JPWO2018025655A1 - Concentrated solution for silicon wafer rough polishing composition - Google Patents

Abstract

The present invention provides a concentrated solution of a silicon wafer rough polishing composition which can exhibit good polishing performance after dilution and which is excellent in stability. The concentrate of the composition for roughly polishing a silicon wafer provided by the present invention contains an abrasive, 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 concentrate is 4.7 or less.

Description

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

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

Japanese Patent Application Publication 2012-89862 Japanese Patent Application Publication 2015-124231

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

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

  According to the present invention, there is provided a concentrate of a silicon wafer rough polishing composition containing 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 concentrate is 4.7 or less. The concentrate having such a constitution exhibits excellent stability and can exhibit good polishing performance after dilution. The above polishing performance is typically a flatness improvement effect.

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

<Concentrate of polishing composition>
(Characteristic)
The concentrate of the polishing composition disclosed herein contains abrasive grains and a water-soluble polymer. The concentrate of the polishing composition may be hereinafter simply referred to as "concentrate". Such a concentrated solution is characterized by 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 being 4.7 or less. Concentrates satisfying the above properties exhibit excellent stability. Although the reason is not particularly limited and interpreted, by satisfying the above ratio [rg / d], the water-soluble polymer is stably present among the abrasive particles in the concentrate. It is considered that the abrasive particles and the water-soluble polymer, which are the main components of the concentrate, can be stably dispersed in the concentrate. In addition, when the concentrate is diluted and used as a polishing solution, by including the water-soluble polymer, it is possible to exhibit good polishing performance to a substrate to be polished, that is, a silicon wafer. Specifically, the polishing performance is a flatness improvement effect. The above ratio [rg / d] is preferably 3.8 or less, more preferably 2.8 or less, still more preferably 2.5 or less, particularly preferably 1.9 or less from the viewpoint of improving the stability. In one particularly preferred embodiment, the ratio [rg / d] is typically less than or equal to 1.0. The lower limit of the ratio [rg / d] is not particularly limited, and may usually be about 0.3 or more, for example, 0.6 or more from the viewpoint of 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)
The abrasive grains disclosed herein are contained in the concentrated liquid at a content such that the interparticle distance d [nm] of the abrasive grain particles 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 technology disclosed herein, as described above, excellent stability is obtained even when the distance d between the abrasive grains is equal to or less than the predetermined value and the abrasive grains are relatively close in the concentrate. It can be realized. The interparticle distance d is more preferably 150 nm or less, still more preferably 100 nm or less, particularly preferably 80 nm or less, from the viewpoint of concentration efficiency of the concentrate. In a particularly preferred embodiment, the interparticle distance d is typically 70 nm or less. Furthermore, within the range satisfying the above ratio [rg / d], the interparticle distance d may be, for example, 60 nm or less, and further 40 nm or less.

In the present specification, the interparticle distance d [nm] of the abrasive particles is assumed to be the close-packing ratio [74%] of the spheres, assuming that the abrasive particles contained in the concentrate are uniformly dispersed. Based on the formula:
_{d [nm] = R S ×} 2-D1
Theoretical value obtained from Here, R _S is the radius [nm] of a sphere that is centered on one abrasive particle and circumscribed with the corresponding sphere of the adjacent abrasive particle, and D 1 is the average primary particle diameter [nm] of the abrasive particle It is. R _S can be reworded as the radius [nm] of a sphere having the volume of the concentrate assigned to one abrasive particle in the concentrate, and is determined by the following method. Specifically, the value obtained by multiplying the volume of the concentrate in a unit volume, for example 1 L, by the filling rate 74% is divided by the number of abrasive particles contained in the concentrate in the unit volume to obtain one abrasive grain. The volume V _S of the largest sized sphere that the particle can occupy is determined, and R _S is determined from the equation: V _S = 4/3 × πR _S ³ ; The number of abrasive particles contained in a unit volume of concentrate is obtained by dividing the weight [g / L] of abrasive particles per concentrate of unit volume, for example, 1 L, by the weight [g] per abrasive particle. It is determined by The weight of the abrasive grains per unit volume of the concentrated liquid is determined from the content and specific gravity of the abrasive grains in the concentrated liquid, and the content and specific gravity of components other than the abrasive grains contained in the concentrated liquid. The specific gravity of the abrasive is, for example, 2.2 g / cm ³ in the case of silica abrasive. The components other than the abrasive grains contained in the concentrate usually have an aqueous solvent as a main component. The weight [g] per abrasive particle is determined from the average primary particle diameter [nm] of the abrasive particles from the spherical volume and the specific gravity of the abrasive particles when the primary particles are regarded as true spheres.

  In the technology disclosed herein, the material and properties of the concentrate and the abrasive grains contained in the polishing composition obtained by diluting the concentrate are not particularly limited, and may be appropriately selected according to the purpose of use, mode of use, etc. it can. Examples of the abrasive 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; Nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of the organic particles include poly (methyl methacrylate) (PMMA) particles, poly (meth) acrylic acid particles, and polyacrylonitrile particles. Such abrasive grains may be used alone or in combination of two or more. In addition, (meth) acrylic acid is a meaning which points out acrylic acid and methacrylic acid generically.

  As the abrasive, inorganic particles are preferable, and particles made of metal or metalloid oxide are particularly preferable. Particularly preferred abrasives in the art disclosed herein include silica particles. The technique disclosed herein can be preferably practiced, for example, in a mode in which the abrasive grains substantially consist of silica particles. Here, "substantially" means that 95% by weight or more, preferably 98% by weight or more, more preferably 99% by weight or more of the particles constituting the abrasive grains are silica particles, and constitute the abrasive grains. 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. The silica particles can be used alone or in combination of two or more. Colloidal silica is particularly preferable because it is resistant to scratching on the surface of the object to be polished and can exhibit good polishing performance. Here, the good polishing performance refers to the performance to reduce the surface roughness and the like. As the colloidal silica, for example, colloidal silica prepared using water glass as a raw material by an ion exchange method, or alkoxide method colloidal silica can be preferably adopted. Water glass is also referred to as sodium silicate. Alkoxide method colloidal silica refers to colloidal silica produced by hydrolysis condensation reaction of alkoxysilane. Colloidal silica can be used singly or in combination of two or more.

  The true specific gravity of the silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and still more preferably 1.7 or more. The polishing rate tends to be high due to the increase of the true specific gravity of silica. From this viewpoint, silica particles having a true specific gravity of 2.0 or more are particularly preferable. In one 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 value measured by a liquid displacement method using ethanol as a displacement liquid can be adopted.

The average primary particle size of the abrasive grains disclosed herein is not particularly limited. The abrasive is typically a silica particle. From the viewpoint of polishing rate etc., the average primary particle diameter is suitably 5 nm or more, preferably 10 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, particularly preferably 45 nm or more. In one particularly preferred embodiment, the average primary particle size is, for example, 50 nm or more. Further, from the viewpoint of scratch prevention 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, still more preferably 70 nm or less. In a particularly preferred embodiment, the average primary particle size of the abrasive may be 60 nm or less, for example 55 nm or less.
In the present specification, the average primary particle diameter means the 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 equation of 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 by BET diameter [nm] = 2727 / BET value [m ² / g]. The measurement of the specific surface area can be performed, for example, using a surface area measurement device manufactured by Micromeritex, trade name "Flow Sorb II 2300".

  The shape of the abrasive may be spherical or non-spherical. The above-mentioned shape is an outer shape. Specific examples of non-spherical particles include peanut shape, bowl shape, confetti shape, rugby ball shape and the like. The peanut shape is, that is, the shape of peanut shell. For example, abrasive grains in which many of the particles have a peanut shape may be preferably employed.

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

  The shape (outer shape) and average aspect ratio of the abrasive grains can be grasped by, for example, electron microscope observation. As a specific procedure for grasping the average aspect ratio, for example, for a predetermined number of silica particles which can recognize the shape of independent particles using a scanning electron microscope (SEM), the smallest circumscribed particle image is used. Draw a rectangle. Here, the predetermined number is, for example, 200. Then, for the rectangle drawn for each particle image, the ratio of the major axis to the minor axis ratio (aspect ratio) is a value obtained by dividing the length of the long side (value of the major axis) by the length of the short side (value of the minor axis) Calculated as). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

  The content (concentration) of the abrasive grains in the concentrate disclosed herein can be, for example, 50% by weight or less. From the viewpoint of the stability and filterability of the concentrate, it is usually appropriate to set the content of abrasive grains to 45% by weight or less, for example 40% by weight or less, typically 35% by weight or less. The content of the abrasive grains 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 further preferred embodiment, the content of the abrasive grains is, for example, 15% by weight or less. The content of the abrasive grains in the concentrate is usually 1% by weight or more, for example, 3% by weight or more, from the viewpoint of the concentration of the abrasive grains in the polishing composition after dilution, convenience in production, distribution, storage, etc. Typically, 5% by weight or more is appropriate. The content of the abrasive grains 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 concentrate disclosed herein, one having an ir radius of gyration which satisfies a ratio [rg / d] equal to or less than a predetermined value is used. The polishing slurry containing such a water-soluble polymer can be well wetted and familiar with the substrate to be polished, and as a result, the polishing performance can be improved. The polishing performance referred to here is typically flatness. The radius of inertia rg of the water-soluble polymer is the size of one water-soluble polymer molecule in an aqueous solution, which can be mainly determined by the hydrophilicity, molecular weight and the like of the polymer. The upper limit value of the inertial radius rg is a value limited in the relative relationship with the inter-particle distance d because the upper limit of the ratio [rg / d] is limited. The radius of inertia rg of the water-soluble polymer according to one aspect is about 500 nm or less and suitably about 300 nm or less. In addition, when a water-soluble polymer having an inertial radius rg of 220 nm or less, more preferably 150 nm or less, is used, the above ratio [rg / d] can be preferably satisfied. The concentration efficiency also tends to be improved. The radius of inertia rg may be about 100 nm or less, for example 70 nm or less. In a preferred embodiment, the radius of inertia rg of the water-soluble polymer is 30 nm or more, more preferably 50 nm or more. From the viewpoint of the wettability of the substrate to be polished, the inertial radius rg is more preferably 80 nm or more, still more preferably 100 nm or more, and particularly preferably 120 nm or more. In one particularly preferred aspect, the radius of inertia rg is, for example, 140 nm or more. According to the technology disclosed herein, the concentrate can achieve excellent stability even when the inertial radius rg of the water-soluble polymer is a predetermined value or more. In addition, when a polishing solution containing a water-soluble polymer having a radius of inertia rg of a predetermined value or more is used, the wettability to the substrate surface is more exhibited, and the polishing performance tends to be further improved. The polishing performance referred to here is typically flatness. The radius of inertia rg of the water-soluble polymer in the present specification is measured by the method described in the examples described later.

  The type of water-soluble polymer contained in the concentrate disclosed herein is not particularly limited, and can be appropriately selected from water-soluble polymer types known in the field of polishing compositions. The water-soluble polymers can be used alone 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 them, from the viewpoint of improving flatness, a cellulose derivative and a starch derivative are preferable, and a cellulose derivative is more preferable.

  Cellulose derivatives are polymers comprising 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. Among these, HEC is preferred.

  Starch derivatives are polymers comprising α-glucose units as the main repeat unit. Specific examples of starch derivatives include pregelatinized starch, pullulan, carboxymethyl starch, cyclodextrin and the like. Among them, pullulan is preferred.

Examples of the polymer containing an oxyalkylene unit include polyethylene oxide (PEO), a block copolymer of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and random copolymer of EO and PO or BO. A combination etc. are illustrated. Among them, block copolymers of EO and PO or random copolymers of EO and PO are preferable. The block copolymer of EO and PO can be a diblock, triblock, etc. comprising PEO blocks and polypropylene oxide (PPO) blocks. Examples of the triblocks include PEO-PPO-PEO triblocks and PPO-PEO-PPO triblocks. Usually, PEO-PPO-PEO triblocks are more preferable.
In the block copolymer or random copolymer of EO and PO, the molar ratio [EO / PO] of EO to PO constituting the copolymer is from the viewpoint of solubility in water, washability, etc. More than 1 is preferable, 2 or more is more preferable, and 3 or more is more preferable. In a further preferred embodiment, the molar ratio [EO / PO] is, for example, 5 or more.

  As the polymer containing a nitrogen atom, any of a polymer containing a nitrogen atom in the main chain and a polymer having a nitrogen atom in a side chain functional group (a pendant group) can be used. The surface roughness of the substrate can be improved by using a polymer containing nitrogen atoms. Examples of polymers containing nitrogen atoms in the main chain include homopolymers and copolymers of N-acyl alkyleneimine type monomers. Specific examples of the N-acyl alkyleneimine type monomer include N-acetyl ethyleneimine, N-propionyl ethyleneimine and the like. As a polymer which has a nitrogen atom in a pendant group, the polymer etc. which contain the monomer unit of a N-vinyl type, for example are mentioned. For example, homopolymers and copolymers of N-vinyl pyrrolidone can be employed. In the technology disclosed herein, at least one of N-vinylpyrrolidone homopolymers and copolymers (hereinafter also referred to as “PVP”) obtained by polymerizing N-vinylpyrrolidone in a proportion of 50 mol% or more is referred to as “PVP”. It is preferably used.

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

In the technology disclosed herein, the molecular weight of the water-soluble polymer can be appropriately set in the range satisfying the ratio [rg / d] equal to or less than a predetermined value. The weight average molecular weight (Mw) of the water-soluble polymer can be about 200 × 10 ⁴ or less, usually 150 × 10 ⁴ or less, for example 100 × 10 ⁴ or less, from the viewpoint of stability, concentration efficiency, etc. It is appropriate. The Mw may be, for example, 50 × 10 ⁴ or less and 30 × 10 ⁴ or less. Further, from the viewpoint of improving the protection of the substrate surface and the polishing performance, usually, Mw is suitably 1 × 10 ⁴ or more, more preferably 10 × 10 ⁴ or more, and still 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. As said cellulose derivative, HEC is mentioned, for example.

  In addition, as Mw of water-soluble polymer, the value (water system, polyethylene oxide conversion) based on the gel permeation chromatography (GPC) of a water system is employable.

  The technology disclosed herein is preferably practiced 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 More preferred is use in combination with one or more of P2. The water soluble polymer P1 is typically a cellulose derivative such as HEC. As the water-soluble polymer P2, 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) are preferable, and a polymer containing a monomer unit of N-vinyl type is more preferable. Among them, homopolymers and copolymers (typically PVP) of N-vinylpyrrolidone and the like are particularly preferable.

  In the technology disclosed herein, when the water-soluble polymer P1 and the water-soluble polymer P2 are used in combination, the compounding 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, and typically 0.5 or more. Further, 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, for example, a cellulose derivative such as HEC, and the water soluble polymer P2 is a polymer including an N-vinyl type monomer unit such as, for example, 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 in the range satisfying the ratio [rg / d] equal to or less than a predetermined value. 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 It is appropriate. The Mw may be, for example, 50 × 10 ⁴ or less and 30 × 10 ⁴ or less. Further, from the viewpoint of improving the protection of the substrate surface and the polishing performance, usually, Mw is suitably 1 × 10 ⁴ or more, more preferably 10 × 10 ⁴ or more, and still 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. 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 usually 150 × 10 ⁴ or less, for example, 50 × 10 ⁴ or less is suitable. From the viewpoint of stability etc., the Mw may be 30 × 10 ⁴ or less, for example 5 × 10 ⁴ or less. Also, from the viewpoint of improving surface protection, normally, Mw of 1 × 10 ⁴ or more is suitable, 2 × 10 ⁴ or more is more preferable, and 3 × 10 ⁴ or more is more preferable. The Mw can be particularly preferably applied to homopolymers and copolymers (typically PVP) of N-vinyl pyrrolidone.

  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. The content is preferably 0.001% by weight or more, more preferably 0.0025% by weight or more, for example, 0.005% by weight or more, from the viewpoint of improving polishing performance and the like. Specifically, the polishing performance is flatness. Further, from the viewpoint of polishing rate and the like, the content is preferably 1 wt% or less, more preferably 0.2 wt% or less, and still more preferably 0.1 wt% or less. It is particularly preferable to set the content to not more than 0.55% by weight. 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 parts by weight or more with respect to 100 parts by weight of the abrasive, and preferably 0.005 parts by weight from the viewpoint of improving the polishing performance and the like. The amount is preferably at least 0.01 part by weight, more preferably at least 0.015 parts by weight. In a further preferable aspect, 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.
Specifically, the polishing performance is flatness. Further, 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 the 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 herein contains a basic compound. In the present specification, a basic compound refers to a compound having a function of dissolving in water to raise the pH of an aqueous solution. As the basic compound, organic or inorganic basic compounds containing nitrogen, hydroxides of alkali metals, hydroxides of alkaline earth metals, various carbonates, hydrogencarbonates and the like can be used. Examples of the nitrogen-containing basic compound 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 alone or in combination of two or more.

  Potassium hydroxide, sodium hydroxide etc. are mentioned as a specific example of the hydroxide of an alkali metal. Specific examples of the carbonate or hydrogen carbonate include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate and the like. Specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine And piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methyl piperazine, guanidine, azoles such as imidazole and triazole, and the like. Specific examples of the quaternary phosphonium compound include quaternary phosphonium hydroxide such as tetramethyl phosphonium hydroxide and tetraethyl phosphonium hydroxide.

As a quaternary ammonium compound, quaternary ammonium salts, such as a tetraalkyl ammonium salt and a hydroxyalkyl trialkyl ammonium salt, can be used preferably. The quaternary ammonium salt is typically a strong base. The anion component in such a quaternary ammonium salt may 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 hydroxides include hydroxides such as tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, tetrabutyl ammonium hydroxide, tetrapentyl ammonium hydroxide and tetrahexyl ammonium hydroxide. Tetraalkyl ammonium; Hydroxyalkyl trialkyl ammonium hydroxide such as 2-hydroxyethyl trimethyl ammonium hydroxide (also referred to as choline); and the like. Among these, tetraalkylammonium hydroxide is preferable, and tetramethylammonium hydroxide (TMAH) is particularly preferable.

The concentrate disclosed herein may comprise a combination of a quaternary ammonium compound and a weak acid salt as described above. The quaternary ammonium compound is, for example, tetraalkylammonium hydroxide such as TMAH. As the weak acid salt, one that can be used for polishing using silica particles and that can exert a desired buffering action in combination with a quaternary ammonium compound can be appropriately selected. A weak acid salt can be used individually by 1 type or in combination of 2 or more types. Specific examples of weak acid salts include sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium orthosilicate, potassium orthosilicate, sodium acetate, potassium acetate, sodium propionate, sodium propionate, potassium propionate, calcium carbonate, calcium hydrogencarbonate And calcium acetate, calcium propionate, magnesium acetate, magnesium propionate, zinc propionate, manganese acetate, cobalt acetate and the like. A weak acid salt in which the anion component is a carbonate ion or a hydrogen carbonate ion is preferred, and a weak acid salt in which the anion component is a carbonate ion is 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 hydrogen carbonate and potassium hydrogen carbonate. Among them, potassium carbonate (K ₂ CO ₃ ) is preferable.

When a quaternary ammonium compound and a weak acid salt are used in combination as a basic compound, the compounding ratio of the quaternary ammonium compound and the weak acid salt is not particularly limited. For example, quaternary ammonium compound: 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, tetraalkylammonium hydroxide such as TMAH. The weak acid salt is, for example, a weak acid salt in which an anion component such as K ₂ CO ₃ is a carbonate ion.

  The content (concentration) of the basic compound in the concentrate disclosed herein is, for example, 0.1% by weight or more from the viewpoint of stability of the concentrate, improvement of the polishing rate by the polishing composition after dilution, etc. 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 still more preferably 0.8% by weight or more. In a further preferred embodiment, the content of the basic compound is, for example, 1.0% by weight or more, and typically 1.2% by weight or more. For example, when the concentrate is used after being diluted at a high magnification, the concentration of abrasive grains after dilution may be relatively low, and the processing power of the abrasive grains may also tend to decrease. Even in such a case, chemical polishing after dilution can be enhanced 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 concentrate is suitably 10% by weight or less, preferably 5% by weight or less, from the viewpoint of storage stability, surface quality and the like. In a preferred embodiment, the content of the basic compound is, for example, 3% by weight or less.

  In addition, the content of the basic compound in the concentrate can also be specified by the relative relationship with the abrasive grains contained in the concentrate. Specifically, the content of the basic compound in the concentrate is suitably 0.1 parts by weight or more with respect to 100 parts by weight of the abrasive, and preferably 1 weight from the viewpoint of improving the polishing rate, etc. The amount is preferably at least 3 parts by weight, more preferably at least 6 parts by weight. The content of the basic compound in the concentrate may be, for example, about 12 parts by weight or more and 22 parts by weight or more. Further, from the viewpoint of stability, surface quality, etc., 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 comprises water. As water, ion exchange 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 the inhibition of the functions of other components contained in the concentrate as much as possible. For example, the purity of water can be increased by operations such as removal of impurity ions by ion exchange resin, removal of foreign matter by filter, and distillation. Moreover, the concentrate disclosed here may further contain the organic solvent which can be uniformly mixed with water as needed. The organic solvents are lower alcohols, lower ketones and the like. Usually, it is preferable that 90 volume% or more of the solvent contained in a concentrate is water, and it is more preferable that 95 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 generic term including the above-mentioned solvent and water.

(Chelating agent)
The concentrate disclosed herein can contain a chelating agent as an optional component. The chelating agent functions to suppress the contamination of the object to be polished by the metal impurities by forming complex ions with the metal impurities which may be contained in the concentrate and capturing the complex ions. Examples of chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, ammonium hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid Sodium diethylene triamine pentaacetate, triethylene tetramine hexaacetic acid and sodium triethylene tetramine hexaacetate. Examples of organic phosphonic acid type chelating agents include 2-aminoethyl phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylene phosphonic acid), ethylene diamine tetrakis (methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) 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-methylphosphorus Includes nosuccinic acid. Among these, organic phosphonic acid type chelating agents are more preferable. Among them, preferred are ethylenediaminetetrakis (methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and diethylene triamine pentaacetic acid. Particularly preferred chelating agents include ethylenediamine tetrakis (methylene phosphonic acid) and diethylene triamine penta (methylene phosphonic acid). The chelating agents can be used alone or in combination of two or more.

(Other ingredients)
The concentrate disclosed herein is an abrasive slurry of a surfactant, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt, an antiseptic agent, an antifungal agent, etc., to the extent that the effects of the present invention are not significantly impaired. You may further contain the well-known additive which may be used for these as needed. As the surfactant, various surfactants such as nonionic, anionic and cationic surfactants can be used. Among them, nonionic surfactants are preferable from the viewpoint of preventing the precipitation of a water-soluble polymer such as polyvinyl alcohol. The polishing slurry is typically a polishing slurry used in a polishing process of a silicon substrate.

The concentrate disclosed herein is preferably substantially free of an oxidizing agent. When the concentrate contains an oxidizing agent, the polishing slurry after diluting the concentrate is supplied to the object to be polished (here, a silicon substrate), whereby 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 referred to 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 that an oxidizing agent is not included at least intentionally.

(PH)
The pH of the concentrate disclosed herein is typically not less than 8.0, preferably not less than 8.5, more preferably not less than 9.0, still more preferably not less than 9.5, such as not less than 10.0 And particularly preferably 10.5 or more. When the pH of the concentrate increases, the pH of the diluted polishing solution also increases, 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 the dissolution of the abrasive grains and suppressing the decrease in the mechanical polishing action by the abrasive grains. Is preferable, and 11.5 or less is more preferable. The abrasive grains are, for example, silica particles.

  In the technique disclosed herein, the pH of the liquid composition is adjusted using a pH meter and calibrated at three points using a standard buffer, and then the glass electrode is put in the composition to be measured, 2 It can be grasped by measuring the value after the lapse of more than a minute and becoming stable. The liquid composition may be a polishing slurry, a concentrate thereof or the like. Moreover, as a pH meter, for example, a glass electrode type hydrogen ion concentration indicator manufactured by Horiba, Ltd. (model number F-23) is used. Furthermore, the standard buffer is phthalate pH buffer pH: 4.01 (25 ° C.), neutral phosphate pH buffer pH: 6.86 (25 ° C.), carbonate pH buffer pH: 10. 01 (25 ° C.).

  The method for preparing the concentrate is not particularly limited. For example, it is good to mix each component contained in a concentrate using well-known mixing apparatuses, such as a wing | blade type | formula stirrer, an ultrasonic dispersion machine, a homomixer. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once, and you may mix in the order set suitably. The same mixing method may be appropriately employed before and after dilution of the concentrate also for the polishing composition described later.

(Dilution)
The concentrate of the polishing composition disclosed herein is used as a polishing solution after being diluted at a magnification of more than 5 times on a volume basis, and then used for rough polishing of a substrate to be polished. Specifically, the substrate to be polished is a silicon wafer. Thus, since the concentration of the components tends to be high in the concentrated solution diluted by a predetermined magnification or more, the components are likely to be separated and aggregated and it is difficult to obtain good stability. In such a configuration, the concentrate exhibits excellent stability by preparing the concentrate such that the ratio [rg / d] is equal to or less than a predetermined value. According to the technology disclosed herein, even in a configuration using a concentrate that is diluted by a factor of greater than 10 times on a volume basis, the concentrate exhibits excellent stability, and the polishing composition after dilution has 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 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 substantially consisting of water from the viewpoint of handleability, workability and the like. The water is typically ion exchanged 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 and diluted, and a mixture containing those components in an amount ratio different from that of the aqueous solvent The solvent may be added and diluted.

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

  The content of the abrasive grains in the polishing composition obtained by diluting the concentrate disclosed herein can be determined by the abrasive grain concentration and the dilution rate in the concentrate. In one aspect, the content is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and still more preferably 0.3% by weight or more. In a further preferred embodiment, the content is, for example, 0.5% by weight or more. Higher polishing rates can be achieved by increasing the abrasive content. The content is usually 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, and still more preferably 3% by weight, from the viewpoint of removability from the object to be polished, etc. % Or less. In a further 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 polishing performance, surface quality improvement, etc. Preferably, it is 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. The content of the water-soluble polymer is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and still more preferably 0.02% by weight, from the viewpoints of stability of the concentrate, polishing rate, washability and the like. It is at most weight percent. In a further preferred embodiment, the content of the water-soluble polymer is, for example, 0.01% by weight or less, and typically 0.005% by weight or less.

  Further, the content of the water-soluble polymer in the polishing composition is suitably 0.001 parts by weight or more with respect to 100 parts by weight of the abrasive, and from the viewpoint of improving the polishing performance, etc., preferably 0. It is at least 005 parts by weight, more preferably at least 0.01 parts by weight, and still more preferably at least 0.015 parts by weight. In a further 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. Specifically, the polishing performance is flatness. Further, 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 the 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.

  In the art disclosed herein, the content of the basic compound in the polishing composition is, for example, suitably 0.001% by weight or more, typically 0.01% by weight or more, and the polishing rate is suitable. From the viewpoint of improvement etc., it is preferably 0.05% by weight or more, more preferably 0.07% by weight or more, and still more preferably 0.09% by weight or more. The 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, and typically 0.2% by weight or less.

  The pH of the polishing composition in the art 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 further preferred embodiment, the pH is, for example, 10.0 or more. As the pH of the polishing solution increases, the polishing rate tends to improve. The upper limit value of the pH of the polishing liquid is not particularly limited, but it is preferably 12.0 or less, for example, 11.5 or less, more preferably 11.0 or less, from the viewpoint of polishing the object to be polished better. . From the viewpoint of surface quality improvement, 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. In addition, the said surface quality improvement is surface roughness reduction typically. The above pH can be preferably applied to, for example, a polishing solution used for polishing a silicon wafer. The polishing solution is, for example, a polishing solution for rough polishing.

<Use>
The technology disclosed herein is preferably applied to polishing using a silicon substrate (particularly a silicon wafer) as a polishing target. A typical example of the silicon wafer mentioned 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 technology disclosed herein is typically a surface made of silicon.

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

<Polishing>
The polishing of the object to be polished can be performed, for example, as follows. That is, the concentrate disclosed herein is diluted to prepare a polishing composition (polishing slurry). Then, the polishing slurry (working slurry) is supplied to a polishing object and polished by a conventional method. In rough polishing of a silicon wafer, typically, the object to be polished (silicon wafer) subjected to the lapping process is set in a polishing apparatus, and the above-described polishing pad is fixed through the polishing pad fixed on the platen of the polishing apparatus. A polishing slurry is supplied to the surface of the object to be polished (surface to be polished). Typically, while the polishing slurry is continuously supplied, the polishing pad is pressed against the surface of the object to be moved relative to each other. The movement is, for example, rotational movement. Polishing of the object to be polished is completed through this polishing process.

  The polishing pad used in the polishing step is not particularly limited. For example, polishing pads of foamed polyurethane type, non-woven type, suede type, etc. can be used. Each polishing pad may or may not include abrasive grains.

  As a polishing apparatus, a double-sided polishing apparatus that simultaneously polishes both surfaces of an object to be polished may be used, or a single-side polishing apparatus may be used to polish only one surface of the object to be polished. Although not particularly limited, for example, a double-side polishing apparatus can be preferably employed in the rough polishing process. The double-sided polishing apparatus is, for example, a batch-type double-sided polishing apparatus. The polishing apparatus may be a single-wafer 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 platen. May be.

<Washing>
The object to be polished after the rough polishing process is typically cleaned before starting the finish polishing process. This washing can be performed using a suitable washing solution. The cleaning solution to be used is not particularly limited, and, for example, SC-1 cleaning solution, SC-2 cleaning solution and the like generally used in the field of semiconductors and the like can be used. The SC-1 cleaning solution is a mixture of ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ) and water (H ₂ O). The SC-2 cleaning solution is a mixture of HCl, H ₂ O ₂ and H ₂ O. The temperature of the cleaning solution can be, for example, in the range of about room temperature or higher to about 90 ° C. or so. Here, room temperature typically refers to about 15 ° C to 25 ° C. From the viewpoint of improving the washing effect, a washing solution of about 50 ° C. to 85 ° C. can be preferably used.

  Polishing of the object to be polished is completed through the above-described rough polishing process, cleaning process, and finish polishing process. The object to be polished is here a silicon substrate, typically a silicon single crystal wafer. Therefore, according to this specification, there is provided a method of producing an abrasive, comprising the above-mentioned polishing step. Specifically, the above-mentioned manufacturing method is a manufacturing method of a silicon wafer.

  As mentioned above, according to this embodiment, the concentrate of the composition for rough polishing of the silicon wafer containing an abrasive grain, a basic compound, and a 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 concentrate is 4.7 or less. The concentrate having such a constitution exhibits excellent stability and can exhibit good polishing performance after dilution. The above polishing performance is typically a flatness improvement effect.

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

  In a preferred embodiment of the concentrate disclosed herein, the inter-particle distance d of the abrasive is 200 nm or less. According to the technology disclosed herein, excellent stability can be realized even if the inter-particle distance d of the abrasive grains is equal to or less than the predetermined value as described above. Further, as described above, the concentrated solution in which the interparticle distance d is equal to or less than a predetermined value may be concentrated to a high concentration, which is advantageous in terms of convenience and cost reduction.

  In a preferred embodiment of the concentrate disclosed herein, the radius of inertia rg of the water-soluble polymer is 30 nm or more. According to the technology disclosed herein, the concentrate can achieve excellent stability even when the radius of inertia of the water-soluble polymer is equal to or greater than the predetermined value as described above. Further, as described above, a polishing liquid having a radius of inertia of a water-soluble polymer of a predetermined value or more can exhibit more excellent polishing performance. The above polishing performance is typically a flatness improvement effect.

  In a preferred embodiment of the concentrate disclosed herein, the concentration of the abrasive is 5% by weight or more. According to the technology disclosed herein, excellent stability can be realized even when the abrasive concentration is equal to or higher than the predetermined value as described above. Further, as described above, the concentrate having an abrasive concentration of a predetermined value or more can be concentrated to 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 polishing solution after dilution tends to exhibit better polishing performance.

  In a preferred embodiment disclosed herein, the concentrate is diluted by a factor of greater than 10 by volume and used for rough polishing of a silicon wafer. According to the technology disclosed herein, the concentrate has excellent stability even at a high concentration ratio such as dilution with a predetermined or higher magnification. Further, the concentrated solution concentrated to a predetermined concentration or more as described above is advantageous in terms of convenience and cost reduction.

  In one exemplary aspect disclosed herein, the concentrate is used to polish a silicon wafer that has undergone lapping. More specifically, the above-mentioned concentrate is used for rough polishing performed before final polishing of a silicon wafer. Rough polishing is also called preliminary polishing.

  The following examples illustrate some of the embodiments of the present invention, but are not intended to limit the present invention to those shown. In the following description, “%” is on a weight basis unless otherwise noted.

«Experiment 1»
Examples 1-1 to 1-11 and Comparative Example 1-1
[Preparation of Concentrated Solution for Polishing Composition]
Example 1-1 by mixing colloidal silica (average primary particle diameter 54 nm) as abrasive grains, water-soluble polymer (HEC, PVP), TMAH, K ₂ CO ₃ , and ion-exchanged water Concentrates of the polishing composition according to 1 to 11 and Comparative Example 1-1 were respectively prepared. The concentrations of abrasive grains and water-soluble polymer in the concentrated solution of each example are as shown in Table 1, and the concentrations of TMAH and K ₂ CO ₃ are 1.62% and 1.05%, respectively. For the concentrated liquid according to each example, the interparticle distance d [nm] of the abrasive grains is determined, and the inertial radius rg [nm] of the water-soluble polymer is measured by the following method. The ratio [rg / d] of the radius of inertia rg [nm] of the water-soluble polymer to d [nm] was determined. The interparticle distance d [nm] of the abrasive in each example, the radius of inertia rg [nm] and the ratio [rg / d] of the water-soluble polymer are shown in Table 1.

[Method of measuring the radius of inertia]
In the measurement of the radius of inertia rg of a water-soluble polymer, first, an aqueous solution is prepared so that the concentration of the water-soluble polymer is in the range of 0.1 to 1 mg / mL, and a light scattering photometer "DLS" is prepared for each prepared sample The measurement was performed every 10 degrees in the range of a measurement angle of 20 to 150 degrees using "-8000" (manufactured by Otsuka Electronics Co., Ltd.), and the inertial radius [nm] was calculated by monotonic plot analysis. When a plurality of water-soluble polymers were contained in the concentrate of the polishing composition, the measurement was carried out by adjusting the water-soluble high molecular weight so as to obtain the concentration ratio.

[Stability]
100 g of the concentrated solution according to each example was placed in a glass tube 2.5 cm in diameter and 25 cm in height, and stored at 25 ° C. by standing. The presence or absence of separation of the water-soluble polymer in the concentrate after 24 hours from the start of storage was visually evaluated according to the following 5 criteria. That is, when separation of the water-soluble polymer is not observed, it is evaluated as "A", and when separation is observed, the case where the layer of the supernatant liquid is less than 2 mm is evaluated as "B" and the supernatant When the layer of liquid is 2 mm or more and less than 4 mm, it is evaluated as "C", and when the layer of supernatant liquid is 4 mm or more and less than 5 mm, it is evaluated as "D". The layer of supernatant liquid is 5 mm or more Case was evaluated as "E". A to D were practically acceptable levels, and E was regarded as a rejection. 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 Concentrated Solution for Polishing Composition]
Example 2 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 Concentrates of the polishing composition according to Comparative Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-2 were prepared. The concentrations of abrasive grains and water-soluble polymer in the concentrated solution 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 to a concentration of 0.043%. With respect to the polishing composition of Example 2-14, polyoxyethylene lauryl ether was added as a nonionic surfactant to have a concentration of 0.001%. For the concentrated liquid according to each example, the distance d [nm] of the abrasive grains is determined, and the radius of inertia rg [nm] of the water-soluble polymer is measured by the same method as in Experiment 1. The ratio [rg / d] of the radius of inertia rg [nm] of the water-soluble polymer to the distance d [nm] was determined. The stability of the concentrate was also evaluated in the same manner as in Experiment 1. The evaluation results of the interparticle distance d [nm], the inertial radius rg [nm] of the water-soluble polymer, the ratio [rg / d] and the concentrate stability are shown in Table 2.

Polishing of silicon wafers
The concentrate according to each example was diluted with ion exchange water at a dilution ratio (volume basis) shown in Table 2 to obtain a polishing solution (working slurry). Rough polishing was performed under the following conditions using this.
(Polishing conditions)
Polishing device: Single-side polishing device manufactured by Nihon Engis, model "EJ-380IN"
Polishing pad: manufactured by Nitta Hearth, trade name "MH S-15A"
Polishing pressure: 26.6 kPa
Slurry flow rate: 100 mL / min Plate rotational speed: 50 rpm
Head rotation speed: 50 rpm
Polishing amount: 8 μm
Work species: Bare Si ^P - <100>
Work size: □ 60 mm × 60 mm

[Polishing performance (flatness)]
The flatness was evaluated by the following method as an alternative evaluation of GBIR. Specifically, using Nikon's evaluation machine "DIGIMICRO MH-15M", the thickness of 36 points is measured at equal intervals on both the vertical and horizontal sides of the polished wafer surface, and the maximum and minimum values are measured. The difference in wafer thickness was defined as the wafer thickness difference, and the value of the wafer thickness difference in each example was evaluated based on the following four criteria. That is, the case where the wafer thickness difference is less than 2.5 μm is evaluated as “A”, and the case where the wafer thickness difference is 2.5 μm or more and less than 3.0 μm is evaluated as “B”. The case of 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 to be a rejection. The results are shown in Table 2.

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

[Concentration efficiency]
The dilution factor of the concentrate according to each example was regarded as the concentration efficiency (concentrable factor), and classified according to the following three criteria. That is, a case where the concentration possible factor is greater than 20 times is "A", a case where the concentration possible factor is more than 10 times and 20 times or less is "B", and a case where the concentration possible factor is 10 times or less C. " The results are shown in Table 2.

  As shown in Table 1, in Experiment 1, the ratio [rg / d] of the ratio [ra] of the radius of inertia rg [nm] of the water-soluble polymer to the inter-particle distance d [nm] of the abrasive grains is 4.7 or less The concentrates according to Examples 1-1 to 1-11 were evaluated as having passed the stability evaluation. In particular, in Examples 1-1 to 1-7 and 1-11 in which the ratio [rg / d] was 2.5 or less, the evaluation result of the stability is A or B, and more excellent stability is obtained. It 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 a rejection level.

  In addition, as shown in Table 2, also in Experiment 2, the concentrated solutions 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 pass 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 evaluation result of the stability is A or B, which is more excellent. Stability was 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 concentrate was a rejection level. Further, in Examples 2-1 to 2-14 using a concentrate containing a water-soluble polymer, the polishing performance (specifically, the flatness) was a pass level while all were a water-soluble polymer. In Comparative Example 2-2 in which the above was not used, good polishing performance (specifically, flatness) could not be obtained.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

Claims (7)

What is claimed is: 1. A concentrate of a silicon wafer rough polishing composition containing abrasive grains, a basic compound and a water-soluble polymer,
The composition for roughly polishing a silicon wafer, wherein 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 in the concentrate is 4.7 or less Liquid concentrate.   The concentrate according to claim 1, wherein the ratio [rg / d] is 2.5 or less.   The concentrate according to claim 1, wherein an interparticle distance d of the abrasive grains is 200 nm or less.   The concentrate according to any one of claims 1 to 3, wherein the inertial radius rg of the water-soluble polymer is 30 nm or more.   The concentrate according to any one of claims 1 to 4, wherein the concentration of the abrasive grains is 5% by weight or more.   The concentrate 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 concentrate according to any one of claims 1 to 6, which is diluted at a magnification of more than 10 times on a volume basis and used for rough polishing of a silicon wafer.