阅读说明：本技术 研磨用组合物 (Polishing composition ) 是由 山口佳子 后藤修 土屋公亮 市坪大辉 于 2020-03-23 设计创作，主要内容包括：本发明所提供的研磨用组合物包含磨粒、作为水溶性高分子的聚乙烯醇系聚合物、碱性化合物及水,且还包含3元以上的多元有机酸(盐)。(The polishing composition provided by the invention comprises abrasive particles, a polyvinyl alcohol polymer as a water-soluble polymer, a basic compound and water, and further comprises a 3-membered or higher polybasic organic acid (salt).)

1. A polishing composition comprising abrasive grains, a polyvinyl alcohol polymer as a water-soluble polymer, a basic compound and water,

and further contains a 3-or more-membered polyvalent organic acid (salt).

2. The polishing composition according to claim 1, wherein the polybasic organic acid (salt) comprises a 3-or more-membered polycarboxylic acid (salt).

3. The polishing composition according to claim 1 or 2, wherein the polybasic organic acid (salt) comprises an ammonium salt of a 3-or more-membered polybasic organic acid.

4. The polishing composition according to any one of claims 1 to 3, wherein the dispersibility represented by the following formula is less than 10.8nm,

dispersivity [ nm ]]＝(d₈₄-d₁₆)/2

Here, d in the formula₈₄Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 84%]，d₁₆Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 16%]。

5. The polishing composition according to any one of claims 1 to 3, further comprising a water-soluble polymer other than the polyvinyl alcohol polymer as the water-soluble polymer,

the dispersibility represented by the following formula is less than 14.2nm,

dispersivity [ nm ]]＝(d₈₄-d₁₆)/2

Here, d in the formula₈₄Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 84%]，d₁₆Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 16%]。

6. The polishing composition according to any one of claims 1 to 5, wherein an increase ratio of electrical conductivity due to the inclusion of the polybasic organic acid (salt) is 3 or less.

7. The polishing composition according to any one of claims 1 to 6, having a pH of 8 to 12.

8. The polishing composition according to any one of claims 1 to 7, wherein the polyvinyl alcohol polymer has a weight average molecular weight of 10 x 10⁴The following.

9. The polishing composition according to any one of claims 1 to 8, further comprising a surfactant.

10. The polishing composition according to any one of claims 1 to 9, wherein the abrasive grains are silica grains.

11. The polishing composition according to any one of claims 1 to 10, which is used in a final polishing step of a silicon wafer.

Technical Field

The present invention relates to a polishing composition.

The present application claims priority from japanese patent application 2019-058620 filed on 26.3.2019, the entire contents of which are incorporated herein by reference.

Background

The surface of a material such as a metal, a semimetal, a nonmetal, or an oxide thereof is precisely polished with the polishing composition. For example, the surface of a silicon wafer used as a component of a semiconductor device or the like is generally processed into a high-quality mirror surface through a grinding step (rough polishing step) and a polishing step (precision polishing step). The polishing process typically includes a pre-polishing process (pre-grinding process) and a final polishing process (finish grinding process). Patent documents 1 to 4 are cited as technical documents relating to polishing compositions mainly used for polishing semiconductor substrates such as silicon wafers.

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. Hei 11-140427

Patent document 2: japanese patent No. 5474400

Patent document 3: japanese patent No. 6029895

Patent document 4: japanese patent No. 6050125

Disclosure of Invention

Problems to be solved by the invention

The polishing composition used in the final polishing step (particularly, in the final polishing step of a semiconductor substrate such as a silicon wafer or other substrates) is required to have a property of realizing a high-quality surface after polishing. The polishing composition for this purpose often contains a water-soluble polymer in addition to abrasive grains and water for the purpose of protecting the surface of an object to be polished or improving wettability.

By using a polyvinyl alcohol polymer as the water-soluble polymer, the wettability of the polished surface can be suitably improved. Further, in recent years, further improvement in surface quality after polishing has been demanded. Accordingly, an object of the present invention is to provide a polishing composition containing a polyvinyl alcohol polymer as a water-soluble polymer, which can improve the surface quality of an object to be polished after polishing.

Means for solving the problems

The polishing composition provided in this specification contains abrasive grains, a polyvinyl alcohol polymer as a water-soluble polymer, a basic compound, and water. The polishing composition further contains a 3-or more-membered polyvalent organic acid (salt). By using the polyvalent organic acid (salt), it is possible to improve the surface quality of the polishing object after polishing by the polishing composition containing the polyvinyl alcohol polymer. For example, haze can be improved.

In the present specification, "acid (salt)" is a term generically referring to an acid and a salt of the acid, and may be represented by "acid and/or a salt thereof". For example, the polishing composition disclosed herein contains a 3-or more-membered polyvalent organic acid (salt) means that the composition contains at least one selected from the group consisting of 3-or more-membered polyvalent organic acids and salts thereof.

A preferred embodiment of the polishing composition contains a 3-or more-membered polycarboxylic acid (salt) as the above-mentioned polybasic organic acid (salt). In this embodiment, the effect of improving the haze can be exhibited appropriately.

A preferable polishing composition of another embodiment contains an ammonium salt of a 3-or more-membered polyvalent organic acid as the polyvalent organic acid (salt). According to the ammonium salt of the polybasic organic acid, the haze can be effectively improved even when it is used in a small amount.

In some embodiments of the polishing composition disclosed herein, the dispersibility of the polishing composition calculated by the following formula is preferably less than 10.8 nm.

Dispersivity [ nm ]]＝(d₈₄-d₁₆)/2；

Here, d in the above formula₈₄Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 84%]，d₁₆Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 16%]. According to the polishing composition, the composition containing the polyvinyl alcohol polymer can effectively improve the haze of the surface of the polished object.

In some embodiments of the polishing composition disclosed herein, the polishing composition further contains a water-soluble polymer other than the polyvinyl alcohol polymer (hereinafter, also referred to as "other water-soluble polymer"). The dispersibility of the polishing composition calculated by the following formula is preferably less than 14.2 nm.

Dispersivity [ nm ]]＝(d₈₄-d₁₆)/2；

Here, d in the above formula₈₄And d₁₆As described above. According to this polishing composition, the combination of the polyvinyl alcohol polymer and the other water-soluble polymer can effectively improve the haze of the surface of the polished object.

In some embodiments of the polishing composition disclosed herein, the increase ratio of the electrical conductivity of the polishing composition obtained by including the organic acid (salt) is 3 or less. This can realize a polishing composition having effectively improved haze.

In a preferred embodiment of the polishing composition disclosed herein, the pH is 8 to 12. When the polishing composition having such a pH is used for polishing, the haze can be more suitably improved.

The polyvinyl alcohol polymer preferably has a weight average molecular weight (Mw) of 10X 10⁴The following. By using a polyvinyl alcohol polymer having such Mw in combination with a polybasic organic acid (salt), the effect of improving haze can be more suitably exerted.

Silica particles are preferably used as the abrasive grains. The effect of improving haze by using a combination of a polyvinyl alcohol polymer and a polybasic organic acid (salt) can be exhibited appropriately in polishing using silica particles as abrasive grains.

The polishing composition disclosed herein is preferably used in the final polishing process of silicon wafers. The final polishing using the polishing composition improves haze and can suitably realize a high-quality silicon wafer surface.

Detailed Description

Preferred embodiments of the present invention will be described below. In addition, matters other than those specifically mentioned in the present specification and matters necessary for the implementation of the present invention can be understood as design matters by those skilled in the art. The present invention can be implemented according to the disclosure of the present specification and the common general knowledge in the art.

The polishing composition disclosed herein contains abrasive grains, a polyvinyl alcohol polymer as a water-soluble polymer, a polybasic organic acid (salt), a basic compound, and water. The content of the polishing composition disclosed herein will be described below.

< abrasive grains >

The polishing composition disclosed herein comprises abrasive particles. The abrasive grains have a function of mechanically polishing the surface of the object to be polished. The material and properties of the abrasive grains are not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like of the polishing composition. Examples of the abrasive particles 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 oxide 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. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles, poly (meth) acrylic acid particles (here, the term (meth) acrylic acid means acrylic acid and methacrylic acid), polyacrylonitrile particles, and the like. Such abrasive grains may be used singly or in combination of 2 or more.

The abrasive grains are preferably inorganic particles, and among them, particles composed of an oxide of a metal or a semimetal are preferable, and silica particles are particularly preferable. In a polishing composition usable 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 significant to use silica particles as abrasive grains. In the technique disclosed herein, for example, the abrasive grains are preferably implemented in such a manner that they are substantially composed of silica particles. Here, "substantially" means that 95 wt% or more (preferably 98 wt% or more, more preferably 99 wt% or more, and may be 100 wt%) of the particles constituting the abrasive grains are silica particles.

Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica, and the like. The silica particles may be used singly or in combination of 2 or more. Colloidal silica is particularly preferably used because a polished surface having excellent surface quality can be easily obtained after polishing. The colloidal silica is preferably colloidal silica prepared by using water glass (Na silicate) as a raw material by an ion exchange method or colloidal silica prepared by an alkoxide method (colloidal silica prepared by a hydrolytic condensation reaction of alkoxysilane). The colloidal silica may be used singly or in combination of 2 or more.

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

The BET diameter (average primary particle diameter) of the abrasive grains (typically, silica particles) is not particularly limited, and is preferably 5nm or more, and more preferably 10nm or more, from the viewpoint of polishing efficiency and the like. The BET diameter is preferably 15nm or more, and more preferably 20nm or more (for example, more than 20nm) from the viewpoint of obtaining a higher polishing effect (for example, effects such as reduction in haze and removal of defects). The BET diameter of the abrasive grains is preferably 100nm or less, more preferably 50nm or less, and still more preferably 40nm or less, from the viewpoint of scratch prevention and the like. In some embodiments, the abrasive grains may have a BET diameter of 35nm or less, 32nm or less, or 30nm or less, from the viewpoint of easily obtaining a surface with a lower haze.

In the present specification, the BET diameter refers to a specific surface area (BET value) measured by the BET method, and is determined by the BET diameter (nm) of 6000/(true density (g/cm)³) xBET value (m)²/g)) of the formula. For example, silica particlesWhen the ratio is larger than the ratio, the ratio is determined by the BET diameter (nm) 2727/BET value (m)²The BET diameter can be calculated as a function of/g). The specific surface area can be measured, for example, using a surface area measuring apparatus manufactured by Micromeritics, trade name "Flow Sorb II 2300".

The shape (profile) of the abrasive grains may be spherical or non-spherical. Specific examples of the non-spherical particles include peanut-shaped particles (i.e., peanut shells), cocoon-shaped particles, caramel-shaped particles, and football-shaped particles. For example, a majority of the particles are suitably formed with peanut-shaped or cocoon-shaped abrasive particles.

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

The shape (profile) or average aspect ratio of the abrasive grains can be grasped by observation with an electron microscope, for example. A specific procedure for grasping the average aspect ratio is to draw a minimum rectangle circumscribing each particle image for a specific number (e.g., 200) of abrasive particles in which the shape of individual particles can be recognized, for example, using a Scanning Electron Microscope (SEM). Next, for the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (the value of the long diameter) by the length of the short side (the value of the short diameter) is calculated as the long diameter/short diameter ratio (aspect ratio). The average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the specific number of particles.

< Water-soluble Polymer >

The polishing composition disclosed herein contains a water-soluble polymer. The water-soluble polymer contributes to protection of the surface of the object to be polished, improvement of wettability of the surface of the object to be polished after polishing, and the like.

(polyvinyl alcohol Polymer)

The polishing composition disclosed herein contains a polyvinyl alcohol polymer as a water-soluble polymer. As the polyvinyl alcohol polymer, there may be mentionedA water-soluble organic substance (typically a water-soluble polymer) containing a vinyl alcohol unit as its repeating unit is used. Here, the vinyl alcohol unit (hereinafter also referred to as "VA unit") means a unit represented by the following chemical formula: -CH₂-ch (oh) -; structural elements of the representation. The polyvinyl alcohol polymer may contain only a VA unit as a repeating unit, or may contain a repeating unit other than a VA unit (hereinafter, also referred to as a "non-VA unit") in addition to the VA unit. The polyvinyl alcohol-based polymer may be a random copolymer comprising a VA unit and a non-VA unit, and may be a block copolymer or a graft copolymer. The polyvinyl alcohol polymer may contain only one kind of non-VA unit, or may contain 2 or more kinds of non-VA units.

The polyvinyl alcohol polymer used in the polishing composition disclosed herein may be unmodified polyvinyl alcohol (non-modified PVA) or modified polyvinyl alcohol (modified PVA). Here, the non-modified PVA means a repeating unit (-CH) substantially not containing a structure in which polyvinyl acetate is produced by hydrolysis (saponification) and vinyl acetate is polymerized₂-CH(OCOCH₃) -) and a repeating unit other than the VA unit. The saponification degree of the non-modified PVA may be, for example, 60% or more, and from the viewpoint of water solubility, 70% or more, or 80% or more, or 90% or more. Among several modes, non-modified PVA having a saponification degree of 95% or more or 98% or more is preferably used as the water-soluble polymer compound.

Examples of the non-VA unit that the modified PVA may contain include, but are not limited to, a repeating unit derived from an N-vinyl type monomer or an N- (meth) acryloyl type monomer described later, a repeating unit derived from ethylene, a repeating unit derived from an alkyl vinyl ether, and a repeating unit derived from a vinyl ester of monocarboxylic acid having 3 or more carbon atoms. As a preferable example of the N-vinyl type monomer, N-vinylpyrrolidone is mentioned. As a preferred example of the above-mentioned N- (meth) acryloyl-type monomer, N- (meth) acryloylmorpholine can be mentioned. Examples of the alkyl vinyl ether include vinyl ethers having an alkyl group having 1 to 10 carbon atoms such as propyl vinyl ether, butyl vinyl ether, and 2-ethylhexyl vinyl ether. Examples of the vinyl ester of monocarboxylic acid having 3 or more carbon atoms include vinyl ester of monocarboxylic acid having 3 or more carbon atoms and 7 or less carbon atoms such as vinyl propionate, vinyl butyrate, vinyl valerate, and vinyl caproate.

The polyvinyl alcohol polymer may also be a modified PVA comprising VA units and non-VA units having at least 1 structure selected from oxyalkylene groups, carboxyl groups, sulfonic acid groups, amino groups, hydroxyl groups, amide groups, imide groups, nitrile groups, ether groups, ester groups, and salts thereof. The polyvinyl alcohol polymer may be a modified PVA in which a part of VA units contained in the polyvinyl alcohol polymer is acetalized with an aldehyde. As the aldehyde, for example, an alkylaldehyde is preferably used, and an alkylaldehyde having an alkyl group having 1 to 7 carbon atoms is preferably used, and among them, n-butyraldehyde is preferably used. As the polyvinyl alcohol polymer, a cation-modified polyvinyl alcohol in which a cationic group such as a quaternary ammonium structure is introduced can be used. Examples of the above-mentioned cationically modified polyvinyl alcohol include those having introduced a cationic group derived from a monomer having a cationic group such as diallyldialkylammonium salt or N- (meth) acryloylaminoalkyl-N, N-trialkylammonium salt.

The proportion of the number of moles of VA units in the number of moles of the total repeating units constituting the polyvinyl alcohol polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. The proportion of the number of moles of the VA unit is not particularly limited, but may be 50% or more, 65% or more, 75% or more, 80% or more, or 90% or more (for example, 95% or more, or 98% or more) in some embodiments. The repeating units constituting the polyvinyl alcohol polymer may be VA units in an amount of substantially 100%. Here, "substantially 100%" means that the polyvinyl alcohol polymer at least intentionally does not contain a non-VA unit, and typically, the proportion of the number of moles of the non-VA unit in the number of moles of the total repeating units is less than 2% (for example, less than 1%) and 0% is included. In some other embodiments, the ratio of the number of moles of the VA unit to the number of moles of the total repeating units constituting the polyvinyl alcohol polymer may be, for example, 95% or less, 90% or less, 80% or less, or 70% or less.

The content (content based on weight) of the VA unit in the polyvinyl alcohol polymer may be, for example, 5 wt% or more, 10 wt% or more, 20 wt% or more, and 30 wt% or more. The content of the VA unit is not particularly limited, but may be 50 wt% or more (e.g., more than 50 wt%), 70 wt% or more, or 80 wt% or more (e.g., 90 wt% or more, 95 wt% or more, or 98 wt% or more) in some embodiments. Substantially 100% by weight of the repeating units constituting the polyvinyl alcohol polymer may be VA units. Here, "substantially 100%" means that the polyvinyl alcohol polymer does not contain at least a non-VA unit as a repeating unit constituting the polyvinyl alcohol polymer intentionally, and the content of the non-VA unit in the polyvinyl alcohol polymer is typically less than 2% by weight (for example, less than 1% by weight). In some other embodiments, the content of the VA unit in the polyvinyl alcohol polymer may be, for example, 95 wt% or less, 90 wt% or less, 80 wt% or less, or 70 wt% or less.

The polyvinyl alcohol polymer may contain a plurality of polymer chains having different VA unit contents in the same molecule. Here, the polymer chain means a portion (segment) constituting a part of a polymer of one molecule. For example, the polyvinyl alcohol polymer may contain, in the same molecule, polymer chain a having a VA unit content of more than 50 wt% and polymer chain B having a VA unit content of less than 50 wt% (i.e., a non-VA unit content of more than 50 wt%).

The polymer chain a may comprise only VA units as repeating units, but may also comprise 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, may be 70% by weight or more, may be 80% by weight or more, and may be 90% by weight or more. In some embodiments, the content of the VA unit in the polymer chain a may be 95 wt% or more, or 98 wt% or more. Substantially 100% by weight of the repeating units constituting the polymer chain a may be VA units.

The polymer chain B may also comprise only non-VA units as repeating units, but may also comprise VA units other than VA units. The content of the non-VA unit in the polymer chain B may be 60% by weight or more, may be 70% by weight or more, may be 80% by weight or more, and may be 90% by weight or more. In some embodiments, the content of the non-VA unit in the polymer chain B may be 95 wt% or more, or 98 wt% or more. It is also possible that substantially 100% by weight of the repeating units constituting the polymer chain B are non-VA units.

Examples of the polyvinyl alcohol polymer containing the polymer chain a and the polymer chain B in the same molecule include a block copolymer and a graft copolymer containing these polymer chains. The graft copolymer may have a structure in which the polymer chain a (main chain) is grafted with the polymer chain B (side chain), or may have a structure in which the polymer chain B (main chain) is grafted with the polymer chain a (side chain). 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 in which a repeating unit derived from an N-vinyl type monomer is a main repeating unit, a polymer chain in which a repeating unit derived from an N- (meth) acryl type monomer is a main repeating unit, and a polymer chain in which an oxyalkylene unit is a main repeating unit. In the present specification, the main repeating unit, when not particularly described, means that the repeating unit is contained in an amount of more than 50% by weight.

As a preferable 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 type polymer chain is cited. The content of the repeating unit derived from the N-vinyl monomer in the N-vinyl 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. Substantially all of the polymer chain B may be a repeating unit derived from an N-vinyl type monomer.

In this specification, examples of the N-vinyl type monomer include a monomer having a nitrogen-containing heterocyclic ring (e.g., a lactam ring) and an N-vinyl chain amide. Specific examples of the N-vinyllactam-type monomer include N-vinylpyrrolidone, N-vinylpiperidone (piperidone), N-vinylmorpholinone (Morpholinone), N-vinylcaprolactam, N-vinyl-1, 3-oxazin-2-one, N-vinyl-3, 5-morpholinodione, and the like. Specific examples of the N-vinyl chain amide include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide. The polymer chain B may be, 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 units are N-vinylpyrrolidone units. 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 in which a repeating unit derived from an N- (meth) acryl-type monomer is a main repeating unit, that is, an N- (meth) acryl-based polymer chain. The content of the repeating unit derived from the N- (meth) acryl-type monomer in the N- (meth) acryl-based polymer chain is typically more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, and 95% by weight or more. Substantially all of the polymer chain B may be a repeating unit derived from an N- (meth) acryl-type monomer.

In this specification, 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 the chain amide having an N- (meth) acryloyl group include (meth) acrylamide; n-alkyl (meth) acrylamides such as N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-N-butyl (meth) acrylamide; n, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, and N, N-di (N-butyl) (meth) acrylamide; and the like. Examples of the cyclic amide having an N- (meth) acryloyl group include N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidine, and the like.

As another example of the polymer chain B, a polymer chain containing an oxyalkylene unit as a main repeating unit, that is, an oxyalkylene-based polymer chain can be cited. The content of the oxyalkylene unit in the oxyalkylene polymer chain is typically more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, and 95% by weight or more. 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, and an oxybutylene unit. Such oxyalkylene units may be repeating units each from a corresponding alkylene oxide. The oxyalkylene unit contained in the oxyalkylene polymer chain may be one kind or 2 or more kinds. For example, an oxyalkylene polymer chain containing an oxyethylene unit and an oxypropylene unit in combination may be used. In the oxyalkylene polymer chain containing 2 or more oxyalkylene units, these oxyalkylene units may be a random copolymer of the corresponding alkylene oxide, a block copolymer or a graft copolymer.

Examples of the polymer chain B include a polymer chain containing a repeating unit derived from an alkyl vinyl ether (e.g., a vinyl ether having an alkyl group having 1 to 10 carbon atoms), a polymer chain containing a repeating unit derived from a vinyl monocarboxylic acid (e.g., a vinyl monocarboxylic acid having 3 or more carbon atoms), a polymer chain in which a part of VA units is acetalized with an aldehyde (e.g., an alkylaldehyde having an alkyl group having 1 to 7 carbon atoms), a polymer chain in which a cationic group (e.g., a cationic group having a quaternary ammonium structure) is introduced, and the like.

As the polyvinyl alcohol polymer in the polishing composition disclosed herein, non-modified PVA, or a combination of non-modified PVA and modified PVA may be used. In the embodiment in which the non-modified PVA and the modified PVA are used in combination, the amount of the modified PVA to be used may be, for example, less than 95% by weight, or 90% by weight or less, or 75% by weight or less, or 50% by weight or less, or 30% by weight or less, or 10% by weight or less, or 5% by weight or less, or 1% by weight or less, based on the total amount of the polyvinyl alcohol polymer contained in the polishing composition. The polishing composition disclosed herein is preferably used, for example, in a form in which only one or 2 or more types of non-modified PVA are used as the polyvinyl alcohol polymer.

The weight average molecular weight (Mw) of the polyvinyl alcohol polymer used in the polishing composition disclosed herein is not particularly limited. Mw of the polyvinyl alcohol polymer is usually suitably 100X 10⁴Hereinafter, it is preferably 30 × 10⁴Hereinafter, it may be 20 × 10⁴The following. When the Mw of the polyvinyl alcohol polymer becomes smaller, the dispersion stability of the polyvinyl alcohol polymer tends to be improved. From this viewpoint, the Mw of the polyvinyl alcohol polymer may be 15X 10 in several embodiments⁴Hereinafter, it may be 10 × 10⁴The following. Further, the Mw of the polyvinyl alcohol polymer is usually suitably 2X 10³Above, it may be 5X 10³Above, it may be 1X 10⁴The above. As the Mw of the polyvinyl alcohol polymer increases, the effect of protecting the polishing object or improving the wettability tends to increase. From this viewpoint, the Mw of the polyvinyl alcohol polymer used in the polishing composition disclosed herein is preferably 5X 10³Above, more preferably 1 × 10⁴Above, it may be 2X 10⁴Above, it may be 5X 10⁴Above, it may be 6X 10⁴Above, it may be 6.5X 10⁴The above.

In the present specification, the weight average molecular weight (Mw) of the water-soluble polymer and the surfactant described later may be a value (in terms of water-based and polyethylene oxide) by water-based Gel Permeation Chromatography (GPC). As the GPC measurement apparatus, the apparatus name "HLC-8320 GPC" available from Tosoh corporation can be used. For example, the measurement can be performed under the following conditions. The same method is also used in the examples described below.

[ GPC measurement conditions ]

Sample concentration: 0.1% by weight

A chromatographic column: TSKgel GMPWXL

A detector: differential refractometer

Eluent: 10 to 8/0 to 2 mM of 100mM sodium nitrate aqueous solution/acetonitrile

Flow rate: 1 mL/min

Measuring temperature: 40 deg.C

Sample injection amount: 200 μ L

The content of the polyvinyl alcohol polymer in the polishing composition (the total amount of 2 or more polyvinyl alcohol polymers when included) is not particularly limited. In some embodiments, the content may be, for example, 0.0001 wt% or more, and is preferably 0.00025 wt% or more, more preferably 0.0004 wt% or more, and for example, 0.0005 wt% or more, from the viewpoint of improvement in polishing performance and surface quality. The upper limit of the content of the polyvinyl alcohol polymer is not particularly limited, and may be, for example, 0.05 wt% or less. From the viewpoints of stability in the concentrated solution stage, polishing rate, cleaning property, and the like, the content of the polyvinyl alcohol polymer is preferably 0.035% by weight or less, more preferably 0.025% by weight or less, further preferably 0.02% by weight or less, particularly preferably 0.015% by weight or less, for example, 0.0125% by weight or less, and typically 0.01% by weight or less. The polishing composition disclosed herein is preferably used in an embodiment in which the content of the polyvinyl alcohol polymer is 0.008 wt% or less, 0.006 wt% or less, or 0.004 wt% or less, for example.

The content of the polyvinyl alcohol polymer (the total amount of 2 or more polyvinyl alcohol polymers when included) can be specified by the relative relationship with the abrasive grains. In some embodiments, the content of the polyvinyl alcohol polymer is, for example, 0.01 parts by weight or more relative to 100 parts by weight of the abrasive grains, and is suitably 0.1 parts by weight or more, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and still more preferably 3 parts by weight or more, from the viewpoint of haze reduction or the like. The content of the polyvinyl alcohol polymer may be, for example, 50 parts by weight or less, or 30 parts by weight or less, based on 100 parts by weight of the abrasive grains. From the viewpoint of dispersion stability of the polishing composition, the content of the polyvinyl alcohol polymer is suitably 15 parts by weight or less, preferably 10 parts by weight or less, more preferably 8 parts by weight or less, and may be 7 parts by weight or less, relative to 100 parts by weight of the abrasive particles. The polishing composition disclosed herein is preferably used in an embodiment in which the content of the polyvinyl alcohol polymer is less than 5 parts by weight, less than 3 parts by weight, or less than 2 parts by weight, based on 100 parts by weight of the abrasive grains.

(other Water-soluble Polymer)

The polishing composition disclosed herein may further contain another water-soluble polymer, that is, a water-soluble polymer other than the polyvinyl alcohol polymer, if necessary, within a range not to impair the effects of the present invention. Other water-soluble polymers known in the field of polishing compositions can be suitably selected. Examples of the other water-soluble polymer include synthetic polymers such as polymers containing an oxyalkylene unit and polymers containing a nitrogen atom; polymers derived from natural products such as cellulose derivatives and starch derivatives; and the like.

Examples of the polymer containing an oxyalkylene unit include polyethylene oxide (PEO), a block copolymer of Ethylene Oxide (EO) and Propylene Oxide (PO) or Butylene Oxide (BO), and a random copolymer of EO and PO or BO. Among them, a block copolymer of EO and PO or a random copolymer of EO and PO is preferable. The block copolymer of EO and PO may be a diblock, triblock, or the like comprising a PEO block and a polypropylene oxide (PPO) block. Examples of the above-mentioned triblock include a PEO-PPO-PEO type triblock and a PPO-PEO-PPO type triblock. Among them, a PEO-PPO-PEO type triblock is more preferable.

In the block copolymer or random copolymer of EO and PO, the molar ratio (EO/PO) of EO and PO constituting the copolymer is preferably greater than 1, more preferably 2 or more, and further preferably 3 or more (for example, 5 or more), from the viewpoint of solubility in water, detergency, or the like.

Non-limiting examples of the nitrogen atom-containing polymer include polymers containing N-vinyl type monomer units; an imine derivative; a polymer comprising N- (meth) acryloyl-type monomer units; and the like.

Examples of the polymer containing an N-vinyl type monomer unit include a polymer containing a repeating unit derived from a monomer having a nitrogen-containing heterocyclic ring (e.g., a lactam ring). Examples of such polymers include homopolymers and copolymers of an N-vinyllactam-type monomer (for example, copolymers having a copolymerization ratio of an N-vinyllactam-type monomer of more than 50% by weight), homopolymers and copolymers of an N-vinyl chain amide (for example, copolymers having a copolymerization ratio of an N-vinyl chain amide of more than 50% by weight), and the like.

Specific examples of the N-vinyllactam-type monomer (i.e., a compound having a lactam structure and an N-vinyl group in one molecule) include N-Vinylpyrrolidone (VP), N-vinylpiperidone, N-vinylmorpholinone, N-Vinylcaprolactam (VC), N-vinyl-1, 3-oxazin-2-one, N-vinyl-3, 5-morpholinodione, and the like. Specific examples of the polymer containing an N-vinyllactam-type monomer unit include polyvinylpyrrolidone, polyvinylcaprolactam, a random copolymer of VP and VC, a random copolymer of one or both of VP and VC and another vinyl monomer (for example, an acrylic monomer, a vinyl ester monomer, or the like), a block copolymer or a graft copolymer containing a polymer chain containing one or both of VP and VC, and the like.

Specific examples of the N-vinyl chain amide include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide.

Examples of the polymer containing an N- (meth) acryloyl-type monomer unit include homopolymers and copolymers of an N- (meth) acryloyl-type monomer (typically, copolymers having a copolymerization ratio of an N- (meth) acryloyl-type monomer exceeding 50% by weight). 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 the chain amide having an N- (meth) acryloyl group include (meth) acrylamide; n-alkyl (meth) acrylamides such as N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-N-butyl (meth) acrylamide; n, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, and N, N-di (N-butyl) (meth) acrylamide; and the like. Examples of the polymer containing a chain amide having an N- (meth) acryloyl group as a monomer unit include a homopolymer of N-isopropylacrylamide and a copolymer of N-isopropylacrylamide (for example, a copolymer in which the copolymerization ratio of N-isopropylacrylamide exceeds 50% by weight).

Examples of the cyclic amide having an N- (meth) acryloyl group include N-acryloylmorpholine, N-acryloylthiomorpholine, N-acryloylpiperidine, N-acryloylpyrrolidine, N-methacryloylmorpholine, N-methacryloylpiperidine, and N-methacryloylpyrrolidine. An example of the polymer containing a cyclic amide having an N- (meth) acryloyl group as a monomer unit is acryloylmorpholine Polymer (PACMO). Typical examples of the acryloylmorpholine-based polymer include homopolymers of N-Acryloylmorpholine (ACMO) and copolymers of ACMO (for example, copolymers in which the copolymerization ratio of ACMO exceeds 50% by weight). The proportion of the number of moles of the ACMO unit in the total number of moles of the repeating units in the acryloylmorpholine-based polymer is usually 50% or more, and preferably 80% or more (for example, 90% or more, and typically 95% or more). The total repeating units of the water-soluble polymer may be substantially composed of ACMO units.

Other examples of the nitrogen atom-containing polymer include homopolymers and copolymers of N-acylalkyleneimine-type monomers. Specific examples of the N-acylalkyleneimine-type monomer include N-acetylethyleneimine and N-propionylethyleneimine.

The cellulose derivative is a polymer containing a β -glucose unit as a main repeating unit, and examples thereof include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose (HEC), and methylhydroxyethyl cellulose. The starch derivative is a polymer containing an α -glucose unit as a main repeating unit, and examples thereof include α starch, pullulan, carboxymethyl starch, and cyclodextrin.

In the techniques disclosed herein, the molecular weight of the other water-soluble polymer is not particularly limited. The weight average molecular weight (Mw) of another water-soluble polymer may be, for example, 100X 10⁴Following from the cleaning propertyFrom the viewpoint of the like, it is usually 60X 10⁴The following is preferred, and may be 50X 10⁴Hereinafter, the value may be 40X 10⁴The following. In some embodiments, the Mw of the other water-soluble polymer is preferably 20X 10⁴The lower limit is, for example, 10X 10⁴Below or 8X 10⁴The following. The Mw of the other water-soluble polymer may be, for example, 2000 or more, and is preferably 5000 or more in general, from the viewpoint of the protection of the object to be polished. In several embodiments, Mw is 1.0X 10⁴The above is preferable, and 1.5X 10 is preferable⁴Above, more preferably 2 × 10⁴Above, more preferably 3 × 10⁴Above, e.g. 4X 10⁴Above, typically 5 × 10⁴Above, it may be 10X 10⁴Above, it may be 20X 10⁴Above, it may be 30X 10⁴The above.

The other water-soluble polymers may be used singly or in combination of 2 or more. The amount of the polyvinyl alcohol polymer and the other water-soluble polymer used is not particularly limited, and may be, for example, 5: 95-95: 5, can also be 10: 90-90: 10, or 25: 75-75: 25.

in some embodiments, the weight ratio (polyvinyl alcohol polymer: other water-soluble polymer) may be, for example, 50: 50-100: 0, also 80: 20-100: 0, also 90: 10-100: 0.

in other embodiments, the polyvinyl alcohol polymer: the weight ratio of the other water-soluble polymer may be, for example, 5: 95-70: 30. 15: 85-50: 50 or 20: 80-40: 60.

the above-mentioned effects obtained by using a 3-or more-membered polyvalent organic acid (salt) can be suitably exhibited even when the polyvinyl alcohol-based polymer and another water-soluble polymer (for example, a synthetic polymer such as a polymer containing an oxyalkylene unit and a nitrogen atom-containing polymer) are combined in this manner.

From the viewpoint of reducing aggregates, improving cleaning properties, and the like, a nonionic polymer is preferably used as the other water-soluble polymer. In addition, from the viewpoint of ease of control of chemical structure or purity, a synthetic polymer is preferably used as another water-soluble polymer. The polishing composition disclosed herein is preferably carried out without substantially using a natural polymer as another water-soluble polymer. The term "not used substantially" means that the amount of the polyvinyl alcohol polymer used is typically 3 parts by weight or less, preferably 1 part by weight or less, inclusive of 0 part by weight or less and the detection limit, based on 100 parts by weight of the polyvinyl alcohol polymer.

(content of Water-soluble Polymer)

The content of the water-soluble polymer in the polishing composition (the total amount of 2 or more types of the water-soluble polymer when included) is not particularly limited. In some embodiments, the content may be, for example, 0.0005 wt% or more, preferably 0.0025 wt% or more, more preferably 0.005 wt% or more, and for example, 0.0075 wt% or more, from the viewpoint of improvement in polishing performance and surface quality. The upper limit of the content of the water-soluble polymer is not particularly limited, and may be, for example, 0.05 wt% or less. From the viewpoint of stability in the concentrated solution stage, polishing rate, cleaning property, and the like, the content of the water-soluble polymer is preferably 0.035% by weight or less, more preferably 0.025% by weight or less, further preferably 0.02% by weight or less, particularly preferably 0.015% by weight or less, for example, 0.0125% by weight or less, and typically 0.01% by weight or less.

The content of the water-soluble polymer (the total amount of 2 or more types of the water-soluble polymer) can be specified by the relative relationship with the abrasive grains. In some embodiments, the content of the water-soluble polymer is, for example, 0.01 parts by weight or more relative to 100 parts by weight of the abrasive particles, and from the viewpoint of haze reduction or the like, 0.1 parts by weight or more is appropriate, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and still more preferably 3 parts by weight or more. The content of the water-soluble polymer may be, for example, 50 parts by weight or less, or 30 parts by weight or less, based on 100 parts by weight of the abrasive grains. From the viewpoint of dispersion stability of the polishing composition, the content of the water-soluble polymer is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, even more preferably 13 parts by weight or less, and may be 12 parts by weight or less, based on 100 parts by weight of the abrasive particles.

< polybasic organic acid (salt) >

The polishing composition disclosed herein contains a 3-or more-membered polyvalent organic acid (salt). The present inventors have found that a polishing composition using a polyvinyl alcohol polymer as a water-soluble polymer further contains a 3-or more-membered polyvalent organic acid (salt), and thereby improves the haze of a polished object after polishing. The reason why such an effect is exhibited is not clear, but is presumed to be, for example, as follows. That is, the polyvinyl alcohol polymer contained in the polishing composition containing the abrasive grains contributes to protection of the polishing object, improvement of wettability of the surface of the polishing object after polishing, and the like, and may cause aggregation of the abrasive grains. When the abrasive grains are aggregated, fine polishing unevenness is likely to occur, and it is difficult to reduce haze. The polishing composition containing abrasive grains and a polyvinyl alcohol polymer has an effect of suppressing aggregation of the abrasive grains and improving dispersibility of the abrasive grains, and contributes to improvement of haze.

As the above-mentioned polybasic organic acid (salt), typically, a polybasic organic acid (salt) having 3 or more functional groups selected from the group consisting of an acid group and a salt thereof in one molecule can be used. The acid group may be, for example, a carboxyl group, a sulfonic acid group, a phosphonic acid group, or the like. The functional groups are each independently selected from the group consisting of carboxyl groups, salts of sulfonic acid groups and sulfonic acid groups, and salts of phosphonic acid groups and phosphonic acid groups. As a preferred example of the polybasic organic acid (salt), a polybasic carboxylic acid (salt) having 3 or more members is mentioned. The number of acid groups (number of carboxyl groups in the case of polycarboxylic acid) in one molecule of the polybasic organic acid (salt) is 3 or more, for example, 3, 4 or 5, preferably 3 or 4. In some embodiments, the polybasic organic acid (salt) may be a hydroxy polybasic organic acid (salt) having 1 or more hydroxy groups in one molecule. A preferable example of the hydroxypolycarboxylic acid (salt) is a hydroxypolycarboxylic acid (salt) having 1 or more hydroxyl groups and 3 or more carboxyl groups in one molecule. By using a hydroxypolycarboxylic acid (salt) as the polybasic organic acid (salt), good dispersibility of the abrasive grains tends to be stably exhibited. Thus, improvement in surface quality (e.g., improvement in haze) is more suitably achieved.

Examples of the polybasic organic acid constituting the polybasic organic acid (salt) include aconitic acid, citric acid, butanetetracarboxylic acid, trimesic acid, trimellitic acid, cyclohexanetricarboxylic acid, pyromellitic acid, mellitic acid, nitrilotris (methylenephosphonic acid) (NTMP), and 2-phosphonobutane-1, 2, 4-tricarboxylic acid (PBTC). Among them, preferred examples include citric acid (salt) and butanetetracarboxylic acid (salt). Examples of the salt of the polybasic organic acid include alkali metal salts such as sodium salts and potassium salts, and ammonium salts. Among them, ammonium salts are preferred. The polybasic organic acids (salts) can be used singly or in combination of 2 or more.

The content of the polybasic organic acid (salt) is not particularly limited, and may be set to exhibit its use effect appropriately. In some embodiments, the content of the polybasic organic acid (salt) may be, for example, 0.0005 wt% or more, 0.001 wt% or more, 0.005 wt% or more, or 0.01 wt% or more, based on the total weight of the polishing composition. The effect of improving the haze can be further exhibited by improving the dispersibility of the abrasive grains due to the increase in the content of the polybasic organic acid (salt). Here, the content of the polybasic organic acid (salt) means the total content of 2 or more kinds of the polybasic organic acid (salt) in the form of being contained. In addition, since the haze improving effect is reduced when the content of the polybasic organic acid (salt) is too large, the content of the polybasic organic acid (salt) may be, for example, 5 wt% or less, or 1 wt% or less, or 0.3 wt% or less, or 0.1 wt% or less, or 0.05 wt% or less, or 0.02 wt% or less in some embodiments. The content of these components is preferably a content in a polishing liquid (Working slurry) supplied to a polishing target.

In some embodiments of the polishing composition disclosed herein, the preferred content of the polybasic organic acid (salt) can be specified by the relative relationship with the abrasive grains contained in the polishing composition. Specifically, the content of the polyvalent organic acid (salt) in the polishing composition is, for example, suitably about 0.01 part by weight or more, preferably about 0.1 part by weight or more, more preferably about 0.5 part by weight or more, and may be about 0.7 part by weight or more, based on 100 parts by weight of the abrasive grains contained in the polishing composition. The content of the polybasic organic acid (salt) is increased relative to the content of the abrasive grains, so that the dispersibility of the abrasive grains can be improved, and the effect of improving the haze can be exerted. Since the haze improving effect is reduced when the content of the polybasic organic acid (salt) is too large relative to the content of the abrasive grains, the content of the polybasic organic acid (salt) is generally about 50 parts by weight or less, preferably about 20 parts by weight or less, more preferably about 10 parts by weight or less, and may be about 6 parts by weight or less, relative to 100 parts by weight of the abrasive grains, in some embodiments. The content of the polybasic organic acid (salt) may be, for example, 5 parts by weight or less, or may be 3 parts by weight or less, relative to 100 parts by weight of the abrasive grains.

In some embodiments of the polishing composition disclosed herein, the preferred content of the polyvalent organic acid (salt) can be specified by a relative relationship with the polyvinyl alcohol polymer contained in the polishing composition. Specifically, the content (A) of the polybasic organic acid (salt)_OA) With the content (A) of the polyvinyl alcohol polymer in the polishing composition_HM) Ratio of (A)_OA/A_HM) For example, the amount of the surfactant is preferably about 0.01 or more by weight, more preferably about 0.05 or more, and still more preferably about 0.1 or more, from the viewpoint of obtaining more favorable dispersibility. Further, when the content of the polyhydric organic acid (salt) is too large relative to the content of the polyvinyl alcohol polymer, the haze improving effect is lowered, so that the ratio (a) is set to be higher than the content of the polyvinyl alcohol polymer_OA/A_HM) Usually, the concentration is preferably about 10 or less, more preferably about 3 or less, still more preferably about 2 or less, and may be about 1 or less. The above ratio (A)_OA/A_HM) For example, it may be 0.7 or less.

The preferable content of the polyvalent organic acid (salt) can be specified by a relative relationship between the water-soluble polymers contained in the polishing composition (in a case where the polyvinyl alcohol polymer and the other water-soluble polymers are combined, the total amount of the polymers is included). Content of polybasic organic acid (salt) (A)_OA) With the content (A) of the water-soluble polymer in the polishing composition_HT) Ratio of (A)_OA/A_HT) For example, about 0.01 or more is suitable on a weight basis, and from the viewpoint of obtaining more favorable dispersibility, about 0.05 or more is preferable,more preferably about 0.1 or more. The polishing composition disclosed herein can be used, for example, in combination with a polyvinyl alcohol polymer and another water-soluble polymer, and the ratio (A) can be adjusted by appropriately selecting the other water-soluble polymer_OA/A_HT) About 0.2 or more, about 0.3 or more, about 0.4 or more, or about 0.5 or more. In addition, when the content of the polybasic organic acid (salt) is too large relative to the content of the water-soluble polymer, the haze improving effect is reduced, so that the ratio (a) is set to be higher than the ratio (a)_OA/A_HT) Usually, the concentration is preferably about 10 or less, more preferably about 7 or less, still more preferably about 5 or less, and may be about 3 or less.

In some embodiments of the polishing composition disclosed herein, the preferable content of the polybasic organic acid (salt) can be specified by the increase ratio of the electrical conductivity of the composition containing the polybasic organic acid (salt). The ratio of the increase in conductivity between the conductivity EC1[ mS/cm ] of the polishing composition disclosed herein and the conductivity EC0[ mS/cm ] of the composition obtained by removing the polyvalent organic acid (salt) from the polishing composition is defined by the following formula: conductivity increase ratio EC1/EC 0. The conductivity increase ratio is usually 1 or more, and typically exceeds 1. In some embodiments, the conductivity increase ratio may be, for example, 1.3 or more, or 1.4 or more, or 1.5 or more, or 1.7 or more, from the viewpoint of further exhibiting the effect of using the polybasic organic acid (salt). From the viewpoint of dispersion stability of the polishing composition, the conductivity increase ratio may be, for example, less than 10, and usually less than 5. In some embodiments, the conductivity increase ratio is preferably 3 or less, and may be, for example, less than 3, less than 2.5, or less than 2. In some other embodiments, the conductivity increase ratio may be, for example, more than 1 and less than 10, or 1.3 or more and less than 7, or 1.5 or more and less than 5, or 2 or more and less than 4.

In order to obtain such an electric conductivity ratio, the content of the polybasic organic acid (salt) is set, whereby a polishing composition having effectively improved haze can be realized. The measurement of the electrical conductivity can be carried out in a usual manner under a condition of a liquid temperature of 25 ℃. The measuring apparatus can be, for example, a conductivity meter manufactured by horiba, model "DS-12". In the examples described later, the conductivity was measured using the conductivity meter.

In some embodiments of the polishing composition disclosed herein, the conductivity EC1[ mS/cm ] of the polishing composition may be, for example, 0.03mS/cm or more, 0.05mS/cm or more, 0.08mS/cm or more, 0.1mS/cm or more, 0.11mS/cm or more, or 0.12mS/cm, from the viewpoint of dispersibility of the abrasive grains. From the viewpoint of dispersion stability of the polishing composition, the conductivity EC1[ mS/cm ] may be, for example, 0.30mS/cm or less, 0.20mS/cm or less, or 0.15mS/cm or less. When the polishing composition having an electrical conductivity satisfying any one of the upper and/or lower limits is used, the haze of the surface of the polished object can be effectively improved.

The polishing composition disclosed herein can be preferably carried out in such a manner that the polishing composition has a conductivity EC1[ mS/cm ] of less than 0.12mS/cm, less than 0.11mS/cm, less than 0.10mS/cm, and further less than 0.08 mS/cm. In this manner, in an embodiment in which the electrical conductivity EC1 is relatively low, it is preferable to use a polyvinyl alcohol polymer as a water-soluble polymer in combination with another water-soluble polymer. In this embodiment, the electric conductivity EC1[ mS/cm ] may be, for example, more than 0.01mS/cm, and preferably more than 0.02mS/cm, or more than 0.03mS/cm, or more than 0.04mS/cm, from the viewpoint of dispersion stability of the polishing composition, or the like. When the polishing composition having an electrical conductivity satisfying any one of the upper and/or lower limits is used, the haze of the surface of the polished object can be effectively improved.

The polishing composition disclosed herein may further contain one or more than 2 acids (salts) selected from the group consisting of inorganic acids (salts), 1-membered organic acids (salts) and 2-membered organic acids (salts) (hereinafter, also referred to as other acids (salts)) as necessary, in addition to the above-mentioned polybasic organic acids (salts) within a range not significantly impairing the effects of the present invention. The other acid (salt) can be used for the purpose of, for example, adjusting the pH and conductivity of the polishing composition. The polishing composition disclosed herein is preferably carried out in a manner substantially free from acids (salts) other than the polybasic organic acids (salts) from the viewpoints of the purification of the composition, the stability of the performance, and the like. Here, the term "substantially free of an acid (salt) other than the polybasic organic acid (salt)" means that 95 to 100% by weight (typically 98 to 100% by weight) of the total amount of the content of the polybasic organic acid (salt) and the content of the other acid (salt) is the polybasic organic acid (salt).

< basic Compound >

The polishing composition disclosed herein contains a basic compound. In the present specification, the basic compound means a compound having a function of dissolving in water and raising the pH of an aqueous solution. As the basic compound, nitrogen-containing organic or inorganic basic compounds, phosphorus-containing basic compounds, alkali metal hydroxides, alkaline earth metal hydroxides, and various carbonates or bicarbonates can be used. Examples of the nitrogen-containing basic compound include a quaternary ammonium compound, ammonia, an amine (preferably a water-soluble amine), and the like. As an example of the phosphorus-containing basic compound, a quaternary phosphonium compound is cited. Such basic compounds may be used singly or in combination of 2 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 the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (. beta. -aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, imidazole, triazole and other azoles. Specific examples of the quaternary phosphonium compound include quaternary phosphonium hydroxides 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 is preferably used. The anionic component of the quaternary ammonium salt may be OH^-、F^-、Cl^-、Br^-、I^-、ClO₄ ^-、BH₄ ^-And the like. Wherein the best isAs an alternative, OH as the anion may be mentioned^-Quaternary ammonium salts of (2), that is, quaternary ammonium hydroxides. Specific examples of the quaternary ammonium hydroxide include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide and tetrahexylammonium hydroxide; hydroxyalkyl trialkylammonium hydroxides such as 2-hydroxyethyl trimethylammonium hydroxide (also referred to as choline); and the like.

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

< surfactant >

The polishing composition disclosed herein may contain a surfactant, if necessary. By adding a surfactant to the polishing composition, the haze of the surface of the object to be polished after polishing can be further reduced. As the surfactant, any of anionic, cationic, nonionic, and amphoteric surfactants can be used. It is generally preferred to use anionic or nonionic surfactants. From the viewpoint of low foaming properties and ease of pH adjustment, nonionic surfactants are more preferable. Examples thereof include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol and polybutylene glycol; polyoxyalkylene derivatives (e.g., polyoxyalkylene adducts) such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glycerol ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; copolymers of various alkylene oxides (e.g., diblock copolymers, triblock copolymers, random copolymers, alternating copolymers); and a nonionic surfactant. The surfactants may be used singly or in combination of 2 or more.

Specific examples of the nonionic surfactant include block copolymers of Ethylene Oxide (EO) and Propylene Oxide (PO) (diblock copolymers, PEO (polyethylene oxide) -PPO (polypropylene oxide) -PEO triblock copolymers, PPO-PEO-PPO triblock copolymers, etc.), random copolymers of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, etc.), Polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene lauryl amine, polyoxyethylene octadecylamine, polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, and the like. Among them, preferable surfactants include a block copolymer of EO and PO (particularly, a triblock copolymer of a PEO-PPO-PEO type), a random copolymer of EO and PO, and a polyoxyethylene alkyl ether (for example, polyoxyethylene decyl ether). The polyoxyethylene alkyl ether is preferably one having an EO addition mole number of about 1 to 10 (e.g., about 3 to 8).

The weight average molecular weight (Mw) of the surfactant is typically less than 2000, and is preferably 1900 or less (for example, less than 1800) from the viewpoint of filterability, cleaning property, and the like. The Mw of the surfactant is usually 200 or more, preferably from the viewpoint of surface activity performance, and the like, and is preferably 250 or more (for example, 300 or more) from the viewpoint of haze reduction effect, and the like. The more preferable range of Mw of the surfactant may vary depending on the kind of the surfactant. For example, when a polyoxyethylene alkyl ether is used as the surfactant, the Mw thereof is preferably 1500 or less, and may be 1000 or less (e.g., 500 or less). For example, when a PEO-PPO-PEO type triblock copolymer is used as the surfactant, the Mw may be, for example, 500 or more, 1000 or more, or 1200 or more.

When the polishing composition disclosed herein contains a surfactant, the content thereof is not particularly limited within a range not significantly hindering the effect of the present invention. In general, from the viewpoint of cleaning performance, the content of the surfactant is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and still more preferably 10 parts by weight or less (for example, 6 parts by weight or less) with respect to 100 parts by weight of the abrasive grains. From the viewpoint of further exhibiting the effect of the surfactant in use, the content of the surfactant is preferably 0.001 parts by weight or more, more preferably 0.005 parts by weight or more, and may be 0.01 parts by weight or more, and may be 0.05 parts by weight or more, relative to 100 parts by weight of the abrasive grains.

When the polishing composition disclosed herein contains a surfactant, the weight ratio (w1/w2) of the content w1 of the water-soluble polymer to the content w2 of the surfactant is not particularly limited, and may be, for example, in the range of 0.01 to 200, preferably in the range of 0.05 to 100, and more preferably in the range of 0.1 to 70.

Alternatively, the polishing composition disclosed herein is preferably carried out in a manner substantially free from a surfactant, from the viewpoint of the simple purification of the composition and the like.

< Water >

The water contained in the polishing composition disclosed herein is preferably ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like. The total content of the transition metal ions is preferably 100ppb or less, for example, in order to avoid inhibiting the effects of other components contained in the polishing composition as much as possible. For example, the purity of water can be improved by removing impurity ions with an ion exchange resin, removing foreign substances with a filter, distillation, or the like.

< other ingredients >

The polishing composition disclosed herein may contain, if necessary, known additives that can be used in polishing compositions (typically, polishing compositions used in the final polishing step of silicon wafers), such as an antiseptic agent and a mildewproofing agent, within a range that does not significantly impair the effects of the present invention. Examples of the preservative and the antifungal agent include isothiazoline compounds, parabens, phenoxyethanol, and the like.

The polishing composition disclosed herein preferably contains substantially no oxidizing agent. When the polishing composition contains an oxidizing agent, for example, in polishing a silicon wafer, the surface of the silicon wafer is oxidized to form an oxide film, and thus the polishing time is prolonged. Specific examples of the oxidizing agent include hydrogen peroxide (H)₂O₂) Sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. The polishing composition substantially free of an oxidizing agent means that the polishing composition is at least intentionally free of an oxidizing agent. Therefore, a polishing composition containing an inevitable trace amount of an oxidizing agent (for example, a 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 0.000001 mol/L or less) derived from a raw material, a production method, or the like is also included in the concept of a polishing composition substantially not containing the oxidizing agent referred to herein.

<pH>

The polishing composition disclosed herein typically has a pH of 8.0 or more, preferably 8.5 or more, and more preferably 9.0 or more. When the pH of the polishing composition becomes high, the polishing performance tends to be improved. From the viewpoint of preventing dissolution of abrasive grains (e.g., silica grains) and suppressing a decrease in mechanical polishing action, the pH of the polishing composition is usually suitably 12.0 or less, preferably 11.0 or less, more preferably 10.8 or less, and still more preferably 10.5 or less.

The pH was adjusted at 3 points using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model F-23) manufactured by horiba, Ltd.) using a standard buffer (a phthalate pH buffer pH: 4.01(25 ℃), a neutral phosphate pH buffer pH: 6.86(25 ℃), and a carbonate pH buffer pH: 10.01(25 ℃)), and the pH was confirmed by placing a glass electrode in the composition to be measured and measuring the value after stabilization for 2 minutes or more.

< dispersibility >

In the technique disclosed herein, the degree of dispersibility of the abrasive grains contained in the polishing composition can be determined, for example, by the following formula:

dispersivity [ nm ]]＝(d₈₄-d₁₆)/2；

The calculated value of the dispersibility is used as a standard, and the dispersibility can be grasped. Here, d in the above formula₈₄Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 84%]，d₁₆Particle diameter [ nm ] at a point where the cumulative curve representing the particle size distribution becomes 16%]。d₈₄And d₁₆Can be obtained by measurement according to a dynamic light scattering method. As the measurement apparatus, for example, a dynamic light scattering particle size distribution measuring apparatus manufactured by Microtrac WaveII, trade name "Nanotrac UPA-UT 151", or the equivalent thereof can be used. The smaller value of the above dispersibility means that the particle size distribution width is narrower. Generally, when aggregation of abrasive grains occurs, the width of the grain size distribution of the abrasive grains tends to be widened. From this, it is found that the polishing composition having a smaller value of the dispersibility can suppress aggregation of the abrasive grains more effectively.

In some embodiments of the polishing composition disclosed herein, the above-mentioned dispersibility is suitably less than 50nm, preferably less than 20nm, more preferably less than 15nm, and still more preferably less than 10.8 nm. In a preferred embodiment, the value of the dispersibility is, for example, 10.5nm or less. The dispersibility is, in principle, 0nm, but from the practical viewpoint may be 1nm or more, 3nm or more, 5nm or more, or 8nm or more.

In the embodiment in which the polishing composition disclosed herein further contains another water-soluble polymer, for example, the dispersibility is less than 14.2nm, and a further favorable haze-improving effect can be exhibited. In this embodiment, the value of the dispersibility may be, for example, 1nm or more, 3nm or more, 5nm or more, 8nm or more, 10nm or more, or 12nm or more.

The above value of dispersibility is preferably applicable to a polishing composition using abrasive grains (e.g., colloidal silica) having a BET diameter of 10nm or more and 35nm or less, more preferably 15nm or more and less than 32nm, for example.

< polishing liquid >

The polishing composition disclosed herein is typically supplied onto the surface of an object to be polished in the form of a polishing liquid containing the polishing composition, and is used for polishing the object to be polished. The polishing liquid can be prepared by, for example, diluting (typically, diluting with water) any of the polishing compositions disclosed herein. Alternatively, the polishing composition can be used as it is as a polishing liquid. That is, the concept of the polishing composition in the technology disclosed herein includes both a polishing liquid (working slurry) supplied to a polishing object for polishing the polishing object and a concentrated liquid (stock solution of the polishing liquid) diluted and used as the polishing liquid.

< concentrated solution >

The polishing composition disclosed herein may be concentrated before being supplied to the polishing object (i.e., a concentrated polishing liquid). The polishing composition of the concentrated form is preferable from the viewpoint of convenience in production, distribution, storage, and the like, cost reduction, and the like. The concentration ratio is not particularly limited, and may be, for example, about 2 to 100 times, and usually about 5 to 50 times (for example, about 10 to 40 times) in terms of volume conversion.

Such a concentrated solution can be used by preparing a polishing liquid (working slurry) by dilution at a desired timing and supplying the polishing liquid to an object to be polished. The dilution may be performed by, for example, adding water to the concentrated solution and mixing the solution.

The content of the abrasive grains in the concentrated solution may be, for example, 25 wt% or less. From the viewpoint of dispersion stability, filterability, and the like of the polishing composition, the content is usually preferably 20% by weight or less, and more preferably 15% by weight or less. In a preferred embodiment, the content of the abrasive grains may be 10 wt% or less, or may be 5 wt% or less. The content of the abrasive grains in the concentrated solution may be, for example, 0.1 wt% or more, preferably 0.5 wt% or more, more preferably 0.7 wt% or more, and still more preferably 1 wt% or more, from the viewpoint of convenience in production, distribution, storage, and the like, cost reduction, and the like.

< preparation of polishing composition >

The polishing composition used in the art disclosed herein may be in a single dosage form or a multi-dosage form, including a two-dosage form. For example, among the constituent components of the polishing composition, a portion a containing at least abrasive grains and a portion B containing at least a part of the remaining components are mixed, and these are mixed and diluted at an appropriate timing as necessary to prepare a polishing liquid.

The method for preparing the polishing composition is not particularly limited. For example, the components constituting the polishing composition may be mixed by using a known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The form of mixing these components is not particularly limited, and for example, all the components may be mixed at once, or may be mixed in an appropriately set order.

< use >

The polishing composition disclosed herein can be suitably used for polishing an object to be polished having various materials and shapes. Examples of the material of the object to be polished include metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, and stainless steel, and alloys thereof; vitreous materials such as quartz glass, aluminosilicate glass, and glassy carbon; ceramic materials such as alumina, silica, sapphire, silicon nitride, tantalum nitride, titanium carbide and the like; compound semiconductor substrate materials such as silicon carbide, gallium nitride, gallium arsenide, and the like; resin materials such as polyimide resins; and the like. These polishing objects may be made of a plurality of materials.

The polishing composition disclosed herein is particularly useful for polishing a surface made of silicon (typically, polishing a silicon wafer). A typical example of the silicon wafer referred to herein is a single crystal silicon wafer, for example, a single crystal silicon wafer obtained by slicing a single crystal silicon ingot (ingot).

The polishing composition disclosed herein is preferably used in a polishing step of an object to be polished (e.g., a silicon wafer). The polishing object may be subjected to a general treatment applicable to the polishing object in a step upstream of the polishing step, such as grinding or etching, before the polishing step with the polishing composition disclosed herein.

The polishing composition disclosed herein is effective for use in a final step of polishing an object (e.g., a silicon wafer) or a polishing step prior thereto, and is particularly preferably used in the final polishing step. Here, the final polishing step is a polishing step at the end of the production process of the object (i.e., a step after this polishing step, in which polishing is not performed).

< grinding >

The polishing composition disclosed herein can be used for polishing an object to be polished, for example, in a manner 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 slurry containing any of the polishing compositions disclosed herein was prepared. The preparation of the polishing liquid includes adding concentration adjustment (e.g., dilution), pH adjustment, and the like to the polishing composition, and the polishing liquid can be prepared. Alternatively, the polishing composition may be used as it is as a polishing liquid.

Then, the polishing liquid was supplied to the object to be polished, and polishing was performed by a conventional method. For example, in the case of finishing polishing of a silicon wafer, typically, the silicon wafer having undergone a polishing step is set in a general polishing apparatus, and a polishing liquid is supplied to a surface to be polished of the silicon wafer by a polishing pad of the polishing apparatus. Typically, the polishing liquid is continuously supplied, and the polishing pad is pressed against the surface to be polished of the silicon wafer, so that the polishing pad and the surface are relatively moved (for example, rotationally moved). 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 a foamed polyurethane type, a nonwoven fabric type, a suede type (leather type), or the like can be used. Each polishing pad may or may not contain abrasive particles. In general, it is preferable to use a polishing pad containing no abrasive grains.

The polishing object polished with the polishing composition disclosed herein is typically cleaned. The cleaning may use a suitable cleaning solution. The cleaning liquid to be used is not particularly limited, and for example, a general SC-1 cleaning liquid (ammonium hydroxide (NH)) used in the field of semiconductors and the like can be used₄OH) and peroxidationHydrogen (H)₂O₂) With water (H)₂O), SC-2 cleaning solution (hydrochloric acid (HCl) and H)₂O₂And H₂A mixture of O), etc. The temperature of the cleaning liquid may range, for example, from room temperature (typically, about 15 ℃ to 25 ℃) to about 90 ℃. From the viewpoint of improving the cleaning effect, it is preferable to use a cleaning liquid of about 50 to 85 ℃.

Examples

The following description relates to several embodiments of the present invention, but the present invention is not intended to be limited to the embodiments. In the following description, "part" and "%" are based on weight unless otherwise specified.

Experimental example 1

< preparation of polishing composition >

(examples 1 to 3)

Abrasive grains, a water-soluble polymer, an acid (salt), a basic compound, a surfactant, and deionized water were mixed to prepare polishing compositions of the respective examples. Colloidal silica (average primary particle diameter: 25nm) was used as abrasive grains, and the content thereof was 0.175%. As the water-soluble polymer, polyvinyl alcohol (non-modified PVA) having a weight average molecular weight (Mw) of about 70000 and a saponification degree of 98% or more was used, and the content thereof was 0.00875%. As the basic compound, ammonia was used in an amount of 0.005%. Polyoxyethylene decyl ether (C10EO5) having an additional mole number of 5 of ethylene oxide was used as a surfactant, and its content was 0.00015%. As the acid (salt), triammonium citrate was used in the amount shown in table 1.

(example 4)

In this example, citric acid was used in the amount shown in Table 1 in place of triammonium citrate. The polishing composition of this example was prepared in the same manner as in example 1.

(example 5)

In this example, butane tetracarboxylic acid was used in the amount shown in Table 1 in place of the triammonium citrate. The polishing composition of this example was prepared in the same manner as in example 1.

Comparative example 1

A polishing composition of this example was prepared in the same manner as in example 1, except that the triammonium citrate was removed from the composition of example 1.

Comparative examples 2 to 5

Polishing compositions of comparative examples 2 to 5 were prepared in the same manner as in example 1, except that the acid (salt) of the type and amount shown in Table 1 was used instead of triammonium citrate.

< measurement of dispersibility >

The particle size distribution of the prepared polishing composition was measured using a dynamic light scattering particle size distribution measuring apparatus manufactured by Microtrac WaveII, trade name "Nanotrac UPA-UT 151". The particle diameter (nm) at the point where the cumulative curve became 84% is defined as d₈₄The particle diameter (nm) at the point where the cumulative curve is 16% is d₁₆By the following formula:

dispersivity [ nm ]]＝(d₈₄-d₁₆)/2；

The value of dispersibility was calculated. The results obtained are shown in Table 1. Table 1 also shows the values of the electrical conductivity measured by the above-described method.

The polishing composition of comparative example 1 had a pH of 10.0, and the polishing compositions of the other examples all had a pH in the range of 9.0 to 9.9.

< polishing of silicon wafer >

A silicon wafer was prepared by pre-polishing a commercially available single Crystal silicon wafer (conductive type: P type, Crystal orientation: 100>, COP (Crystal ordered Particle: Crystal defect)) having a diameter of 200mm, which was polished and etched as an object to be polished, under the following polishing conditions 1. Pre-polishing was performed using a polishing slurry containing 1.0% abrasive particles (colloidal silica having a BET diameter of 35 nm) and 0.068% potassium hydroxide in deionized water.

[ polishing Condition 1]

A grinding device: single-side grinding device model "PNX-322" manufactured by Kyowa machine tool, K.K "

Grinding load: 15kPa

Rotation speed of the platform: 30rpm

Rotation speed of polishing head (carrier): 30rpm

Polishing the pad: fuji Miss of love of Fuji, product name "FP 55"

Supply rate of pre-polishing liquid: 550 mL/min

Temperature of the pre-polishing liquid: 20 deg.C

Temperature of platform cooling water: 20 deg.C

Grinding time: 3 minutes

The pre-polished silicon wafers were polished under the following polishing conditions 2 using the polishing compositions prepared in the respective examples as polishing liquids.

[ polishing Condition 2]

A grinding device: model of single-side grinding device "PNX-322" made by Kyowa machine tool, Kyowa Kaisha "

Grinding load: 15kPa

Rotation speed of the platform: 30rpm

Rotation speed of polishing head (carrier): 30rpm

Polishing the pad: product name "POLYPAS 27 NX" of Fuji Miss of love "

Supply rate of polishing liquid: 400 mL/min

Temperature of the polishing liquid: 20 deg.C

Temperature of platform cooling water: 20 deg.C

Grinding time: 4 minutes

Taking off the polished silicon wafer from the polishing device, using NH₄OH(29％)：H₂O₂(31%): deionized water (DIW) ═ 1: 1: 12 (volume ratio) of cleaning solution (SC-1 cleaning). Specifically, 2 cleaning tanks 1 and 2 were prepared, and the cleaning solution was stored in each of these cleaning tanks and maintained at 60 ℃. The polished silicon wafer was immersed in a 1 st cleaning tank for 5 minutes, immersed in ultrapure water, passed through a rinsing tank to which ultrasonic waves were applied, immersed in a 2 nd cleaning tank for 5 minutes, immersed in ultrapure water, passed through a rinsing tank to which ultrasonic waves were applied, and dried using a Spin Dryer (Spin Dryer).

< haze measurement >

The cleaned surface of the silicon wafer was examined by a wafer inspection apparatus manufactured by KLA-Tencor, trade name "Surfscan SP2^XP", haze (ppm) was measured in DWO mode. Conversion of the results obtainedThe haze value of comparative example 1 is a relative value (haze ratio) of 100%, and is shown in table 1. When the haze ratio is less than 100%, the haze improving effect is confirmed.

[ Table 1]

TABLE 1

As shown in table 1, it was confirmed that examples 1 to 5 using a polybasic organic acid (salt) have a significant haze improving effect compared to comparative example 1. In these examples, the dispersibility (nm) value of the polishing composition was significantly reduced as compared to comparative example 1, which contributes to the improvement of the haze. Further, the effect of improving the haze was not observed in comparative examples 2 to 5 using 1-or 2-membered acid (salt) as compared with comparative example 1.

The polishing composition of reference example 2 prepared in the same manner as in reference example 1 had a dispersibility of 51.2nm, except that the polyvinyl alcohol was changed to hydroxyethyl cellulose (HEC), and the dispersibility of the polishing composition of reference example 1 was 23.3nm, except that triammonium citrate was not used. That is, unlike the results shown in table 1, the polishing composition using HEC alone as a water-soluble polymer did not show any improvement in dispersibility due to the polybasic organic acid (salt).

Experimental example 2

< preparation of polishing composition >

(example 6)

As the water-soluble polymer, polyvinyl alcohol (non-modified PVA) having a weight average molecular weight (Mw) of about 70000 and a saponification degree of 98% or more and Polyacryloylmorpholine (PACMO) having a weight average molecular weight (Mw) of about 350000 were used. The content of the polyvinyl alcohol is 0.00263 percent, and the content of the polyacryloylmorpholine is 0.00560 percent. The content of C10EO5 was 0.00007%, and the content of triammonium citrate was 0.0042%. The polishing composition of this example was prepared in the same manner as in example 1.

Comparative example 6

The polishing composition of this example was prepared in the same manner as in example 6, except that triammonium citrate was removed from the composition of example 6.

< evaluation >

The prepared polishing composition was subjected to dispersibility measurement, silicon wafer polishing, and haze measurement in the same manner as in experimental example 1. The results are shown in Table 2. The haze value obtained in example 6 was converted into a relative value (haze ratio) in which the haze value of comparative example 6 was 100%. The results are shown in Table 2.

[ Table 2]

TABLE 2

As shown in table 2, it was confirmed that the addition of a polyvalent organic acid (salt) to the composition of comparative example 6 significantly improves the haze effect in comparison between example 6 and comparative example 6, which are polishing compositions containing a polyvinyl alcohol polymer and another water-soluble polymer in combination.

Specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The techniques described in the claims include those in which various modifications and changes are made to the specific examples illustrated above.