WO2018025655A1

WO2018025655A1 - Liquid concentrate of composition for rough-polishing silicon wafers

Info

Publication number: WO2018025655A1
Application number: PCT/JP2017/026405
Authority: WO
Inventors: 雄彦村瀬; 恵谷口; 圭祐沼田; 麗子秋月; 公亮土屋
Original assignee: 株式会社フジミインコーポレーテッド
Priority date: 2016-08-02
Filing date: 2017-07-21
Publication date: 2018-02-08
Also published as: JP6916792B2; JPWO2018025655A1; TWI744369B; TW201811975A

Abstract

Provided is a liquid concentrate of a composition for rough-polishing silicon wafers, which, when being diluted, is able to deliver preferable polishing performance, and which exhibits excellent stability. The liquid concentrate of a composition for rough-polishing silicon wafers provided by the present invention comprises abrasive particles, a basic compound, and a water-soluble polymer, wherein the ratio [rg/d] of the radius of gyration rg [nm] of the water-soluble polymer to the inter-particle distance d [nm] of the abrasive particles is 4.7 or less.

Description

Silicon wafer rough polishing composition concentrate

The present invention relates to a concentrate of a composition for rough polishing of silicon wafers.
This application claims priority based on Japanese Patent Application No. 2016-152324 filed on Aug. 2, 2016, the entire contents of which are incorporated herein by reference.

Generally, the surface of a silicon substrate used for manufacturing a semiconductor product is finished to a high-quality mirror surface through a lapping process and a polishing process. The polishing process typically includes a preliminary polishing process and a finishing polishing process. The preliminary polishing process is also called a rough polishing process. The finish polishing process is also called a finish polishing process. This type of polishing composition may be in a concentrated form before being supplied to the object to be polished, from the viewpoint of convenience in manufacturing, distribution, storage, etc. and cost reduction. That is, the polishing composition may be in the form of a concentrated concentrate of polishing liquid. The prepared concentrated liquid is diluted with water and used for polishing. Patent document 1 is mentioned as a literature which discloses this kind of prior art. Patent Document 2 is a document disclosing the radius of inertia of hydroxycellulose used in the polishing composition.

Japanese Patent Application Publication No. 2012-89862 Japanese Patent Application Publication No. 2015-124231

As a result of examining the performance improvement of the silicon wafer rough polishing composition, the present inventors have obtained knowledge that the polishing performance is improved as the water-soluble polymer is added and the inertia radius is larger. . The polishing performance here is typically flatness, for example, GBIR (Global Backside Ideal Range). However, on the other hand, if the inertial radius of the water-soluble polymer is too large, the stability at the stage of the concentrate tends to decrease. Specifically, since the concentrated liquid contains components such as abrasive grains and water-soluble polymers at a higher concentration than when used, there is a risk that good stability such as separation and aggregation of the contained components may not be obtained. is there. Even in the form of a concentrated solution of high concentration, if a polishing composition that is excellent in stability and can exhibit good polishing performance after dilution is provided, it is advantageous in terms of convenience and cost reduction, There are great practical advantages.

The present invention has been made in view of the above circumstances, and provides a concentrated liquid of a composition for rough polishing of silicon wafers that can exhibit good polishing performance after dilution and has excellent stability. The purpose is to do.

According to the present invention, there is provided a concentrated liquid for a silicon wafer rough polishing composition comprising abrasive grains, a basic compound and a water-soluble polymer. The ratio [rg / d] of the radius of inertia rg [nm] of the water-soluble polymer to the interparticle distance d [nm] of the abrasive grains in the concentrated liquid is 4.7 or less. The concentrated liquid having such a configuration exhibits excellent stability and can exhibit good polishing performance after dilution. The polishing performance is typically a flatness improving effect.

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.

<Concentrated liquid of polishing composition>
(Characteristic)
The concentrate of the polishing composition disclosed herein contains abrasive grains and a water-soluble polymer. Hereinafter, the concentrated liquid of the polishing composition may be simply abbreviated as “concentrated liquid”. Such a concentrated liquid is characterized by a ratio [rg / d] of the inertia radius rg [nm] of the water-soluble polymer to the interparticle distance d [nm] of the abrasive grains being 4.7 or less. A concentrated solution satisfying the above characteristics exhibits excellent stability. The reason for this is not particularly limited, but when the ratio [rg / d] is satisfied, the water-soluble polymer is stably present between the abrasive grains in the concentrate. This is presumably because the abrasive particles and the water-soluble polymer, which are the main components of the concentrate, can be stably dispersed in the concentrate. Further, when the concentrated liquid is diluted and used as a polishing liquid, the polishing performance can be exhibited with respect to the substrate to be polished, that is, the silicon wafer, by including the water-soluble polymer. Specifically, the polishing performance is an effect of improving flatness. The ratio [rg / d] is preferably 3.8 or less, more preferably 2.8 or less, still more preferably 2.5 or less, and particularly preferably 1.9 or less, from the viewpoint of improving stability. In a particularly preferred embodiment, the ratio [rg / d] is typically 1.0 or less. The lower limit of the above ratio [rg / d] is not particularly limited, and can usually be about 0.3 or more, for example, 0.6 or more, from the viewpoint of the concentration efficiency of the concentrate, polishing performance, and the like. The interparticle distance d [nm] of the abrasive grains and the inertial radius rg [nm] of the water-soluble polymer are measured by the method described later.

(Abrasive grains)
The abrasive grains disclosed herein are contained in the concentrated liquid in such a content that the inter-particle distance d [nm] of the abrasive grains satisfies the above ratio [rg / d]. In a preferred embodiment, the interparticle distance d of the abrasive grains is 200 nm or less. According to the technique disclosed here, the inter-particle distance d of the abrasive grains is not more than a predetermined value as described above, and excellent stability can be achieved even when the abrasive grains are relatively close to each other in the concentrated liquid. Can be realized. The interparticle distance d is more preferably 150 nm or less, further preferably 100 nm or less, and particularly preferably 80 nm or less from the viewpoint of the concentration efficiency of the concentrate. In a particularly preferred embodiment, the interparticle distance d is typically 70 nm or less. Further, the inter-particle distance d may be, for example, 60 nm or less, further 40 nm or less, within a range that satisfies the ratio [rg / d].

In the present specification, the inter-particle distance d [nm] of the abrasive grains is assumed to be the closest packed ratio [74%] of the spheres assuming that the abrasive grains contained in the concentrate are uniformly dispersed. Based on the formula:
d [nm] = R _S × 2-D1
It is a theoretical value obtained from Here, R _S is the radius [nm] of a sphere that is centered on one abrasive grain and circumscribes the corresponding sphere of the adjacent abrasive grain, and D1 is the average primary particle diameter [nm] of the abrasive grain. It is. R _S is the concentrate can be rephrased as the radius [nm] of a sphere having a volume of concentrate to be assigned to one of the abrasive particles is determined in the following manner. Specifically, a value obtained by multiplying the volume of a concentrated liquid of a unit volume, for example, 1 L, by a filling rate of 74% is divided by the number of abrasive grains contained in the concentrated liquid of the unit volume, thereby obtaining one abrasive grain. It obtains the volume _{V S} of the maximum size of the sphere which particles can occupy the _{formula: V S = 4/3 ×} πR S 3; the _{R S} is determined. The number of abrasive grains contained in a unit volume of concentrated liquid is obtained by dividing the weight [g / L] of abrasive grains per concentrated volume of unit volume, for example, 1 L, by the weight [g] per abrasive grain. Is required. The weight of the abrasive grains per unit volume of the concentrate is determined from the content and specific gravity of the abrasive grains in the concentrate and the content and specific gravity of components other than the abrasive grains contained in the concentrate. The specific gravity of the abrasive grains is, for example, 2.2 g / cm ³ in the case of silica abrasive grains. Components other than the abrasive grains contained in the concentrated liquid usually have an aqueous solvent as a main component. The weight [g] per abrasive grain particle is determined from the average primary particle diameter [nm] of the abrasive grain particle and the specific volume of the abrasive grain particle when the primary particle is regarded as a true sphere.

In the technology disclosed herein, the material and properties of the abrasive grains contained in the concentrated liquid and the polishing composition diluted with the concentrated liquid are not particularly limited, and can be appropriately selected according to the purpose of use, usage mode, and the like. it can. 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, poly (meth) acrylic acid particles, 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. In addition, (meth) acrylic acid is the meaning which points out acrylic acid and methacrylic acid comprehensively.

As the abrasive, inorganic particles are preferable, and particles made of metal or metalloid oxide are particularly preferable. A particularly preferable abrasive grain in the technology disclosed herein includes silica particles. The technique disclosed here can be preferably implemented, for example, in a mode in which the abrasive grains are substantially composed of silica particles. Here, “substantially” means that 95% by weight or more, preferably 98% by weight or more, more preferably 99% by weight or more of the particles constituting the abrasive grains are silica particles. 100% by weight of the particles may be silica particles.

Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica and the like. Silica particles can be used alone or in combination of two or more. Colloidal silica is particularly preferable because scratches are hardly generated on the surface of the object to be polished and good polishing performance can be exhibited. Here, good polishing performance refers to performance that reduces surface roughness. As the colloidal silica, for example, colloidal silica produced using water glass as a raw material by an ion exchange method or alkoxide colloidal silica can be preferably used. Water glass is also called Na silicate. The alkoxide colloidal silica refers to colloidal silica produced by hydrolysis condensation reaction of alkoxysilane. Colloidal silica can be used alone or in combination of two or more.

The true specific gravity of 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. As the true specific gravity of silica increases, the polishing rate tends to increase. From this viewpoint, silica particles having a true specific gravity of 2.0 or more are particularly preferable. In a particularly preferred embodiment, the true specific gravity is, for example, 2.1 or more. The upper limit of the true specific gravity of silica is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less. As the true specific gravity of silica, a measured value by a liquid substitution method using ethanol as a substitution liquid can be adopted.

The average primary particle diameter of the abrasive grains disclosed herein is not particularly limited. The abrasive grains are typically silica particles. From the viewpoint of polishing rate and the like, the average primary particle size is suitably 5 nm or more, preferably 10 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, and particularly preferably 45 nm or more. In a particularly preferred embodiment, the average primary particle diameter is, for example, 50 nm or more. From the viewpoint of preventing scratches and the like, the average primary particle diameter of the abrasive grains is suitably about 200 nm or less, preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less. In a particularly preferred embodiment, the average primary particle size of the abrasive grains can be 60 nm or less, for example 55 nm or less.
In addition, in this specification, the average primary particle diameter is BET diameter [nm] = 6000 / (true density [g / cm ³ ] × BET value [m ² / g]) from the specific surface area measured by the BET method. The particle diameter calculated by the formula Here, the specific surface area measured by the BET method is referred to as a BET value. For example, in the case of silica particles, the BET diameter can be calculated from BET diameter [nm] = 2727 / BET value [m ² / g]. The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritex Corporation, a trade name “Flow Sorb II 2300”.

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

Although not particularly limited, the average value of the major axis / minor axis ratio of the abrasive grains is theoretically 1.0 or more, preferably 1.05 or more, and more preferably 1.1 or more. The average value of the major axis / minor axis ratio of the abrasive grains is also referred to as an average aspect ratio. By increasing the average aspect ratio, a higher polishing rate can be achieved. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less, from the viewpoint of reducing scratches.

The shape (outer shape) and average aspect ratio of the abrasive grains can be grasped by, for example, observation with an electron microscope. As a specific procedure for grasping the average aspect ratio, for example, with a scanning electron microscope (SEM), for a predetermined number of silica particles capable of recognizing the shape of independent particles, the minimum circumscribing each particle image is performed. Draw a rectangle. Here, the predetermined number is, for example, 200. 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.

The content (concentration) of abrasive grains in the concentrate disclosed herein can be, for example, 50% by weight or less. From the viewpoint of the stability of the concentrate, filterability, and the like, it is usually appropriate that the content of abrasive grains be 45% by weight or less, for example 40% by weight or less, typically 35% by weight or less. The content of the abrasive is preferably 30% by weight or less, more preferably 25% by weight or less, and still more preferably 20% by weight or less. In a more preferred embodiment, the content of the abrasive grains is, for example, 15% by weight or less. The content of the abrasive grains in the concentrated liquid is usually 1% by weight or more, for example, 3% by weight or more, from the viewpoints of the abrasive grain concentration of the polishing composition after dilution, convenience of production, distribution, storage and the like. Typically, it is suitable to be 5% by weight or more. The content of the abrasive is preferably 8% by weight or more. In a preferred embodiment, the content of the abrasive grains is, for example, 10% by weight or more, and further 12% by weight or more.

(Water-soluble polymer)
As the water-soluble polymer contained in the concentrated liquid disclosed herein, those having a radius of gyration (rg) satisfying a ratio [rg / d] of a predetermined value or less are used. The polishing slurry containing such a water-soluble polymer is well wetted and familiar with the substrate to be polished, and as a result, the polishing performance can be improved. The polishing performance here is typically flatness. The inertia radius rg of the water-soluble polymer is the size of one molecule of the water-soluble polymer in the aqueous solution, which can be mainly determined by the hydrophilicity, molecular weight, etc. of the polymer. The upper limit value of the inertia radius rg is a value limited in the relative relationship with the interparticle distance d because the upper limit of the ratio [rg / d] is limited. The inertial radius rg of the water-soluble polymer according to one embodiment is about 500 nm or less, and suitably about 300 nm or less. Further, when a water-soluble polymer having an inertia radius rg of 220 nm or less, more preferably 150 nm or less is used, the above ratio [rg / d] can be preferably satisfied. Concentration efficiency also tends to improve. The inertia radius rg may be about 100 nm or less, for example 70 nm or less. In a preferred embodiment, the water-soluble polymer has an inertial radius rg of 30 nm or more, and more preferably 50 nm or more. From the viewpoint of wettability of the substrate to be polished, the inertia radius rg is more preferably 80 nm or more, further preferably 100 nm or more, and particularly preferably 120 nm or more. In a particularly preferred embodiment, the inertia radius rg is, for example, 140 nm or more. According to the technique disclosed herein, even if the inertia radius rg of the water-soluble polymer is equal to or greater than a predetermined value, the concentrated liquid can realize excellent stability. In addition, when a polishing liquid containing a water-soluble polymer having an inertia radius rg of a predetermined value or more is used, wettability to the substrate surface is better exhibited and the polishing performance tends to be further improved. The polishing performance here is typically flatness. In addition, the inertial radius rg of the water-soluble polymer in the present specification is measured by the method described in Examples described later.

The type of the water-soluble polymer contained in the concentrate disclosed herein is not particularly limited, and can be appropriately selected from water-soluble polymer species known in the field of polishing compositions. A water-soluble polymer can be used singly or in combination of two or more. Examples of the water-soluble polymer include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms, polyvinyl alcohol and the like. Among these, from the viewpoint of improving flatness, cellulose derivatives and starch derivatives are preferable, and cellulose derivatives are more preferable.

Cellulose derivatives are polymers containing β-glucose units as the main repeating unit. Specific examples of the cellulose derivative include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose and the like. Of these, HEC is preferable.

Starch derivatives are polymers that contain α-glucose units as the main repeating unit. Specific examples of starch derivatives include pregelatinized starch, pullulan, carboxymethyl starch, and cyclodextrin. Of these, pullulan is preferred.

Polymers containing oxyalkylene units include polyethylene oxide (PEO), block copolymers of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and random copolymerization of EO and PO or BO. Examples include coalescence. Among these, a block copolymer of EO and PO or a random copolymer of EO and PO is preferable. The block copolymer of EO and PO may be a diblock body, a triblock body or the like including a PEO block and a polypropylene oxide (PPO) block. Examples of the triblock body include a PEO-PPO-PEO type triblock body and a PPO-PEO-PPO type triblock body. Usually, a PEO-PPO-PEO type triblock body is more preferable.
In the block copolymer or random copolymer of EO and PO, the molar ratio [EO / PO] of EO and PO constituting the copolymer is 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. In a more preferred embodiment, the molar ratio [EO / PO] is, for example, 5 or more.

As the polymer containing a nitrogen atom, both a polymer containing a nitrogen atom in the main chain and a polymer having a nitrogen atom in a side chain functional group (pendant group) can be used. By using a polymer containing nitrogen atoms, the surface roughness of the substrate can be improved. Examples of the polymer containing a nitrogen atom in the main chain include homopolymers and copolymers of N-acylalkylenimine type monomers. Specific examples of the N-acylalkyleneimine monomer include N-acetylethyleneimine, N-propionylethyleneimine and the like. Examples of the polymer having a nitrogen atom in the pendant group include a polymer containing an N-vinyl type monomer unit. For example, homopolymers and copolymers of N-vinylpyrrolidone can be employed. In the technology disclosed herein, at least one of a homopolymer and a copolymer of N-vinylpyrrolidone obtained by polymerizing N-vinylpyrrolidone at a ratio of 50 mol% or more (hereinafter also referred to as “PVP”). Preferably used.

When polyvinyl alcohol is used as the water-soluble polymer, the saponification degree of the polyvinyl alcohol is not particularly limited.

In the technique disclosed herein, the molecular weight of the water-soluble polymer can be appropriately set within a range that satisfies a ratio [rg / d] of a predetermined value or less. The weight average molecular weight (Mw) of the water-soluble polymer can be about 200 × 10 ⁴ or less from the viewpoint of stability, concentration efficiency, etc., and is usually 150 × 10 ⁴ or less, for example, 100 × 10 ⁴ or less. Is appropriate. The Mw, for example 50 × 10 ⁴ or less, or may be 30 × 10 ⁴ or less. Further, from the viewpoint of protecting the substrate surface and improving the polishing performance, usually, Mw is suitably 1 × 10 ⁴ or more, more preferably 10 × 10 ⁴ or more, and even more preferably 20 × 10 ⁴ or more. The Mw may be, for example, 50 × 10 ⁴ or more and 100 × 10 ⁴ or more. The above Mw can be particularly preferably applied to cellulose derivatives. Examples of the cellulose derivative include HEC.

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

The technique disclosed herein is preferably implemented in a mode in which two or more water-soluble polymers are used in combination. From the viewpoint of achieving both polishing performance (flatness) and surface roughness, one or more water-soluble polymers P1 selected from cellulose derivatives and starch derivatives, and water-soluble polymers other than cellulose derivatives and starch derivatives The combined use with 1 type or 2 types or more of P2 is more preferable. The water-soluble polymer P1 is typically a cellulose derivative such as HEC. The water-soluble polymer P2 is preferably a polymer containing a nitrogen atom in the main chain, a polymer having a nitrogen atom in the side chain functional group (pendant group), and more preferably a polymer containing an N-vinyl type monomer unit. Among these, N-vinylpyrrolidone homopolymers and copolymers (typically PVP) are particularly preferred.

In the technique disclosed herein, when the water-soluble polymer P1 and the water-soluble polymer P2 are used in combination, the blending ratio of the water-soluble polymer P1 and the water-soluble polymer P2 is not particularly limited. The ratio [P2 / P1] of the content of the water-soluble polymer P2 to the content of the water-soluble polymer P1 is suitably 0.1 or more. The ratio [P2 / P1] is, for example, 0.25 or more, typically 0.5 or more. The ratio [P2 / P1] is suitably about 10 or less. The ratio [P2 / P1] is, for example, 2.5 or less, typically less than 1. The water-soluble polymer P1 is a cellulose derivative such as HEC, and the water-soluble polymer P2 is a polymer containing an N-vinyl type monomer unit such as PVP.

In the embodiment in which the water-soluble polymers P1 and P2 are used in combination, the molecular weight of the water-soluble polymer P1 can be appropriately set within a range that satisfies a ratio [rg / d] of a predetermined value or less. The weight average molecular weight (Mw) of the water-soluble polymer P1 can be about 200 × 10 ⁴ or less from the viewpoint of stability, concentration efficiency, etc., and is usually 150 × 10 ⁴ or less, for example, 100 × 10 ⁴ or less. Is appropriate. The Mw may be, for example, 50 × 10 ⁴ or less and 30 × 10 ⁴ or less. Further, from the viewpoint of protecting the substrate surface and improving the polishing performance, usually, Mw is suitably 1 × 10 ⁴ or more, more preferably 10 × 10 ⁴ or more, and even more preferably 20 × 10 ⁴ or more. The Mw, for example 50 × 10 ⁴ or more, may be 100 × 10 ⁴ or more. The above Mw can be particularly preferably applied to cellulose derivatives. The cellulose derivative is, for example, HEC.

Further, the molecular weight of the water-soluble polymer P2 is not particularly limited. The weight average molecular weight (Mw) of the water-soluble polymer P2 can be about 300 × 10 ⁴ or less, and is usually 150 × 10 ⁴ or less, for example, 50 × 10 ⁴ or less. From the viewpoint of stability and the like, the Mw may be 30 × 10 ⁴ or less, for example, 5 × 10 ⁴ or less. From the viewpoint of the surface protection improvement, typically, Mw is suitably 1 × 10 ⁴ or more, more preferably 2 × 10 ⁴ or more, more preferably 3 × 10 ⁴ or more. The above Mw can be particularly preferably applied to homopolymers and copolymers (typically PVP) of N-vinylpyrrolidone.

The content (concentration) of the water-soluble polymer in the concentrate disclosed herein is not particularly limited, and can be, for example, 0.0001% by weight or more. From the viewpoint of improving polishing performance, the preferable content is 0.001% by weight or more, more preferably 0.0025% by weight or more, for example, 0.005% by weight or more. The polishing performance is specifically flatness. Further, from the viewpoint of polishing rate and the like, the content is preferably 1% by weight or less, more preferably 0.2% by weight or less, further preferably 0.1% by weight or less, It is particularly preferable that the content be 0.05% by weight or less. In a particularly preferred embodiment, the content of the water-soluble polymer is, for example, 0.02% by weight or less.

In addition, the content of the water-soluble polymer in the concentrate disclosed herein can also be specified by the relative relationship with the abrasive grains contained in the concentrate. Specifically, the content of the water-soluble polymer is suitably 0.001 part by weight or more with respect to 100 parts by weight of the abrasive grains, and preferably 0.005 weight from the viewpoint of improving the polishing performance. Part or more, more preferably 0.01 part by weight or more, and still more preferably 0.015 part by weight or more. In a more preferred embodiment, the content of the water-soluble polymer is, for example, 0.03 parts by weight or more with respect to 100 parts by weight of the abrasive grains.
The polishing performance is specifically flatness. From the viewpoint of stability, polishing rate, etc., the content of the water-soluble polymer is suitably 10 parts by weight or less, preferably 1 part by weight or less, more preferably 100 parts by weight of abrasive grains. Is 0.5 parts by weight or less, more preferably 0.1 parts by weight or less. In a further preferred embodiment, the content of the water-soluble polymer is, for example, 0.05 parts by weight or less with respect to 100 parts by weight of the abrasive grains.

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

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

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

The concentrate disclosed herein may contain a combination of a quaternary ammonium compound and a weak acid salt as described above. The quaternary ammonium compound is, for example, a tetraalkylammonium hydroxide such as TMAH. As the weak acid salt, one that can be used for polishing using silica particles and can exhibit a desired buffering action in combination with a quaternary ammonium compound can be appropriately selected. The weak acid salts can be used alone or in combination of two or more. Specific examples of weak acid salts include sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium orthosilicate, potassium orthosilicate, sodium acetate, potassium acetate, sodium propionate, potassium propionate, calcium carbonate, calcium bicarbonate , Calcium acetate, calcium propionate, magnesium acetate, magnesium propionate, zinc propionate, manganese acetate, cobalt acetate and the like. Weak acid salts in which the anion component is carbonate ion or hydrogen carbonate ion are preferred, and weak acid salts in which the anion component is carbonate ion are particularly preferred. Moreover, as a cation component, alkali metal ions, such as potassium and sodium, are suitable. Particularly preferred weak acid salts include sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate. Of these, potassium carbonate (K ₂ CO ₃ ) is preferable.

When a quaternary ammonium compound and a weak acid salt are used in combination as the basic compound, the blending ratio of the quaternary ammonium compound and the weak acid salt is not particularly limited. For example, the quaternary ammonium compound: the weak acid salt Is suitably 1: 9 to 9: 1, preferably 3: 7 to 8: 2, more preferably 5: 5 to 7: 3. The quaternary ammonium compound is, for example, a tetraalkylammonium hydroxide such as TMAH. The weak acid salt is, for example, a weak acid salt whose anion component such as K ₂ CO ₃ is a carbonate ion.

The content (concentration) of the basic compound in the concentrated liquid disclosed herein is, for example, 0.1% by weight or more from the viewpoint of stability of the concentrated liquid, improvement of the polishing rate by the polishing composition after dilution, and the like. Specifically, the content is suitably 0.3% by weight or more, preferably 0.5% by weight or more, more preferably 0.6% by weight or more, and further preferably 0.8% by weight or more. In a more preferred embodiment, the content of the basic compound is, for example, 1.0% by weight or more, typically 1.2% by weight or more. For example, when the concentrated liquid is used after being diluted at a high magnification, the abrasive concentration after dilution is relatively low, and the processing force by the abrasive may tend to decrease. Even in such a case, chemical polishing after dilution can be strengthened by increasing the amount of the basic compound at the stage of the concentrate. The upper limit of the content of the basic compound in the concentrated solution is suitably 10% by weight or less, preferably 5% by weight or less, from the viewpoints of storage stability and surface quality. In a preferred embodiment, the content of the basic compound is, for example, 3% by weight or less.

Also, the content of the basic compound in the concentrate can be specified by the relative relationship with the abrasive grains contained in the concentrate. Specifically, the content of the basic compound in the concentrated solution is suitably 0.1 parts by weight or more with respect to 100 parts by weight of the abrasive grains, and preferably 1 weight from the viewpoint of improving the polishing rate. Part or more, more preferably 3 parts by weight or more, still more preferably 6 parts by weight or more. The content of the basic compound in the concentrated liquid may be, for example, about 12 parts by weight or more and 22 parts by weight or more. From the viewpoint of stability and surface quality, the content of the basic compound is suitably 50 parts by weight or less, preferably 30 parts by weight or less, with respect to 100 parts by weight of the abrasive grains. The content of the basic compound in the concentrate may be, for example, 20 parts by weight or less and 10 parts by weight or less with respect to 100 parts by weight of the abrasive grains.

(water)
The concentrate disclosed herein typically contains water. As water, ion exchange water (deionized water), pure water, ultrapure water, distilled water and 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 concentrate. 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. Moreover, the concentrate disclosed here may further contain an organic solvent that can be uniformly mixed with water, if necessary. The organic solvent is a lower alcohol, a lower ketone or the like. Usually, 90% by volume or more of the solvent contained in the concentrate is preferably water, and more preferably 95% by volume or more is water. In a more preferred embodiment, typically 99 to 100% by volume of the solvent contained in the concentrate is water. In the present specification, the term “aqueous solvent” may be used as a general term including the solvent and water.

(Chelating agent)
The concentrated liquid disclosed herein can contain a chelating agent as an optional component. The chelating agent functions to suppress contamination of the object to be polished by metal impurities by forming complex ions with metal impurities that can be contained in the concentrated liquid and capturing them. Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid-based 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 chelating agents are more preferred. Of these, ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and diethylenetriaminepentaacetic acid are preferable. Particularly preferred chelating agents include ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). A chelating agent can be used individually by 1 type or in combination of 2 or more types.

(Other ingredients)
The concentrated liquid disclosed herein is a polishing slurry such as a surfactant, organic acid, organic acid salt, inorganic acid, inorganic acid salt, preservative, antifungal agent, etc., as long as the effect of the present invention is not significantly hindered. You may further contain the well-known additive which may be used for this as needed. As the surfactant, various surfactants such as nonionic, anionic and cationic can be used. Of these, nonionic surfactants are preferred from the viewpoint of preventing precipitation of water-soluble polymers such as polyvinyl alcohol. The polishing slurry is typically a polishing slurry used in a silicon substrate polishing process.

It is preferable that the concentrate disclosed here contains substantially no oxidizing agent. If the concentrate contains an oxidizing agent, the polishing slurry after dilution of the concentrate is supplied to the object to be polished (here, the silicon substrate), so that the surface of the object to be polished is oxidized and oxidized. This is because a film may be formed, which may reduce the polishing rate. Specific examples of the oxidizing agent herein include hydrogen peroxide (H ₂ O ₂ ), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, and the like. In addition, that a concentrate does not contain an oxidizing agent substantially means not containing an oxidizing agent at least intentionally.

(PH)
The pH of the concentrate disclosed herein is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, even more preferably 9.5 or higher, such as 10.0 or higher. And particularly preferably 10.5 or more. When the pH of the concentrated liquid is increased, the pH of the diluted polishing liquid is also increased, and the polishing performance tends to be improved. On the other hand, the pH of the concentrate is suitably 12.0 or less and 11.8 or less from the viewpoint of preventing dissolution of the abrasive grains and suppressing the reduction of the mechanical polishing action by the abrasive grains. Preferably, it is 11.5 or less. The abrasive grains are, for example, silica particles.

In the technique disclosed herein, the pH of the liquid composition is adjusted to 3 using a pH buffer and a standard buffer solution, and then the glass electrode is placed in the composition to be measured. It can be grasped by measuring the value after a minute or more has passed and stabilized. The liquid composition may be a polishing slurry, a concentrated liquid thereof, or the like. As the pH meter, for example, a glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by HORIBA, Ltd. is used. Further, the standard buffer solutions are phthalate pH buffer solution pH: 4.01 (25 ° C.), neutral phosphate pH buffer solution pH: 6.86 (25 ° C.), carbonate pH buffer solution pH: 10. 01 (25 ° C.).

The method for preparing the concentrate is not particularly limited. For example, each component contained in the concentrate 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. For the polishing composition described later, the same mixing method can be appropriately employed before and after dilution of the concentrate.

(Dilution)
The concentrate of the polishing composition disclosed herein is diluted with a magnification larger than 5 times on a volume basis and prepared as a polishing liquid, and then used for rough polishing of a substrate to be polished. The substrate to be polished is specifically a silicon wafer. In this way, the concentrated solution diluted at a predetermined magnification or more tends to have a high concentration of components, so that the components are easily separated and aggregated, and it is difficult to obtain good stability. In such a configuration, the concentrated solution exhibits excellent stability by preparing the concentrated solution so that the ratio [rg / d] is not more than a predetermined value. According to the technology disclosed herein, even in a configuration using a concentrated solution that is diluted at a magnification larger than 10 times on a volume basis, the concentrated composition exhibits excellent stability when diluted, and the polishing composition after dilution is Good polishing performance can be realized. The dilution ratio may be 15 times or more, for example, 25 times or more on a volume basis. The upper limit of the dilution ratio is not particularly limited, but may be about 50 times or less, for example, 40 times or less, typically 35 times or less on a volume basis.

The above dilution can be performed at a desired timing. Typically, the dilution can be performed by adding the aqueous solvent to the concentrate and mixing. The aqueous solvent is typically water. As the liquid used for dilution, it is preferable to use an aqueous solvent consisting essentially of water from the viewpoints of handleability and workability. The water is typically ion exchange water. The aqueous solvent is, for example, an aqueous solvent in which 99.5 to 100% by volume is water. 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.

<Polishing composition>
The polishing composition disclosed herein contains abrasive grains, a water-soluble polymer, and a basic compound contained in the concentrated liquid described above. Moreover, it typically contains water, and may further contain a chelating agent and other components as optional components. Since these specific examples are as described above, description thereof will not be repeated here. The polishing composition is also referred to as a polishing liquid or a polishing slurry.

The content of abrasive grains in the polishing composition obtained by diluting the concentrated liquid disclosed herein can be determined by the abrasive grain concentration and dilution ratio in the concentrated liquid. In one embodiment, the content is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and further preferably 0.3% by weight or more. In a more preferred embodiment, the content is, for example, 0.5% by weight or more. Higher polishing rates can be achieved by increasing the abrasive content. Further, from the viewpoint of removability from the polishing object, the content is usually suitably 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, and further preferably 3% by weight. % Or less. In a more preferred embodiment, the content is, for example, 2% by weight or less.

The content of the water-soluble polymer in the polishing composition is suitably 1 × 10 ⁻⁵ wt% or more, for example, 5 × 10 ⁻⁵ wt% or more, from the viewpoint of improving polishing performance and surface quality. Yes, preferably 1 × 10 ⁻⁴ wt% or more. In a preferred embodiment, the content of the water-soluble polymer is, for example, 2 × 10 ⁻⁴ wt% or more. The upper limit of the content of the water-soluble polymer in the polishing composition can be, for example, 1% by weight or less. From the viewpoint of the stability of the concentrate, polishing rate, detergency, etc., the content of the water-soluble polymer is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and even more preferably 0.02. % By weight or less. In a more preferred embodiment, the content of the water-soluble polymer is, for example, 0.01% by weight or less, typically 0.005% by weight or less.

In addition, the content of the water-soluble polymer in the polishing composition is suitably 0.001 part by weight or more with respect to 100 parts by weight of the abrasive grains. It is 005 weight part or more, More preferably, it is 0.01 weight part or more, More preferably, it is 0.015 weight part or more. In a more preferred embodiment, the content of the water-soluble polymer in the polishing composition is, for example, 0.03 parts by weight or more with respect to 100 parts by weight of the abrasive grains. The polishing performance is specifically flatness. From the viewpoint of stability, polishing rate, etc., the content of the water-soluble polymer is suitably 10 parts by weight or less, preferably 1 part by weight or less, more preferably 100 parts by weight of abrasive grains. Is 0.5 parts by weight or less, more preferably 0.1 parts by weight or less. In a more preferred embodiment, the content of the water-soluble polymer is, for example, 0.05 parts by weight or less with respect to 100 parts by weight of the abrasive grains.

In the technique disclosed herein, it is appropriate that the content of the basic compound in the polishing composition is, for example, 0.001% by weight or more, typically 0.01% by weight or more. From the viewpoint of improvement and the like, it is preferably 0.05% by weight or more, more preferably 0.07% by weight or more, and further preferably 0.09% by weight or more. Stability can also be improved by increasing the content of the basic compound. The upper limit of the content of the basic compound is suitably 5% by weight or less, and preferably 1% by weight or less from the viewpoint of surface quality and the like. In a preferred embodiment, the content of the basic compound is, for example, 0.5% by weight or less, typically 0.2% by weight or less.

The pH of the polishing composition in the technique disclosed herein is preferably 8.0 or more, for example 8.5 or more, more preferably 9.0 or more, and still more preferably 9.5 or more. In a more preferred embodiment, the pH is, for example, 10.0 or more. When the pH of the polishing liquid increases, the polishing rate tends to improve. Although the upper limit of the pH of the polishing liquid is not particularly limited, it is preferably 12.0 or less, for example, 11.5 or less, and more preferably 11.0 or less, from the viewpoint of better polishing the object to be polished. . From the viewpoint of improving the surface quality, the pH is more preferably 10.8 or less. In a further preferred embodiment, the pH is, for example, 10.6 or less, typically 10.5 or less. The improvement in surface quality is typically a reduction in surface roughness. The pH can be preferably applied to, for example, a polishing liquid used for polishing a silicon wafer. The polishing liquid is, for example, a polishing liquid for rough polishing.

<Application>
The technique disclosed herein is preferably applied to polishing using a silicon substrate (particularly a silicon wafer) as an object to be polished. A typical example of the silicon wafer here is a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The surface to be polished in the technique disclosed herein is typically a surface made of silicon.

The silicon substrate is subjected to general treatment that can be applied to the silicon substrate in a process upstream of the rough polishing process, such as lapping and etching, before the polishing process using the polishing liquid disclosed herein. May be. In the technique disclosed herein, a finish polishing step can be performed on the silicon substrate after the polishing step using the polishing liquid. The finishing process includes one or more polishing processes, and the final polishing is performed to finish the silicon wafer into a high-quality mirror surface. Note that final polishing refers to the final polishing step in the manufacturing process of the object. That is, final polishing refers to a process in which no further polishing is performed after that process. Therefore, the polishing liquid disclosed herein and the concentrated liquid before dilution can be used for polishing a silicon wafer that has undergone lapping. Further, the polishing liquid and the concentrated liquid can be used for rough polishing performed before final polishing of the silicon wafer. Rough polishing is also called preliminary polishing.

<Polishing>
Polishing of the object to be polished can be performed, for example, as follows. That is, the concentrate disclosed here is diluted to prepare a polishing composition (polishing slurry). Next, the polishing slurry (working slurry) is supplied to the object to be polished and polished by a conventional method. In rough polishing of a silicon wafer, typically, an object to be polished (silicon wafer) that has undergone a lapping process is set in a polishing apparatus, and the above-mentioned is performed through a polishing pad fixed to a surface plate (polishing surface plate) of the polishing apparatus. A polishing slurry is supplied to the surface of the object to be polished (surface to be polished). Typically, while continuously supplying the polishing slurry, the polishing pad is pressed against the surface of the object to be polished, and the two are relatively moved. The movement is, for example, a rotational movement. The polishing of the object to be polished is completed through this polishing step.

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

As the polishing apparatus, a double-side polishing apparatus that simultaneously polishes both sides of the object to be polished, or a single-side polishing apparatus that polishes only one side of the object to be polished may be used. Although not particularly limited, for example, a double-side polishing apparatus can be preferably employed in the rough polishing step. The double-side polishing apparatus is, for example, a batch type double-side polishing apparatus. The polishing apparatus may be a single wafer type polishing apparatus configured to polish one polishing object at a time, or a batch type polishing apparatus capable of simultaneously polishing a plurality of polishing objects on the same surface plate. But you can.

<Washing>
The object to be polished that has finished the rough polishing step is typically cleaned before the finish polishing step is started. This washing can be performed using an appropriate washing solution. The cleaning liquid to be used is not particularly limited, and for example, a common SC-1 cleaning liquid, SC-2 cleaning liquid, etc. in the field of semiconductors can be used. The SC-1 cleaning liquid is a mixed liquid of ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ), and water (H ₂ O). The SC-2 cleaning solution is a mixed solution of HCl, H ₂ O ₂ and H ₂ O. The temperature of the cleaning liquid can be, for example, in the range from room temperature to about 90 ° C. Here, room temperature typically means about 15 ° C. to 25 ° C. From the viewpoint of improving the cleaning effect, a cleaning solution of about 50 ° C. to 85 ° C. can be preferably used.

The polishing of the object to be polished is completed through the rough polishing process, the cleaning process, and the final polishing process as described above. Here, the polishing object is a silicon substrate, typically a silicon single crystal wafer. Therefore, according to this specification, a method for producing a polished article including the polishing step is provided. Specifically, the manufacturing method is a method for manufacturing a silicon wafer.

As mentioned above, according to this embodiment, the concentrate of the composition for silicon wafer rough polishing containing an abrasive grain, a basic compound, and water-soluble polymer is provided. The ratio [rg / d] of the radius of inertia rg [nm] of the water-soluble polymer to the interparticle distance d [nm] of the abrasive grains in the concentrated liquid is 4.7 or less. The concentrated liquid having such a configuration exhibits excellent stability and can exhibit good polishing performance after dilution. The polishing performance is typically a flatness improving effect.

In a preferred embodiment of the concentrate disclosed herein, the ratio [rg / d] is 2.5 or less. By configuring in this way, more excellent stability is realized.

In a preferred embodiment of the concentrate disclosed herein, the interparticle distance d of the abrasive grains is 200 nm or less. According to the technology disclosed herein, excellent stability can be realized even when the inter-particle distance d of the abrasive grains is not more than a predetermined value as described above. Further, as described above, the concentrated solution having the interparticle distance d of not more than a predetermined value can be concentrated at a high concentration, which is advantageous in terms of convenience and cost reduction.

In a preferred embodiment of the concentrate disclosed herein, the water-soluble polymer has an inertia radius rg of 30 nm or more. According to the technique disclosed here, even if the inertial radius of the water-soluble polymer is not less than a predetermined value as described above, the concentrated liquid can realize excellent stability. In addition, as described above, a polishing liquid having a water-soluble polymer having an inertial radius of a predetermined value or more can exhibit more excellent polishing performance. The polishing performance is typically a flatness improving effect.

In a preferred embodiment of the concentrated liquid disclosed herein, the concentration of the abrasive grains is 5% by weight or more. According to the technology disclosed herein, excellent stability can be achieved even when the abrasive grain concentration is a predetermined value or more. Further, as described above, a concentrated liquid having an abrasive concentration equal to or higher than a predetermined value can be concentrated at a high concentration, which is advantageous in terms of convenience and cost reduction.

In a preferred embodiment of the concentrate disclosed herein, the concentration of the water-soluble polymer is in the range of 0.001 to 0.05% by weight. By setting the concentration of the water-soluble polymer in the above range, the concentrated solution tends to be excellent in stability, and the diluted polishing solution tends to exhibit better polishing performance.

In a preferred embodiment disclosed herein, the concentrated solution is diluted by a factor larger than 10 times on a volume basis and used for rough polishing of a silicon wafer. According to the technique disclosed herein, the concentrated solution is excellent in stability even at a high concentration ratio that is diluted at a predetermined magnification or higher. Moreover, the concentrated liquid concentrated to a predetermined concentration or more as described above is advantageous in terms of convenience and cost reduction.

In a typical embodiment disclosed herein, the concentrated solution is used for polishing a lapped silicon wafer. More specifically, the concentrated solution is used for rough polishing performed before final polishing of the silicon wafer. Rough polishing is also called preliminary polishing.

Hereinafter, some examples relating to the present invention will be described. However, the present invention is not intended to be limited to the examples shown in the examples. In the following description, “%” is based on weight unless otherwise specified.

≪Experiment 1≫
<Examples 1-1 to 1-11 and Comparative Example 1-1>
[Preparation of polishing composition concentrate]
By mixing colloidal silica (average primary particle size 54 nm) as abrasive grains, water-soluble polymer (HEC, PVP), TMAH, K ₂ CO ₃ and ion-exchanged water, Example 1-1 Concentrates of the polishing compositions according to ˜1-11 and Comparative Example 1-1 were prepared. The concentration of the abrasive grains and the water soluble polymer in the concentrate in each example are as shown in Table 1, the concentration of TMAH and _K 2 CO ₃ is 1.62% and 1.05%. For the concentrated liquid according to each example, the interparticle distance d [nm] of the abrasive grains was determined, and the inertia radius rg [nm] of the water-soluble polymer was measured by the following method. The ratio [rg / d] of the inertial radius rg [nm] of the water-soluble polymer to d [nm] was determined. Table 1 shows the interparticle distance d [nm] of the abrasive grains, the inertial radius rg [nm] and the ratio [rg / d] of the water-soluble polymer in each example.

[Measurement method of inertia radius]
In order to measure the inertia radius rg of the water-soluble polymer, first, an aqueous solution was prepared so that the concentration of the water-soluble polymer was in the range of 0.1 to 1 mg / mL, and a light scattering photometer “DLS” was prepared for each of the prepared samples. Using “−8000” (manufactured by Otsuka Electronics Co., Ltd.), measurement was performed every 10 degrees within a measurement angle range of 20 to 150 degrees, and the inertia radius [nm] was calculated by 1-concentration plot analysis. In the case where a plurality of types of water-soluble polymers were contained in the concentrated liquid of the polishing composition, the measurement was performed by adjusting the amount of the water-soluble polymer so that the concentration ratio thereof was reached.

[Stability]
100 g of the concentrated liquid according to each example was placed in a glass tube having a diameter of 2.5 cm and a height of 25 cm, and was allowed to stand at 25 ° C. and stored. The presence or absence of separation of the water-soluble polymer in the concentrate after 24 hours from the start of storage was evaluated visually according to the following 5 criteria. That is, when separation of the water-soluble polymer was not observed, it was evaluated as “A”. When separation was observed, the case where the supernatant liquid layer was less than 2 mm was evaluated as “B”. The case where the liquid layer was 2 mm or more and less than 4 mm was evaluated as “C”, the case where the supernatant liquid layer was 4 mm or more and less than 5 mm was evaluated as “D”, and the supernatant liquid layer was 5 mm or more. The case was evaluated as “E”. A to D were practically acceptable levels, and E was considered unacceptable. The results are shown in Table 1.

≪Experiment 2≫
<Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-2>
[Preparation of polishing composition concentrate]
By mixing colloidal silica (average primary particle diameter 54 nm) as abrasive grains, water-soluble polymer (HEC, PVP, PVA), TMAH, K ₂ CO ₃ and ion-exchanged water, Example 2 Concentrates of polishing compositions according to -1 to 2-14 and Comparative Examples 2-1 to 2-2 were prepared. The concentrations of the abrasive grains and the water-soluble polymer in the concentrated liquid of each example are as shown in Table 2, and TMAH and K ₂ CO ₃ are each 0.067% in the polishing composition (polishing liquid) after dilution. And 0.043% to the concentrate. In the polishing composition of Example 2-14, polyoxyethylene lauryl ether was added as a nonionic surfactant to a concentration of 0.001%. For the concentrated liquid according to each example, the interparticle distance d [nm] of the abrasive grains was determined, and the inertial radius rg [nm] of the water-soluble polymer was measured by the same method as in Experiment 1. From the obtained value, the particle The ratio [rg / d] of the inertial radius rg [nm] of the water-soluble polymer to the inter-space distance d [nm] was determined. Further, the stability of the concentrate was also evaluated by the same method as in Experiment 1. Table 2 shows the evaluation results of the interparticle distance d [nm], the radius of inertia rg [nm] of the water-soluble polymer, the ratio [rg / d], and the concentrate stability.

[Silicon wafer polishing]
The concentrated liquid according to each example was diluted with ion exchange water at a dilution rate (volume basis) shown in Table 2 to obtain a polishing liquid (working slurry). Using this, rough polishing was performed under the following conditions.
(Polishing conditions)
Polishing device: Single-side polishing device manufactured by Nippon Engis Co., Ltd. Model “EJ-380IN”
Polishing pad: Product name “MH S-15A”, manufactured by Nitta Haas
Polishing pressure: 26.6 kPa
Slurry flow rate: 100 mL / min Plate rotation speed: 50 rpm
Head rotation speed: 50 rpm
Polishing amount: 8μm
Work species: Bare Si ^P - <100>
Work size: □ 60mm × 60mm

[Polishing performance (flatness)]
As an alternative evaluation of GBIR, the flatness was evaluated by the following method. Specifically, using an evaluation machine “DIGIMICRO MH-15M” manufactured by Nikon, the thickness of 36 points is measured at regular intervals of 6 points in the vertical and horizontal directions on the polished wafer surface, and the maximum and minimum values are measured. Was defined as a wafer thickness difference, and the wafer thickness difference value in each example was evaluated according to the following four criteria. That is, the case where the wafer thickness difference was less than 2.5 μm was evaluated as “A”, the case where the wafer thickness difference was 2.5 μm or more and less than 3.0 μm was evaluated as “B”, and the wafer thickness difference was The case where it was 3.0 μm or more and 3.2 μm or less was evaluated as “C”, and the case where the wafer thickness difference was larger than 3.2 μm was evaluated as “D”. A to C were practically acceptable levels, and D was considered unacceptable. The results are shown in Table 2.

[Polishing performance (surface roughness Ra)]
For each silicon wafer after rough polishing according to each example (test piece after rough polishing and subsequent cleaning), the surface roughness Ra was measured using a non-contact surface shape measuring device (trade name “NewView 5032”, manufactured by Zygo). (Arithmetic mean surface roughness) was measured. The obtained measured value was converted into a relative value with the surface roughness Ra of Comparative Example 2-1 as 100% and evaluated in the following two steps. The results are shown in Table 2.
A: 100% or less B: More than 100%

[Concentration efficiency]
The dilution ratio of the concentrated liquid according to each example was regarded as the concentration efficiency (concentration ratio), and classified according to the following three criteria. That is, the case where the concentration possible concentration is larger than 20 times is “A”, the case where the concentration possible concentration is larger than 10 times and 20 times or less is “B”, and the case where the concentration possible concentration is 10 times or less is “ C ”. The results are shown in Table 2.

As shown in Table 1, in Experiment 1, the ratio [rg / d] of the radius of inertia rg [nm] of the water-soluble polymer to the interparticle distance d [nm] of the abrasive grains was 4.7 or less. The concentrated solutions according to Examples 1-1 to 1-11 were evaluated as acceptable. In particular, in Examples 1-1 to 1-7 and 1-11 in which the above ratio [rg / d] was 2.5 or less, the stability evaluation result was A or B, and more excellent stability was obtained. Could be achieved. On the other hand, in Comparative Example 1-1 in which the ratio [rg / d] was larger than 4.7, the stability of the concentrate was at a reject level.

Further, as shown in Table 2, also in Experiment 2, the concentrates according to Examples 2-1 to 2-14 in which the ratio [rg / d] was 4.7 or less were evaluated for stability. It was a passing level. In particular, in Examples 2-1 to 2-10, 2-13, and 2-14 in which the ratio [rg / d] was 2.5 or less, the stability evaluation result was A or B, which was more excellent. Stability could be achieved. On the other hand, in Comparative Example 2-1, in which the ratio [rg / d] was larger than 4.7, the stability of the concentrated solution was at a reject level. In Examples 2-1 to 2-14 using a concentrated solution containing a water-soluble polymer, the polishing performance (specifically, the flatness) was all acceptable, whereas the water-soluble polymer was In Comparative Example 2-2 in which no was used, good polishing performance (specifically, flatness) could not be obtained.

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

A concentrated liquid for a silicon wafer rough polishing composition comprising abrasive grains, a basic compound and a water-soluble polymer,
The ratio [rg / d] of the radius of inertia rg [nm] of the water-soluble polymer to the interparticle distance d [nm] of the abrasive grains in the concentrated liquid is 4.7 or less, the composition for rough polishing of silicon wafers Product concentrate.
The concentrated solution according to claim 1, wherein the ratio [rg / d] is 2.5 or less.
The concentrated liquid according to claim 1 or 2, wherein an interparticle distance d of the abrasive grains is 200 nm or less.
The concentrated solution according to any one of claims 1 to 3, wherein the water-soluble polymer has an inertia radius rg of 30 nm or more.
The concentrated liquid according to any one of claims 1 to 4, wherein the concentration of the abrasive grains is 5% by weight or more.
The concentrated solution according to any one of claims 1 to 5, wherein the concentration of the water-soluble polymer is in the range of 0.001 to 0.05% by weight.
The concentrated solution according to any one of claims 1 to 6, which is used for rough polishing of a silicon wafer after being diluted at a magnification larger than 10 times on a volume basis.