KR20190098145A - Polishing Compositions and Polishing Methods - Google Patents

Abstract

The polishing composition which can further reduce the micro defect and haze of the wafer after grinding | polishing is provided. The polishing composition contains silica particles, a basic compound, and polyglycerol, and the mass ratio of silica to polyglycerine is 0.9 or less. The basic compound may be at least one selected from alkali metal hydroxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides. It is preferable that a polishing composition further contains the polyhydric alcohol which is a nonionic surfactant.

Description

Polishing Compositions and Polishing Methods

The present invention relates to a polishing composition and a polishing method.

Polishing of a semiconductor wafer by CMP is realized by high-level smoothing and flattening by performing three-step or four-step multistep polishing. In the finishing polishing process performed at the final stage, the main purpose is to reduce haze (surface blur) and minute defects.

The polishing composition used in the final polishing step of the semiconductor wafer generally contains a water-soluble polymer such as hydroxyethyl cellulose (HEC). The water-soluble polymer has a role of making the surface of the semiconductor wafer hydrophilic and suppresses damage to the semiconductor wafer due to adhesion of abrasive grains to the surface, excessive chemical etching, aggregation of abrasive grains, and the like. It is known that by this, a haze and a microdefect can be reduced.

Since HEC uses cellulose which is a natural raw material, the water-insoluble impurity derived from cellulose may be contained. Therefore, in the polishing composition containing HEC, a small defect may occur under the influence of this impurity.

HEC is often used molecular weight of several hundred thousand to one million. The higher the molecular weight, the more likely the filter is to be clogged, and the more difficult to pass through the filter having a small pore diameter. Therefore, when the water-soluble high molecular weight polymer is used, it becomes difficult to remove coarse particles. Moreover, since agglomeration of abrasive grains also tends to occur, there is a concern also in the long term stability of the polishing composition.

Japanese Laid-Open Patent Publication No. 2015-109423 discloses a silicon wafer polishing composition comprising 0.01 to 0.5 mass% of silica particles, a nitrogen-containing basic compound, and a water-soluble polymer. The water-soluble polymer of this polishing composition has a ratio of the number of oxygen atoms derived from hydroxyl groups and the number of oxygen atoms derived from polyoxyalkylene from 0.8 to 10.

In recent years, with the progress of miniaturization of the design rules of semiconductor devices, more stringent management is required for microdefects on the surface of semiconductor wafers.

It is an object of the present invention to provide a polishing composition and a polishing method that can further reduce fine defects and haze of a wafer after polishing.

The polishing composition according to one embodiment of the present invention contains silica particles, a basic compound, and polyglycerol, and the mass ratio of the silica particles to the polyglycerol is 0.9 or less.

In the polishing composition according to one embodiment of the present invention, the basic compound may be at least one selected from alkali metal hydroxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides.

It is preferable that the polishing composition by one embodiment of the present invention further contains a polyhydric alcohol which is a nonionic surfactant.

In the polishing composition according to one embodiment of the present invention, the polyhydric alcohol is preferably a polychain polyoxyalkylene alkyl ether.

In the polishing composition according to one embodiment of the present invention, it is preferable that the polyoxyalkylene alkyl ether of the polychain is at least one selected from polyoxyalkylene methyl glucoside and polyoxyalkylene polyglyceryl ether.

The polishing method according to one embodiment of the present invention includes a step of finishing polishing a silicon wafer using the polishing composition described above and a foamed urethane pad having a hardness of 80 or less.

According to the present invention, microdefects and haze of the wafer after polishing can be further reduced.

MEANS TO SOLVE THE PROBLEM The present inventors made various examination in order to solve said subject. As a result, the following findings were obtained.

By using polyglycerol as the water-soluble polymer and setting the mass ratio of the silica particles to the polyglycerol to 0.9 or less, the affinity between the dispersion medium and the surface of the silica particles is improved, and the dispersion medium and the silica particles are easily fused. Thereby, soft grinding | polishing to a wafer is performed, the flaw by a particle is suppressed and surface defects are reduced.

Moreover, by adding the polyhydric alcohol which is a nonionic surfactant to polyglycerol, a dispersion medium becomes easy to fuse to a wafer. As a result, the protection of the wafer is increased, surface defects can be further reduced, and a smooth surface can be realized.

Polyglycerol is usually smaller in molecular weight than HEC. Therefore, when polyglycerol is used as a water-soluble polymer, it is thought that silica particle becomes difficult to aggregate. However, as a result of investigation by the present inventors, when polyglycerol is used as a water-soluble polymer, it turned out that silica particle rather becomes easy to aggregate. This reason is considered as follows.

When the water-soluble polymer is HEC, since several molecules have a three-dimensional network structure, clusters containing silica particles are formed. Therefore, even if the density | concentration of a silica particle is high, aggregation will hardly occur. On the other hand, in the case of polyglycerin, since clusters like HEC are not formed, the distance between particles becomes shorter by increasing the concentration of silica particles. This makes polyglycerol adsorb | suck to a silica particle, and it becomes easy to condense. In addition, polyglycerol has a lower molecular weight than HEC, and the number of molecules increases at the same concentration ratio. Therefore, the adsorbed water of the molecule also becomes larger than the HEC.

By making the mass ratio of the silica particles to polyglycerol 0.9 or less, aggregation of the silica particles can also be suppressed. Thereby, long-term stability of a polishing composition can be improved.

Finish polishing of a silicon wafer is usually performed using a suede type polishing pad. However, in the polishing composition described above, the haze can be further reduced by polishing using a foamed urethane type polishing pad.

This invention was completed based on these knowledge. Hereinafter, the polishing composition according to one embodiment of the present invention will be described in detail.

The polishing composition according to one embodiment of the present invention contains silica particles, a basic compound, and polyglycerol, and the mass ratio of silica particles to polyglycerine is 0.9 or less.

Silica particle is mix | blended with a polishing composition as an abrasive grain. As the silica particles, those commonly used in this field can be used. For example, colloidal silica, fumed silica, or the like can be used.

Although content of a silica particle is not specifically limited, For example, it is less than 3 mass% of the whole polishing composition (stock solution). Preferably the upper limit of content of a silica particle is 1 mass%, More preferably, it is 0.5 mass%, More preferably, it is 0.25 mass%. The minimum of content of a silica particle becomes like this. Preferably it is 0.015 mass%, More preferably, it is 0.075 mass%.

The basic compound is chemically polished by etching the surface of the wafer. A basic compound is an amine compound, an inorganic alkali compound, etc., for example.

The amine compound is, for example, primary amine, secondary amine, tertiary amine, quaternary ammonium and its hydroxide, heterocyclic amine and the like. Specifically, ammonia, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, Hexylamine, cyclohexylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine (DETA), triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, monoethanolamine, diethanolamine, triethanolamine, N- (β-aminoethyl) ethanolamine, anhydrous piperazine, piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, piperazine hydrochloride, guanidine carbonate and the like.

Examples of the inorganic alkali compounds include hydroxides of alkali metals, salts of alkali metals, hydroxides of alkaline earth metals, salts of alkaline earth metals, and the like. The inorganic alkali compound is specifically potassium hydroxide, sodium hydroxide, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate and the like.

The basic compound mentioned above may be used individually by 1 type, and may mix and use 2 or more types. Among the basic compounds described above, hydroxides of alkali metals, salts of alkali metals, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides are preferable. Although content of the sum total of a basic compound is not specifically limited, For example, it is 0.0003-1.2 mass% of the whole polishing composition (stock solution). The minimum of content of a basic compound becomes like this. Preferably it is 0.003 mass%. The upper limit of the content of the basic compound is preferably 0.6% by mass.

The polishing composition according to the present embodiment contains polyglycerol as a water-soluble polymer. Polyglycerol forms a dispersion medium with a basic compound, and adsorb | sucks on the surface of a silica particle and the wafer surface. As a dispersion medium adsorb | sucks on the surface of a silica particle, grinding | polishing by a silica particle becomes soft and polishing defect is suppressed. In addition, by adsorbing the dispersion medium on the wafer surface, polishing defects and adhesion of foreign matter are suppressed.

Although the structure of polyglycerol is not specifically limited, For example, a linear type, a branched type, a dendrimer type, etc. are mentioned. Although the weight average molecular weight of polyglycerol is not specifically limited, For example, it is 100-20000. The minimum of the weight average molecular weight of polyglycerol becomes like this. Preferably it is 300, More preferably, it is 500. Preferably the upper limit of the weight average molecular weight of polyglycerol is 10000, More preferably, it is 5000.

Although content of polyglycerol is not specifically limited, For example, it is 0.15-3 mass% of the whole polishing composition (stock solution). The minimum of content of polyglycerol becomes like this. Preferably it is 0.2 mass%, More preferably, it is 0.3 mass%. Preferably the upper limit of content of a polyglycerol is 2.5 mass%, More preferably, it is 2.0 mass%.

In the polishing composition according to the present embodiment, the mass ratio (content of silica particles / content of polyglycerol) of silica particles to polyglycerol is 0.9 or less. By setting the mass ratio of silica particles to polyglycerine to 0.9 or less, the affinity of the surface of the silica particle with the dispersion medium which consists of a polyglycerol and a basic compound becomes high, and a dispersion medium and a silica particle become easy to fuse. The upper limit of the mass ratio of silica particles to polyglycerol is preferably 0.8, and more preferably 0.7. The lower limit of the mass ratio of silica particles to polyglycerol is preferably 0.005, more preferably 0.01.

The polishing composition according to the present embodiment may further contain a polyhydric alcohol which is a nonionic surfactant. The polyhydric alcohol which is a nonionic surfactant enters between the molecule | numerator of a polyglycerol, and a molecule | numerator, and adsorb | sucks tightly to the surface of a silica particle and a wafer. Thereby, a dispersion medium becomes easy to fuse to the surface of a silica particle and a wafer. As a result, surface defects can be further reduced, and a smooth surface can be realized.

The polyhydric alcohol (hereinafter, simply referred to as "polyhydric alcohol") as a nonionic surfactant is specifically N, N, N ', N'-tetrakis polyoxyethylene polyoxypropylene ethylene Diamine (poloxamine), polyvinyl alcohol, polyalkylene glycol, polyoxyalkylene alkyl ether (linear, poly-chain), polyoxyalkylene fatty acid ester, polyoxyalkylene alkylamine and the like.

Polyalkylene glycol is specifically, polyethyleneglycol, polypropylene glycol, etc. Specific examples of the linear polyoxyalkylene alkyl ether include polyoxyethylene polyoxypropylene glycol (poloxamer), polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether and the like. The polyoxyalkylene alkyl ether of the poly-chain type is specifically an alkylene oxide derivative (polyoxyalkylene methyl glucoside) of methyl glucoside, polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, polyoxyalkylene Polyglyceryl ether, polyoxyalkylene pentaerythritol ether, polyoxyalkylene trimethylol propane, polyoxypropylene sorbitol and the like. More specifically, polyoxyethylene methyl glucoside, polyoxypropylene methyl glucoside, polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, polyoxyethylene polyoxypropylene glyceryl ether, polyoxyethylene diglyceryl ether , Polyoxypropylene diglyceryl ether, polyoxyethylene polyglyceryl ether, polyoxypropylene polyglyceryl ether, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene trimethylol propane, polyoxypropylene sole Bit etc. Polyoxyalkylene fatty acid ester is polyoxyethylene monolaurate, polyoxyethylene monostearate, etc. specifically ,. Polyoxyalkylene alkylamine is polyoxyethylene laurylamine, polyoxyethylene oleyl amine, etc. specifically ,. Among these compounds, poly-chain polyoxyalkylene alkyl ethers are preferable, and polyoxyalkylene methyl glucoside or polyoxyalkylene polyglyceryl ether is particularly suitable.

Although the weight average molecular weight of a polyhydric alcohol is not specifically limited, For example, it is 100-30000. The lower limit of the weight average molecular weight of the polyhydric alcohol is preferably 200, and more preferably 500. The upper limit of the weight average molecular weight of the polyhydric alcohol is preferably 10000, and more preferably 1000.

Although content of polyhydric alcohol is not specifically limited, For example, it is 0.003-0.3 mass% of the whole polishing composition (stock solution). The minimum of content of a polyhydric alcohol becomes like this. Preferably it is 0.005 mass%, More preferably, it is 0.015 mass%. The upper limit of the content of the polyhydric alcohol is preferably 0.25% by mass, more preferably 0.15% by mass.

The polishing composition according to the present embodiment may further contain a pH adjuster. The pH of the polishing composition according to the present embodiment is preferably 8.0 to 12.0.

The polishing composition according to the present embodiment can optionally contain a compounding agent generally known in the field of the polishing composition in addition to the above.

The polishing composition according to the present embodiment is produced by appropriately mixing silica particles, basic compounds, polyglycerol and other compounding materials and adding water. The polishing composition according to the present embodiment is produced by sequentially mixing silica particles, basic compounds, polyglycerol and other compounding materials in water. As a means to mix these components, the means commonly used in the technical field of polishing compositions, such as a homogenizer and an ultrasonic wave, is used.

The polishing composition described above is used for polishing a silicon wafer after dilution with water to an appropriate concentration.

The polishing composition according to the present embodiment can be used particularly suitably for finish polishing of a silicon wafer.

The polishing composition according to the present embodiment is suitable for polishing using a low hardness urethane foam pad. By using the polishing composition according to the present embodiment and the polishing pad of low hardness foamed urethane type, a coating film of a polymer having an appropriate film thickness can be formed, and the balance between wafer protection and defect removal can be maintained. By setting the scraping amount appropriate for the film thickness, a balanced polishing effect can be exhibited with low damage. In addition, by lowering the concentration of the silica particles, agglomeration during polishing can be suppressed, resulting in low defects.

The hardness of a polishing pad is 80 or less by the hardness of JIS-A standard. If the hardness of the polishing pad exceeds 80, the contact area (contact area) between the wafer and the pad becomes small, so that defect removal becomes difficult. The upper limit of the hardness of the polishing pad is preferably 78, more preferably 75. The lower limit of the hardness of the polishing pad is preferably 40, more preferably 50.

EXAMPLE

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to these examples.

[Polishing Example 1]

The polishing compositions of Examples 1 to 8 and Comparative Examples 1 to 4 shown in Table 1 were produced.

In Table 1, the "particle diameter" of "silica particle" shows the average secondary particle diameter of a silica particle. "NH ₄ OH" represents an aqueous ammonia solution. "PGL" represents the polyglycerol of the weight average molecular weight 3000. "HEC" represents the hydroxyethyl cellulose of the weight average molecular weight 800000. Polyoxypropylene methyl glucoside of the weight average molecular weight 775 was used for the polyhydric alcohol. In addition, the remainder of each polishing composition is water.

The polishing composition of Example 1 contained 0.297 mass% of colloidal silica, 0.045 mass% of aqueous ammonia, and 0.45 mass% of polyglycerols. The polishing compositions of Examples 2 to 4 are based on the polishing composition of Example 1, and the content of colloidal silica is 0.15% by mass, 0.075% by mass, and 0.030% by mass, respectively. The polishing compositions of Examples 5 to 8 contain 0.015% by mass, 0.045% by mass, 0.060% by mass, and 0.075% by mass of polyoxypropylenemethylglucoside, respectively, based on the polishing composition of Example 1 .

The polishing composition of Comparative Example 1 contained 10.5 mass% of colloidal silica, 0.39 mass% of aqueous ammonia solution, and 0.36 mass% of hydroxyethyl cellulose. The polishing composition of Comparative Example 2 contained 0.204 mass% of colloidal silica, 0.009 mass% of aqueous ammonia solution, and 0.339 mass% of hydroxyethyl cellulose.

The polishing composition of Comparative Example 3 contained 1.5 mass% of colloidal silica, 0.045 mass% of aqueous ammonia solution and 0.75 mass% of polyglycerol. The polishing composition of Comparative Example 4 contained 1.5% by mass of colloidal silica, 0.06% by mass of an aqueous ammonia solution, and 0.75% by mass of polyglycerol.

Using the polishing compositions of these examples and comparative examples, the 12-inch silicon wafer was polished. The conductivity type of the silicon wafer was P type, and the resistivity used was 0.1 ohm cm or more and less than 100 ohm cm. The polished surface was made into the <100> surface. As the polishing apparatus, SPP800S single-side polishing apparatus manufactured by Okamoto Machine Tools Co., Ltd. was used. As the polishing pad, a foamed urethane polishing pad having a hardness of 73 was used. The polishing composition was diluted 30 times and fed at a feed rate of 0.6 L / min. The rotational speed of the surface plate was 40 rpm, the rotational speed of the carrier was 39 rpm, and the polishing load was 100 gf / cm ² , and polishing was performed for 4 minutes.

Microscopic defects and haze of the silicon wafer after polishing were measured. The micro defects were measured using a wafer surface inspection apparatus MAGICS M5640 (manufactured by Lasertec). Haze used wafer surface inspection apparatus LS6600 (made by Hitachi Engineering Co., Ltd.). The results are shown in Table 1 above.

As shown in Table 1, in Examples 1 to 8 in which polyglycerol was used as the water-soluble polymer and the mass ratio of silica particles to polyglycerine was 0.9 or less, all of the microdefects were compared with Comparative Examples 1 to 4. The number was reduced. In particular, in Examples 5-8 containing a polyhydric alcohol, the number of micro defects was remarkably reduced. Moreover, in Examples 5-8 containing polyhydric alcohol, haze was also significantly improved.

On the other hand, from the comparison of Examples 1-4, even if it changed content of a silica particle in the range whose mass ratio of the silica particle with respect to polyglycerol is 0.9 or less, the big difference was not seen in the number of micro defects.

In order to investigate in more detail the relationship between the mass ratio of the silica particles to the polyglycerol and the microdefects, the interface characteristics of the silica particles and the dispersion medium were evaluated by pulse NMR described below.

The dispersion medium molecules in contact with or adsorbed on the particle surface and the dispersion medium molecules in the dispersion medium bulk (free dispersion medium molecules not in contact with the particle surface) have different responses to the change in the magnetic field. In general, the movement of liquid molecules adsorbed on the particle surface is limited, but the liquid molecules in the bulk liquid can move freely. As a result, the NMR relaxation time of the liquid molecules adsorbed on the particle surface becomes shorter than the NMR relaxation time of the liquid molecules in the bulk liquid. The NMR relaxation time observed in the liquid in which the particles are dispersed is an average of two relaxation times reflecting the liquid volume concentration on the particle surface and the liquid volume concentration in the free state.

Rv is the inverse (time constant) of the NMR relaxation time observed in the polishing composition in which the silica particles are dispersed, and Rb is the inverse of the NMR relaxation time (time constant) observed in the polishing composition before the particles are dispersed. (Rav / Rb) -1 is calculated. Rsp is an index of affinity between the dispersion medium and the particle surface, and if the total surface area of the particles is the same, the larger the Rsp, the higher the affinity between the dispersion medium and the particle surface.

In the present Example, relaxation time was measured using the pulse NMR apparatus Acorn area by Xigo nanotools. Measurement conditions were magnetic field: 0.3T, measurement frequency: 13 MHz, measurement nucleus: ¹ H NMR, measurement method: CPMG pulse sequence method, sample amount: 1 ml, and temperature: 25 ° C.

About the polishing composition of Examples 1 and 7 mentioned above, relaxation time was measured. Moreover, as the comparative example 5, the polishing composition which made content of a silica particle 3 mass% based on the polishing composition of Example 7 was produced, and the relaxation time was measured similarly. The results are shown in Table 2.

"Rb ^{- 1} " in Table 2 is the relaxation time observed in the polishing composition (blank) before dispersing the silica particles, and "Rav ^{- 1} " is the relaxation time observed in the polishing composition in which the silica particles are dispersed. . "Volume fraction" is the volume fraction of the silica particle in the whole polishing composition, and was calculated from the content and density of the silica particle. "Affinity" is obtained by dividing Rsp = (Rav / Rb) -1 by the volume fraction of silica particles. When comparing affinities between samples with different particle concentrations, the rsp should be rigorously divided by the total surface area of the particles, but in this comparison all silica particles with the same average particle diameter were used. The total surface area of is proportional to the volume fraction.

From the comparison between Example 7 and Comparative Example 5, it can be seen that the affinity is remarkably improved by setting the mass ratio of silica particles to polyglycerol to 0.9 or less. From this result, it is thought that the microdefect was reduced by making the mass ratio of the silica particle to polyglycerol 0.9 or less by the improvement of the affinity of a silica particle and a dispersion medium. Moreover, it turns out that the affinity of a silica particle and a dispersion medium further improves by containing a polyhydric alcohol from the comparison of Example 1 and Example 7.

From the above result, it was confirmed that surface defects can be reduced by using polyglycerol as a water-soluble polymer and making content of a silica particle less than 0.3 mass%.

Next, the number of coarse particles (number of particles having a particle diameter of 0.5 μm or more) of the polishing composition was measured. The measurement of the number of coarse particles used AccuSizer FX Nano Dual manufactured by Particle Sizing System. The results are shown in Table 3.

As can be seen from the comparison between Example 7 and Comparative Example 5, the number of coarse particles was significantly reduced by setting the mass ratio of silica particles to polyglycerine to 0.9 or less. From this result, it turns out that aggregation of a silica particle can be suppressed by making the mass ratio of the silica particle with respect to polyglycerol 0.9 or less.

[Polishing example 2]

The polishing compositions of Examples 1, 6, 7, 9 to 16, and Comparative Example 6 described in Table 4 were prepared. In addition, in order to make it easy to compare with the grinding | polishing example 1, the thing of the same formulation was attached | subjected the same Example number (Example 1, 6, 7).

The polishing composition of Example 9 has a content of colloidal silica as 0.400% by mass based on the polishing composition of Example 1. The polishing compositions of Examples 10 to 12 are based on the polishing composition of Example 1, and the polyglycerol content is set to 0.75% by mass, 0.9% by mass and 1.8% by mass, respectively. In the polishing composition of Example 13, a polyhydric alcohol (polyoxypropylene methyl glucoside) was added to the polishing composition of Example 12. The polishing composition of Examples 13-16 adds the polyhydric alcohol (refer to the periphery of Table 3) different from each other to the polishing composition of Example 1, respectively.

The polishing composition of Comparative Example 6 is obtained by replacing polyglycerol of the polishing composition of Example 1 with hydroxyethyl cellulose.

The 12-inch silicon wafer was polished using the polishing compositions of Examples and Comparative Examples described in Table 4. The polishing pad was subjected to polishing under the same conditions as in Polishing Example 1 except that a suede-type polishing pad (Verbal RN-H manufactured by Nita Haas Co., Ltd.) was used as the polishing pad. Haze was measured. In addition, the affinity and the number of coarse particles were measured in the same manner as in the polishing example 1. The results are shown in Table 5.

Also from this result, it was confirmed that surface defects can be reduced by using polyglycerol as the water-soluble polymer and making the mass ratio of silica particles to polyglycerol 0.9 or less.

Finish polishing of a silicon wafer is normally performed using a suede type polishing pad as in Polishing Example 2. In the conventional polishing composition, it is preferable to use a suede type polishing pad rather than a foamed urethane type pad. On the other hand, in the polishing compositions of Examples 1, 6, and 7, when the polishing example 1 and the polishing example 2 are compared, the fine defects are about the same, but the haze has less polishing example 1. That is, in the case of the polishing composition according to the present embodiment, it was found that by polishing using a foamed urethane-type pad, the haze can be further reduced to the same or less.

In the above, embodiment of this invention was described. Embodiment mentioned above is only the illustration for implementing this invention. Therefore, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate without departing from the spirit thereof.

Claims (6)

With silica particles,
A basic compound,
Contains polyglycerin,
Polishing composition whose mass ratio of the said silica particle with respect to the said polyglycerol is 0.9 or less. The method according to claim 1,
The basic compound is at least one member selected from hydroxides of alkali metals, salts of alkali metals, ammonia, amines, ammonium salts and quaternary ammonium hydroxides. The method according to claim 1 or 2,
A polishing composition further comprising a polyhydric alcohol that is a nonionic surfactant. The method according to claim 3,
The polyhydric alcohol is a polychain polyoxyalkylene alkyl ether, polishing composition. The method according to claim 4,
The polycyclic polyoxyalkylene alkyl ether is at least one kind selected from polyoxyalkylene methyl glucoside and polyoxyalkylene polyglyceryl ether. A polishing method comprising the step of finishing polishing a silicon wafer using the polishing composition according to any one of claims 1 to 5 and a foamed urethane pad having a hardness of 80 or less.