JP2017101248A - Polishing composition, manufacturing method of polishing composition and manufacturing method of polished article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition capable of effectively reducing the number of fine particles existing on a surface after polishing.SOLUTION: There is provided a polishing composition containing an abrasive grain, a water-soluble polymer and water. Weight average molecular weight of the water-soluble polymer is 20×10or less. The polishing composition has a ratio of 95% accumulative diameter D95 to 50% accumulative diameter D50 (D95/D50) of 2.00 or less in a particle diameter distribution based on volume for particles in the polishing composition measured by a dynamic light scattering method at a concentration with content of the abrasive grain of 0.2 mass%.SELECTED DRAWING: None

Description

  The present invention relates to a polishing composition used for polishing an object to be polished. Specifically, the present invention relates to a polishing composition used mainly for polishing semiconductor substrates such as silicon wafers and other substrates.

The surface of a silicon wafer used as a component of a semiconductor device or the like is generally finished into a high-quality mirror surface through a lapping process (rough polishing process) and a polishing process (precision polishing process). The polishing process typically includes a primary polishing process (primary polishing process) and a final polishing process (final polishing process). Patent documents 1 and 2 are mentioned as technical literature about a constituent for polish mainly used for a use which polishes semiconductor substrates, such as a silicon wafer. Patent Document 3 is a technical document relating to a polishing composition mainly used for polishing a magnetic disk, and Patent Document 4 is used mainly for polishing a glass substrate.
About polishing composition

JP 2010-034509 A JP 2011-061089 A JP 2001-323254 A JP 2002-180034 A

  In recent years, higher quality surfaces have been required for semiconductor substrates such as silicon wafers and other substrates, and various investigations have been made on polishing compositions that can meet such requirements. For example, Patent Document 1 discloses a foreign substance that can increase the number of fine particles (Light Point Defects: LPD) on a polished semiconductor substrate by using a low-viscosity water-soluble polymer compound as a semiconductor wetting agent. A technique is described that makes it easier to remove by filtration. Patent Documents 3 and 4 describe techniques for obtaining a high-quality surface by controlling the particle size distribution of abrasive grains (abrasives). However, even with such a technique, there have been cases where it has not been possible to sufficiently meet the recent required level of surface quality after polishing.

  Therefore, an object of the present invention is to provide a polishing composition that can effectively reduce the number of fine particles (LPD) present on the surface after polishing. Another object of the present invention is to provide a method for producing such a polishing composition. Another related object is to provide a method for producing a polished article having a surface with a reduced number of LPDs.

  When polishing an object to be polished using a polishing composition containing abrasive grains and a water-soluble polymer (water-soluble polymer compound) in water, depending on the type of the water-soluble polymer, the water-soluble polymer may be contained in the polishing composition. Adsorbing with the abrasive grains, the abrasive grains may be present in the polishing composition as granules larger than their own size. Such a granule behaves like a particle in the polishing composition, and the behavior can affect the mechanical action during polishing. In the polishing composition containing abrasive grains and a water-soluble polymer in water, the inventors pay attention to the size of the particles in consideration of the presence of the above-mentioned granules as a physical property value different from the size of the abrasive grains themselves. did. That is, when the water-soluble polymer is adsorbed to the abrasive grains, the unit exhibiting particle-like behavior in the polishing composition is regarded as particles, and the size is considered as the size of the particles contained in the polishing composition. As a result of adopting the dynamic light scattering method as a method for accurately grasping the particle size distribution of the particles, the results of intensive studies on the relationship between the particle size distribution of the particles and the number of LPDs on the polished surface The present invention was completed by finding that the number of LPDs can be effectively reduced when the particle size distribution of the particles satisfies a predetermined condition.

The polishing composition provided by this specification contains an abrasive grain, a water-soluble polymer, and water. Here, the weight average molecular weight (Mw) of the water-soluble polymer is 20 × 10 ⁴ or less. The polishing composition comprises particles in the polishing composition measured by a dynamic light scattering method at a concentration at which the abrasive grain content is 0.2% by mass (abrasive grains alone, around the abrasive grains). In the volume-based particle size distribution of the adsorbed water-soluble polymer, the aggregate of abrasive grains and water-soluble polymer, etc.), the ratio of 95% cumulative diameter D95 to 50% cumulative diameter D50 (D95 / D50) is 2.00 or less. According to such a polishing composition, the number of LPDs can be effectively reduced on the polished surface.

  The particle size distribution of the particles in the polishing composition is preferably such that the ratio of 95% cumulative diameter D95 to 10% cumulative diameter D10 (D95 / D10) is 3.00 or less. According to such polishing composition, the number of LPDs can be reduced more favorably.

Examples of the abrasive grains, the average primary particle diameter _{D P1} of the abrasive grains may employ preferably those in the range of approximately 15Nm～30nm. According to the polishing composition containing such abrasive grains, a reduction in the number of LPDs and a reduction in haze can be achieved at a higher level.

Examples of the abrasive grains, the average secondary particle diameter _{D P2} of the abrasive grains can be preferably used those in the range of approximately 20 nm to 50 nm. According to the polishing composition containing such abrasive grains, a reduction in the number of LPDs and a reduction in haze can be achieved at a higher level.

In a preferred embodiment of the polishing composition, the volume average particle diameter D _A of the particles in the polishing composition and the average secondary particle diameter D _{P2 of the} abrasive grains measured by the dynamic light scattering method The difference may be less than 10 nm. According to such a polishing composition, a higher LPD number reduction effect can be realized.

  The polishing composition disclosed herein can be preferably implemented in an embodiment that further contains a basic compound in addition to the abrasive grains, the water-soluble polymer and water. According to the polishing composition of this embodiment, the polishing efficiency can be improved by the action of the basic compound.

According to this specification, a method for producing a polishing composition comprising abrasive grains, a water-soluble polymer, a basic compound, and water is also provided. The method includes preparing a dispersion liquid containing the abrasive grains, the basic compound, and water (can be prepared, purchased, received, etc.). Moreover, preparing the aqueous solution containing the said water-soluble polymer and water may be included. Moreover, it may include adding and mixing the aqueous solution to the dispersion. Such a production method is such that the water-soluble polymer has a weight average molecular weight of 20 × 10 ⁴ or less and particles in the polishing composition (abrasive grains alone, those in which a water-soluble polymer is adsorbed around the abrasive grains, abrasive grains) It is suitable as a method for producing a polishing composition in which the particle size distribution of particles and a water-soluble polymer may satisfy the predetermined D95 / D50.

According to this specification, the polishing liquid (herein, “liquid” means that the slurry is included) is supplied to the object to be polished, and the surface of the object to be polished is polished with the polishing liquid. There is provided a method for producing a polished article. In the polishing object manufacturing method, a polishing liquid containing abrasive grains, a water-soluble polymer, and water is used as the polishing liquid supplied to the object to be polished. In the polishing liquid, as the particles, the above-mentioned abrasive grains and the particles on which the abrasive grains are adsorbed with the water-soluble polymer are contained. The water-soluble polymer has a weight average molecular weight of 20 × 10 ⁴ or less. The polishing liquid has a D95 / D50 of 2.00 or less in a volume-based particle size distribution of particles in the polishing liquid measured by a dynamic light scattering method. According to this manufacturing method, the number of LPDs can be effectively suppressed on the polished surface. Therefore, an abrasive (for example, a semiconductor substrate such as a silicon wafer) having a higher quality surface can be provided.

  The technique disclosed here can be preferably applied to polishing of a silicon wafer after polishing, for example, lapping. A particularly preferable application target is final polishing of a silicon wafer.

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

<Abrasive>
The material and properties of the abrasive grains contained in the polishing composition disclosed herein are not particularly limited, and can be appropriately selected according to the purpose of use and usage of the polishing composition. Examples of the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, oxide particles such as bengara particles; Examples thereof include nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid). And polyacrylonitrile particles. Such an abrasive grain may be used individually by 1 type, and may be used in combination of 2 or more type.

  As said abrasive grain, an inorganic particle is preferable, and the particle | grains which consist of a metal or a metalloid oxide are especially preferable. Particularly preferred abrasive grains include silica particles. Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica and the like. Colloidal silica and fumed silica are preferable as silica particles from the viewpoint that scratches are hardly generated on the surface of the object to be polished and a surface having a lower haze can be realized. Of these, colloidal silica is preferred. For example, colloidal silica can be preferably employed as abrasive grains of a polishing composition used for polishing (particularly final polishing) of a silicon wafer.

  The true specific gravity of the silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. By increasing the true specific gravity of silica, the polishing rate (amount of removing the surface of the object to be polished per unit time) can be improved when polishing the object to be polished (for example, a silicon wafer). From the viewpoint of reducing scratches generated on the surface (polished surface) of the object to be polished, silica particles having a true specific gravity of 2.2 or less are preferable. As the true specific gravity of silica, a measured value by a liquid substitution method using ethanol as a substitution liquid can be adopted.

  In the technique disclosed herein, the abrasive grains contained in the polishing composition may be in the form of primary particles or in the form of secondary particles in which a plurality of primary particles are aggregated. Further, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In a preferred embodiment, at least a part of the abrasive grains is contained in the polishing composition in the form of secondary particles.

In the art disclosed herein, the average primary particle diameter D _P1 of the abrasive grains may be a value particle size distribution of particles in the polishing composition can satisfy a predetermined condition are not particularly limited. In a preferred embodiment, the average primary particle diameter _{D P1} of the abrasive grains is at 5nm or more, and more preferably 10nm or more. The increased average primary particle diameter D _P1 of the abrasive grains, the higher the polishing rate can be achieved. Higher polishing effect (e.g., reduced haze, effects such as removal of defects) from the viewpoint of obtaining an average primary particle diameter _{D P1} is preferably at least 15 nm, more 20nm (e.g. 20nm greater) are more preferred. Further, in view of filterability, etc. of the polishing composition, the average primary particle diameter _{D P1} is preferably less than 60 nm, 50 nm or less (e.g., 40nm or less) are more preferred. Moreover, smoother highly surface (e.g., lower surface haze) from the viewpoint of easy to realize, average primary particle diameter D _P1 is preferably less than 35 nm, more preferably 32nm or less, More preferably, it is 30 nm or less (for example, less than 30 nm).

In the technique disclosed herein, the average primary particle diameter D _P1 of the abrasive grains is, for example, from the specific surface area S (m ² / g) measured by the BET method, of D _P1 = 2720 / S (nm). It can be calculated by an equation. The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritex Corporation, a trade name “Flow Sorb II 2300”.

The average secondary particle diameter D _{P2 of the} abrasive grains (referring to the volume average secondary particle diameter of the abrasive grains itself) should be a value that allows the particle size distribution of the particles in the polishing composition to satisfy a predetermined condition. There is no particular limitation. In a preferred embodiment, the average secondary particle diameter _DP2 is 10 nm or more, more preferably 20 nm or more. The increased average abrasive grain of the secondary particle diameter D _P2, higher polishing rate can be achieved. From the viewpoint of obtaining a higher polishing effect, average secondary particle diameter _{D P2} is preferably at 30nm or more, more preferably 35nm or more, further preferably more than 40nm (e.g. 40nm greater). Further, from the viewpoint of filterability of the polishing composition, average secondary particle diameter _{D P2} is appropriately 90nm or less, preferably 80nm or less, more preferably 70 nm. Moreover, smoother highly surface (e.g., lower surface haze) from the viewpoint of easily realizing an average secondary particle diameter _{D P2} is suitably less than 60 nm, preferably not more than 55 nm, 50 nm or less (e.g. (Less than 50 nm) is more preferable.
Use the average secondary particle diameter D _P2 of the abrasive grains, the measurement sample an aqueous dispersion of abrasive grains of interest (containing no water-soluble polymer.), For example, manufactured by Nikkiso Co., Ltd. of the type to "UPA-UT151" It can be measured by the dynamic light scattering method.

The average secondary particle diameter D _P2 of the abrasive grains is generally equal to or greater than the average primary particle diameter D _P1 of the abrasive grains (D _P2 / D _P1 ≧ 1) and is typically larger than D _P1 (D _P2 / D _P1 > 1). Although not particularly limited, from the viewpoint of polishing effect and surface smoothness after polishing, it is appropriate that the D _P2 / D _P1 of the abrasive grains is usually in the range of 1.2 to 3. The range of 6-2.5 is preferable, and the range of 1.7-2.3 (for example, more than 1.8 and 2.2 or less) is more preferable.

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

  Although not particularly limited, the average value of the major axis / minor axis ratio (average aspect ratio) of the primary particles of the abrasive grains is preferably 1.0 or more, more preferably 1.05 or more, and still more preferably 1. .1 or more. Higher polishing rates can be achieved by increasing the average aspect ratio of the abrasive grains. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less, from the viewpoint of reducing scratches.

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

<Water-soluble polymer>
The kind of water-soluble polymer contained in the polishing composition disclosed here is not particularly limited. For example, among the water-soluble polymers known in the field of polishing compositions, particles in the polishing composition can exhibit a desired particle size distribution in a polishing composition having an abrasive concentration of 0.2% by mass. Can be selected. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types.

  The water-soluble polymer may have at least one functional group selected from a cationic group, an anionic group and a nonionic group in the molecule. The water-soluble polymer may have, for example, a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary nitrogen structure, a heterocyclic structure, a vinyl structure, a polyoxyalkylene structure, etc. in the molecule.

  Examples of water-soluble polymers that can be preferably used in the polishing composition disclosed herein include cellulose derivatives, polymers containing oxyalkylene units, polymers containing monomer units derived from N-vinyl lactam, imine derivatives, polyvinyl alcohol, A pullulan etc. are mentioned.

  Specific examples of the cellulose derivative (hereinafter also referred to as “water-soluble polymer PA”) include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, and the like. Of these, hydroxyethyl cellulose is preferred.

The polymer containing an oxyalkylene unit (hereinafter also referred to as “water-soluble polymer PB”) is an oxyalkylene unit having 2 to 6 carbon atoms (typically a structural unit represented by —C _n H _2n O—. And n is an integer of 2 to 6.) or a polymer containing two or more thereof. The polymer whose carbon atom number of the said oxyalkylene unit is 2-3 is preferable. Examples of such a polymer include polyethylene oxide, a block copolymer of ethylene oxide (EO) and propylene oxide (PO), a random copolymer of EO and PO, and the like.
The block copolymer of EO and PO may be a diblock body, a triblock body or the like containing a polyethylene oxide block (PEO) and a polypropylene oxide block (PPO). Examples of the triblock body include a PEO-PPO-PEO type triblock body and a PPO-PEO-PPO type triblock body. Usually, a PEO-PPO-PEO type triblock body is more preferable.

As the PEO-PPO-PEO type triblock body, a polymer represented by the following general formula (1) can be preferably used.
HO- (EO) _a- (PO) _b- (EO) _c -H (1)
In the general formula (1), EO represents an oxyethylene unit (—CH ₂ CH ₂ O—), PO represents an oxypropylene unit (—CH ₂ CH (CH ₃ ) O—), and a, b and c are Each represents an integer of 1 or more (typically 2 or more).
In the general formula (1), the total of a and c is preferably in the range of 2 to 1000, more preferably in the range of 5 to 500, and still more preferably in the range of 10 to 200. B in the general formula (1) is preferably in the range of 2 to 200, more preferably in the range of 5 to 100, and still more preferably in the range of 10 to 50.

  In the 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, detergency, and the like. It is preferably larger than 1, more preferably 2 or more, and further preferably 3 or more (for example, 5 or more).

  Examples of polymers containing monomer units derived from N-vinyl lactam (hereinafter also referred to as “water-soluble polymer PC”) include N-vinyl lactam monomers such as N-vinyl pyrrolidone (VP) and N-vinyl caprolactam (VC). These homopolymers and copolymers can be mentioned. Specific examples include polyvinylpyrrolidone, polyvinylcaprolactam, random copolymers of VP and VC, random copolymers of one or both of VP and VC with other vinyl monomers (for example, acrylic monomers, vinyl ester monomers, etc.). Examples thereof include a polymer, a block copolymer containing a polymer segment containing one or both of VP and VC, and a graft copolymer (for example, a graft copolymer obtained by grafting polyvinyl pyrrolidone to polyvinyl alcohol).

  As the imine derivative (hereinafter also referred to as “water-soluble polymer PD”), poly (N-acylalkyleneimine) or the like can be used. Specific examples include poly (N-acetylethyleneimine), poly (N-propionylethyleneimine), poly (N-caproylethyleneimine), poly (N-benzoylethyleneimine), poly (N-acetylpropyleneimine). , Poly (N-butyrylethyleneimine) and the like.

  When polyvinyl alcohol is used as the water-soluble polymer, the saponification degree of the polyvinyl alcohol is preferably 65 mol% or more, more preferably 70 mol% or more. The degree of saponification of polyvinyl alcohol is theoretically 100 mol% or less.

  The polishing composition disclosed herein can be preferably implemented in an embodiment containing at least a water-soluble polymer PA and / or polyvinyl alcohol as a water-soluble polymer. Especially, the aspect containing at least water-soluble polymer PA (typically hydroxyethyl cellulose) as a water-soluble polymer is preferable. As a suitable example of such a polishing composition, a polishing composition in which the main component (typically a component exceeding 50% by mass) of the water-soluble polymer is hydroxyethyl cellulose, 80% by mass or more (more preferably) of the water-soluble polymer. A polishing composition or the like in which 90% by mass or more, typically 100% by mass) is hydroxyethyl cellulose.

The technology disclosed herein is typically performed in a mode using a water-soluble polymer having a weight average molecular weight (Mw) of 20 × 10 ⁴ or less (typically 1 × 10 ^{4 to} 20 × 10 ⁴ ). The From the viewpoint of filterability and the like of the polishing composition, the Mw of the water-soluble polymer is preferably 18 × 10 ⁴ or less, and more preferably 15 × 10 ⁴ or less. Further, from the viewpoint that the preferable particle size distribution disclosed herein is easily realized, a water-soluble polymer having an Mw of 12 × 10 ⁴ or less (for example, 10 × 10 ⁴ or less, more preferably 8.5 × 10 ⁴ or less) is preferable. . On the other hand, generally, when the Mw of the water-soluble polymer increases, the haze reduction effect tends to increase. From such a viewpoint, usually, a water-soluble polymer having Mw of 1 × 10 ⁴ or more can be preferably used.

The more preferable range of Mw may vary depending on the type of water-soluble polymer. For example, the Mw of the water-soluble polymer PA is typically 20 × 10 ⁴ or less, preferably 18 × 10 ⁴ or less, more preferably 15 × 10 ⁴ or less, and even more preferably 12 × 10 ⁴ or less (for example, 10 × 10 4 ⁴ or less, and further 8.5 × 10 ⁴ or less). The Mw of the water-soluble polymer PA is typically 1 × 10 ⁴ or more, preferably 2 × 10 ⁴ or more, more preferably 3 × 10 ⁴ or more, and even more preferably 5 × 10 ⁴ or more (for example, 7 × 10 4 ⁴ or more). For example, the Mw of the water-soluble polymer PB is preferably 20 × 10 ⁴ or less, more preferably 15 × 10 ⁴ or less. The Mw of the water-soluble polymer PB is typically 1 × 10 ⁴ or more. For example, the Mw of the water-soluble polymer PC is preferably 10 × 10 ⁴ or less, more preferably 5 × 10 ⁴ or less, and further preferably 3 × 10 ⁴ or less. The Mw of the water-soluble polymer PC is typically 1 × 10 ⁴ or more. For example, the Mw of the water-soluble polymer PD is preferably 20 × 10 ⁴ or less, more preferably 10 × 10 ⁴ or less (for example, 5 × 10 ⁴ or less). The Mw of the water-soluble polymer PD is typically 1 × 10 ⁴ or more. The Mw of polyvinyl alcohol as a water-soluble polymer is typically 6 × 10 ⁴ or less, preferably 5.5 × 10 ⁴ or less, more preferably 3 × 10 ⁴ or less (for example, 2 × 10 ⁴ or less). is there. The Mw of polyvinyl alcohol is typically 1 × 10 ⁴ or more.

The relationship between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the water-soluble polymer is not particularly limited. For example, those in which the relationship between Mw and Mn satisfies the following formula: Mw / Mn ≦ 5.0 can be preferably used. From the viewpoint that the preferable particle size distribution disclosed herein is easily realized, the Mw / Mn of the water-soluble polymer is preferably 4.8 or less, more preferably 4.6 or less. In principle, Mw / Mn is 1.0 or more. As Mw and Mn of the water-soluble polymer, values based on GPC (aqueous: polyethylene oxide equivalent) can be adopted.
The more preferable range of Mw / Mn may vary depending on the type of water-soluble polymer. For example, the Mw / Mn of the water-soluble polymer PA is preferably 4.8 or less, more preferably 4.6 or less. For example, the Mw / Mn of the water-soluble polymer PB is preferably 4.0 or less, more preferably 3.5 or less, and still more preferably 3.0 or less. For example, the Mw / Mn of the water-soluble polymer PC is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. For example, the Mw / Mn of the water-soluble polymer PD is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less.
On the other hand, for example, the Mw / Mn of the water-soluble polymer PA is preferably 2.0 or more, more preferably 3.0 or more. For example, the Mw / Mn of the water-soluble polymer PB is preferably 1.05 or more. For example, the Mw / Mn of the water-soluble polymer PC is preferably 1.05 or more. For example, the Mw / Mn of the water-soluble polymer PD is preferably 1.05 or more.
Further, Mw / Mn of polyvinyl alcohol as the water-soluble polymer is preferably 4.0 or less, more preferably 3.5 or less, and further preferably 3.0 or less. The Mw / Mn of polyvinyl alcohol as the water-soluble polymer is preferably 1.05 or more.

  As the Mw and Mn of the water-soluble polymer, values based on gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent) can be adopted.

  Although it does not specifically limit, content of a water-soluble polymer can be 0.01 mass part or more with respect to 100 mass parts of abrasive grains. The content of the water-soluble polymer with respect to 100 parts by mass of the abrasive is suitably 0.05 parts by mass or more, preferably 0.1 parts by mass from the viewpoint of improving the surface smoothness after polishing (for example, reducing haze and defects). As mentioned above, More preferably, it is 0.5 mass part or more (for example, 1 mass part or more). Further, the content of the water-soluble polymer with respect to 100 parts by mass of the abrasive grains can be, for example, 40 parts by mass or less from the viewpoint of polishing rate, detergency, etc. 15 parts by mass or less, more preferably 10 parts by mass or less.

<Water>
As water contained in the polishing composition disclosed herein, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like can be preferably used. The water to be used preferably has, for example, a total content of transition metal ions of 100 ppb or less in order to avoid as much as possible the action of other components contained in the polishing composition. For example, the purity of water can be increased by operations such as removal of impurity ions with an ion exchange resin, removal of foreign matter with a filter, distillation, and the like.
The polishing composition disclosed herein may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water, if necessary. Usually, it is preferable that 90 volume% or more of the solvent contained in polishing composition is water, and it is more preferable that 95 volume% or more (typically 99-100 volume%) is water.

  The polishing composition disclosed herein (typically a slurry-like composition) has, for example, a solid content (non-volatile content; NV) of 0.01% by mass to 50% by mass, and the balance Is preferably an aqueous solvent (water or a mixed solvent of water and the above-mentioned organic solvent) or a form in which the balance is an aqueous solvent and a volatile compound (for example, ammonia). A form in which the NV is 0.05 to 40% by mass is more preferable. In addition, the said solid content (NV) refers to the ratio of the mass which the residue after drying polishing composition at 105 degreeC for 24 hours occupies for the said polishing composition.

<Basic compound>
The polishing composition disclosed herein typically contains a basic compound in addition to the abrasive grains, the water-soluble polymer and water. Here, the basic compound refers to a compound having a function of increasing the pH of the composition when added to the polishing composition. The basic compound serves to chemically polish the surface to be polished, and can contribute to an improvement in the polishing rate. In addition, the basic compound can be useful for improving the dispersion stability of the polishing composition.

  As the basic compound, an organic or inorganic basic compound containing nitrogen, an alkali metal or alkaline earth metal hydroxide, various carbonates, bicarbonates, or the like can be used. For example, alkali metal hydroxide, quaternary ammonium hydroxide or a salt thereof, ammonia, amine and the like can be mentioned. 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 quaternary ammonium hydroxide or a salt thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like. Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like. Such basic compounds can be used singly or in combination of two or more.

  Preferred basic compounds from the viewpoint of improving the polishing rate include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, hydrogen carbonate. Sodium and sodium carbonate are mentioned. Of these, preferred are ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide. More preferred are ammonia and tetramethylammonium hydroxide. A particularly preferred basic compound is ammonia.

<Surfactant>
The polishing composition disclosed herein is preferably practiced in a mode including a surfactant (typically a water-soluble organic compound having a molecular weight of less than 1 × 10 ⁴ ) in addition to abrasive grains, a water-soluble polymer and water. Can be done. By using the surfactant, the dispersion stability of the polishing composition can be improved. Moreover, it can be easy to reduce the haze of the polished surface. Surfactant can be used individually by 1 type or in combination of 2 or more types.

  As the surfactant, an anionic or nonionic surfactant can be preferably used. From the viewpoint of low foaming property and ease of pH adjustment, a nonionic surfactant is more preferable. 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 Nonionic surfactants such as polyoxyalkylene adducts such as esters and polyoxyethylene sorbitan fatty acid esters; copolymers of plural types of oxyalkylene (diblock type, triblock type, random type, alternating type); It is done.

  Specific examples of nonionic activators include block copolymers of EO and PO (diblock bodies, PEO-PPO-PEO type triblock bodies, PPO-PEO-PPO type triblock bodies, etc.), EO and PO, and the like. Random copolymers of polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, poly Oxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, Reoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrene Phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxy Ethylene distearate, polyoxyethylene monooleate , Polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetra Examples include oleic acid polyoxyethylene sorbitol, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil. Among them, preferable surfactants include block copolymers of EO and PO (particularly, PEO-PPO-PEO type triblock), random copolymers of EO and PO, and polyoxyethylene alkyl ethers (for example, polyoxyethylene alkyl ethers). Oxyethylene decyl ether).

The molecular weight of the surfactant is typically less than 1 × 10 ⁴ and is preferably 9500 or less from the viewpoints of filterability of the polishing composition, cleanability of the object to be polished, and the like. The molecular weight of the surfactant is typically 200 or more, preferably 250 or more, and more preferably 300 or more (for example, 500 or more) from the viewpoint of the haze reduction effect and the like. The molecular weight of the surfactant may be a weight average molecular weight (Mw) determined by GPC (aqueous, polyethylene glycol equivalent) or a molecular weight calculated from a chemical formula.
The more preferable range of the molecular weight of the surfactant may vary depending on the type of the surfactant. For example, when a block copolymer of EO and PO is used as the surfactant, the Mw is preferably 1000 or more, more preferably 2000 or more, and even more preferably 5000 or more.

When the polishing composition disclosed herein contains a surfactant, the content is not particularly limited as long as it does not significantly impair the effects of the present invention. Usually, from the viewpoint of detergency and the like, the content of the surfactant with respect to 100 parts by mass of the abrasive is suitably 20 parts by mass or less, preferably 15 parts by mass or less, and 10 parts by mass or less (for example, 6 parts by mass) Part or less) is more preferable. From the viewpoint of better exerting the effect of using the surfactant, the surfactant content relative to 100 parts by mass of the abrasive is suitably 0.001 parts by mass or more, preferably 0.005 parts by mass or more, 0.01 More than mass part (for example, 0.1 mass part or more) is more preferable.
Further, the mass ratio (W1 / W2) between the content W1 of the water-soluble polymer and the content W2 of the surfactant is not particularly limited, but can be, for example, in the range of 0.01 to 20, A range of 15 is preferable, and a range of 0.1 to 10 is more preferable.

<Other ingredients>
The polishing composition disclosed herein is a polishing agent such as a chelating agent, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt, a preservative, and an antifungal agent, as long as the effects of the present invention are not significantly hindered. A known additive that can be used in a composition for polishing (typically, a polishing composition used for final polishing of a silicon wafer) may be further contained as necessary.

  Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid Diethylenetriamine sodium pentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic). Acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid Ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphospho Nosuccinic acid is included. Of these, organic phosphonic acid-based chelating agents are more preferable, and ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are particularly preferable. A particularly preferred chelating agent is ethylenediaminetetrakis (methylenephosphonic acid).

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, organic 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. An organic acid and its salt, and an inorganic acid and its salt can be used individually by 1 type or in combination of 2 or more types.
Examples of antiseptics and fungicides include isothiazoline compounds, paraoxybenzoates, phenoxyethanol and the like.

<Application>
The polishing composition disclosed herein can be applied to polishing an object to be polished having various materials and shapes. The material of the object to be polished is, for example, a metal or semimetal such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, or an alloy thereof; glass such as quartz glass, aluminosilicate glass, or glassy carbon. A ceramic material such as alumina, silica, sapphire, silicon nitride, tantalum nitride and titanium carbide; a compound semiconductor substrate material such as silicon carbide, gallium nitride and gallium arsenide; a resin material such as polyimide resin; Of these, an object to be polished formed of a plurality of materials may be used. Especially, it is suitable for grinding | polishing of the to-be-polished object provided with the surface which consists of silicon | silicone.
The shape of the workpiece is not particularly limited. The polishing composition disclosed herein can be preferably applied to polishing an object having a flat surface such as a plate shape or a polyhedron shape.

  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 producing a polished article (for example, a method for producing a silicon wafer) including a final polishing step using the polishing composition is provided. Note that final polishing refers to the final polishing step in the manufacturing process of the object (that is, a step in which no further polishing is performed after that step). The polishing composition disclosed herein also refers to a polishing step upstream of final polishing (a step between a rough polishing step and a final polishing step. Typically, the polishing composition includes at least a primary polishing step; Secondary polishing, tertiary polishing, etc. may be included.), For example, it may be used in a polishing process performed immediately before final polishing.

  The polishing composition disclosed herein can be particularly preferably used for polishing a silicon wafer. For example, it is suitable as a polishing composition used for final polishing of a silicon wafer or a polishing process upstream thereof. For example, application to polishing (typically final polishing or polishing immediately before) of a silicon wafer prepared to have a surface roughness of 0.01 nm to 100 nm by an upstream process is effective. Application to final polishing is particularly preferable.

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

  The content of the abrasive grains in the polishing liquid is not particularly limited, but is typically 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, for example, It is 0.15 mass% or more. By increasing the abrasive content, higher polishing rates can be achieved. From the viewpoint of realizing a surface having a lower haze, usually, the content is suitably 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less, For example, it is 1 mass% or less.

The content of the water-soluble polymer in the polishing liquid is not particularly limited, and can be, for example, 1 × 10 ⁻⁴ mass% or more. From the viewpoint of haze reduction or the like, the preferable content is 5 × 10 ⁻⁴ mass% or more, more preferably 1 × 10 ⁻³ mass% or more, for example, 2 × 10 ⁻³ mass% or more. Further, from the viewpoint that the preferable particle size distribution disclosed herein is easily realized, the content is preferably 0.2% by mass or less, and 0.1% by mass or less (for example, 0.05% by mass or less). More preferably.

When using a surfactant, the content of the surfactant in the polishing liquid is not particularly limited, and can be, for example, 1 × 10 ⁻⁴ mass% or more. From the viewpoint of haze reduction or the like, the preferable content is 5 × 10 ⁻⁴ mass% or more, more preferably 1 × 10 ⁻³ mass% or more, for example, 2 × 10 ⁻³ mass% or more. Further, from the viewpoint of detergency and polishing rate, the content is preferably 0.2% by mass or less, and more preferably 0.1% by mass or less (for example, 0.05% by mass or less).

  When a basic compound is used, the content of the basic compound in the polishing liquid is not particularly limited. From the viewpoint of improving the polishing rate, the content is usually preferably 0.001% by mass or more, more preferably 0.003% by mass or more of the polishing liquid. Further, from the viewpoint of haze reduction or the like, the content is preferably less than 0.4% by mass, and more preferably less than 0.25% by mass.

  The pH of the polishing liquid is not particularly limited. For example, pH 8.0-12.0 is preferable and 9.0-11.0 is more preferable. It is preferable to contain a basic compound so as to obtain a polishing liquid having such a pH. The pH can be preferably applied to, for example, a polishing liquid used for polishing a silicon wafer (for example, a polishing liquid for final polishing).

<Particles contained in polishing composition>
The polishing composition disclosed herein may include a single abrasive particle or a particle formed by adsorbing an abrasive and a water-soluble polymer. The particles are, for example, abrasive particles, a form in which one or more molecules of polymer are adsorbed on the surface of one abrasive particle, and a form in which two or more abrasive particles are adsorbed to one molecule of polymer. It may be a form in which one or more abrasive grains and two or more polymers are adsorbed, a form in which other components (for example, a surfactant) in the polishing composition are further adsorbed to the abrasive grains and the water-soluble polymer, and the like. . In a polishing composition used for polishing an object to be polished, it is generally considered that particles of a plurality of forms as exemplified above are mixed. The presence of particles formed by adsorbing the abrasive grains and the water-soluble polymer in the polishing composition means that when the average particle diameter of the particles in the polishing composition is measured, the value is the average of the abrasive grains. It can be grasped by becoming larger than the value of the particle diameter.

  The particle size distribution of the particles contained in the polishing liquid (working slurry) supplied to the object to be polished is obtained, for example, by performing particle size measurement based on a dynamic light scattering method using the polishing liquid as a measurement sample. I can grasp it. This particle diameter measurement can be performed, for example, using a model ““ UPA-UT151 ”manufactured by Nikkiso Co., Ltd.

  According to the study by the present inventors, the ratio D95 / D50 of D95 (95% cumulative diameter) to D50 (50% cumulative diameter) in the particle size distribution obtained by the above particle diameter measurement is 2.00 or less. According to the composition, the number of LPDs can be clearly reduced as compared with a polishing composition having D95 / D50 larger than 2.00.

In carrying out the technology disclosed herein, it is not necessary to clarify the reason why the above-mentioned problem is solved by limiting the D95 / D50 of the particles to 2.00 or less. It is done.
That is, the size of the particles contained in the polishing composition (abrasive grains alone, those in which a water-soluble polymer is adsorbed around the abrasive grains, or aggregates of abrasive grains and a water-soluble polymer, etc.) can be further increased. When it becomes larger, the damage given to the surface to be polished becomes larger, so that defects tend to occur easily. In addition, the presence of coarse particles can cause non-uniform polishing, which can impair the smoothness of the surface. Furthermore, coarse particles tend to be in contact with or close to the surface of the object to be polished (that is, where both of them are likely to interact), so the residence time on the surface of the object to be polished tends to be long. It tends to remain on the rear surface. In particular, large particles exceeding D95 are likely to remain and are not easily removed by cleaning after polishing. This can be a factor for increasing the number of LPDs in the surface inspection of the polished article. Further, when the particle size distribution of the particles contained in the polishing composition is widened, among these particles, the persistence on the surface of the polished product and the variation in the removability during cleaning increase. Here, a countermeasure of stricter cleaning conditions in order to absorb the variation in removability and reduce residues on the surface of the polished article is also conceivable. However, if the cleaning conditions are excessively strict, the surface of the polished article is removed by the cleaning. There is a concern that haze will rise due to rough weather.

  On the other hand, if there are few coarse particles (for example, remarkably large particles exceeding D95) and there is little variation in the removability from the surface of the abrasive, the residue on the surface of the abrasive will be maintained even if relatively mild cleaning conditions are applied. Can be removed with high accuracy. In the polishing composition provided by the technique disclosed herein, the D95 / D50 of the particles contained in the polishing composition is suppressed to a predetermined value or less (specifically, 2.00 or less). In addition, there are few coarse particles with high persistence and low removability, and there may be little variation in particle size (and hence variation in persistence and removability). It is considered that this can effectively reduce the number of LPDs.

The effect of setting the upper limit of D95 / D50 of the particles contained in the polishing composition to a predetermined value or less can be better exhibited by a combination with a water-soluble polymer having an Mw of 20 × 10 ⁴ or less. This is because a water-soluble polymer having an Mw of 20 × 10 ⁴ or less generally has low persistence on the surface after polishing or high removability by washing. According to the polishing composition using a water-soluble polymer having Mw of 20 × 10 ⁴ or less and D95 / D50 being suppressed to 2.00 or less, the surface of the polished product remains even if milder cleaning conditions are applied. Objects can be removed with high accuracy. This can achieve a higher quality surface.

  In the technology disclosed herein, the D95 / D50 of the particles is preferably 1.80 or less, more preferably 1.70 or less, from the viewpoint of obtaining a higher LPD number reduction effect. The lower limit of D95 / D50 is 1 in principle. From the viewpoint of dispersion stability and ease of preparation of the polishing composition, D95 / D50 is suitably 1.20 or more, preferably 1.30 or more, more preferably 1.40 or more (for example, 1.45 or more). preferable.

  Although not particularly limited, the polishing composition disclosed herein has an aspect in which the ratio D95 / D10 of D95 (95% cumulative diameter) to D10 (10% cumulative diameter) of the particles is 3.00 or less. Can be preferably implemented. According to such an embodiment, a higher effect of reducing the number of LPDs can be exhibited as compared with a polishing composition having a larger D95 / D10. Further, from the viewpoint of reducing the number of LPDs, D95 / D10 is preferably 2.70 or less, and more preferably 2.50 or less. The lower limit of D95 / D10 is 1 in principle. From the viewpoints of dispersion stability and ease of preparation of the polishing composition, D95 / D10 is suitably 1.50 or more, preferably 1.80 or more (for example, 2.00 or more).

Each of D50, D95 and D10 of the particles is not particularly limited as long as it can realize the preferable particle size distribution disclosed herein. D10, D50, and D95 have a relationship of D10 ≦ D50 ≦ D95 in principle.
From the viewpoint of polishing rate, D50 is preferably more than 10 nm, more preferably more than 20 nm. From the viewpoint of obtaining a higher polishing effect, D50 is preferably 30 nm or more, more preferably 35 nm or more, and further preferably 40 nm or more (for example, more than 40 nm). Further, from the viewpoint of filterability of the polishing composition, D50 is suitably 90 nm or less, preferably 80 nm or less, and more preferably 70 nm or less. From the viewpoint of easily realizing a surface with higher smoothness (for example, a surface with lower haze), D50 is suitably less than 60 nm, preferably 55 nm or less, and more preferably 50 nm or less (eg, less than 50 nm).
From the viewpoint of polishing rate and the like, D95 is preferably 50 nm or more, and more preferably 60 nm or more (for example, 65 nm or more). From the viewpoint of improving the effect of reducing the number of LPDs and reducing scratches, D95 is suitably 120 nm or less, preferably 110 nm or less, more preferably 100 nm or less, and particularly preferably 90 nm or less (for example, 85 nm or less).
D10 is typically 10 nm or more, and is suitably 20 nm or more from the viewpoint of polishing efficiency and the like, preferably 30 nm or more, and more preferably 32 nm or more. In light of ease of preparation of the polishing composition, D10 is suitably less than 60 nm, preferably less than 50 nm, and more preferably less than 40 nm.

Although not particularly limited, from the viewpoint of obtaining a higher quality surface of the particles having a volume average particle diameter D _A which is obtained by a particle size measurement of particles in the polishing composition is appropriately 100nm or less 80 nm or less, preferably 70 nm or less, more preferably 60 nm or less (for example, 55 nm or less). Polishing effect (e.g., reduced haze, effects such as removal of the defect) is from the viewpoint of, _{D A} is suitably more than 20 nm, is preferably at least 30 nm, more preferably at least 35 nm, further preferably not less than 40 nm. _A preferred embodiment of the technology disclosed herein includes an embodiment in which DA is greater than 45 nm (for example, 50 nm or more).

The particle size distribution of the particles in the polishing composition is, for example, selection of water-soluble polymer (composition, Mw, Mw / Mn, molecular structure, etc.), selection of abrasive grains (size (D _P1 , D _P2, etc.), Shape, particle size distribution, etc.), the amount of water-soluble polymer used for the abrasive grains, the presence or absence of the use of a surfactant, and the type and amount in use.

  As described above, the particle size of the particles in the polishing composition can be measured using a polishing composition having a concentration that is actually supplied to the object to be polished as a measurement sample. In general, even if the NV is varied in the range of about 0.05 to 5% by mass while maintaining the ratio of each component, the particle size distribution is not significantly affected. According to the polishing composition in which the particle size distribution measured at a concentration of 0.2% by mass (that is, the particle size distribution obtained using the polishing composition having the above concentration as a measurement sample) satisfies a predetermined condition. Not only when this polishing composition is used for polishing as a polishing liquid having an abrasive concentration of 0.2% by mass, the polishing composition may be used for other abrasive concentrations (for example, in the range of about 0.05 to 5% by mass). The above-described effects can be obtained even when the concentration is different from 0.2% by mass.

  It is desirable that the measurement sample has a pH that is not significantly different from the pH of the polishing composition (polishing liquid) that is actually supplied to the object to be polished. For example, it is preferable to measure the particle size distribution of a measurement sample having a pH of 8.0 to 12.0 (more preferably pH 9.0 to 11.0, typically about pH 10.0 to 10.5). The above pH range can be preferably applied to, for example, a polishing composition for final polishing of a silicon wafer.

Although not particularly limited, the polishing compositions disclosed herein, the difference between the volume average particle diameter D _A and the average abrasive grain of the secondary particle diameter D _P2 of particles in the polishing composition is 20nm It can be preferably implemented in the following aspects. D _A -D _P2 is more preferably 15 nm or less (typically 0 to 15 nm), further preferably 10 nm or less (for example, 0 or more and less than 10 nm), and particularly preferably 7 nm or less. D _A -D _P2 is small (i.e., abrasive grains and a change in the volume average particle diameter due to the water-soluble polymer is adsorbed is not excessive) polishing composition tends abundance of coarse particles is small Therefore, it is preferable. According to such a polishing composition, a higher-quality polished surface can be realized. _A polishing composition in which D _A -D _P2 satisfies the above value and the Mw of the water-soluble polymer is 20 × 10 ⁴ or less (more preferably 15 × 10 ⁴ or less) is particularly preferable.

Although not particularly limited, the polishing compositions disclosed herein, the ratio of particles having a volume average particle diameter _{D A} for 50% cumulative diameter D50 of the particles _(D A / D50) is 1.40 or less It is preferable that _A polishing liquid having a small ratio (D _A / D50) is preferred because it tends to have few coarse particles. From this viewpoint, D _A / D50 is more preferably 1.20 or less, and further preferably 1.10 or less (for example, less than 1.10). The lower limit of D _A / D50 is 1 in principle.

<Preparation of polishing composition>
The polishing composition disclosed herein can be produced by an appropriate method capable of obtaining a polishing composition that satisfies the desired D95 / D50. For example, each component contained in the polishing composition may be mixed using a well-known mixing device such as a blade-type stirrer, an ultrasonic disperser, or a homomixer. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once and may be mixed in the order set suitably.

  Although it does not specifically limit, about the polishing composition of the composition containing a basic compound, from a viewpoint which manufactures the polishing composition which satisfy | fills desired D95 / D50 stably (with high reproducibility), for example, the following A manufacturing method can be preferably adopted.

In the polishing composition manufacturing method disclosed herein, the polishing composition, which is the manufacturing object, includes abrasive grains, a water-soluble polymer, a basic compound, and water, and the Mw of the water-soluble polymer is 20 × 10 ⁴ or less. The polishing composition contains, as particles, abrasive grains, grains composed of abrasive grains and a water-soluble polymer, and the content of the abrasive grains is 0.2% by mass. It can be preferably applied to the production of a polishing composition having a D95 / D50 of 2.00 or less in the volume-based particle size distribution of the particles measured by a dynamic light scattering method. In the production method, a dispersion containing abrasive grains (for example, silica particles), a basic compound, and water (hereinafter, also referred to as “basic abrasive dispersion”) is prepared, and the basic abrasive dispersion and water-soluble are prepared. With a functional polymer.

  The basic abrasive dispersion in which the abrasive grains and the basic compound coexist in this way does not contain a basic compound because the electrostatic repulsion of the abrasive grains is enhanced by the basic compound (typical) The dispersion stability of the abrasive grains is higher than that of a substantially neutral abrasive dispersion. For this reason, compared with the aspect which adds a basic compound after adding a water-soluble polymer to a neutral abrasive grain dispersion liquid, and the aspect which mixes a neutral abrasive grain dispersion liquid, a water-soluble polymer, and a basic compound at once. Thus, local aggregation of the abrasive grains is difficult to occur. Therefore, according to the above-mentioned method of mixing the water-soluble polymer with the basic abrasive dispersion, the adsorption of the abrasive and the water-soluble polymer can be progressed uniformly (in other words, the generation of coarse particles is suppressed). And a polishing composition satisfying the desired D95 / D50 can be stably produced (with good reproducibility).

The water-soluble polymer is preferably mixed with the basic abrasive dispersion in the form of an aqueous solution previously dissolved in water (hereinafter also referred to as “polymer aqueous solution”). Thereby, local agglomeration of the abrasive grains is further suppressed, and adsorption between the abrasive grains and the water-soluble polymer can be progressed more uniformly.
When mixing the basic abrasive dispersion and the aqueous polymer solution, it is preferable to add the aqueous polymer solution to the basic abrasive dispersion. According to such a mixing method, for example, compared with a mixing method in which a basic abrasive dispersion is added to an aqueous polymer solution, the adsorption of the abrasive grains and the water-soluble polymer can proceed more uniformly. When the abrasive grains are silica particles (for example, colloidal silica particles), it is particularly meaningful to employ a mixing method in which a polymer aqueous solution is added to the basic abrasive dispersion as described above.

  The basic abrasive dispersion is composed of at least a part of the abrasive grains and at least a part of the basic compound among the abrasive grains, the water-soluble polymer, the basic compound and the water constituting the polishing composition as the production objective. And at least a portion of water. For example, an embodiment in which the above-mentioned abrasive dispersion contains all of the abrasive grains constituting the polishing composition, at least a part of the basic compound, and at least a part of water can be preferably employed.

  The content of the basic compound in the basic abrasive dispersion is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more. By increasing the content of the basic compound, the occurrence of local aggregation during the preparation of the polishing composition tends to be better suppressed. The content of the basic compound in the basic abrasive dispersion is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. By reducing the content of the basic compound, the content of the basic compound in the polishing composition can be easily adjusted.

  The pH of the basic abrasive dispersion is preferably 8 or more, more preferably 9 or more. Due to the increase in pH, when a water-soluble polymer or an aqueous solution thereof is added to this basic abrasive dispersion, the occurrence of local aggregation tends to be better suppressed. Therefore, the polishing composition satisfying the desired D95 / D50 can be more stably produced by making the adsorption of the abrasive grains and the water-soluble polymer more uniformly. The pH of the basic abrasive dispersion is preferably 12 or less, more preferably 11.5 or less, and further preferably 10.5 or less. By setting the pH of the basic abrasive dispersion lower on the basic side, the amount of the basic compound necessary for the preparation of the dispersion is reduced, so the content of the basic compound in the polishing composition The adjustment becomes easier. For example, when the abrasive grains are silica particles, it is advantageous from the viewpoint of suppressing the dissolution of silica that the pH is not too high. The pH of the mixture can be adjusted by the blending amount of the basic compound.

  Such a basic abrasive dispersion can be prepared by mixing abrasive grains, a basic compound, and water. For the mixing, for example, a well-known mixing device such as a blade-type stirrer, an ultrasonic disperser, or a homomixer can be used. The aspect which mixes each component contained in a basic abrasive dispersion liquid is not specifically limited, For example, all the components may be mixed at once and you may mix in the order set suitably. As an example of a preferred embodiment, there is an embodiment in which a substantially neutral dispersion containing abrasive grains and water and a basic compound or an aqueous solution thereof are mixed.

  When the water-soluble polymer is mixed with the basic abrasive dispersion in the form of an aqueous solution (polymer aqueous solution), the content of the water-soluble polymer in the polymer aqueous solution is preferably 0.02% by mass or more, more preferably 0. 0.05% by mass or more, more preferably 0.1% by mass or more. By increasing the content of the water-soluble polymer, the content of the water-soluble polymer in the polishing composition can be easily adjusted. The content of the water-soluble polymer in the polymer aqueous solution is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. By reducing the content of the water-soluble polymer, local agglomeration of the abrasive grains tends to be better suppressed when the aqueous polymer solution is mixed with the basic abrasive dispersion.

  The aqueous polymer solution is preferably adjusted from near neutral to near basic, more preferably basic. More specifically, the pH of the polymer aqueous solution is preferably 8 or more, more preferably 9 or more. The pH adjustment can be typically performed using a part of the basic compound constituting the polishing composition. When the aqueous polymer solution is added to the basic abrasive dispersion by increasing the pH of the aqueous polymer solution, local agglomeration of the abrasive particles can be better suppressed. This makes it possible to more uniformly manufacture the polishing composition satisfying the desired D95 / D50 by allowing the adsorption of the abrasive grains and the water-soluble polymer to proceed more uniformly. The pH of the aqueous polymer solution is preferably 12 or less, more preferably 10.5 or less. When the pH of the aqueous polymer solution is lowered on the basic side, the amount of the basic compound necessary for the preparation of the aqueous polymer solution is reduced, so that the content of the basic compound in the polishing composition can be easily adjusted. For example, when the abrasive grains are silica particles, it is advantageous from the viewpoint of suppressing the dissolution of silica that the pH is not too high.

  The rate at which the aqueous polymer solution is charged into the basic abrasive dispersion (feed rate) is preferably 500 mL / min or less, more preferably 100 mL / min or less, and even more preferably 1 L of the dispersion. Is 50 mL / min or less. By reducing the charging speed, local agglomeration of the abrasive grains can be better suppressed.

  In a preferred embodiment, the aqueous polymer solution can be filtered before being added to the basic abrasive dispersion. By filtering the polymer aqueous solution, the amount of foreign matters and aggregates contained in the polymer aqueous solution can be reduced. This makes it possible to more uniformly manufacture the polishing composition satisfying the desired D95 / D50 by allowing the adsorption of the abrasive grains and the water-soluble polymer to proceed more uniformly.

  The filtration method is not particularly limited. For example, in addition to natural filtration performed at normal pressure, known filtration methods such as suction filtration, pressure filtration, and centrifugal filtration can be appropriately employed. The filter used for filtration is preferably selected on the basis of the opening. From the viewpoint of production efficiency of the polishing composition, the opening of the filter is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.2 μm. Further, from the viewpoint of enhancing the effect of removing foreign substances and aggregates, the aperture of the filter is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. The material and structure of the filter are not particularly limited. Examples of the filter material include cellulose, nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass. Examples of the filter structure include depth, pleats, and membranes.

  In the polishing composition manufacturing method described above, a polishing composition obtained by mixing a basic abrasive dispersion and a water-soluble polymer or an aqueous solution thereof is a polishing liquid (working slurry) or substantially the same NV as this. In some cases, the present invention can be applied to a concentrated liquid described later. Even when a basic abrasive dispersion and a water-soluble polymer or an aqueous solution thereof are mixed to obtain a concentrated liquid, and the concentrated liquid is diluted to prepare a polishing liquid, the above-described procedure in the preparation of the concentrated liquid is performed. (In other words, first, a basic abrasive dispersion containing abrasive grains and a basic compound is prepared, and a procedure in which a water-soluble polymer or an aqueous solution thereof is mixed) is applied to the abrasive grains and the water-soluble polymer. Can be uniformly promoted. By diluting the concentrated liquid thus prepared, a polishing liquid satisfying the desired D95 / D50 can be manufactured stably (with good reproducibility).

<Polishing>
The polishing composition disclosed herein can be suitably used for polishing an object to be polished, for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method for polishing an object to be polished using the polishing composition disclosed herein will be described.
That is, a polishing liquid (typically a slurry-like polishing liquid, sometimes referred to as a polishing slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include preparing a polishing liquid by adding operations such as concentration adjustment (for example, dilution) and pH adjustment to the polishing composition as described above. Or you may use polishing composition as polishing liquid as it is.

  Next, the polishing liquid is supplied to the object to be polished and polished by a conventional method. For example, when final polishing of a silicon wafer is performed, the silicon wafer that has undergone the lapping process and the primary polishing process is set in a general polishing apparatus, and the surface of the silicon wafer (surface to be polished) is passed through a polishing pad of the polishing apparatus. ) Is supplied to the polishing liquid. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface of the silicon wafer to relatively move (for example, rotate) the two. The polishing of the object to be polished is completed through the polishing process.

  The polishing step as described above may be a part of a manufacturing process of a polished object (for example, a substrate such as a silicon wafer). Therefore, according to this specification, a method for producing a polished article (preferably a method for producing a silicon wafer) including the above polishing step is provided.

In a preferred embodiment of the method for producing a polished article disclosed herein, the polishing liquid supplied to the object to be polished in the polishing step includes abrasive grains, a water-soluble polymer, and water, and the Mw of the water-soluble polymer is 20 × 10 ⁴ or less, and the polishing liquid contains abrasive grains, grains composed of abrasive grains and a water-soluble polymer as particles, and the volume-based particle size distribution of the particles measured by a dynamic light scattering method In the above, a polishing liquid having D95 / D50 of 2.00 or less can be preferably used. The abrasive grain concentration of the polishing liquid is not particularly limited, and may be, for example, about 0.05 to 5% by mass. That is, the polishing article manufacturing method disclosed herein can be preferably implemented in such a manner that D95 / D50 measured for the polishing liquid actually supplied to the object to be polished is in the above range. According to such an embodiment, a polished article (for example, a silicon wafer) in which generation of fine defects is particularly effectively suppressed can be manufactured.

  In addition, the polishing pad used in the polishing process using the polishing liquid containing the polishing composition disclosed herein is not particularly limited. For example, any of non-woven fabric type, suede type, those containing abrasive grains, those not containing abrasive grains, etc. may be used.

<Washing>
A polished article polished with the polishing composition disclosed herein is typically washed after polishing. This washing can be performed using an appropriate washing solution. The cleaning liquid to be used is not particularly limited. For example, an SC-1 cleaning liquid (ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ), water (H ₂ O) and the like that are common in the field of semiconductors and the like. Hereinafter, cleaning with the SC-1 cleaning liquid is referred to as “SC-1 cleaning”), SC-2 cleaning liquid (mixed liquid of HCl, H ₂ O ₂ and H ₂ O), etc. Can be used. The temperature of the cleaning liquid can be, for example, about room temperature to about 90 ° C. From the viewpoint of improving the cleaning effect, a cleaning solution of about 50 ° C to 85 ° C can be preferably used.

<Concentrate>
The polishing composition disclosed herein may be in a concentrated form (that is, in the form of a concentrated liquid of polishing liquid) before being supplied to the object to be polished. The polishing composition in such a concentrated form is advantageous from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage and the like. The concentration ratio can be, for example, about 2 to 100 times in terms of volume, and usually about 5 to 50 times is appropriate. The concentration rate of the polishing composition according to a preferred embodiment is 10 to 30 times, for example, 15 to 25 times.

  Thus, the polishing composition in the form of a concentrated liquid can be used in such a manner that a polishing liquid is prepared by diluting at a desired timing and the polishing liquid is supplied to an object to be polished. The dilution can be typically performed by adding and mixing the above-mentioned aqueous solvent to the concentrated solution. In addition, when the aqueous solvent is a mixed solvent, only a part of the components of the aqueous solvent may be added for dilution, and a mixture containing these components in a different ratio from the aqueous solvent. A solvent may be added for dilution.

  NV of the said concentrate can be 50 mass% or less, for example. From the viewpoint of the stability of the polishing composition (for example, the dispersion stability of the abrasive grains) and filterability, the NV of the concentrated liquid is usually suitably 40% by mass or less, and 30% by mass or less. More preferably, it is 20 mass% or less, for example, 15 mass% or less. Further, from the viewpoint of convenience, cost reduction, etc. during production, distribution, storage, etc., the NV of the concentrate is suitably 0.5% by mass or more, preferably 1% by mass or more, more preferably Is 3 mass% or more, for example, 5 mass% or more.

  The content of abrasive grains in the concentrated liquid can be, for example, 50% by mass or less. In general, the content is preferably 45% by mass or less, more preferably 40% by mass or less, from the viewpoints of stability of the polishing composition (for example, dispersion stability of abrasive grains) and filterability. . In a preferred embodiment, the abrasive content may be 30% by mass or less, or 20% by mass or less (for example, 15% by mass or less). In addition, from the viewpoint of convenience, cost reduction, etc. during production, distribution, storage, etc., the content of the abrasive grains can be, for example, 0.5% by mass or more, preferably 1% by mass or more, and more preferably. Is 3% by mass or more.

The content of the water-soluble polymer in the concentrated liquid can be, for example, 3% by mass or less. In general, the content is preferably 1% by mass or less, more preferably 0.5% by mass or less, from the viewpoints of filterability and detergency of the polishing composition. Further, the content, manufacturing, distribution, in terms of convenience and cost reduction, etc. at the time of such storage typically is suitably to be at 1 × 10 ^-3 wt% or more, preferably 5 × 10 ^{- It is 3} % by mass or more, more preferably 1 × 10 ⁻² % by mass or more.

A polishing composition according to a preferred embodiment is 25 mL or more in a filtration test conducted under the following conditions when the content of abrasive grains is 5% by mass (typically in the form of a concentrated solution). Have a level of filterability that can be filtered (i.e., pass through the filter without changing the filter).
[Filtration test conditions]
Test temperature: 25 ° C
Filtration differential pressure: 50 kPa (suction filtration)
Filter used: Disc filter made by Nippon Pole Co., Ltd., trade name “Ulchipore (registered trademark) N66” (diameter 47 mm, rated filtration accuracy 0.2 μm)

Thus, the polishing composition which shows favorable filterability is suitable for the use in the aspect manufactured, distribute | circulated or preserve | saved in the form of the concentrate with comparatively high abrasive grain content, for example.
The reason why the content of the abrasive grains in the filtration test is 5% by mass is to facilitate the evaluation of the filterability of the polishing composition, and the abrasive in the polishing composition disclosed herein. It is not intended to limit the content of the grains to 5% by mass.

  The polishing composition disclosed herein may be a one-part type or a multi-part type including a two-part type. For example, the liquid A containing a part of the constituent components (typically components other than the aqueous solvent) of the polishing composition and the liquid B containing the remaining components are mixed to prepare the polishing object. You may be comprised so that it may be used for grinding | polishing. The technique disclosed here can be preferably implemented, for example, in the form of a one-pack type polishing composition.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.

<Preparation of polishing composition>
Example 1
A pH 7.0 colloidal silica dispersion containing colloidal silica as abrasive grains at a concentration of 20% was prepared. The colloidal silica had an average primary particle size of 24 nm and an average secondary particle size of 46 nm. The average primary particle size was measured using a surface area measuring device manufactured by Micromeritex, Inc., trade name “Flow Sorb II 2300”, and the average secondary particle size was measured using the colloidal silica dispersion. It is a volume average secondary particle diameter measured using a model “UPA-UT151” manufactured by Nikkiso Co., Ltd. as a sample (the same applies in the following examples).
Aqueous ammonia containing ammonia (NH ₃ ) at a concentration of 29% as a basic compound was added to the colloidal silica dispersion to prepare a basic dispersion having a pH of 10.3. A polymer aqueous solution containing Mw8 × 10 ⁴ hydroxyethyl cellulose (hereinafter sometimes referred to as “HEC-A”) at a concentration of 1.5% and adjusted to pH 9.0 with ammonia was prepared. Added to the basic dispersion and mixed. Further, ultrapure water was added to prepare a polishing composition concentrate having an abrasive concentration of 3.5%. This concentrated solution was diluted with ultrapure water so that the abrasive concentration was 0.2% to prepare a polishing solution having the composition shown in Table 1. The contents of the water-soluble polymer and ammonia in this polishing liquid are 5 parts and 2.5 parts, respectively, with respect to 100 parts of the abrasive grains. The resulting polishing liquid had a pH of 10.1.

Using the polishing liquid thus obtained (abrasive grain concentration of 0.2%) as a measurement sample, particle size measurement (volume basis) based on the dynamic light scattering method is performed with a model “UPA-UT151” manufactured by Nikkiso Co., Ltd. D10 (10% cumulative diameter), D50 (50% cumulative diameter), D95 (95% cumulative diameter), D95 / D50, D95 / D10 and D _A (volume average particle diameter) of the particles contained in the measurement sample Asked.

(Example 2)
Instead of the polymer aqueous solution of Example 1, Mw 12 × 10 ⁴ hydroxyethyl cellulose (hereinafter sometimes referred to as “HEC-B”) was contained at a concentration of 1.5%, and adjusted to pH 9.0 with ammonia. An aqueous polymer solution was used. Otherwise in the same manner as in Example 1, a polishing liquid having the composition shown in Table 1 was prepared. Further, the particle diameter was measured in the same manner as in Example 1 using this polishing liquid as a measurement sample.

(Example 3)
Colloidal silica as an abrasive grain (average primary particle diameter 35 nm, average secondary particle diameter 66 nm) at a concentration of 20% in a pH 7.0 colloidal silica dispersion and 29% ammonia (NH ₃ ) as a basic compound A basic dispersion liquid having a pH of 10.3 was prepared by adding ammonia water at a concentration of 1 to 10. To this basic dispersion, an aqueous polymer solution containing HEC-B at a concentration of 4% and a surfactant at a concentration of 4.8% and adjusted to pH 7.0 with ammonia was added. As a surfactant, a PEO-PPO-PEO block copolymer (Mw9000) is used, and its use amount is 0.024% in the polishing liquid (4.8 parts with respect to 100 parts of abrasive grains). It adjusted so that it might become. Further, ultrapure water was added to prepare a polishing composition concentrate having an abrasive concentration of 9.2%. This concentrated solution was diluted with ultrapure water so that the abrasive concentration was 0.5% to prepare a polishing solution having the composition shown in Table 1. The amount of the water-soluble polymer and aqueous ammonia used is adjusted so that the content of the water-soluble polymer and ammonia per surface area of the abrasive grains contained in the unit volume of polishing liquid is approximately the same as that of the polishing liquid of Example 1. did.
The particle diameter was measured in the same manner as in Example 1 using a sample prepared by further diluting the polishing liquid with ultrapure water and adjusting the abrasive concentration to 0.2%.

Example 4
Instead of the aqueous polymer solution of Example 1, an aqueous polymer solution containing polyvinyl alcohol having a Mw of 1.3 × 10 ⁴ (degree of saponification of 95 mol% or more; hereinafter sometimes referred to as “PVA-A”) at a concentration of 2%. It was used. Otherwise in the same manner as in Example 1, a polishing liquid having the composition shown in Table 1 was prepared. The particle diameter was measured in the same manner as in Example 1 using this polishing liquid as a measurement sample.

(Example 5)
Instead of the polymer aqueous solution of Example 1, a polymer aqueous solution containing Mw 5.3 × 10 ⁴ polyvinyl alcohol (degree of saponification of 95 mol% or more; hereinafter sometimes referred to as “PVA-B”) at a concentration of 2%. It was used. Otherwise in the same manner as in Example 1, a polishing liquid having the composition shown in Table 1 was prepared. The particle diameter was measured in the same manner as in Example 1 using this polishing liquid as a measurement sample.

(Comparative Example 1)
Instead of the polymer aqueous solution of Example 1, an aqueous polymer solution having a pH of 7.0 containing Mw 25 × 10 ⁴ hydroxyethyl cellulose (hereinafter sometimes referred to as “HEC-C”) at a concentration of 1.5% was used. . Otherwise in the same manner as in Example 1, a polishing liquid having the composition shown in Table 1 was prepared. The particle diameter was measured in the same manner as in Example 1 using this polishing liquid as a measurement sample.

(Comparative Example 2)
Instead of the polymer aqueous solution of Example 1, a pH 7.0 aqueous polymer solution containing Mw50 × 10 ⁴ hydroxyethyl cellulose (hereinafter sometimes referred to as “HEC-D”) at a concentration of 1% was used. Otherwise in the same manner as in Example 1, a polishing liquid having the composition shown in Table 1 was prepared. The particle diameter was measured in the same manner as in Example 1 using this polishing liquid as a measurement sample.

(Comparative Example 3)
Instead of the polymer aqueous solution of Example 1, an aqueous polymer solution having a pH of 7.0 containing Mw 120 × 10 ⁴ hydroxyethyl cellulose (hereinafter sometimes referred to as “HEC-E”) at a concentration of 1% was used. Otherwise in the same manner as in Example 1, a polishing liquid having the composition shown in Table 1 was prepared. The particle diameter was measured in the same manner as in Example 1 using this polishing liquid as a measurement sample.

(Comparative Example 4)
Colloidal silica as an abrasive grain (average primary particle diameter 35 nm, average secondary particle diameter 66 nm) at a concentration of 20% in a pH 7.0 colloidal silica dispersion and 29% ammonia (NH ₃ ) as a basic compound A basic dispersion liquid having a pH of 10.3 was prepared by adding ammonia water at a concentration of 1 to 10. To this basic dispersion, an aqueous polymer solution containing 1% HEC-C and 5% surfactant and adjusted to pH 7.0 with ammonia was added. As the surfactant, a PEO-PPO-PEO block copolymer (Mw9000) was used. Further, ultrapure water was added to prepare a polishing composition concentrate having an abrasive concentration of 9.2%. This concentrated solution was diluted with ultrapure water so that the abrasive concentration was 0.5% to prepare a polishing solution having the composition shown in Table 1.
The particle diameter was measured in the same manner as in Example 1 using a sample prepared by further diluting the polishing liquid with ultrapure water and adjusting the abrasive concentration to 0.2%.

(Comparative Example 5)
A colloidal silica dispersion having a pH of 7.0 containing 20% of colloidal silica (average primary particle size 53 nm, average secondary particle size 80 nm) as abrasive grains is mixed with 29% of ammonia (NH ₃ ) as a basic compound. A basic dispersion liquid having a pH of 10.3 was prepared by adding ammonia water at a concentration of 1 to 10. To this basic dispersion, an aqueous polymer solution having a pH of 7.0 containing 1.5% HEC-B and 5% surfactant was added. As the surfactant, a PEO-PPO-PEO block copolymer (Mw9000) was used. Further, ultrapure water was added to prepare a polishing composition concentrate having an abrasive concentration of 9.2%. This concentrated solution was diluted with ultrapure water so that the abrasive concentration was 0.5% to prepare a polishing solution having the composition shown in Table 1.
The particle diameter was measured in the same manner as in Example 1 using a sample prepared by further diluting the polishing liquid with ultrapure water and adjusting the abrasive concentration to 0.2%.

<Polishing of silicon wafer>
The surface of the silicon wafer was polished under the following conditions using the polishing liquid according to each example. A silicon wafer having a diameter of 300 mm, a conductivity type of P type, a crystal orientation of <100>, and a resistivity of 0.1 Ω · cm or more and less than 100 Ω · cm is a polishing slurry (manufactured by Fujimi Incorporated, The surface roughness was adjusted to 0.1 nm to 10 nm by performing preliminary polishing using a trade name “GLANZOX 2100”).

[Polishing conditions]
Polishing machine: Single wafer polishing machine manufactured by Okamoto Machine Tool Co., Ltd. Model “PNX-332B”
Polishing table: Final polishing 1st stage and 2nd stage after preliminary polishing were carried out using 2 tables at the back stage among the 3 tables of the polishing machine.
(The following conditions are the same for each table.)
Polishing load: 15 kPa
Plate rotation speed: 30 rpm
Head rotation speed: 30rpm
Polishing time: 2 minutes Polishing liquid temperature: 20 ° C
Polishing liquid supply rate: 2.0 l / min

<Washing>
The polished silicon wafer was cleaned at 60 ° C. and 6 ° C. using a cleaning solution of NH ₄ OH (29%): H ₂ O ₂ (31%): deionized water (DIW) = 1: 3: 30 (volume ratio). Washing was performed under the condition of min x 2 tank (no ultrasonic application) (SC-1 cleaning). More specifically, two cleaning tanks are prepared, the cleaning liquid is accommodated in each of the first and second cleaning tanks and held at 60 ° C., and the polished silicon wafer is stored in the first cleaning tank. It was immersed in the 2nd washing tank for 6 minutes through the rinse tank by ultrapure water after that for 6 minutes.

<Evaluation of number of fine particles>
The number of particles having a size of 0.037 μm or more present on the surface of a silicon wafer having a diameter of 300 mm after cleaning was counted using a wafer inspection apparatus manufactured by KLA-Tencor Corporation, trade name “Surfscan SP2.” The results are shown in the “LPD number” column of Table 1 in the following three stages.
A: The number of particles is less than 5000 B: The number of particles is 5000 or more and less than 20000 C: The number of particles is 20000 or more

<Filtration evaluation>
The filterability of the polishing composition was evaluated as follows. That is, the polishing composition concentrate according to each example was adjusted to a concentration at which the abrasive content was 5%, and this was suction filtered under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 50 kPa. As a filter, a disk filter manufactured by Nippon Pole Co., Ltd., trade name “Ulchipore (registered trademark) N66” (diameter 47 mm, rated filtration accuracy 0.2 μm) was used. From the volume of the polishing composition that passed through the filter until the flow of the polishing composition that passed through the filter stopped, the filterability was evaluated at the following two levels. The obtained results are shown in the column of “Filterability” in Table 1.
A: The volume of the polishing composition that has passed through the filter is 25 mL or more.
C: The volume of the polishing composition that has passed through the filter is less than 25 mL.

<Haze measurement>
The surface of the cleaned silicon wafer was measured for haze (ppm) in the DWO mode using a wafer inspection apparatus manufactured by KLA-Tencor Corporation, trade name “Surfscan SP2.” The measurement results are shown in Table 1 in the following two stages.
A: Less than 0.065 ppm B: 0.065 ppm or more

As shown in Table 1, according to Examples 1 to 5 using a water-soluble polymer having an Mw of 20 × 10 ⁴ or less and a polishing liquid having a D95 / D50 of 2.00 or less, Comparative Examples 1 to Compared to 5, the number of fine particles (LPD) was clearly reduced, and a polished surface equivalent to or better than Comparative Examples 1 to 5 was obtained in terms of low haze. The polishing compositions according to Examples 1 to 5 had good filterability and were suitable for industrial use. From the viewpoint of haze reduction, using hydroxyethyl cellulose as a water-soluble polymer, and a volume average particle diameter D _A is 60nm or less (more specifically, more than 45 nm 55 nm or less) in Examples 1 and 2 using the polishing liquid is Especially good results were obtained.

On the other hand, Comparative Examples 1 to 3 using a polishing liquid having a water-soluble polymer Mw larger than 20 × 10 ⁴ and D95 / D50 larger than 2.00 had a large number of LPDs on the polished surface. In particular, Comparative Examples 2 and 3 having a D95 / D50 of greater than 3.00 had a larger number of LPDs than Comparative Example 1, and the polishing composition had low filterability and high haze. . Moreover, even if D95 / D50 is 2.00 or less, in the polishing liquid of Comparative Example 4 where the Mw of the water-soluble polymer used is larger than 20 × 10 ⁴ , the effect of reducing the number of LPDs as in Examples 1 to 5 is It was not obtained. Moreover, although the water-soluble polymer whose Mw is 20 × 10 ⁴ or less is used, Comparative Example 5 in which D95 / D50 is larger than 2.00 has a large number of LPDs and poor filterability.

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

Claims (8)

A polishing composition comprising abrasive grains, a water-soluble polymer, and water,
The water-soluble polymer has a weight average molecular weight of 20 × 10 ⁴ or less,
The polishing composition is a volume-based particle size distribution of particles in the polishing composition measured by a dynamic light scattering method at a concentration such that the content of the abrasive grains is 0.2% by mass. Polishing composition whose ratio (D95 / D50) of 95% cumulative diameter D95 to 50% cumulative diameter D50 is 2.00 or less.   2. The polishing composition according to claim 1, wherein in the particle size distribution of the particles in the polishing composition, a ratio (D95 / D10) of 95% cumulative diameter D95 to 10% cumulative diameter D10 is 3.00 or less. . The average primary particle diameter _{D P1} of the abrasive grains is 15Nm～30nm, polishing composition according to claim 1 or 2. The abrasive grains having an average secondary particle diameter _{D P2} is 20 nm to 50 nm, the polishing composition according to any one of claims 1 to 3. The polishing composition, the difference between the volume average particle diameter D _A and the abrasive grains having an average secondary particle diameter D _P2 for particles in the polishing composition to be measured by the dynamic light scattering method 10nm The polishing composition according to any one of claims 1 to 4, which is less than 5.   The polishing composition according to any one of claims 1 to 5, further comprising a basic compound. A method for producing a polishing composition comprising abrasive grains, a water-soluble polymer, a basic compound, and water, comprising:
Preparing a dispersion containing the abrasive grains, the basic compound and water;
Preparing an aqueous solution containing the water-soluble polymer and water; and adding and mixing the aqueous solution to the dispersion;
Including
Here, the water-soluble polymer has a weight average molecular weight of 20 × 10 ⁴ or less,
The polishing composition is a volume-based particle size distribution of particles in the pre-polishing composition measured by a dynamic light scattering method at a concentration at which the abrasive grain content is 0.2% by mass, Polishing composition manufacturing method whose ratio (D95 / D50) of 95% cumulative diameter D95 with respect to 50% cumulative diameter D50 is 2.00 or less. Supplying a polishing liquid to the object to be polished; and polishing the surface of the object to be polished with the polishing liquid;
A method for producing a polished article comprising:
Here, as the polishing liquid supplied to the object to be polished,
Containing abrasive grains, a water-soluble polymer and water,
The water-soluble polymer has a weight average molecular weight of 20 × 10 ⁴ or less,
In the volume-based particle size distribution of particles in the polishing liquid measured by the dynamic light scattering method, the ratio of the 95% cumulative diameter D95 to the 50% cumulative diameter D50 (D95 / D50) is 2.00 or less. Polished article manufacturing method using polishing liquid.