 6.5 × 10 ⁴ or more).

The upper limit of Mw of the polyvinyl alcohol polymer used in the polishing composition disclosed herein is not particularly limited. The Mw of the polyvinyl alcohol-based polymer is usually suitably 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 achieving both the polishing rate and the 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 this specification, the weight average molecular weight (Mw) of the polyvinyl alcohol polymer, the dispersant, the water-soluble polymer and the surfactant is a value based on an aqueous gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent). ) Can be adopted. As the GPC measuring apparatus, the model name “HLC-8320GPC” manufactured by Tosoh Corporation may be used. The measurement conditions should be as follows. The same method is adopted for the embodiments described later.
[GPC measurement conditions]
Sample concentration: 0.1% by weight
Column: TSKgel GMPW _XL
Detector: differential refractometer Eluent: 100 mM sodium nitrate aqueous solution / acetonitrile = 10-8 / 0-2
Flow rate: 1 mL / min Measurement temperature: 40 ° C
Sample injection volume: 200 μL

<Polyvinyl alcohol polymer dispersant>
The polishing composition disclosed herein contains a polyvinyl alcohol polymer dispersant (hereinafter also simply referred to as “dispersant”). According to the technique disclosed herein, the dispersant has at least one ether bond in the molecule. According to the polishing composition containing both the dispersant and the polyvinyl alcohol-based polymer, it is possible to realize a polishing composition in which aggregation of the polyvinyl alcohol-based polymer is suppressed and dispersion stability is improved. In carrying out the technology disclosed herein, it is not necessary to elucidate the mechanism by which the dispersant containing an ether bond in the molecule contributes to the suppression of aggregation of the polyvinyl alcohol polymer, but according to such a dispersant, This is considered to be because hydrogen atoms between the hydroxyl groups of the polyvinyl alcohol polymer are inhibited by hydrogen bonding between the oxygen atom of the ether bond contained in the polymer and the hydroxy group of the polyvinyl alcohol polymer. However, it is not limited to this mechanism.

As the dispersant contained in the polishing composition disclosed herein, various compounds can be used with an appropriate content without any limitation as long as an ether bond is included in the molecule. The dispersant contained in the polishing composition disclosed herein may be a compound having one ether bond in the molecule or a polyether having two or more ether bonds in the molecule. . The dispersant may be a polymer compound or a compound that is not a polymer. In the case where the dispersant is a polymer compound, the ether bond may be contained in the polymer main chain, in the side chain, or in both the main chain and the side chain. It may be. In the case where the dispersant is a compound that is not a polymer, the dispersant may generally be a compound that can be grasped as a surfactant. The said dispersing agent can be used individually by 1 type or in combination of 2 or more types. The dispersant is preferably water-soluble.

Examples of compounds having one ether bond in the molecule include diethyl ether and tetrahydrofuran. 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 a polyether having two or more ether bonds in the molecule. It is preferable.

For example, as a dispersant that can be suitably used, a polyether having an ether bond in the main chain may be mentioned. Examples of the polyether having an ether bond in the main chain include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, Polyoxyalkylene derivatives such as polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, polyoxyethylene sorbitan fatty acid esters (for example, polyoxyalkylene adducts); copolymers of plural types of oxyalkylene (for example, diblock) Type copolymer, triblock type copolymer, random type copolymer, alternating copolymer); and the like. Alternatively, other examples include cellulose derivatives, starch derivatives, and the like.

Specifically, a block copolymer of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymer, PEO (polyethylene oxide) -PPO (polypropylene oxide) -PEO triblock, PPO- Oxyalkylene copolymers such as PEO-PPO type triblock copolymers, etc., random copolymers of EO and PO;
Oxyalkylene polymers such as polyethylene 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, polyoxy Polyoxyethylene alkyl ethers such as ethylene oleyl ether; Ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene alkyl phenyl ether such as polyoxyethylene dodecyl phenyl ether; polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine , Polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate , Polyoxyethylene sorbitan monopaltiminate, polyoxymonostearate Chirensorubitan, monooleate polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan, polyoxyethylene sorbit tetraoleate, polyoxyethylene castor oil, polyoxyalkylene derivatives such as polyoxyethylene hydrogenated castor oil; and the like.

Alternatively, as other specific examples, cellulose derivatives such as hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose; pregelatinized starch, pullulan, carboxymethyl starch, And starch derivatives such as cyclodextrin;

Also, other dispersants that can be suitably used include polyethers having an ether bond in the side chain. Examples of the polyether having an ether bond in the side chain include polyacryloylmorpholine (PACMO).

Among them, polyoxyethylene alkyl ether, HEC and PACMO may be mentioned as dispersants suitably used for the polishing composition disclosed herein. Of these, polyoxyethylene alkyl ether is preferred.

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

In the polishing composition disclosed herein, from the viewpoint of suitably improving the dispersion stability of the polyvinyl alcohol polymer, the ratio of the content of the polyvinyl alcohol polymer and the dispersant contained in the polishing composition is appropriate. It is preferably designed to be in the range. 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, 0.8. 04 to 4).

For example, in an embodiment in which the dispersant contains a polyoxyalkylene derivative such as polyoxyethylene alkyl ether, the molar ratio of the content of the polyvinyl alcohol polymer to the content of the dispersant in the polishing composition is 1 or less. Preferably, it is 0.5 or less, more preferably 0.1 or less (for example, 0.07 or less). Moreover, the molar ratio of the content of the polyvinyl alcohol polymer to the content of the dispersant in such an embodiment is usually 0.01 or more, preferably 0.02 or more, more preferably 0.03 or more. Yes, more preferably 0.04 or more. When the polyvinyl alcohol polymer and the dispersant are contained at such a blending ratio, aggregation of the polyvinyl alcohol polymer is appropriately suppressed, and a polishing composition that can reduce surface defects after polishing is easily realized.

For example, in an embodiment in which the dispersant includes a water-soluble polymer (typically, HEC or PACMO) including a repeating unit having an ether bond, the content of the polyvinyl alcohol-based polymer relative to the content of the dispersant in the polishing composition Is preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less (for example, 4 or less). Further, the molar ratio of the content of the polyvinyl alcohol polymer to the content of the dispersant in such an embodiment is usually 0.1 or more, preferably 0.3 or more, more preferably 0.5 or more. Yes, more preferably 1 or more. When the polyvinyl alcohol polymer and the dispersant are contained at such a blending ratio, aggregation of the polyvinyl alcohol polymer is appropriately suppressed, and a polishing composition that can reduce surface defects after polishing is easily realized.

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. Moreover, Mw of a dispersing agent is 100x10 < ⁴ > or less normally, Preferably it is 70x10 < ⁴ > or less, More preferably, it is 50x10 < ⁴ > or less.

For example, when the dispersant is a polyoxyalkylene derivative such as polyoxyethylene alkyl ether, the Mw of the dispersant is preferably 3000 or less, more preferably 1500 or less, still more preferably 700 or less, and particularly preferably 500. It is as follows. When the dispersant is a polyoxyalkylene derivative, the Mw of the dispersant is preferably 100 or more, more preferably 200 or more, and still more preferably 300 or more. According to the polishing composition containing the dispersant having Mw in such a range, surface defects after polishing can be highly reduced.

In the case where the dispersant is a water-soluble polymer (typically HEC or PACMO) containing a repeating unit having an ether bond, the Mw of the dispersant may be 1 × 10 ⁴ or more, and 5 × 10 ⁴ may be more, it may also be 10 × 10 ⁴ or more, may be 20 × 10 ⁴ or more. Further, 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 Mw, the polished surface can be appropriately protected, and surface defects after polishing can be highly reduced.

As a dispersant used in the polishing composition disclosed herein, a compound having an Mw of less than 1 × 10 ⁴ and a compound having an Mw of 1 × 10 ⁴ or more may be used in combination. For example, 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 as the dispersant. Good. The dispersant used in the polishing composition disclosed herein preferably contains a polyoxyalkylene derivative such as polyoxyethylene alkyl ether. In the case where the polyoxyalkylene derivative and the water-soluble polymer are used in combination as a dispersant, the content of the water-soluble polymer with respect to the entire dispersant is preferably more than 50% by weight, more preferably 70% by weight or more. Yes, more preferably 80% by weight or more, 85% by weight or more, or 90% by weight or more.

As a dispersant used in the polishing composition disclosed herein, a compound having an Mw of less than 1 × 10 ⁴ may be used alone. For example, it can also be implemented in an embodiment in which only a polyoxyalkylene derivative such as polyoxyethylene alkyl ether is used as a dispersant.

<Water-soluble polymer>
The polishing composition disclosed herein may further contain a water-soluble polymer other than the above-described polyvinyl alcohol-based polymer and dispersant as necessary, as long as the effects of the present invention are not significantly hindered. . The water-soluble polymer may have at least one functional group selected from a cationic group, an anionic group, and a nonionic group in the molecule. The water-soluble polymer may have, for example, a hydroxyl group, a carboxy group, a sulfo group, a primary amide structure, a heterocyclic structure, a vinyl structure, etc. in the molecule. From the viewpoints of reducing aggregates and improving detergency, a nonionic polymer can be preferably employed as the water-soluble polymer.

Examples of the water-soluble polymer include a polymer containing a nitrogen atom. As the polymer containing a nitrogen atom, any of a polymer containing a nitrogen atom in the main chain and a polymer having a nitrogen atom in a side chain functional group (pendant group) can be used. Examples of the polymer containing a nitrogen atom in the main chain include homopolymers and copolymers of N-acylalkylenimine type monomers. Specific examples of the N-acylalkyleneimine monomer include N-acetylethyleneimine, N-propionylethyleneimine and the like. Examples of the polymer having a nitrogen atom in the pendant group include a polymer containing an N-vinyl type monomer unit. For example, homopolymers and copolymers of N-vinylpyrrolidone can be employed.

The polishing composition disclosed herein can be carried out in an embodiment that does not substantially contain a water-soluble polymer other than the polyvinyl alcohol polymer and the dispersant.

<Surfactant>
The polishing composition disclosed herein may further contain a surfactant other than the above-described dispersant as required, as long as the effects of the present invention are not significantly hindered. As the surfactant, any of anionic, cationic, nonionic, and amphoteric can be used. The polishing composition disclosed herein can be carried out in a mode that does not substantially contain a surfactant other than the dispersant.

<Water>
As water contained in the polishing composition disclosed herein, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like can be preferably used. The water to be used preferably has, for example, a total content of transition metal ions of 100 ppb or less in order to avoid as much as possible the action of other components contained in the polishing composition. For example, the purity of water can be increased by operations such as removal of impurity ions with an ion exchange resin, removal of foreign matter with a filter, distillation, and the like.

<Basic compound>
The polishing composition disclosed herein contains a basic compound. In the present specification, the basic compound refers to a compound having a function of dissolving in water and increasing the pH of an aqueous solution. As the basic compound, an organic or inorganic basic compound containing nitrogen, an alkali metal hydroxide, an alkaline earth metal hydroxide, various carbonates, bicarbonates, or the like can be used. Examples of basic compounds containing nitrogen include quaternary ammonium compounds, quaternary phosphonium compounds, ammonia, amines (preferably water-soluble amines), and the like. Such basic compounds can be used singly or in combination of two or more.

Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Specific examples of the carbonate or bicarbonate 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-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like. Specific examples of the quaternary phosphonium compound include quaternary phosphonium hydroxide such as tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide.

As the quaternary ammonium compound, a quaternary ammonium salt (typically a strong base) such as a tetraalkylammonium salt or a hydroxyalkyltrialkylammonium salt can be preferably used. The anionic component in such a quaternary ammonium salt can be, for example, OH ⁻ , F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , BH ₄ ^{− and the} like. As Among these preferred examples, the anion is OH ^- a is a quaternary ammonium salt, i.e., include quaternary ammonium hydroxide. Specific examples of quaternary ammonium hydroxide include hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, and tetrahexylammonium hydroxide. Tetraalkylammonium hydroxide; hydroxyalkyltrialkylammonium hydroxide such as 2-hydroxyethyltrimethylammonium hydroxide (also referred to as choline); and the like.

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

<Other ingredients>
In addition, the polishing composition disclosed herein is a chelating agent, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt, an antiseptic, an antifungal agent, etc., as long as the effect of the present invention is not significantly hindered. A known additive that can be used in a polishing slurry (typically, a polishing slurry used in a polishing process of a silicon wafer) may be further contained as necessary.

It is preferable that the polishing composition disclosed herein does not substantially contain an oxidizing agent. If the polishing composition contains an oxidizing agent, the supply of the composition may oxidize the surface of the silicon substrate to produce an oxide film, which may reduce the polishing rate. Because. Here, that the polishing composition substantially does not contain an oxidant means that at least intentionally no oxidant is blended, and a trace amount of oxidant is inevitably contained due to raw materials and manufacturing methods. It can be tolerated. The trace amount means that the molar concentration of the oxidizing agent 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 0.00. 00000 mol / L or less). The polishing composition according to a preferred embodiment does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably implemented in an embodiment that does not contain, for example, hydrogen peroxide, sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate.

<PH>
The pH of the polishing composition disclosed herein is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, even more preferably 9.3 or higher, for example 9. 5 or more. When the pH of the polishing composition increases, the polishing efficiency tends to improve. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (for example, silica particles) and suppressing a decrease in mechanical polishing action, the pH of the polishing composition is suitably 12.0 or less, and 11.0 Is preferably 10.8 or less, more preferably 10.8 or less, and even more preferably 10.5 or less.

For the pH, a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by Horiba, Ltd.) is used, and a standard buffer solution (phthalate pH buffer solution: pH 4.01 (25 ° C.)). , Neutral phosphate pH buffer solution pH: 6.86 (25 ° C), carbonate pH buffer solution pH: 10.01 (25 ° C)) It can grasp | ascertain by putting into a composition and measuring the value after passing for 2 minutes or more and stabilizing.

<Application>
The polishing composition in the technique disclosed herein can be applied to polishing a polishing object having various materials and shapes. The material of the polishing object is, for example, a metal or semimetal such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, or an alloy thereof; glass such as quartz glass, aluminosilicate glass, glassy carbon, etc. A ceramic material such as alumina, silica, sapphire, silicon nitride, tantalum nitride, and titanium carbide; a compound semiconductor substrate material such as silicon carbide, gallium nitride, and gallium arsenide; a resin material such as polyimide resin; Of these, a polishing object composed of a plurality of materials may be used.

The polishing composition in the technique disclosed herein can be particularly preferably used for polishing a surface made of silicon (typically polishing a silicon wafer). A typical example of the silicon wafer here is a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot.

The polishing composition disclosed herein can be preferably applied to a polishing process of an object to be polished (for example, a silicon wafer). Before the polishing process with the polishing composition disclosed herein, the polishing object is subjected to a general treatment that can be applied to the polishing object in a process upstream of the polishing process, such as lapping and etching. May be.

The polishing composition disclosed herein can be preferably used, for example, in polishing an object to be polished (for example, a silicon wafer) prepared to have a surface roughness of 0.1 nm to 100 nm by an upstream process. The surface roughness Ra of the object to be polished can be measured using, for example, a laser scan type surface roughness meter “TMS-3000WRC” manufactured by Schmitt® Measurement® System® Inc. Use in final polishing (finish polishing) or polishing immediately before is effective, and use in final polishing is particularly preferable. Here, the final polishing refers to the final polishing step in the manufacturing process of the target product (that is, a step in which no further polishing is performed after that step).

<Polishing composition>
The polishing composition disclosed herein is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition, and used for polishing the polishing object. The polishing liquid may be prepared, for example, by diluting (typically diluting with water) any of the polishing compositions disclosed herein. Or you may use this polishing composition as polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein is used as a polishing liquid diluted with a polishing liquid (working slurry) that is supplied to a polishing object and used for polishing the polishing object. Both concentrates (ie, stock solutions of polishing liquid) are included. Another example of the polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

(Polishing liquid)
The content of the 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, It is 0.15% by weight or more. By increasing the abrasive content, higher polishing rates can be achieved. From the viewpoint of dispersion stability of particles in the polishing composition, the content is usually suitably 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, for example, 1% by weight or less, and may be 0.7% by weight or less. In a preferred embodiment, the content may be 0.5% by weight or less, or 0.2% by weight or less.

The concentration of the polyvinyl alcohol polymer in the polishing liquid is not particularly limited and can be, for example, 0.0001% by weight or more. From the viewpoint of haze reduction or the like, the preferred concentration is 0.0005% by weight or more, more preferably 0.001% by weight or more, for example 0.003% by weight or more, and may be 0.005% by weight or more. . From the viewpoint of polishing rate and the like, the concentration of the polyvinyl alcohol-based polymer is usually preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and 0.05% by weight or less. (For example, 0.01% by weight or less) or 0.008% by weight or less may be used.

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

When the polishing composition disclosed herein contains a basic compound, the concentration of the basic compound in the polishing liquid is not particularly limited. From the viewpoint of improving the polishing rate, the concentration is usually preferably 0.001% by weight or more of the polishing liquid, and more preferably 0.003% by weight or more (eg, 0.005% by weight or more). . From the viewpoint of haze reduction or the like, the concentration is suitably less than 0.3% by weight, preferably less than 0.1% by weight, and less than 0.05% by weight (for example, 0.03%). More preferably, it is less than% by weight.

(Concentrated liquid)
The polishing composition disclosed herein is in a concentrated form before being supplied to the object to be polished (that is, it is in the form of a concentrated concentrate of the polishing liquid and can also be grasped as a stock solution of the polishing liquid). There may be. The polishing composition in such a concentrated form is advantageous from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage and the like. The concentration ratio is not particularly limited, and can be, for example, about 2 to 100 times in terms of volume, and usually about 5 to 50 times (for example, about 10 to 40 times) is appropriate.

Such a concentrated liquid can be used in such a manner that a polishing liquid (working slurry) is prepared by diluting at a desired timing and the polishing liquid is supplied to an object to be polished. The dilution can be performed, for example, by adding water to the concentrated solution and mixing.

The content of abrasive grains in the concentrated liquid can be, for example, 50% by weight or less. From the viewpoint of handling properties of the concentrated liquid (for example, dispersion stability and filterability of abrasive grains), the abrasive grain content in the concentrated liquid is preferably 45% by weight or less, more preferably 40% by weight. It is as follows. In addition, from the viewpoint of convenience in manufacturing, distribution, storage, etc. and cost reduction, the content of abrasive grains can be, for example, 0.5% by weight or more, preferably 1% by weight or more, and more preferably Is 3% by weight or more.

(Preparation of polishing composition)
The polishing composition used in the technology disclosed herein may be a one-part type or a multi-part type including a two-part type. For example, among the constituents of the polishing composition, Part A containing at least abrasive grains and Part B containing at least a part of the remaining components are mixed, and these are mixed and diluted at an appropriate timing as necessary. Thus, the polishing liquid may be prepared.

The method for preparing the polishing composition is not particularly limited. For example, it is good to mix each component which comprises polishing composition using well-known mixing apparatuses, such as a wing-type stirrer, an ultrasonic disperser, a homomixer. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once and may be mixed in the order set suitably.

<Polishing>
The polishing composition disclosed herein can be used for polishing a polishing object, for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method for polishing an object to be polished (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 polishing liquid may include preparing the polishing liquid by adding operations such as concentration adjustment (for example, dilution) and pH adjustment to the polishing composition. Or you may use polishing composition as polishing liquid as it is.

Next, the polishing liquid is supplied to the object to be polished and polished by a conventional method. For example, when performing final polishing of a silicon wafer, typically, a silicon wafer that has undergone a lapping process is set in a general polishing apparatus, and a polishing liquid is applied to the surface to be polished of the silicon wafer through a polishing pad of the polishing apparatus. Supply. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface to be polished of the silicon wafer to move both relatively (for example, rotational movement). The polishing of the object to be polished is completed through this polishing step.

The polishing pad used in the polishing step is not particularly limited. For example, a polishing pad of foamed polyurethane type, non-woven fabric type, suede type or the like can be used. Each polishing pad may include abrasive grains or may not include abrasive grains. Usually, a polishing pad not containing abrasive grains is preferably used.

An object to be polished polished using the polishing composition disclosed herein is typically cleaned. The washing can be performed using an appropriate washing solution. The cleaning solution to be used is not particularly limited. For example, an SC-1 cleaning solution (ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ), water (H ₂ O), etc. SC-2 cleaning liquid (mixed liquid of HCl, H ₂ O ₂ and H ₂ O), etc. can be used. The temperature of the cleaning liquid can be, for example, in the range of room temperature (typically about 15 ° C. to 25 ° C.) or more and 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.

Hereinafter, some examples relating to the present invention will be described. However, the present invention is not intended to be limited to the examples shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified. In addition, PVA in the following description is a saponified product of polyvinyl acetate.

<Evaluation of dispersion stability>
The dispersion stability of an aqueous solution containing a dispersant or a water-soluble polymer other than the dispersant used in the following examples was evaluated as follows. First, a test solution for evaluating dispersion stability was prepared as follows.

(Example 1A)
Polyvinyl alcohol (PVA), a dispersant, and water were mixed to prepare an aqueous solution containing 0.11% of PVA and the balance being water, and used as a test solution according to Example 1A. As the PVA, one having Mw of 7 × 10 ⁴ and a saponification degree of 98% or more was used. As the dispersant, polyoxyethylene octyl ether (hereinafter also referred to as “C8PEO6”) having an ethylene oxide addition mole number of 6 was used.

(Example 2A)
In place of C8PEO6, an aqueous solution containing the same components as in Example 1A at the same concentration except that polyacryloylmorpholine (PACMO) having a Mw of 39 × 10 ⁴ was used as a dispersant was prepared in Example 2A. This test solution was used.

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

(Example 4A)
An aqueous solution containing the same components as used in Example 3A at the same concentration except that no dispersant was used was prepared as a test solution according to Example 4A.

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

(Example 6A)
Except not using PVA, the aqueous solution which contains the same component used by Example 5A by the same density | concentration was prepared, and it was set as the test liquid which concerns on Example 6A.

The molar ratio of the content of PVA to the content of the dispersant having an ether bond in each test solution of Example 1A to Example 3A was as indicated in the corresponding column of Table 1.

Next, 20 ml of each test solution of Examples 1A to 6A was collected, put into a container with a lid of 80 ml capacity, and shaken at a shaking strength of 300 spm in an environment of 23 ° C. While the container was shaken, the presence or absence of precipitates in the container was visually confirmed every 12 hours. The dispersion stability of each test solution was good (◯) when no precipitate was formed even after shaking for 72 hours or more in the shaking test under the above test conditions, and was precipitated by shaking for 24 hours or more and less than 72 hours. Evaluation was made in three stages, where a product was acceptable (Δ), and a product with precipitates formed by shaking for less than 24 hours was regarded as defective (x). The evaluation results are shown in the column of dispersion stability in Table 1.

As shown in Table 1, the test solutions of Examples 1A to 3A containing a dispersant having an ether bond in the molecule were compared with the test solutions of Examples 4A to 5A containing no dispersant. Dispersion stability was obviously improved. Moreover, since the test solution of Example 6A not containing PVA showed good dispersion stability, it was suggested that a factor that impairs the dispersion stability of the test solution is derived from aggregation of PVA. Similarly, the test solution prepared in the same manner except that the PVA used in the test solution of Example 4A was replaced with PVA having a molecular weight of 1.1 × 10 ⁴ and a saponification degree of 98% or more. As a result of the evaluation, the dispersion stability of this test solution was evaluated as acceptable (Δ), and it was found that the test solution of Example 4A had lower dispersion stability than this test solution. From this, it was shown that PVA aggregation tends to occur according to a test solution containing PVA having a high molecular weight.

<Pre-stage polishing process>
Next, the content of the pre-polishing process applied to the following examples is shown.
(Pre-polishing process)
A pre-polishing composition containing 0.9% abrasive grains and 0.1% basic compound with the balance being water was prepared. As abrasive grains, colloidal silica having a BET diameter of 35 nm was used. Potassium hydroxide (KOH) was used as the basic compound.
This pre-polishing composition was used as it was as a polishing liquid (working slurry), and a silicon wafer as an object to be polished was polished under the pre-polishing conditions described below. As a silicon wafer, a commercially available silicon single crystal wafer having a diameter of 300 mm and finished lapping and etching (conduction type: P type, crystal orientation: <100>, resistivity: 1 Ω · cm or more and less than 100 Ω · cm, COP free) is used. did.

[Pre-polishing conditions]
Polishing device: Single wafer polishing machine manufactured by Okamoto Machine Tool Co., Ltd. Model “PNX-332B”
Polishing load: 20 kPa
Plate rotation speed: 20 rpm
Carrier rotation speed: 20rpm
Polishing pad: Product name “FP55”, manufactured by Fujibo Atago Co., Ltd.
Polishing liquid supply rate: 1 liter / min Polishing liquid temperature: 20 ° C.
Surface plate cooling water temperature: 20 ° C
Polishing time: 2 minutes

<Preparation of polishing composition and final polishing>
(Example 1B)
A polishing composition containing abrasive grains, polyvinyl alcohol (PVA), a dispersant, and a basic compound, with the balance being water, was prepared and used as the polishing composition according to Example 1B. As abrasive grains, colloidal silica having a BET diameter of 25 nm was used. As the PVA, one having Mw of 7 × 10 ⁴ and a saponification degree of 98% or more was used. As the dispersant, polyoxyethylene octyl ether (C8PEO6) having an ethylene oxide addition mole number of 6 was used. Ammonia was used as the basic compound. The concentration of each component in the polishing composition according to Example 1B was 3.3% for abrasive grains, 0.11% for PVA, and 0.21% for basic compounds.
Using the diluted solution obtained by diluting the polishing composition 20 times with deionized water (DIW) as a polishing solution (working slurry), the silicon wafer that has been subjected to the previous polishing step is polished under the following finish polishing conditions. did.

[Finishing polishing conditions]
Polishing device: Single wafer polishing machine manufactured by Okamoto Machine Tool Co., Ltd. Model “PNX-332B”
Polishing load: 15 kPa
Plate rotation speed: 30 rpm
Carrier rotation speed: 30rpm
Polishing pad: Polishing pad manufactured by Fujibo Atago Co., Ltd., trade name “POLYPAS27NX”
Polishing liquid supply rate: 2 l / min Polishing liquid temperature: 20 ° C.
Surface plate cooling water temperature: 20 ° C
Polishing time: 4 minutes

The polished silicon wafer is removed from the polishing apparatus, and a cleaning solution of NH ₄ OH (29%): H ₂ O ₂ (31%): deionized water (DIW) = 2: 5.3: 48 (volume ratio) is used. (SC-1 wash). More specifically, a cleaning tank equipped with an ultrasonic oscillator having a frequency of 720 kHz is prepared, the cleaning liquid is stored in the cleaning tank and held at 70 ° C., and the polished silicon wafer is immersed in the cleaning tank for 6 minutes, After that, rinsing with ultrapure water was performed. After repeating this process twice, the silicon wafer was dried.

(Example 2B)
A polishing composition of Example 2B was prepared so as to contain the same components as in Example 1B at the same concentration except that PACMO having an Mw of 39 × 10 ⁴ was used as a dispersant instead of C8PEO6. Except for using this polishing composition, the silicon wafer that had undergone the previous polishing step was subjected to final polishing, washing, and drying in the same manner as in Example 1B.

(Example 3B)
The polishing composition of Example 3B was prepared in the same manner as Example 1B, except that HEC having an Mw of 26 × 10 ⁴ was used as the dispersant instead of C8PEO6. The concentration of each component in the polishing composition according to Example 3B was 3.3% for abrasive grains, 0.10% for PVA, and 0.23% for basic compounds. Except for using this polishing composition, the silicon wafer that had undergone the previous polishing step was subjected to final polishing, washing, and drying in the same manner as in Example 1B.

(Example 4B)
A polishing composition of Example 4B was prepared in the same manner as in Example 1B, except that the dispersant was not used. The concentration of each component in the polishing composition according to Example 4B was 3.3% for abrasive grains, 0.10% for PVA, and 0.21% for basic compounds. Except for using this polishing composition, the silicon wafer that had undergone the previous polishing step was subjected to final polishing, washing, and drying in the same manner as in Example 1B.

(Example 5B)
The polishing composition of Example 5B was prepared in the same manner as Example 1B, except that PVP having Mw of 1.7 × 10 ⁴ was used instead of C8PEO6. The concentration of each component in the polishing composition according to Example 5B was 3.3% for abrasive grains, 0.10% for PVA, 0.05% for PVP, and 0.21% for basic compounds. Except for using this polishing composition, the silicon wafer that had undergone the previous polishing step was subjected to final polishing, washing, and drying in the same manner as in Example 1B.

(Example 6B)
A polishing composition of Example 6B was prepared so as to contain the same components as in Example 5B at the same concentration except that PVA was not used. Except for using this polishing composition, the silicon wafer that had undergone the previous polishing step was subjected to final polishing, washing, and drying in the same manner as in Example 1B.

The molar ratio of the content of PVA to the content of the dispersant having an ether bond in each of the polishing compositions of Examples 1B to 3B was as indicated in the corresponding column of Table 2.

<Evaluation of surface defects>
The following evaluation was performed about the silicon wafer obtained by said each example.
(LPD count measurement)
The number of LPDs larger than 32 nm present on the surface (polished surface) of the silicon wafer was measured using a wafer inspection device (trade name “SURFSCAN SP2 xp” manufactured by KLA Tencor). The number of LPDs measured is shown in the corresponding column of Table 2 in the following three stages. A smaller number of LPDs indicates that surface defects on the polished surface are reduced.
◎: 100 or less ○: 101 or more and 1000 or less ×: 1001 or more

As shown in Table 2, according to the polishing compositions of Examples 1B to 3B containing PVA and a dispersant having an ether bond in the molecule, the polishing compositions of Examples 4B to 5B containing no dispersant Compared with the composition, the number of LPDs was clearly reduced, and surface defects on the polished surface were reduced. In particular, according to the polishing composition of Example 1B using C8PEO6 as a dispersant, surface defects were significantly reduced.

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

Claims (7)

1. A polishing composition comprising abrasive grains and water,
   It further includes a polyvinyl alcohol polymer and a dispersant for the polyvinyl alcohol polymer,
   The dispersant contains an ether bond in the molecule,
   Polishing composition whose molar ratio of content of the said polyvinyl alcohol-type polymer with respect to content of the said dispersing agent is 0.01-10.
2. The polishing composition according to claim 1, wherein the polyvinyl alcohol-based polymer has a weight average molecular weight of 3 × 10 ⁴ or more.
3. The polishing composition according to claim 1 or 2, wherein a weight average molecular weight of the dispersant is smaller than a weight average molecular weight of the polyvinyl alcohol polymer.
4. The polishing composition according to any one of claims 1 to 3, wherein the dispersant contains polyoxyethylene alkyl ether.
5. The polishing composition according to any one of claims 1 to 4, wherein the dispersant has a weight average molecular weight of 1500 or less.
6. The polishing composition according to any one of claims 1 to 5, wherein the abrasive grains are silica particles.
7. The polishing composition according to any one of claims 1 to 6, which is used for polishing a surface made of silicon.