JP7353051B2 - Composition for polishing silicon wafers - Google Patents

Description

The present invention relates to a polishing composition used for polishing silicon wafers.

The surface of a silicon wafer used as a component of a semiconductor product is generally finished into a high-quality mirror surface through a lapping process (rough polishing process) and a polishing process (precision polishing process). The polishing process typically includes a preliminary polishing process (preliminary polishing process) and a final polishing process (final polishing process). Technical documents related to silicon wafer polishing compositions include, for example, Patent Documents 1 to 6.

Japanese Patent Application Publication No. 2016-009759 Patent No. 5890583 International Publication No. 2014/034425 Patent No. 5892638 International Publication No. 2016/129215 International Publication No. 2016/132676

A polishing composition used in a final polishing process (particularly a final polishing process for semiconductor substrates such as silicon wafers and other substrates) is required to have the ability to achieve a high-quality surface after polishing. In addition to abrasive grains and water, polishing compositions for such uses often contain water-soluble polymers for purposes such as protecting the surface of the object to be polished and improving wettability. The water-soluble polymer contributes to reducing defects and haze on the polished surface by adsorbing to or desorbing from the abrasive grains or silicon wafer.

On the other hand, in recent years, higher quality surfaces have been required for semiconductor substrates such as silicon wafers and other substrates. For this reason, there is a need for a polishing composition that can provide a substrate surface with even lower haze. Therefore, an object of the present invention is to provide a silicon wafer polishing composition that contains a water-soluble polymer and can improve the surface quality of a polished object after polishing.

The silicon wafer polishing composition provided by this specification includes abrasive grains, a water-soluble polymer, a basic compound, and water, and the water-soluble polymer is N-(meth)acryloylmorpholine. (hereinafter also referred to as "morpholine polymer") and vinyl alcohol polymer. The relationship between the content W _A of the morpholine polymer (content on a weight basis) and the content W _B (content on a weight basis) of the vinyl alcohol polymer is expressed by the following formula: W _A /(W _A +W _B )>0.900; is satisfied. According to such a polishing composition, the surface quality of a silicon wafer after polishing can be improved. For example, haze can be improved.

In some embodiments of the polishing composition disclosed herein, the content W _A of the morpholine polymer is preferably 2.0×10 ⁻³ % by weight or more. In such an embodiment, the haze improving effect can be suitably exhibited when used in combination with the above-mentioned vinyl alcohol-based polymer.

In some embodiments of the polishing composition disclosed herein, the content W _B of the vinyl alcohol polymer is preferably 15.0×10 ⁻⁴ % by weight or less. In such an embodiment, the effect of improving haze can be suitably exhibited.

As the above-mentioned vinyl alcohol polymer, one having a weight average molecular weight of more than 1×10 ⁴ can be preferably employed. In a polishing composition containing a combination of a small amount of a vinyl alcohol polymer having such a weight average molecular weight and the above-mentioned morpholine polymer, the haze improving effect is more suitably exhibited.

In some embodiments of the polishing composition disclosed herein, the polishing composition further includes a surfactant. In the configuration of such a polishing composition, the haze on the surface of the polishing object after polishing can be further effectively improved.

A polishing composition according to a preferred embodiment includes a surfactant containing a polyoxyalkylene structure as the surfactant. In such an embodiment, haze can be improved more suitably.

Silica particles are preferably used as the abrasive grains. The effect of improving haze by using a combination of a morpholine polymer and a vinyl alcohol polymer is suitably exhibited in polishing using silica particles as abrasive grains.

The polishing composition disclosed herein can be preferably used in the final polishing process of silicon wafers. By performing final polishing using the polishing composition described above, haze can be improved and a high quality silicon wafer surface can be suitably realized.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than those specifically mentioned in this specification that are necessary for implementing the present invention can be understood as matters designed by those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the field.

The polishing composition disclosed herein includes abrasive grains, a water-soluble polymer, a basic compound, and water. The polishing composition includes a morpholine polymer and a vinyl alcohol polymer as the water-soluble polymer. Hereinafter, the contents of the polishing composition disclosed herein will be explained.

<Abrasive>
The polishing composition disclosed herein contains abrasive grains. Abrasive grains function 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 manner of use of the polishing composition. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, red iron particles; Examples include nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles and poly(meth)acrylic acid particles (here, (meth)acrylic acid refers comprehensively to acrylic acid and methacrylic acid.) , polyacrylonitrile particles, etc. Such abrasive grains may be used alone or in combination of two or more.

The abrasive grains are preferably inorganic particles, particularly preferably particles made of metal or metalloid oxides, and particularly preferably silica particles. In a polishing composition that can be used for polishing (for example, final polishing) a polishing target having a surface made of silicon, such as a silicon wafer described below, it is particularly meaningful to employ silica particles as the abrasive grain. The technique disclosed herein can be preferably implemented, for example, in an embodiment in which the abrasive grains essentially consist of silica particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and may be 100% by weight) of the particles constituting the abrasive grains. It means that it is a silica particle.

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

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 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 grains (for example, silica particles), a value measured by a liquid displacement method using ethanol as a displacement liquid may be adopted.

The BET diameter of the abrasive grains (typically silica particles) is not particularly limited, but from the viewpoint of polishing efficiency and the like, it is preferably 5 nm or more, more preferably 10 nm or more. From the viewpoint of obtaining higher polishing effects (for example, haze reduction, defect removal, etc. effects), the BET diameter is preferably 15 nm or more, and more preferably 20 nm or more (for example, more than 20 nm). Further, from the viewpoint of preventing scratches, etc., the BET diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and still more preferably 40 nm or less. In some embodiments, the BET diameter of the abrasive grains may be less than 35 nm, less than 32 nm, or less than 30 nm, from the viewpoint of making it easier to obtain a surface with a lower haze.

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

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

Although not particularly limited, the average value of the long axis/breadth axis ratio (average aspect ratio) of the abrasive grains is in principle 1.0 or more, preferably 1.05 or more, more preferably 1.1 or more. It is. Higher polishing efficiency can be achieved by increasing the average aspect ratio. Further, the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and even 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 determined, for example, by observation using an electron microscope. A specific procedure for determining the average aspect ratio is, for example, using a scanning electron microscope (SEM) to examine each particle of a predetermined number (for example, 200) of abrasive grains that allow the shapes of independent particles to be recognized. Draw the smallest rectangle circumscribing the image. Then, for the rectangle drawn for each particle image, the length of the long side (value of the major axis) is divided by the length of the short side (value of the minor axis), and the value is calculated as the major axis / minor axis ratio (aspect ratio). ). The average aspect ratio can be determined by arithmetic averaging the aspect ratios of the predetermined number of particles.

<Water-soluble polymer>
The polishing composition disclosed herein contains a water-soluble polymer. Water-soluble polymers can be useful for protecting the surface of the object to be polished, improving the wettability of the surface of the object to be polished after polishing, and the like.

(Water-soluble polymer having a structural unit derived from N-(meth)acryloylmorpholine)
The polishing composition disclosed herein includes a water-soluble polymer (morpholine polymer) having a structural unit derived from N-(meth)acryloylmorpholine. Such structural units have excellent usability because their hydrolyzability under alkaline conditions is sufficiently suppressed. For example, at pH 10.0 and 25° C., hydrolysis can be almost 100% inhibited for at least 2 months. Further, such structural units exhibit appropriate adsorption properties to abrasive grains and wafers. Therefore, a water-soluble polymer compound mainly composed of the above structural units exhibits excellent alkali resistance and good etching resistance even when forming a polishing composition together with a basic compound or the like. Furthermore, a polymer having such a structural unit can disperse abrasive grains well even if it has a high molecular weight (for example, a weight average molecular weight of about 300,000 or more, or even about 600,000 or more).

The morpholine polymer preferably has a structural unit derived from N-(meth)acryloylmorpholine of 10 mol% or more and 100 mol% or less, more preferably, for example, 20 mol% or more, 30 mol% or more, and 40 mol%. The amount is 50 mol% or more. More preferably, it is 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, 98 mol% or more, 99 mol% or more, and 100 mol%. In some embodiments, the morpholine polymer contains structural units derived from N-(meth)acryloylmorpholine, for example, 50 mol% or more and 100 mol% or less, preferably 70 mol% or more and 100 mol%, and more preferably 90 mol% or more and 100 mol%. Those having the following range can be used.

In addition to the structural unit, the morpholine polymer can have other monomer-derived structural units copolymerizable with the structural unit. Other monomers are not particularly limited, but examples include (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. ) Acrylic acid alkyl esters; (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid and other unsaturated acids and their alkyl esters; unsaturated acid anhydrides such as maleic anhydride; 2-acrylamide Sulfonic acid group-containing monomers such as -2-methylpropanesulfonic acid and its salts; methyl (meth)acrylamide, ethyl (meth)acrylamide, n-propyl (meth)acrylamide, isopropyl (meth)acrylamide, n-butyl ( N-alkyl (meth)acrylamides such as meth)acrylamide and 2-ethylhexyl (meth)acrylamide; methylaminopropyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, ethylaminopropyl (meth)acrylamide and diethylaminopropyl (meth)acrylamide (di)alkylaminoalkylamides such as acrylamide; (di)alkylaminoalkyls such as methylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, ethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; (Meth)acrylates; Aromatic vinyl compounds such as styrene, vinyltoluene and vinylxylene; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-hexyl Alkyl vinyl ethers having an alkyl group having 1 to 10 carbon atoms, such as vinyl ether, 2-ethylhexyl vinyl ether, n-octyl vinyl ether, n-nonyl vinyl ether, and n-decyl vinyl ether; vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate , vinyl ester compounds such as vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl piperate, and vinyl versatate; α-olefins such as ethylene, propylene, and butylene; One type or two or more types can be used.

The amount of other monomers used in the morpholine polymer can be in the range of 0 mol% to 90 mol%, for example, 0 mol% to 50 mol%, 0 mol% to 30 mol%, 0 mol% to 20 mol%. Hereinafter, the range of 0 mol% or more and 10 mol% or less is more preferable. When the amount of other monomers used is 50 mol% or less, the amount of N-(meth)acryloylmorpholine used is 50 mol% or more, and the effect of using the morpholine polymer in the polishing composition disclosed herein is It tends to perform better. For example, the effect of improving haze can be better exhibited.

The weight average molecular weight _MwA of the morpholine polymer is not particularly limited, but can be, for example, 10,000 or more, preferably 50,000 or more, and more preferably 100,000 or more. It is preferable that Mw _A is 10,000 or more from the viewpoint of sufficiently protecting the surface of the wafer. The weight average molecular weight _MwA of the morpholine polymer is not particularly limited, but can be, for example, 1,000,000 or less, preferably 800,000 or less, and more preferably 700,000 or less. be. It is preferable that Mw _A is 1,000,000 or less from the viewpoint of dispersibility of abrasive grains. Further, the number average molecular weight Mn _A of the morpholine polymer is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more. The number average molecular weight Mn _A of the morpholine polymer is, for example, preferably 300,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less. In addition, in this specification, the weight average molecular weight and number average molecular weight of the water-soluble polymer and the surfactant described below are values based on aqueous gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent) or from chemical formulas. The calculated molecular weight can be used. As the GPC measuring device, it is preferable to use the model name "HLC-8320GPC" manufactured by Tosoh Corporation. The measurement can be performed, for example, under the following conditions. A similar method is adopted for the embodiments described below.
[GPC measurement conditions]
Sample concentration: 0.1% by weight
Column: TSKgel GMPWXL
Detector: Differential refractometer Eluent: 100mM sodium nitrate aqueous solution/acetonitrile = 10-8/0-2
Flow rate: 1 mL/min Measurement temperature: 40°C
Sample injection volume: 200μL

Further, it is preferable that the molecular weight distribution (PDI) of the morpholine polymer is narrow. Specifically, the value obtained by dividing the weight average molecular weight Mw _A by the number average molecular weight Mn _A is preferably 4.0 or less, more preferably 3.5 or less, and 3.0 or less. More preferred. A molecular weight distribution (PDI) of 4.0 or less is advantageous from the viewpoint of exhibiting sufficient surface protection and avoiding deterioration in the dispersibility of abrasive grains caused by high molecular weight substances.

Morpholine polymers can be obtained by known methods or commercially available.

The content _WA (content on a weight basis) of the morpholine polymer in the polishing composition is not particularly limited. For example, it can be set to 1.0×10 ⁻⁴ % by weight or more. From the viewpoint of reducing haze, etc., the content is preferably 5.0×10 ⁻⁴ % by weight or more, more preferably 1.0×10 ⁻³ % by weight or more, and even more preferably 2.0×10 ⁻³ % by weight. That's all. For example, it may be 5.0 x 10 ^-3 weight % or more, 8.0 x 10 ^-3 weight % or more, 9.0 x 10 ^-3 weight % or more, and 1.0 x 10 ^-2 weight %. % or more. Further, from the viewpoint of polishing rate, etc., the content W _A is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and 0.05% by weight or less (for example, 0.2% by weight or less). 02% by weight or less) is more preferable. In addition, when the polishing composition contains two or more types of morpholine polymers, the content W _A refers to the total content (weight-based content) of all the morpholine polymers contained in the polishing composition. It refers to

The content of the morpholine polymer (if two or more types of morpholine polymers are included, the total amount thereof) can also be specified by the relative relationship with the abrasive grain. Although not particularly limited, in some embodiments, the content of the morpholine polymer relative to 100 parts by weight of abrasive grains can be, for example, 0.01 parts by weight or more, and from the viewpoint of reducing haze, etc. It is appropriate that the amount is at least 0.5 parts by weight, more preferably at least 1 part by weight, even more preferably at least 3 parts by weight. For example, the amount may be 4 parts by weight or more, 5 parts by weight or more, or 6 parts by weight or more. Further, the content of the morpholine polymer based on 100 parts by weight of the abrasive grains may be, for example, 50 parts by weight or less, or 30 parts by weight or less. From the viewpoint of dispersion stability of the polishing composition, in some embodiments, the content of the morpholine polymer relative to 100 parts by weight of the abrasive grains is suitably 15 parts by weight or less, preferably 10 parts by weight. The amount is more preferably 8 parts by weight or less, and may be 7 parts by weight or less.

(vinyl alcohol polymer)
The polishing composition disclosed herein includes a vinyl alcohol polymer as a water-soluble polymer. As the vinyl alcohol polymer, a water-soluble organic substance (typically a water-soluble polymer) containing a vinyl alcohol unit as a repeating unit is used. Here, the vinyl alcohol unit (hereinafter also referred to as "VA unit") is a structural moiety represented by the following chemical formula: -CH ₂ -CH(OH)-; The vinyl alcohol polymer may contain only VA units as repeating units, or may contain repeating units other than VA units (hereinafter also referred to as "non-VA units") in addition to VA units. The vinyl alcohol polymer may be a random copolymer containing VA units and non-VA units, or may be a block copolymer or a graft copolymer. The vinyl alcohol polymer may contain only one type of non-VA unit, or may contain two or more types of non-VA units.

The vinyl alcohol polymer used in the polishing composition disclosed herein may be unmodified polyvinyl alcohol (unmodified PVA) or modified polyvinyl alcohol (modified PVA). Here, unmodified PVA is produced by hydrolyzing (saponifying) polyvinyl acetate, and contains repeating units (-CH ₂ -CH(OCOCH ₃ )-) of vinyl polymerized structure of vinyl acetate and non-VA units. A vinyl alcohol polymer that does not substantially contain repeating units. The degree of saponification of the unmodified PVA may be, for example, 60% or more, and from the viewpoint of water solubility, it may be 70% or more, 80% or more, or 90% or more. In some embodiments, unmodified PVA having a saponification degree of 95% or more or 98% or more can be preferably employed as the water-soluble polymer compound.

Examples of non-VA units that can be included in modified PVA include repeating units derived from N-vinyl type monomers and N-(meth)acryloyl type monomers, repeating units derived from ethylene, and repeating units derived from alkyl vinyl ethers, which will be described later. units, repeating units derived from vinyl esters of monocarboxylic acids having 3 or more carbon atoms, and the like, but are not limited thereto. A preferred example of the N-vinyl type monomer is N-vinylpyrrolidone. A suitable example of the N-(meth)acryloyl type monomer is N-(meth)acryloylmorpholine. The alkyl vinyl ether may be a vinyl ether having an alkyl group having 1 to 10 carbon atoms, such as propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, and the like. The vinyl ester of a monocarboxylic acid having 3 or more carbon atoms is a vinyl ester of a monocarboxylic acid having 3 or more carbon atoms and 7 or less carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, vinyl hexanoate, etc. obtain.

The vinyl alcohol polymer has VA units and at least one group selected from oxyalkylene groups, carboxy groups, sulfo groups, amino groups, hydroxyl groups, amide groups, imide groups, nitrile groups, ether groups, ester groups, and salts thereof. It may also be a modified PVA containing a non-VA unit having a structure. Further, the vinyl alcohol polymer may be modified PVA in which a portion of VA units contained in the vinyl alcohol polymer are acetalized with aldehyde. As the aldehyde, for example, an alkyl aldehyde can be preferably used, and an alkyl aldehyde having an alkyl group having 1 or more and 7 or less carbon atoms is preferable, and n-butyraldehyde is particularly preferable. As the vinyl alcohol polymer, cationically modified polyvinyl alcohol into which a cationic group such as a quaternary ammonium structure has been introduced may be used. The above-mentioned cation-modified polyvinyl alcohol is introduced with a cationic group derived from a monomer having a cationic group such as diallyldialkylammonium salt, N-(meth)acryloylaminoalkyl-N,N,N-trialkylammonium salt, etc. The following are examples of what has been done.

The ratio of the number of moles of VA units to the number of moles of all repeating units constituting the vinyl alcohol polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. . Although not particularly limited, in some embodiments, the molar ratio of the VA units may be 50% or more, 65% or more, 75% or more, 80% or more, It may be 90% or more (for example, 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the vinyl alcohol polymer may be VA units. Here, "substantially 100%" means that the vinyl alcohol polymer does not contain non-VA units, at least intentionally, and typically the number of moles of non-VA units relative to the number of moles of all repeating units. The ratio is less than 2% (for example, less than 1%), including the case where it is 0%. 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 vinyl alcohol polymer may be, for example, 95% or less, may be 90% or less, or may be 80% or less. It may be 70% or less.

The content of VA units (content on a weight basis) in the vinyl alcohol polymer may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight or more. Although not particularly limited, in some embodiments, the content of the VA unit may be 50% by weight or more (for example, more than 50% by weight), 70% by weight or more, and 80% by weight or more (for example, more than 50% by weight). For example, it may be 90% by weight or more, 95% by weight or more, or 98% by weight or more). Substantially 100% by weight of the repeating units constituting the vinyl alcohol polymer may be VA units. Here, "substantially 100% by weight" means that at least intentionally no non-VA units are contained as repeating units constituting the vinyl alcohol-based polymer, and typically non-VA units in the vinyl alcohol-based polymer. This means that the content of is less than 2% by weight (for example, less than 1% by weight). In some other embodiments, the content of VA units in the vinyl alcohol 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 vinyl alcohol polymer may contain a plurality of polymer chains having different contents of VA units in the same molecule. Here, the polymer chain refers to a portion (segment) that constitutes a part of one molecule of polymer. For example, vinyl alcohol-based polymers have a polymer chain A with a content of VA units greater than 50% by weight and a content of VA units less than 50% by weight (i.e. a content of non-VA units greater than 50% by weight). ) may be included in the same molecule.

Polymer chain A may contain only VA units as repeating units, or may contain non-VA units in addition to VA units. The content of VA units in 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 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.

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

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

Examples of polymer chain B include a polymer chain whose main repeating unit is a repeating unit derived from an N-vinyl type monomer, and a polymer chain whose main repeating unit is a repeating unit derived from an N-(meth)acryloyl type monomer. , a polymer chain having an oxyalkylene unit as a main repeating unit, and the like. In addition, in this specification, the main repeating unit refers to a repeating unit contained in an amount exceeding 50% by weight, unless otherwise specified.

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 type polymer chain. The content of repeating units derived from N-vinyl monomers in the N-vinyl polymer chain is typically more than 50% by weight, may be 70% by weight or more, and may be 85% by weight or more. The content may be 95% by weight or more. Substantially all of the polymer chain B may be repeating units derived from N-vinyl type monomers.

In this specification, examples of N-vinyl type monomers include monomers having nitrogen-containing heterocycles (eg, lactam rings) and N-vinyl linear amides. Specific examples of N-vinyllactam type monomers include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl- Examples include 3,5-morpholinedione. Specific examples of the N-vinyl chain amide include N-vinylacetamide, N-vinylpropionamide, N-vinylbutyric acid amide, and the like. Polymer chain B is, for example, an N-vinyl polymer chain in which more than 50% by weight (for example, 70% or more, or 85% or more, or 95% or more) of its repeating units are N-vinylpyrrolidone units. obtain. Substantially all of the repeating units constituting polymer chain B may be N-vinylpyrrolidone units.

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

In this specification, examples of N-(meth)acryloyl type monomers include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. Examples of linear amides having an N-(meth)acryloyl group include (meth)acrylamide; N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl( N-alkyl (meth)acrylamide such as meth)acrylamide, Nn-butyl(meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide ) acrylamide, N,N-dialkyl (meth)acrylamide such as N,N-diisopropyl (meth)acrylamide, 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.

Other examples of the polymer chain B include a polymer chain containing an oxyalkylene unit as a main repeating unit, that is, an oxyalkylene-based polymer chain. The content of oxyalkylene units 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 polymer chain B may be oxyalkylene units.

Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxybutylene units, and the like. Each such oxyalkylene unit can be a repeating unit derived from the corresponding alkylene oxide. The number of oxyalkylene units contained in the oxyalkylene polymer chain may be one type, or two or more types. For example, it may be an oxyalkylene polymer chain containing a combination of oxyethylene units and oxypropylene units. In an oxyalkylene polymer chain containing two or more types of oxyalkylene units, those oxyalkylene units may be random copolymers of corresponding alkylene oxides, block copolymers, or graft copolymers. Good too.

Still other examples of polymer chain B include polymer chains containing repeating units derived from alkyl vinyl ethers (e.g. vinyl ethers having an alkyl group having 1 to 10 carbon atoms), monocarboxylic acid vinyl esters (e.g. vinyl ethers having an alkyl group having 1 to 10 carbon atoms); Polymer chains containing repeating units derived from (vinyl esters of monocarboxylic acids of 3 or more), in which some of the VA units are acetalized with aldehydes (e.g., alkyl aldehydes having an alkyl group having 1 to 7 carbon atoms) Examples thereof include a polymer chain, a polymer chain into which a cationic group (for example, a cationic group having a quaternary ammonium structure) is introduced, and the like.

As the vinyl alcohol polymer in the polishing composition disclosed herein, unmodified PVA, modified PVA, or a combination of unmodified PVA and modified PVA may be used. In an embodiment in which unmodified PVA and modified PVA are used in combination, the amount of modified PVA used relative to the total amount of vinyl alcohol polymer contained in the polishing composition may be, for example, less than 50% by weight, and may be 30% by weight or less. , 10% by weight or less, 5% by weight or less, or 1% by weight or less. The polishing composition disclosed herein can be preferably implemented, for example, in an embodiment using only one or more types of unmodified PVA as the vinyl alcohol polymer.

In the polishing composition disclosed herein, the relationship between the content W _A of the morpholine polymer (content on a weight basis) and the content W _B (content on a weight basis) of the vinyl alcohol polymer is expressed by the following formula: W _A /(W _A +W _B )>0.900; is satisfied. By lowering the ratio of the content of the vinyl alcohol polymer to the content of the morpholine polymer, the ability to improve haze can be better exhibited. W _A /(W _A +W _B ) may be, for example, 0.910 or more, 0.920 or more, or 0.930 or more. Further, the value of the formula: _WA / ( _WA + _WB ) is in principle less than 1.000. In some embodiments, the value of W _A /(W _A +W _B ) may be, for example, 0.999 or less, 0.980 or less, or 0.965 or less.

The reason why the haze improvement performance described above is obtained is not particularly limited, but the reason is that morpholine polymer and vinyl alcohol polymer have different adsorption properties to abrasive grains and the object to be polished (silicon wafer in this case). By setting the content ratio in a specific range, it is possible to proceed with polishing while appropriately protecting the object to be polished during polishing, and furthermore, by improving the wettability of the surface of the object to be polished after polishing, haze can be reduced. is considered to be effectively improved.

The content W _B (content on a weight basis) of the vinyl alcohol polymer used in the polishing composition disclosed herein is not particularly limited. In some embodiments, from the viewpoint of improving polishing performance and surface quality, the content W _B may be, for example, 0.1×10 ⁻⁴ % by weight or more, and is usually 0.3×10 ⁻⁴ % by weight. % or more, preferably 0.5 x 10 ^-4 weight % or more, more preferably 0.8 x 10 ^-4 weight % or more, for example 1 x 10 ^-4 weight % or more, and for example 2 ×10 ⁻⁴ % by weight or more. Furthermore, from the viewpoint of polishing performance, surface quality improvement, cleanability, etc., the content W _B is preferably 50×10 ⁻⁴ % by weight or less, more preferably 30×10 ⁻⁴ % by weight or less. , more preferably 15×10 ⁻⁴ % by weight or less (for example, 10×10 ⁻⁴ % by weight or less, further, eg, 8×10 ⁻⁴ % by weight or less, further, eg, 6×10 ⁻⁴ % by weight or less). In addition, when the polishing composition contains two or more types of vinyl alcohol polymers, the content _W refers to the total content of all vinyl alcohol polymers contained in the polishing composition. .

The content of the vinyl alcohol polymer can also be specified by its relative relationship with the abrasive grains. Although not particularly limited, in some embodiments, the content of the vinyl alcohol polymer based on 100 parts by weight of abrasive grains can be, for example, 0.001 parts by weight or more, and 0.001 parts by weight or more from the viewpoint of reducing haze. 0.005 parts by weight or more, preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, still more preferably 0.1 parts by weight or more, for example 0.2 parts by weight or more. . Further, the content of the vinyl alcohol polymer based on 100 parts by weight of the abrasive grains may be, for example, 30 parts by weight or less, or 10 parts by weight or less. From the viewpoint of dispersion stability of the polishing composition, in some embodiments, it is appropriate that the content of the vinyl alcohol polymer is 5 parts by weight or less, preferably 3 parts by weight, based on 100 parts by weight of the abrasive grains. part by weight or less, may be less than 1 part by weight, may be less than 0.5 part by weight, or may be less than 0.4 part by weight.

The weight average molecular weight (Mw _B ) of the vinyl alcohol polymer used in the polishing composition disclosed herein is not particularly limited. The Mw _B of the vinyl alcohol polymer is usually suitably 100×10 ⁴ or less, preferably 30×10 ⁴ or less, and may be 20×10 ⁴ or less. From the viewpoint of detergency, in some embodiments, the Mw _B of the vinyl alcohol polymer may be 15×10 ⁴ or less, or 10×10 ⁴ or less. Further, the Mw _B of the vinyl alcohol polymer is usually suitably 2×10 ³ or more, and may be 5×10 ³ or more, or 1×10 ⁴ or more. As the Mw _B of the vinyl alcohol polymer increases, the effect of protecting the object to be polished and improving wettability tends to increase. From this point of view, the Mw _B of the vinyl alcohol polymer used in the polishing composition disclosed herein is preferably greater than 1×10 ⁴ , more preferably 2×10 ⁴ or more, and 4 It may be ×10 ⁴ or more, 5 × 10 ⁴ or more, 6 × 10 ⁴ or more, or 6.5 × 10 ⁴ or more.

(Other water-soluble polymers)
The polishing composition disclosed herein may contain other water-soluble polymers, i.e., water-soluble polymers other than morpholine polymers and vinyl alcohol polymers, as necessary, to the extent that the effects of the present invention are not significantly impaired. It may further contain. Other water-soluble polymers can be appropriately selected from water-soluble polymers known in the field of polishing compositions. Examples of other water-soluble polymers include synthetic polymers such as polymers containing oxyalkylene units and polymers containing nitrogen atoms; polymers derived from natural products such as cellulose derivatives and starch derivatives; and the like.

Polymers containing oxyalkylene units include polyethylene oxide (PEO), block copolymers of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and random copolymers of EO and PO or BO. Examples include merging. Among these, block copolymers of EO and PO or random copolymers of EO and PO are preferred. The block copolymer of EO and PO may be a diblock, triblock, or the like containing a PEO block and a polypropylene oxide (PPO) block. Examples of the triblock body include a PEO-PPO-PEO type triblock body and a PPO-PEO-PPO type triblock body. Among these, a PEO-PPO-PEO type triblock is more preferred.
In a block copolymer or random copolymer of EO and PO, the molar ratio (EO/PO) of EO and PO constituting the copolymer is determined from the viewpoint of solubility in water, washability, etc. It is preferably larger than 1, more preferably 2 or more, and even more preferably 3 or more (for example, 5 or more).

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

Cellulose derivatives are polymers containing β-glucose units as main repeating units, such as methylcellulose, ethylcellulose, hydroxyethylcellulose (HEC), methylhydroxyethylcellulose, and the like. Furthermore, starch derivatives are polymers containing α-glucose units as main repeating units, such as pregelatinized starch, pullulan, carboxymethyl starch, cyclodextrin, and the like.

In the technology disclosed herein, the molecular weight of other water-soluble polymers is not particularly limited. The weight average molecular weight (Mw _C ) of the other water-soluble polymers may be, for example, 100×10 ⁴ or less, and from the viewpoint of cleaning properties, 60×10 ⁴ or less is usually appropriate, and 30×10 ⁴ or less It may be preferably 20×10 ⁴ or less, for example 10×10 ⁴ or less, typically 8×10 ⁴ or less. Further, from the viewpoint of protecting the object to be polished, the Mw _C of the other water-soluble polymer may be, for example, 2000 or more, and is usually preferably 5000 or more. In some embodiments, Mw _C is suitably 1.0×10 ⁴ or more, preferably 1.5×10 ⁴ or more, more preferably 2×10 ⁴ or more, still more preferably 3×10 ⁴ or more, e.g. It is 4×10 ⁴ or more, typically 5×10 ⁴ or more.

Other water-soluble polymers can be used alone or in combination of two or more. Although not particularly limited, the relationship between the total amount of morpholine polymer and vinyl alcohol polymer in the polishing composition and the amount of other water-soluble polymers used may be, for example, 5:95 to 5:95 by weight. The ratio may be 95:5, 10:90 to 90:10, or 25:75 to 75:25. In some embodiments, the weight ratio (total content of morpholine polymer and vinyl alcohol polymer: content of other water-soluble polymers) may be, for example, 50:50 to 100:0:20, The ratio may be 80:20 to 100:0 or 90:10 to 100:0.

From the viewpoint of reducing aggregates and improving washability, nonionic polymers can be preferably employed as other water-soluble polymers. Furthermore, from the viewpoint of ease of control of chemical structure and purity, synthetic polymers can be preferably employed as other water-soluble polymers. The polishing composition disclosed herein can be preferably implemented in an embodiment in which polymers derived from natural products are not substantially used as other water-soluble polymers. Moreover, the polishing composition disclosed herein can be preferably implemented in an embodiment in which water-soluble polymers other than morpholine-based polymers and vinyl alcohol-based polymers are not substantially used. Here, "substantially not used" means that the amount used is typically 3 parts by weight or less, preferably 1 part by weight or less, based on 100 parts by weight of the total content of the morpholine polymer and vinyl alcohol polymer. Good, including 0 parts by weight or below the detection limit.

(Content of water-soluble polymer)
The content (weight-based content) of the water-soluble polymer in the polishing composition is not particularly limited. For example, it can be set to 1.0×10 ⁻⁴ % by weight or more. From the viewpoint of reducing haze, etc., the content is preferably 5.0×10 ⁻⁴ % by weight or more, more preferably 1.0×10 ⁻³ % by weight or more, and even more preferably 2.0×10 ⁻³ % by weight. For example, it is 5.0×10 ^-3 % by weight or more. In addition, from the viewpoint of polishing rate, etc., the above content is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and 0.05% by weight or less (for example, 0.02% by weight or less). % or less) is more preferable. In addition, when the polishing composition contains two or more types of water-soluble polymers, the above content refers to the total content (content on a weight basis) of all water-soluble polymers contained in the polishing composition. It refers to

The content of the water-soluble polymer (if two or more types of water-soluble polymers are included, the total amount thereof) can also be specified by the relative relationship with the abrasive grain. Although not particularly limited, in some embodiments, the content of the water-soluble polymer relative to 100 parts by weight of abrasive grains can be, for example, 0.01 parts by weight or more, and 0.01 parts by weight or more from the viewpoint of reducing haze. The amount is suitably 1 part by weight or more, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 3 parts by weight or more. Further, the content of the water-soluble polymer relative to 100 parts by weight of the abrasive grains may be, for example, 50 parts by weight or less, or 30 parts by weight or less. From the viewpoint of dispersion stability of the polishing composition, in some embodiments, the content of water-soluble polymer per 100 parts by weight of abrasive grains is suitably 15 parts by weight or less, preferably 10 parts by weight. parts by weight or less, more preferably 8 parts by weight or less, and may be 7 parts by weight or less.

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

Specific examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, and the like. Specific examples of carbonates or hydrogen carbonates 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, anhydrous piperazine. , piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, and azoles such as imidazole and triazole. Specific examples of quaternary phosphonium compounds include quaternary phosphonium hydroxides such as tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide.

As the quaternary ammonium compound, quaternary ammonium salts (typically strong bases) such as tetraalkylammonium salts and hydroxyalkyltrialkylammonium salts can be preferably used. The anionic component in such quaternary ammonium salts can be, for example, OH ⁻ , F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , BH ₄ ⁻ and the like. Among these, preferred examples include quaternary ammonium salts in which the anion is OH ^- , ie, quaternary ammonium hydroxide. Specific examples of quaternary ammonium hydroxide include 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 hydroxides, quaternary ammonium hydroxides, and ammonia can be preferably used. Among these, tetraalkylammonium hydroxide (eg, tetramethylammonium hydroxide) and ammonia are more preferred, and ammonia is particularly preferred.

<Surfactant>
The polishing composition disclosed herein may contain a surfactant, if necessary. By containing a surfactant in the polishing composition, haze on the surface of the polishing object after polishing can be better reduced. As the surfactant, any of anionic, cationic, nonionic, and amphoteric surfactants can be used. Usually, anionic or nonionic surfactants can be preferably employed. From the viewpoint of low foaming properties and ease of pH adjustment, nonionic surfactants are more preferred. For example, oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol; polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene glyceryl ether fatty acid Polyoxyalkylene derivatives (e.g. polyoxyalkylene adducts) such as esters and polyoxyethylene sorbitan fatty acid esters; copolymers of multiple types of oxyalkylenes (e.g. diblock copolymers, triblock copolymers, Nonionic surfactants such as random copolymers, alternating copolymers); The surfactant preferably includes a surfactant containing a polyoxyalkylene structure. Surfactants can be used alone or in combination of two or more.

Specific examples of nonionic surfactants containing a polyoxyalkylene structure include block copolymers (diblock type copolymers, PEO (polyethylene oxide)-PPO) of ethylene oxide (EO) and propylene oxide (PO); (Polypropylene oxide)-PEO triblock, PPO-PEO-PPO triblock copolymer, etc.), random copolymer 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, polyoxy Ethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, poly Oxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monostearin Acid ester, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, mono Examples include polyoxyethylene sorbitan oleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil. Among these, preferred surfactants include block copolymers of EO and PO (particularly PEO-PPO-PEO type triblock copolymers), random copolymers of EO and PO, and polyoxyethylene alkyl ethers ( For example, polyoxyethylene decyl ether) can be mentioned.

The weight average molecular weight (Mws) of the surfactant is typically less than 2,000, and preferably 1,900 or less (for example, less than 1,800) from the viewpoint of filterability, washability, etc. Further, the Mws of the surfactant is usually suitably 200 or more from the viewpoint of surfactant ability, etc., and preferably 250 or more (for example, 300 or more) from the viewpoint of haze reduction effect. A more preferable range of Mws of the surfactant may vary depending on the type of the surfactant. For example, when polyoxyethylene alkyl ether is used as a surfactant, its Mws is preferably 1,500 or less, and may be 1,000 or less (for example, 500 or less). Further, for example, when a PEO-PPO-PEO type triblock copolymer is used as a surfactant, its Mws may be, for example, 500 or more, 1000 or more, and even 1200 or more. Good too.

When the polishing composition disclosed herein contains a surfactant, its content is not particularly limited as long as it does not significantly impede the effects of the present invention. Normally, from the viewpoint of cleaning properties, it is appropriate to keep the content of surfactant to 100 parts by weight of abrasive grains at 20 parts by weight or less, preferably 15 parts by weight or less, and 10 parts by weight or less (for example, 6 parts by weight). part or less) is more preferable. From the viewpoint of better demonstrating the effect of using the surfactant, the surfactant content per 100 parts by weight of abrasive grains is suitably 0.001 parts by weight or more, preferably 0.005 parts by weight or more, and 0.01 parts by weight or more. It may be at least 0.05 part by weight or more.

When the polishing composition disclosed herein contains a surfactant, the weight ratio between the morpholine polymer content _WA and the surfactant content W _S (W _A /W _S ) is not particularly limited. , for example, in the range of 0.01 to 200, usually preferably in the range of 0.05 to 100, and more preferably in the range of 0.1 to 80. Further, the weight ratio (W _B /W _S ) between the vinyl alcohol polymer content W _B and the surfactant content W _S is not particularly limited, and may be in the range of 0.01 to 100, for example. , usually preferably in the range of 0.05 to 50, more preferably in the range of 0.1 to 10 (for example, in the range of 0.1 to 6). Further, the weight ratio (W _T /W _S ) between the total content W _T of the morpholine polymer and the vinyl alcohol polymer and the content W _S of the surfactant is not particularly limited, and is, for example, in the range of 1 to 200. Usually, the range is preferably from 10 to 100, and more preferably from 20 to 80.
Alternatively, from the viewpoint of simplifying the composition, the polishing composition disclosed herein may be preferably implemented in an embodiment substantially free of surfactant.

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

<Other ingredients>
The polishing composition disclosed herein may contain polishing compositions such as organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, antifungal agents, etc., to the extent that the effects of the present invention are not significantly impaired. If necessary, it may further contain known additives that can be used in polishing products (typically, polishing compositions used in the final polishing process of silicon wafers). Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid; aromatic carboxylic acids such as benzoic acid and phthalic acid; citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid; Examples include sulfonic acid and organic phosphonic acid. Examples of organic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of organic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, and the like. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of inorganic acids. Organic acids and their salts, and inorganic acids and their salts can be used singly or in combination of two or more. Examples of preservatives and antifungal agents include isothiazoline compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

It is preferable that the polishing composition disclosed herein does not substantially contain an oxidizing agent. This is because if the polishing composition contains an oxidizing agent, the surface of the silicon wafer to be polished will be oxidized to form an oxide film, which will lengthen the required polishing time. Specific examples of the oxidizing agent herein include hydrogen peroxide (H ₂ O ₂ ), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, and the like. Note that the term "the polishing composition does not substantially contain an oxidizing agent" means that the polishing composition does not contain an oxidizing agent, at least intentionally. Therefore, 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, depending on the raw materials, manufacturing method, etc. A polishing composition that inevitably contains an oxidizing agent of mol/L or less, particularly preferably 0.000001 mol/L or less is the concept of a polishing composition that does not substantially contain an oxidizing agent. can be included in

<pH>
The pH of the polishing composition disclosed herein is typically 8.0 or higher, preferably 8.5 or higher, and more preferably 9.0 or higher. As the pH of the polishing composition increases, polishing efficiency tends to improve. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (for example, silica particles) and suppressing a decrease in mechanical polishing action, it is appropriate that the pH of the polishing composition is usually 12.0 or less, and 11. It is preferably at most .0, more preferably at most 10.8, even more preferably at most 10.5.

To measure the pH, use a pH meter (for example, Horiba's glass electrode hydrogen ion concentration indicator (model number F-23)), and use a standard buffer solution (phthalate pH buffer pH: 4.01 (25°C)). , neutral phosphate pH buffer pH: 6.86 (at 25°C), and carbonate pH buffer at pH 10.01 (at 25°C)). It can be determined by adding it to the composition and measuring the value after it has stabilized for 2 minutes or more.

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

<Concentrated liquid>
The polishing composition disclosed herein may be in a concentrated form (that is, in the form of a concentrated polishing liquid) before being supplied to the object to be polished. The polishing composition in such a concentrated form is advantageous from the viewpoint of convenience and cost reduction during manufacturing, distribution, storage, and the like. The concentration ratio is not particularly limited, and can be, for example, about 2 times to 100 times in terms of volume, and usually about 5 times to 50 times (for example, about 10 times to 40 times) is appropriate.
Such a concentrated liquid can be diluted at a desired timing to prepare a polishing liquid (working slurry), and the polishing liquid can be used in such a manner as to be 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 concentrate can be, for example, 25% by weight or less. From the viewpoint of dispersion stability and filterability of the polishing composition, the content is usually preferably 20% by weight or less, more preferably 15% by weight or less. In one preferred embodiment, the content of abrasive grains may be 10% by weight or less, or 5% by weight or less. Further, from the viewpoint of convenience and cost reduction during manufacturing, distribution, storage, etc., the content of abrasive grains in the concentrate can be, for example, 0.1% by weight or more, preferably 0.5% by weight. % or more, more preferably 0.7% by weight or more, still more preferably 1% by weight or more.

<Preparation of polishing composition>
The polishing composition used in the technique disclosed herein may be of a single-component type or a multi-component type such as a two-component type. For example, part A containing at least abrasive grains among the constituent components of the polishing composition and part B containing at least a portion of the remaining components are mixed, and these are mixed and diluted at appropriate timing as necessary. The polishing liquid may be prepared by the polishing liquid.

The method for preparing the polishing composition is not particularly limited. For example, each component constituting the polishing composition may be mixed using a well-known mixing device such as a blade stirrer, an ultrasonic disperser, or a homomixer. The manner 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.

<Application>
The polishing composition disclosed herein can be used for polishing a polishing object (silicon wafer) made of single crystal silicon. The shape of the object to be polished is not particularly limited. The polishing composition disclosed herein is preferably applied, for example, to polishing a flat object to be polished, such as a plate or polyhedron, or to polishing an edge of the object (for example, polishing a wafer edge). obtain.

The polishing composition disclosed herein can be preferably used for final polishing of an object to be polished. Therefore, according to this specification, a method for manufacturing a polished article (for example, a method for manufacturing a silicon wafer) including a final polishing step using the polishing composition described above is provided. Note that the final polishing refers to the final polishing step in the process of manufacturing the target product (that is, a step in which no further polishing is performed after that step). The polishing composition disclosed herein also includes a polishing step upstream of the final polishing (refers to a preliminary polishing step between the rough polishing step and the final polishing step, typically including at least a primary polishing step). , and may further include secondary, tertiary, etc. polishing steps), for example, it may be used in a polishing step performed immediately before final polishing.

The polishing composition disclosed herein can be particularly preferably used for polishing silicon wafers. For example, it is suitable as a polishing composition used in final polishing of silicon wafers or in polishing steps upstream therefrom. For example, it is effective to apply it to polishing (typically final polishing or polishing immediately before polishing) of a silicon wafer whose surface has been prepared to have a surface roughness of 0.01 nm to 100 nm by an upstream process. Application to finishing polishing is particularly preferred.

<Polishing>
The polishing composition disclosed herein can be used for polishing an object to be polished, for example, in a mode including the following operations. Hereinafter, one preferred embodiment of a method for polishing a silicon wafer as an object to be polished using the polishing composition disclosed herein will be described.
That is, a polishing liquid containing one of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include preparing the polishing liquid by subjecting the polishing composition to operations such as concentration adjustment (for example, dilution) and pH adjustment. Alternatively, the polishing composition may be used as it is as a polishing liquid.

Next, the polishing liquid is supplied to the object to be polished, and the object is polished by a conventional method. For example, when final polishing a silicon wafer, typically the silicon wafer that has undergone the lapping 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, a polishing pad is pressed against the surface of the silicon wafer to be polished, and the two are moved relative to each other (for example, rotated). After this polishing step, polishing of the object to be polished is completed.

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

A polishing object polished using the polishing composition disclosed herein is typically cleaned. Cleaning can be performed using a suitable cleaning solution. The cleaning solution 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 is common in the field of semiconductors, etc.) is used. A mixed solution of HCl, H 2 O 2 and H 2 O), an SC-2 cleaning solution (a mixed solution of HCl, H ₂ O ₂ and H ₂ O), etc. can be used. The temperature of the cleaning liquid can range from, for example, room temperature (typically about 15°C to 25°C) to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning solution having a temperature of about 50° C. to 85° C. can be preferably used.

Hereinafter, some examples relating to the present invention will be described, but the present invention is not intended to be limited to what is shown in these examples. In the following description, "parts" and "%" are based on weight unless otherwise specified.

<Preparation of polishing composition>
(Examples 1 to 9 and Comparative Examples 1 to 3)
Polishing compositions according to each example were prepared by mixing abrasive grains, water-soluble polymers, basic compounds, surfactants, and deionized water. Colloidal silica (average primary particle size: 25 nm) was used as the abrasive grain, and its content was 0.175%. As the water-soluble polymer, polyacryloylmorpholine (hereinafter referred to as "PACMO") having a weight average molecular weight of about 350,000 and an amount shown in Table 1 was used. Further, as the water-soluble polymer, polyvinyl alcohol (unmodified PVA) having a weight average molecular weight of about 70,000 and a degree of saponification of 98% or more was used as shown in Table 1. Ammonia was used as the basic compound, and its content was 0.005%. As the surfactant, polyoxyethylene decyl ether (C10EO5) with an added mole of ethylene oxide of 5 was used, and its content was 0.00015%.

(Comparative Examples 4-5)
A polishing composition according to this example was prepared in the same manner as in Example 1, except that PACMO was not used as the water-soluble polymer and polyvinyl alcohol was used in the amount shown in Table 1.

(Comparative Examples 6-7)
A polishing composition according to this example was prepared in the same manner as in Example 1, except that PACMO in the amount shown in Table 1 was used as the water-soluble polymer and polyvinyl alcohol was not used.

<Polishing of silicon wafer>
As a polishing target, a commercially available silicon single crystal wafer (conductivity type: P type, crystal orientation: <100>, COP (Crystal Originated Particle: crystal defect) free) with a diameter of 200 mm that had been lapped and etched was subjected to the following polishing conditions 1. A silicon wafer that had been pre-polished was prepared. Preliminary polishing was performed using a polishing solution containing 1.0% abrasive grains (colloidal silica with an average primary particle size of 35 nm) and 0.068% potassium hydroxide in deionized water.

[Polishing conditions 1]
Polishing device: Single-fed polishing device model “PNX-322” manufactured by Okamoto Machine Tools Co., Ltd.
Polishing load: 15kPa
Rotation speed of surface plate: 30 rpm
Head (carrier) rotation speed: 30 rpm
Polishing pad: Manufactured by Fujibo Ehime Co., Ltd. Product name: “FP55”
Supply rate of preliminary polishing liquid: 550mL/min
Temperature of preliminary polishing liquid: 20℃
Surface plate cooling water temperature: 20℃
Polishing time: 3min

Using the polishing composition according to each example prepared above as a polishing liquid, the silicon wafer after the preliminary polishing was polished under the following polishing conditions 2.

[Polishing conditions 2]
Polishing device: Single-fed polishing device model “PNX-322” manufactured by Okamoto Machine Tools Co., Ltd.
Polishing load: 15kPa
Rotation speed of surface plate: 30 rpm
Head (carrier) rotation speed: 30 rpm
Polishing pad: Manufactured by Fujibo Ehime Co., Ltd. Product name: “POLYPAS27NX”
Polishing liquid supply rate: 400mL/min
Polishing liquid temperature: 20℃
Surface plate cooling water temperature: 20℃
Polishing time: 4min

The silicon wafer after polishing was removed from the polishing equipment and cleaned using a cleaning solution of NH ₄ OH (29%): H ₂ O ₂ (31%): deionized water (DIW) = 1:1:12 (volume ratio). (SC-1 wash). Specifically, two cleaning tanks, a first and a second, were prepared, and the cleaning liquid was stored in each of the cleaning tanks and maintained at 60°C. The polished silicon wafer is immersed in a first cleaning tank for 5 minutes, then immersed in ultrapure water and passed through a rinsing tank where ultrasonic waves are applied, then immersed in a second cleaning tank for 5 minutes, and then immersed in ultrapure water. After passing through a rinsing tank in which the sample was immersed in water and subjected to ultrasonic waves, it was dried using a spin dryer.

<Haze measurement>
The haze (ppm) of the cleaned silicon wafer surface was measured in DWO mode using a wafer inspection device manufactured by KLA-Tencor, trade name "Surfscan SP2 ^XP ". The obtained results are shown in Table 1 in terms of relative values (haze ratio) with the haze value of Comparative Example 4 as 100%. If the haze ratio is less than 100%, it can be said that the haze improving effect can be significantly confirmed, and the smaller the value of the haze ratio, the higher the haze improving effect.

As shown in Table 1, PACMO and polyvinyl alcohol were adjusted so that the relationship between the content W _A of PACMO and the content W _B of polyvinyl alcohol satisfied the formula: W _A /(W _A + W _B )>0.900; The polishing compositions of Examples 1 to 9 used in combination have higher haze than the polishing compositions of Comparative Examples 1 to 3 that satisfy the formula: W _A /(W _A + W _B )≦0.900; showed an improvement effect. In addition, the polishing compositions of Examples 1 to 9 are the polishing compositions of Comparative Examples 4 and 5 using only polyvinyl alcohol as the water-soluble polymer, and the polishing compositions of Comparative Examples 6 and 7 using only PACMO. It showed a high haze improvement effect compared to the composition.

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

Claims (7)

Contains abrasive grains, a water-soluble polymer, a basic compound, and water,
The water-soluble polymer includes a water-soluble polymer and a vinyl alcohol-based polymer having a structural unit derived from N-(meth)acryloylmorpholine,
The content W _A of the water-soluble polymer having a structural unit derived from N-(meth)acryloylmorpholine (content on a weight basis), the content W _B (content on a weight basis) of the vinyl alcohol-based polymer, and The relationship is as follows:
0.980≧ _WA /( _WA + _WB ) ≧0.910 ;
A silicon wafer polishing composition that satisfies the following requirements. The composition for polishing a silicon wafer according to claim 1, wherein the content W _A of the water-soluble polymer having a structural unit derived from N-(meth)acryloylmorpholine is 2.0×10 ⁻³ % by weight or more. thing. The composition for polishing a silicon wafer according to claim 1 or 2, wherein the content W _B of the vinyl alcohol polymer is 15.0×10 ⁻⁴ % by weight or less. The silicon wafer polishing composition according to any one of claims 1 to 3, wherein the vinyl alcohol polymer has a weight average molecular weight of more than 1 x ¹⁰⁴ . The silicon wafer polishing composition according to any one of claims 1 to 4, further comprising a surfactant. The silicon wafer polishing composition according to claim 5, wherein the surfactant includes a surfactant containing a polyoxyalkylene structure. The composition for polishing a silicon wafer according to any one of claims 1 to 6, wherein the abrasive grains are silica particles.