JPWO2019187969A1 - Polishing composition - Google Patents

Abstract

Provided is a polishing composition containing a polyvinyl alcohol-based polymer, which can suppress agglutination of the polyvinyl alcohol-based polymer contained in the composition and effectively reduce surface defects. The polishing composition provided by the present invention contains abrasive grains and water. The polishing composition further contains a polyvinyl alcohol-based polymer and a dispersant for the polyvinyl alcohol-based polymer. The dispersant contains an ether bond in the molecule. The molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant is 0.01 or more and 10 or less.

Description

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

Precision polishing using a polishing composition is performed on the surface of materials such as metals, metalloids, non-metals, and oxides thereof. For example, the surface of a silicon wafer used as a component of a semiconductor device is generally finished into a high-quality mirror surface through a wrapping step (coarse polishing step) and a polishing step (precision polishing step). The polishing step typically includes a pre-polishing step (pre-polishing step) and a finishing polishing step (final polishing step). Patent Document 1 is mentioned as a technical document relating to a polishing composition mainly used for polishing a semiconductor substrate such as a silicon wafer.

Japanese Patent Application Publication No. 2010-34509

The polishing composition used in the finish polishing step (particularly, the finish polishing step of a semiconductor substrate such as a silicon wafer or other substrate) is required to have the ability to realize a surface having low haze and few surface defects after polishing. In addition to abrasive grains and water, many polishing compositions for such applications contain a water-soluble polymer for the purpose of protecting the surface of the object to be polished and improving wettability. For example, Patent Document 1 discloses a polishing composition for a silicon wafer 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 sophistication of the required level of surface quality after polishing, the conventional polishing composition using a polyvinyl alcohol-based polymer tends to lack the effect of reducing surface defects.

The present invention has been made in view of the above points, and an object of the present invention is to provide a polishing composition containing a polyvinyl alcohol-based polymer, which can effectively reduce surface defects. ..

The present inventors considered that the aggregation of the polyvinyl alcohol-based polymer contained in the polishing composition may be a factor causing the above-mentioned surface defects, and found a polishing composition suitable for suppressing such aggregation. The present invention was completed.
According to the present invention, a polishing composition containing abrasive grains and water is provided. The polishing composition further contains a polyvinyl alcohol-based polymer and a dispersant for the polyvinyl alcohol-based polymer. The dispersant contains an ether bond in the molecule. Further, the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant is 0.01 or more and 10 or less. According to such a configuration, since the polyvinyl alcohol-based polymer and the dispersant of the polyvinyl alcohol-based polymer are contained in an appropriate mixing ratio, the aggregation of the polyvinyl alcohol-based polymer in the polishing composition acts as an action of the dispersant. Is properly suppressed. According to the polishing composition containing the polyvinyl alcohol-based polymer in which aggregation is suppressed in this way, surface defects of the object to be polished after polishing are appropriately reduced.

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

In a preferred embodiment, the weight average molecular weight of the polyvinyl alcohol-based polymer is 3 × 10 ⁴ or more. Since a polyvinyl alcohol-based 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 the polyvinyl alcohol-based 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-based polymer. According to such a configuration, a polishing composition capable of appropriately suppressing agglutination of the polyvinyl alcohol-based polymer and reducing surface defects of the object to be polished can be realized.

In another preferred embodiment of the polishing composition disclosed herein, the dispersant comprises a polyoxyethylene alkyl ether. According to the structure containing such a dispersant, agglutination of the polyvinyl alcohol-based polymer can be more appropriately suppressed, and a polishing composition with further improved reduction of surface defects can be realized.

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 structure containing such a dispersant, agglutination of the polyvinyl alcohol-based polymer can be more appropriately suppressed, and a polishing composition with further improved reduction of surface defects can be realized.

In another preferred embodiment of the polishing composition disclosed herein, the abrasive grains are silica particles. In polishing using silica particles as abrasive grains, the ability to reduce surface defects of the object to be polished can be more effectively exhibited 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, in polishing where the object to be polished is a surface made of silicon, the surface of the object to be polished is protected by the action of a polyvinyl alcohol-based polymer whose aggregation is suppressed by the action of the dispersant. Therefore, the defects on the surface can be appropriately reduced.

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

<Abrasive grains>
The polishing composition disclosed herein includes abrasive grains. 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 and mode of use of the polishing composition. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; Nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate can be mentioned. Specific examples of the organic particles include polymethylmethacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid means to comprehensively refer to acrylic acid and methacrylic acid). , Polyacrylonitrile particles and the like. One type of such abrasive grains may be used alone, or two or more types may be used in combination.

As the abrasive grains, inorganic particles are preferable, particles made of metal or metalloid oxides are preferable, and silica particles are particularly preferable. In a polishing composition that can be used for polishing (for example, finish polishing) an object to be polished having a surface made of silicon, such as a silicon wafer described later, it is particularly meaningful to use silica particles as abrasive grains. The technique disclosed herein can be preferably carried out, for example, in a manner 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, and may be 100% by weight) of the particles constituting the abrasive grains. It means that it is a silica particle.

Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica and the like. The silica particles may be used alone or in combination of two or more. The use of colloidal silica is particularly preferable because it is easy to obtain a polished surface having excellent surface quality after polishing. As the colloidal silica, for example, colloidal silica prepared from water glass (Na silicate) by an ion exchange method or colloidal silica produced by an alkoxide method (a colloidal silica produced by a hydrolysis condensation reaction of alkoxysilane) is preferably adopted. be able to. Colloidal silica can be used alone or in combination of two or more.

The true specific gravity of the abrasive grain constituent material (for example, silica constituting the silica particles) is preferably 1.5 or more, more preferably 1.6 or more, still 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 scratch prevention and the like, the BET diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, still more 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) can be easily obtained. As the abrasive grains used in such a polishing composition, abrasive grains 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) are preferable.

In the present specification, the BET diameter is defined as 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 size 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, for example, by using a surface area measuring device manufactured by Micromeritex Co., Ltd., 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 cocoon shape, a konpeito shape, a rugby ball shape, and the like. For example, abrasive grains in which many of the particles are peanut-shaped or cocoon-shaped can be preferably adopted.

Although not particularly limited, the average value (average aspect ratio) of the major axis / minor axis ratio of the abrasive grains is, in principle, 1.0 or more, preferably 1.05 or more, and more preferably 1.1 or more. Is. Higher polishing efficiency can be achieved by increasing the average aspect ratio. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, still more preferably 1.5 or less, from the viewpoint of scratch reduction and the like.

The shape (outer shape) and average aspect ratio of the abrasive grains can be grasped by, for example, observing with an electron microscope. As a specific procedure for grasping the average aspect ratio, for example, for a predetermined number (for example, 200) of abrasive particles that can recognize the shape of independent particles using a scanning electron microscope (SEM), each particle is used. Draw the smallest rectangle circumscribing the image. Then, for the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (value of the major axis) by the length of the short side (value of the minor axis) is the major axis / minor axis ratio (aspect ratio). ). The 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 comprises 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 a repeating unit thereof. 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 generated, for example, by hydrolyzing (saponifying) a _{repeating unit (-CH 2-} CH (OCOCH ₃ )-) having a structure in which vinyl acetate is polymerized with vinyl. According to the polishing composition containing a polyvinyl alcohol-based polymer, the wettability of the surface of the object to be polished is improved, and it is easy to realize a surface having low haze and few surface defects after polishing.

Polyvinyl alcohol-based polymers have a hydroxy group (OH group) in the molecule. Therefore, the polyvinyl alcohol-based polymer has a property of easily aggregating due to the action of hydrogen bonds within 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 is lowered, the performance of reducing surface defects after polishing may be lowered. According to the technique disclosed herein, by using a polyvinyl alcohol-based polymer and a dispersant for a polyvinyl alcohol-based polymer described later in combination, agglomeration of the polyvinyl alcohol-based polymer is appropriately suppressed and dispersion stability is improved. Composition 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 contains 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 can 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 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 ester group, and a salt thereof. Can be. The polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, and may be a block copolymer or a graft copolymer. The polyvinyl alcohol-based polymer may contain only one type of non-VA unit as the non-VA unit, or may contain 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-based 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 proportion of the number of moles of the VA unit may be 50% or more, 65% or more, 75% or more, or 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-based polymer may be VA units. Here, "substantially 100%" means that the polyvinyl alcohol-based polymer does not contain non-VA units at least intentionally. 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 a surface with few surface defects after polishing. Easy to achieve. Further, since PVA having a high degree of saponification tends to aggregate more easily, it is meaningful to apply the present invention to PVA having a high degree of saponification (for example, PVA having a degree of saponification of 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 polymer may be, for example, 95% or less, 90% or less, or 80% or less. However, 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 or more. Although not particularly limited, in some embodiments, the content of the VA unit may be 50% by weight or more (for example, more than 50% by weight), 70% by weight or more, or 80% by weight or more (for example, more than 50% by weight). For example, 90% by weight or more, 95% by weight or more, or 98% by weight or more) may be used. 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 a non-VA unit is not contained as a repeating unit constituting the polyvinyl alcohol-based polymer, at least intentionally. 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 portion (segment) that constitutes a part of one molecule of polymer. For example, polyvinyl alcohol-based polymers have a polymer chain A with a VA unit content of more than 50% by weight and a VA unit content of less than 50% by weight (ie, a non-VA unit content of more than 50% by weight). ) 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 VA units 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 the non-VA unit 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 polyvinyl alcohol-based polymers containing the polymer chain A and the 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 on a polymer chain A (main chain), or a polymer chain A (side chain) on a polymer chain B (main chain). It may be a graft copolymer having a structure in which a chain) is grafted. In one embodiment, a polyvinyl alcohol-based polymer having a structure in which the polymer chain B is grafted onto the 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. Chains are mentioned. Unless otherwise specified, the main repeating unit in the present specification means a repeating unit contained in excess of 50% by weight.

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

Examples of N-vinyl type monomers include monomers having a nitrogen-containing heterocycle (eg, lactam ring) and N-vinyl chain amides. Specific examples of the N-vinyllactam type monomer include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazine-2-one, and N-vinyl-. Examples thereof include 3,5-morpholindione. 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-based 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 is 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-based polymer chain. The content of the repeating unit derived from the N- (meth) acryloyl-type monomer in the N- (meth) acryloyl-based polymer chain is typically more than 50% by weight, may be 70% by weight or more, and may be 85% by weight or more. It may be 95% by weight or more, and may be 95% by weight or more. Substantially all of the polymer chain B may be a repeating unit derived from an N- (meth) acryloyl-type monomer.

Examples of N- (meth) acryloyl-type monomers include chain amides having an N- (meth) acryloyl group and cyclic amides having an N- (meth) acryloyl group. Examples of chain amides having an N- (meth) acryloyl group are (meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl ( N-alkyl (meth) acrylamide such as meta) acrylamide and Nn-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) ) N, N-dialkyl (meth) acrylamide such as acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) (meth) acrylamide; and the like. Examples of cyclic amides having an N- (meth) acryloyl group include N- (meth) acryloyl morpholine, N- (meth) acryloyl pyrrolidine and the like.

Another example of the polymer chain B is a polymer chain containing an oxyalkylene unit as a main repeating unit, that is, an oxyalkylene-based polymer chain. The content of the oxyalkylene unit in the oxyalkylene polymer chain is typically more than 50% by weight, may be 70% by weight or more, may be 85% by weight or more, and may be 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 the oxyalkylene unit include an oxyethylene unit, an oxypropylene unit, an oxybutylene unit 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 an oxyethylene unit and an oxypropylene unit in combination. In an oxyalkylene polymer chain containing two or more kinds of oxyalkylene units, those oxyalkylene units may be random copolymers of corresponding alkylene oxides, block copolymers or graft copolymers. May be good.

Other examples of the polymer chain B include a polymer chain containing an alkyl vinyl ether unit, a structural unit obtained by acetalizing polyvinyl alcohol and an aldehyde, and the like as a main repeating unit. Among these, a vinyl ether unit having an alkyl group having 1 to 10 carbon atoms (alkyl vinyl ether unit), a vinyl ester unit derived from a monocarboxylic acid having 1 to 7 carbon atoms (monocarboxylic acid vinyl ester unit), and the like. It is preferable to select from the group consisting of structural units obtained by acetalizing polyvinyl alcohol and an aldehyde having an alkyl group having 1 or more and 7 or less carbon atoms.

Examples of the vinyl ether unit having an alkyl group having 1 or more and 10 or less carbon atoms include a propyl vinyl ether unit, a butyl vinyl ether unit, a 2-ethylhexyl vinyl ether unit 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 pentanate units, vinyl hexanoate units and the like.

The polyvinyl alcohol-based polymer used in the polishing composition disclosed herein may be unmodified PVA (non-modified PVA), or modified PVA which is a copolymer containing VA units and non-VA units. It may be. Non-modified PVA and modified PVA may be used in combination. The polyvinyl alcohol-based 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-based polymer, a polishing composition in which aggregation of the non-modified PVA is suitably suppressed can be obtained. Therefore, it is more meaningful to apply the present invention to a polishing composition containing non-modified PVA. For example, when the modified PVA and the non-modified PVA are used in combination as the polyvinyl alcohol-based polymer, the content of the modified PVA is preferably less than 50% by weight, more preferably less than the total amount of the polyvinyl alcohol-based polymer. It may be 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 aspects of the polishing composition disclosed herein, polyvinyl alcohol (PVA) containing only non-modified PVA may be preferably adopted as the polyvinyl alcohol-based polymer.

The weight average molecular weight (Mw) of the polyvinyl alcohol-based polymer used in the polishing composition disclosed herein 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 wettability of the surface after polishing tends to increase. Further, as the Mw of the polyvinyl alcohol-based polymer increases, the dispersion stability of the polyvinyl alcohol-based polymer tends to decrease, so that the application significance of the present invention increases. From this point of view, the Mw of the polyvinyl alcohol-based 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 × is 10 ⁴ or more, and particularly preferably 6 × 10 ⁴ or more (e.g., 6.5 × 10 ⁴ or more).

The upper limit of Mw of the polyvinyl alcohol-based polymer used in the polishing composition disclosed herein is not particularly limited. Mw of the polyvinyl alcohol-based polymer is usually suitably 100 × 10 ⁴ or less, preferably 30 × 10 ⁴ or less, may be a 20 × 10 ⁴ or less (e.g., 15 × 10 ⁴ or less). From the viewpoint of satisfying both the surface protection of the object to be polished and the polishing rate, Mw of the polyvinyl alcohol-based polymer may also be 10 × 10 ⁴ or less, or may be 8 × 10 ⁴ or less.

In the present specification, the weight average molecular weight (Mw) of the polyvinyl alcohol-based polymer, the dispersant, the water-soluble polymer and the surfactant is a value based on water-based gel permeation chromatography (GPC) (water-based, polyethylene oxide conversion). ) Can be adopted. As the GPC measuring device, it is preferable to use the model name "HLC-8320GPC" manufactured by Tosoh Corporation. The measurement conditions should be as follows. The same method is adopted for the examples described later.
[GPC measurement conditions]
Sample concentration: 0.1% by weight
Column: TSKgel GMPW _XL
Detector: Differential refractometer Eluent: 100 mM aqueous sodium nitrate solution / acetonitrile = 10-8 / 0-2
Flow velocity: 1 mL / min Measurement temperature: 40 ° C
Sample injection volume: 200 μL

<Dispersant for polyvinyl alcohol polymer>
The polishing composition disclosed herein contains a dispersant for a polyvinyl alcohol-based polymer (hereinafter, also simply referred to as “dispersant”). According to the techniques disclosed herein, the dispersant has at least one ether bond in the molecule. According to the polishing composition containing the dispersant and the polyvinyl alcohol-based polymer in combination, 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 techniques disclosed herein, it is not necessary to elucidate the mechanism by which a dispersant containing an ether bond in the molecule contributes to the suppression of aggregation of a polyvinyl alcohol-based polymer, but according to such a dispersant, the dispersant It is considered that this is because the oxygen atom of the ether bond contained in the above and the hydroxy group of the polyvinyl alcohol-based polymer are hydrogen-bonded to inhibit the hydrogen bond between the hydroxy groups of the polyvinyl alcohol-based polymer. However, it is not limited to this mechanism.

As the dispersant contained in the polishing composition disclosed herein, various compounds can be used in an appropriate content without particular limitation as long as the molecule contains an ether bond. The dispersant contained in the polishing composition disclosed herein may be a compound having one ether bond in the molecule, or may be a polyether having two or more ether bonds in the molecule. .. Further, the dispersant may be a polymer compound or a non-polymer compound. When the dispersant is a polymer compound, the ether bond may be contained in the main chain of the polymer, may be contained in the side chain, or may be contained in both the main chain and the side chain. You may be. Moreover, when the dispersant is a compound which is not a polymer, the dispersant may be a compound which can be generally grasped as a surfactant. The above dispersants may be used alone or in combination of two or more. The dispersant is 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 an aqueous polishing composition and improving the dispersion stability of a polyvinyl alcohol-based polymer, the dispersant is a polyether having two or more ether bonds in the molecule. Is preferable.

For example, as a dispersant that can be preferably used, a polyether having an ether bond in the main chain can 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, and polyoxyethylene alkyl amine. Polyoxyalkylene derivatives such as polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters (eg, polyoxyalkylene adducts); copolymers of multiple oxyalkylenes (eg, diblock). Type copolymers, triblock type copolymers, random type copolymers, alternating copolymers); 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 type copolymer, PEO (polypropylene oxide) -PPO (polypropylene oxide) -PEO type triblock body, PPO- PEO-PPO type triblock copolymers, etc.), oxyalkylene copolymers such as 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; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether; polyoxyethylene styrene Phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene monolauric acid ester, polyoxyethylene monostearic acid ester, polyoxyethylene distearate, polyoxyethylene monooleic acid ester , Polyoxyethylene dioleic acid ester, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopartimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraolein Examples thereof include oxyalkylene derivatives such as polyoxyethylene sorbit acid, polyoxyethylene hydrogen chloride oil, and polyoxyethylene hydrogenated castor oil.

Alternatively, as another specific example, 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, purulan, carboxymethyl starch, etc. Starch derivatives such as cyclodextrin; and the like.

Further, as another dispersant that can be preferably used, a polyether having an ether bond in the side chain can be mentioned. Examples of the polyether having an ether bond in the side chain include polyacryloyl morpholine (PACMO).

Among them, polyoxyethylene alkyl ethers, HEC and PACMO are examples of dispersants preferably used in the polishing compositions disclosed herein. Of these, polyoxyethylene alkyl ether is preferable.

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 number of carbon atoms of the alkyl group is preferably 5 or more, more preferably 6 or more, and further preferably 7 or more. For example, the number of carbon atoms of 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 is, for example, 8. 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. It is more preferably 9 or less, further preferably 8 or less, and particularly preferably 7 or less. From the viewpoint of reducing surface defects after polishing, the dispersant used in the polishing composition disclosed herein is preferably polyoxyethylene octyl ether having an ethylene oxide addition molar number of 4 to 10 (for example, 6). Can be used.

In the polishing composition disclosed herein, the ratio of the content of the polyvinyl alcohol-based polymer to the dispersant contained in the polishing composition is appropriate from the viewpoint of preferably improving the dispersion stability of the polyvinyl alcohol-based polymer. 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, and more preferably 0.02 or more and 5 or less (for example, 0. 04 or more and 4 or less).

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 may be 1 or less. It is preferably 0.5 or less, and even more preferably 0.1 or less (for example, 0.07 or less). The molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant in such an embodiment is usually 0.01 or more, preferably 0.02 or more, and more preferably 0.03 or more. Yes, more preferably 0.04 or more. When the polyvinyl alcohol-based polymer and the dispersant are contained in such a blending ratio, aggregation of the polyvinyl alcohol-based polymer is appropriately suppressed, and it is easy to realize a polishing composition capable of reducing surface defects after polishing.

For example, in an embodiment in which the dispersant comprises a water-soluble polymer (typically HEC or PACMO) containing 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. The molar ratio of is preferably 15 or less, more preferably 10 or less, still more preferably 5 or less (for example, 4 or less). The molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant in such an embodiment is usually 0.1 or more, preferably 0.3 or more, and more preferably 0.5 or more. Yes, more preferably 1 or more. When the polyvinyl alcohol-based polymer and the dispersant are contained in such a blending ratio, aggregation of the polyvinyl alcohol-based polymer is appropriately suppressed, and it is easy to realize a polishing composition capable of reducing 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, and more preferably 300 or more. Also, Mw of the dispersing agent is usually at 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 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, still more preferably 300 or more. According to the polishing composition containing a dispersant having Mw in such a range, surface defects after polishing can be highly reduced.

When 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. Also, Mw of the dispersing agent may also be 100 × 10 ⁴ or less, may also be 50 × 10 ⁴ or less, may also be 45 × 10 ⁴ or less, or may be 40 × 10 ⁴ or less ..

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

As the dispersing agent used in the polishing composition disclosed herein, the compound Mw is less than 1 × 10 ^4, Mw may be used in combination with the compound is 1 × 10 ⁴ or more. For example, as the 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. Good. The dispersant used in the polishing composition disclosed herein preferably contains a polyoxyalkylene derivative such as polyoxyethylene alkyl ether. When the polyoxyalkylene derivative and the water-soluble polymer are used in combination as the dispersant, the content of the water-soluble polymer in the entire dispersant is preferably larger 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 the dispersing agent used in the polishing compositions disclosed herein, Mw may be used a compound which is less than 1 × 10 ⁴ alone. For example, it can also be carried out in an embodiment in which only a polyoxyalkylene derivative such as polyoxyethylene alkyl ether is used as the dispersant.

<Water-soluble polymer>
The polishing composition disclosed herein may further contain a water-soluble polymer other than the above-mentioned polyvinyl alcohol-based polymer and dispersant, if necessary, as long as the effects of the present invention are not significantly impaired. .. 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, or the like in the molecule. From the viewpoint of reducing agglomerates and improving detergency, a nonionic polymer can be preferably used 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, either a polymer having a nitrogen atom in the main chain or a polymer having a nitrogen atom in a side chain functional group (pendant group) can be used. Examples of polymers containing a nitrogen atom in the main chain include homopolymers and copolymers of N-acylalkyleneimine-type monomers. Specific examples of the N-acylalkyleneimine type monomer include N-acetylethyleneimine and N-propionylethyleneimine. 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 adopted.

The polishing composition disclosed herein can be carried out in a manner substantially free of water-soluble polymers other than polyvinyl alcohol-based polymers and dispersants.

<Surfactant>
The polishing composition disclosed herein may further contain a surfactant other than the above-mentioned dispersant, if necessary, as long as the effects of the present invention are not significantly impaired. As the surfactant, any of anionic, cationic, nonionic and amphoteric ones can be used. The polishing composition disclosed herein can be carried out in a manner substantially free of a surfactant other than a dispersant.

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

<Basic compound>
The polishing composition disclosed herein contains a basic compound. As used herein, the term "basic compound" refers to a compound having a function of dissolving in water and raising 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, hydrogen carbonate and the like can be used. Examples of nitrogen-containing basic compounds include quaternary ammonium compounds, quaternary phosphonium compounds, ammonia, amines (preferably water-soluble amines) and the like. Such basic compounds may be used alone or in combination of two or more.

Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonate or hydrogen carbonate include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, 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, and piperazine anhydride. , 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 hydroxides such as tetramethylammonium 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. Anionic component in such quaternary ammonium salts are, for ^{example, OH -, F -, Cl} -, Br -, I -, ClO 4 -, BH 4 - may be like. Among them, a preferable example is a ^{quaternary ammonium salt having an anion of OH −,} that is, a quaternary ammonium hydroxide. Specific examples of the quaternary ammonium hydroxide include hydroxylation of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide and tetrahexylammonium hydroxide. Tetraalkylammonium; 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 hydroxide, quaternary ammonium hydroxide and ammonia can be preferably used. Among them, tetraalkylammonium hydroxide (for example, tetramethylammonium hydroxide) and ammonia are more preferable, and ammonia is particularly preferable.

<Other ingredients>
In addition, the polishing compositions disclosed herein include chelating agents, organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, fungicides, etc., as long as the effects of the present invention are not significantly impaired. , A known additive that can be used in a polishing slurry (typically, a polishing slurry used in a polishing step of a silicon wafer) may be further contained, if necessary.

The polishing composition disclosed herein preferably contains substantially no oxidizing agent. If the polishing composition contains an oxidizing agent, the supply of the composition may oxidize the surface of the silicon substrate to form an oxide film, which may reduce the polishing rate. Because. Here, the fact that the polishing composition does not substantially contain an oxidizing agent means that the oxidizing agent is not blended at least intentionally, and a trace amount of the oxidizing agent is inevitably contained due to the raw material, the manufacturing method, or the like. Can be tolerated. The above-mentioned 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, and particularly preferably 0. It means that it is 0000001 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 carried out 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, still more preferably 9.3 or higher, for example 9. 5 or more. As the pH of the polishing composition increases, the polishing efficiency tends to improve. On the other hand, from the viewpoint of preventing the dissolution of abrasive grains (for example, silica particles) and suppressing the decrease in mechanical polishing action, the pH of the polishing composition is preferably 12.0 or less, and 11.0. It is preferably less than or equal to, 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 Seisakusho) was used, and a standard buffer solution (phthalate pH buffer solution pH: 4.01 (25 ° C.)) was used. , Neutral phosphate pH buffer pH: 6.86 (25 ° C), carbonate pH buffer pH: 10.01 (25 ° C)) After three-point calibration, the glass electrode was measured. It can be grasped by putting it in the composition and measuring the value after it has stabilized after 2 minutes or more.

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

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 referred to 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 step of an object to be polished (for example, a silicon wafer). The object to be polished is subjected to general treatments such as wrapping and etching which can be applied to the object to be polished in a process upstream of the polishing process, such as wrapping and etching, before the polishing step by the polishing composition disclosed herein. You may.

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. It is effective to use it in final polishing (finish polishing) or immediately before it, and it is particularly preferable to use it in final polishing. Here, the final policing refers to the final policing step in the manufacturing process of the target product (that is, a step in which no further policing is performed after the step).

<Polishing composition>
The polishing composition disclosed herein is typically supplied to an object to be polished in the form of a polishing liquid containing the composition for polishing, and is used for polishing the object to be polished. The polishing liquid may be prepared, for example, by diluting (typically diluting with water) any of the polishing compositions disclosed herein. Alternatively, the polishing composition may be used as it is as a polishing liquid. That is, the concept of the polishing composition in the technique disclosed herein includes a polishing liquid (working slurry) supplied to the polishing object and used for polishing the polishing object, and diluted and used as the polishing liquid. Both with the concentrate (ie, the stock solution of the polishing solution) are included. As another example of the polishing liquid containing the polishing composition disclosed herein, there is a polishing liquid obtained by adjusting the pH of the composition.

(Abrasive liquid)
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, and more preferably 0.10% by weight or more, for example. It is 0.15% by weight or more. Higher polishing rates can be achieved by increasing the content of abrasive grains. From the viewpoint of dispersion stability of particles in the polishing composition, the content is usually preferably 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, still 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-based 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 and the like, the preferable 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. .. Further, from the viewpoint of polishing speed 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. It may be (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 can be, for example, 0.0001% by weight or more, preferably 0.0003% by weight or more. 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% by weight or more and 0.002% by weight or less, or 0.0002% by weight or more and 0.001% by weight or less. In another preferred embodiment, the concentration of the dispersant in the polishing liquid may be 0.005% by weight or more and 0.03% by weight 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 speed, the above concentration is usually preferably 0.001% by weight or more, and more preferably 0.003% by weight or more (for example, 0.005% by weight or more) of the polishing liquid. .. Further, from the viewpoint of haze reduction and the like, the above concentration is preferably less than 0.3% by weight, preferably less than 0.1% by weight, and less than 0.05% by weight (for example, 0.03). It is more preferable to use less than% by weight).

(Concentrate)
The polishing composition disclosed herein is in a concentrated form (that is, in the form of a concentrated solution of a polishing solution, which can also be grasped as a stock solution of a polishing solution) before being supplied to the object to be polished. There may be. The polishing composition in such a concentrated form is advantageous from the viewpoint of convenience and cost reduction in 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 suitable.

Such a concentrated liquid can be used in an embodiment in which 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 concentrate and mixing.

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

(Preparation of polishing composition)
The polishing composition used in the technique disclosed herein may be a one-dosage form or a multi-dosage form including a two-dosage form. For example, part A containing at least abrasive grains among the constituents of the polishing composition and part B containing at least a part of the remaining components are mixed, and these are mixed and diluted at appropriate timings as necessary. This may be configured so that the polishing liquid is prepared.

The method for preparing the polishing composition is not particularly limited. For example, it is preferable to mix each component constituting the polishing composition using a well-known mixing device such as a blade type stirrer, an ultrasonic disperser, and a homomixer. The mode in which these components are mixed is not particularly limited, and for example, all the components may be mixed at once, or may be mixed in an appropriately set order.

<Polishing>
The polishing composition disclosed herein can be used for polishing an object to be polished, for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method of 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. The preparation of 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. 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 polishing is performed by a conventional method. For example, when performing finish polishing of a silicon wafer, typically, the silicon wafer that has undergone the wrapping process is set in a general polishing device, and a polishing liquid is applied to the surface to be polished of the silicon wafer through the polishing pad of the polishing device. Supply. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface to be polished of the silicon wafer to relatively move (for example, rotationally move) the two. Polishing of the object to be polished is completed through such a polishing step.

The polishing pad used in the polishing step is not particularly limited. For example, a polishing pad such as a polyurethane foam type, a non-woven fabric type, or a suede type can be used. Each polishing pad may or may not contain abrasive grains. Usually, a polishing pad containing no abrasive grains is preferably used.

The object to be polished, which has been polished using the polishing composition disclosed herein, is typically washed. Cleaning can be performed using a suitable cleaning solution. The cleaning solution to be used is not particularly limited, and for example, SC-1 cleaning solution (ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ), and water (H ₂ O), which are common in the field of semiconductors and the like. (Mixed solution of), SC-2 cleaning solution (mixed solution of HCl, H ₂ O ₂ and H ₂ O) and the like 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 higher and up to about 90 ° C. From the viewpoint of improving the cleaning effect, a cleaning liquid having a temperature of about 50 ° C. to 85 ° C. can be preferably used.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples. In the following description, "part" 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 the aqueous solution containing the dispersant or the 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, which was used as the test solution according to Example 1A. The PVA, Mw is 7 × 10 ^4, was used for more than a saponification degree of 98%. As the dispersant, polyoxyethylene octyl ether having 6 moles of ethylene oxide (hereinafter, also referred to as “C8PEO6”) was used.

(Example 2A)
Instead of C8PEO6, except that the Mw as a dispersing agent were used 39 × 10 ⁴ Poly acryloylmorpholine (PACMO), the same ingredients as used in Example 1A to prepare an aqueous solution containing the same concentration, the Example 2A The test solution was used.

(Example 3A)
Instead of C8PEO6, except that the Mw as a dispersing agent were used 26 × 10 ⁴ hydroxyethylcellulose (HEC), to prepare a test solution of Example 3A in the same manner as Example 1A. 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 those used in Example 3A at the same concentration was prepared except that a dispersant was not used, and used as the test solution according to Example 4A.

(Example 5A)
Instead of C8PEO6, Mw, except for using 1.7 × 10 ⁴ of polyvinylpyrrolidone (PVP), to prepare a test solution of Example 5A in the same manner as Example 1A. 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)
An aqueous solution containing the same components as those used in Example 5A at the same concentration was prepared except that PVA was not used, and used as the test solution according to Example 6A.

The molar ratio of the content of PVA to the content of the dispersant having an ether bond in each of the test solutions of Examples 1A to 3A was as shown in the corresponding column of Table 1, respectively.

Next, 20 ml of each test solution of Examples 1A to 6A was collected, placed in a container with a lid having a capacity of 80 ml, and shaken at a shaking intensity of 300 spm in an environment of 23 ° C. While shaking the container, the presence or absence of precipitates in the container was visually confirmed every 12 hours. Regarding the dispersion stability of each test solution, in the shaking test under the above test conditions, those in which no precipitate was formed even after shaking for 72 hours or more were good (○), and those in which no precipitate was formed were precipitated by shaking for 24 hours or more and less than 72 hours. The evaluation was made on a three-point scale, with the one in which a substance was formed as acceptable (Δ) and the one in which a precipitate was formed by shaking for less than 24 hours as a defect (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 found in the solution as compared with the test solutions of Examples 4A to 5A containing no dispersant. Dispersion stability was clearly improved. In addition, the test solution of Example 6A containing no PVA showed good dispersion stability, suggesting that the factor impairing the dispersion stability of the test solution is derived from the aggregation of PVA. Further, the PVA used in the test solution example 4A, a molecular weight of 1.1 × 10 ^4, similarly dispersion stability for the test solutions prepared in the same way except that instead of it a degree of saponification of 98% or more PVA When the properties were evaluated, the dispersion stability of this test solution could be evaluated (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 the test solution containing PVA having a high molecular weight tends to cause agglutination of PVA.

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

[Preliminary polishing conditions]
Polishing equipment: Single-wafer polishing machine manufactured by Okamoto Machine Tool Co., Ltd., model "PNX-332B"
Polishing load: 20 kPa
Surface plate rotation speed: 20 rpm
Carrier rotation speed: 20 rpm
Polishing pad: Fujibo Ehime, Inc., product name "FP55"
Polishing liquid supply rate: 1 liter / minute Polishing liquid temperature: 20 ° C
Surface plate cooling water temperature: 20 ° C
Polishing time: 2 minutes

<Preparation of polishing composition and finish polishing>
(Example 1B)
A polishing composition containing abrasive grains, polyvinyl alcohol (PVA), a dispersant, and a basic compound and having a balance of water was prepared to prepare the polishing composition according to Example 1B. Colloidal silica having a BET diameter of 25 nm was used as the abrasive grains. The PVA, Mw is 7 × 10 ^4, was used for more than a saponification degree of 98%. As the dispersant, polyoxyethylene octyl ether (C8PEO6) having 6 moles of ethylene oxide added 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 a diluted solution obtained by diluting this polishing composition 20 times with deionized water (DIW) as a polishing solution (working slurry), a silicon wafer that has completed the above-mentioned pre-stage polishing step is polished under the following finish polishing conditions. did.

[Finishing conditions]
Polishing equipment: Single-wafer polishing machine manufactured by Okamoto Machine Tool Co., Ltd., model "PNX-332B"
Polishing load: 15 kPa
Surface plate rotation speed: 30 rpm
Carrier rotation speed: 30 rpm
Polishing pad: Polishing pad made by Fujibo Ehime, trade name "POLYPAS27NX"
Polishing liquid supply rate: 2 liters / minute Polishing liquid temperature: 20 ° C
Surface plate cooling water temperature: 20 ° C
Polishing time: 4 minutes

The silicon wafer after polishing 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. Was washed (SC-1 washing). More specifically, a cleaning tank equipped with an ultrasonic oscillator having a frequency of 720 kHz is prepared, the cleaning liquid is contained 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)
Instead of C8PEO6, except that the Mw was used PACMO of 39 × 10 ⁴ as a dispersant, so as to contain the same ingredients as Example 1B at the same concentrations, to prepare a polishing composition of example 2B. In the same manner as in Example 1B except that this polishing composition was used, the silicon wafer that had completed the pre-stage polishing step was finish-polished, washed, and dried.

(Example 3B)
Instead of C8PEO6, except that the Mw of using 26 × 10 ⁴ of HEC as a dispersant, to prepare a polishing composition of Example 3B in the same manner as Example 1B. 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. In the same manner as in Example 1B except that this polishing composition was used, the silicon wafer that had completed the pre-stage polishing step was finish-polished, washed, and dried.

(Example 4B)
The polishing composition of Example 4B was prepared in the same manner as in Example 1B except that no dispersant was 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. In the same manner as in Example 1B except that this polishing composition was used, the silicon wafer that had completed the pre-stage polishing step was finish-polished, washed, and dried.

(Example 5B)
Instead of C8PEO6, Mw, except for using PVP of 1.7 × 10 ^4, to prepare a polishing composition of Example 5B in the same manner as Example 1B. 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. In the same manner as in Example 1B except that this polishing composition was used, the silicon wafer that had completed the pre-stage polishing step was finish-polished, washed, and dried.

(Example 6B)
The 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. In the same manner as in Example 1B except that this polishing composition was used, the silicon wafer that had completed the pre-stage polishing step was finish-polished, washed, and dried.

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 shown in the corresponding column of Table 2.

<Evaluation of surface defects>
The silicon wafers obtained by each of the above examples were evaluated as follows.
(MPD number measurement)
The number of LPDs larger than 32 nm existing on the surface (polished surface) of the silicon wafer was measured using a wafer inspection device (manufactured by KLA Tencor Co., Ltd., trade name "SURFSCAN SP2 XP"). The number of measured LPDs is shown in the corresponding column of Table 2 in the following three stages. The smaller the number of LPDs, the smaller the surface defects on the polished surface.
⊚: 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, for polishing of Examples 4B to 5B containing no dispersant. Compared with the composition, the number of LPDs was clearly reduced, and the surface defects on the polished surface were reduced. In particular, according to the polishing composition of Example 1B using C8PEO6 as the 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 claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

Claims (7)

A polishing composition containing abrasive grains and water.
Further containing a polyvinyl alcohol-based polymer and a dispersant for the polyvinyl alcohol-based polymer,
The dispersant contains an ether bond in the molecule and contains
A polishing composition in which the molar ratio of the content of the polyvinyl alcohol-based polymer to the content of the dispersant is 0.01 or more and 10 or less. The weight average molecular weight of the polyvinyl alcohol-based polymer is 3 × 10 ⁴ or more, the polishing composition according to claim 1. The polishing composition according to claim 1 or 2, wherein the weight average molecular weight of the dispersant is smaller than the weight average molecular weight of the polyvinyl alcohol-based polymer. The polishing composition according to any one of claims 1 to 3, wherein the dispersant contains a polyoxyethylene alkyl ether. 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. The polishing composition according to any one of claims 1 to 5, wherein the abrasive grains are silica particles. The polishing composition according to any one of claims 1 to 6, which is used for polishing a surface made of silicon.