JP2002338232A - Secondary flocculated colloidal silica, method for producing the same and abrasive composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce secondary flocculated colloidal silica which ensures a high polishing speed when used as an abrasive for a semiconductor device or the like, and to provide a method for producing the colloidal silica at a low cost. SOLUTION: The secondary flocculated colloidal silica is obtained by adding a flocculant for silica particles to monodisperse colloidal silica to form spherical flocculated secondary particles and by further adding active silicic acid to integrate the flocculated particles. The secondary flocculated colloidal silica particles have surface ruggedness, the ratio Y (X1/X2) of the geometric average particle diameter (X1) obtained from TEM (transmission electron microscope) transmission projected images to the equivalent particle diameter (X2) calculated from the surface areas of the silica particles is in the range of 1.3-2.5 and the geometric average particle diameter is in the range of 20-200 nm. The silica particles have superior properties as an abrasive in the surface polishing of electronic materials such as a semiconductor device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a silicon wafer,
The present invention relates to secondary aggregated colloidal silica used in polishing of electronic materials such as a compound semiconductor wafer, a semiconductor device wafer, a magnetic disk substrate, and a quartz substrate, and a method of manufacturing the same at low cost.

[0002]

2. Description of the Related Art Colloidal silica conventionally manufactured using commercially available alkali silicate as a raw material is used as an abrasive for silicon wafers, an adhesive binder for a phosphor in the manufacture of cathode ray tubes,
It has been used for various purposes such as a gelling agent for electrolyte in a battery and a thixotropic or scattering inhibitor. The shape of the silica particles of colloidal silica generally used for such an application is a true spherical shape or a shape close thereto, so that the purpose of the polishing agent is to improve the polishing characteristics, and in the case of the binder, the adhesion or the forming property is improved. For the purpose of improving the film properties, attempts have been made to change the shape of the silica particles from spherical to spherical or to increase the particle size by agglomeration.

[0003] For example, in the case of binders,
No. 12 and JP-A-7-118008, non-spherical and elongated particles produced by adding a Ca salt or the like are disclosed in JP-A-4-2140.
No. 22 discloses flat particles. In addition, JP
JP-A-01-11433 states that slender beads are produced by adding Ca salt or the like, and that the particles have good polishing properties. On the other hand, as to colloidal silica aggregated in a spherical shape, US Pat. No. 3,591,518 describes a method for producing from metallic silicon. U.S. Pat. No. 3,607,774 describes a method for producing agglomerated colloidal silica in which the measured particle size by the light scattering method and the measured particle size by the Sears method are several times different.

[0004]

Colloidal silica has been used as a polishing agent for electronic materials such as silicon wafers, compound semiconductor wafers, semiconductor device wafers, magnetic disk substrates, and quartz substrates. In response to this, grades having a large particle size have been increasingly preferred. However, in the case of true spherical colloidal silica, in order to produce a single particle having a large particle diameter as it is, a so-called build-up process in which silica is further deposited on the surface of the particle to grow the particle, which is a long time, is required. And the production cost of the particles is high. In the above-mentioned polishing treatment of electronic materials, a reduction in polishing time and a reduction in polishing cost are also required. Therefore, a colloidal material having a relatively large particle diameter, which can be efficiently polished in a short time and is inexpensive. There is a need for silica or colloidal silica that can be polished at a high speed even if the particle diameter is not so large.

As a method for increasing the particle size of colloidal silica at a relatively low cost, a method of aggregating silica particles is described in US Pat. No. 3,591,518. Since the diameter is as small as 8 nm and the irregularities on the surface of the aggregate are almost smooth, improvement in polishing characteristics cannot be expected. Also, US Patent No. 3
Japanese Patent No. 607774 describes a method for producing colloidal silica in which the measured particle size by the light scattering method and the measured particle size by the Sears method are several times different. The fact that the particle diameter measured by the light scattering method and the equivalent diameter calculated from the specific surface area measured by the Sears method are several times different suggests that the particle shape is not spherical, but US Pat. There is no specific description, the principle of the production method is unclear, and there is a step of evaporating a large amount of water. The Sears method is described in G. W. Se
ars, Jr. Is “Analytical Chemistry” 28,1981〜
1983 (1956) is a method for determining the equivalent diameter of the irregular-shaped particles are described in, for 0.1 N-NaOH was required to titrate from pH4 to pH9 colloidal silica corresponding to SiO ₂ of 1.5g The specific surface area of the colloidal silica was determined from the amount, and the equivalent diameter was calculated from this.

On the other hand, a method of improving the polishing characteristics by adding a Ca salt or the like to make the silica particles into an elongated bead shape (Japanese Patent Laid-Open No. 2001-11433) discloses a method in which a high concentration of Ca salt or the like is used in addition to the silica component. Since it is inevitable, contamination of the electronic material to be polished thereby and clogging of the filter at the time of circulating use of colloidal silica in the polishing step become problems. Accordingly, the objects of the present invention are thus silicon wafers, compound semiconductor wafers, semiconductor device wafers,
As a colloidal silica used as an abrasive for electronic materials such as magnetic disk substrates and quartz substrates, it can be manufactured at low cost, and has a relatively large particle size rather than a spherical particle shape, and therefore has excellent polishing efficiency. An object of the present invention is to provide colloidal silica particles suitable as an abrasive and a method for producing the same.

[0007]

Means for Solving the Problems In order to achieve such an object, the inventors of the present invention have conducted intensive studies and found that monodispersed colloidal silica has a relatively large particle diameter, Further, the present inventors have found a method for producing silica particles having irregularities on the surface of the silica particles, and a colloidal silica containing such silica particles.

That is, the present invention relates to a method of calculating the geometric average particle diameter (X1) obtained from a transmission projection image of colloidal silica particles by an electron beam and the equivalent particle diameter (X2) calculated from the surface area of the silica particles. The secondary aggregated colloidal silica is characterized in that the ratio Y (X1 / X2) is in the range of 1.3 to 2.5 and the geometric average particle size is in the range of 20 to 200 nm. In addition, the present invention is characterized in that a coagulant of silica particles is added to monodisperse colloidal silica to form substantially spherical aggregated secondary particles, and then active silica is added to integrate the aggregated particles. This is a method for producing aggregated colloidal silica. Furthermore, the present invention provides a ratio Y () of a geometric average particle diameter (X1) obtained from a transmission projection image of colloidal silica silica particles by an electron beam and an equivalent particle diameter (X2) calculated from the surface area of the silica particles. X1 /
X2) is in the range of 1.3 to 2.5, and contains a secondary aggregated colloidal silica having a geometric average particle size in the range of 20 to 200 nm. A composition.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The secondary agglomerated colloidal silica of the present invention is a secondary agglomerated colloidal silica containing silica particles in which several to a dozen or more silica primary particles having irregularities caused by primary particles on the surface of the silica particles are aggregated. Agglomerated colloidal silica, the geometric mean particle diameter (X1) determined from a transmission projection image of the silica particles by an electron beam, and the equivalent particle diameter (X2) calculated from the surface area of the silica particles measured by the nitrogen adsorption BET method. The ratio Y
(X1 / X2) is not less than 1.3 and not more than 2.5,
The feature is that the geometric average particle diameter is in the range of 20 to 200 nm. According to another expression, the secondary agglomerated colloidal silica of the present invention is a colloidal silica containing silica particles having irregularities on the particle surface, a so-called `` shag-like '' shape, and an electron beam of the silica particles. The geometric mean particle size (X
The ratio Y (X1 / X2) between 1) and the equivalent particle size (X2) calculated from the surface area of the particles measured by the Sears method is 1.3 or more and 2.5 or less, and the geometric average particle size is 2
Characteristically, it is in the range of 0 to 200 nm.

Here, the ratio Y represents the degree of unevenness of the surface of the silica particles. If the ratio Y is in the range of 1.3 or more and 2.5 or less, the surface has a certain degree of unevenness and the whole Substantially spherical particles, that is, agglomerated particles having several to tens of protrusions per particle, for example, those having a special shape such as plate-like or string-like particles have this value. It exceeds 2.5 and is not included in the particles of the present invention. Further, if the ratio Y is 1.0, it is a perfect spherical shape, but the particles of the present invention do not include such a true spherical shape, and necessarily have a certain degree of unevenness on the surface of the particles, That is, it is an agglomerated particle having several to several tens of protrusions per particle, and is a so-called "giggle-shaped" particle.

The ratio Y is obtained by calculating the geometric average particle diameter (X1) obtained from a transmission projection image of the silica particles by an electron beam and the equivalent particle diameter (X1) calculated by measuring the surface area of the silica particles.
2), and this ratio (X1 / X2) is obtained. First, the geometric mean particle diameter determined from a transmission projection image by an electron beam is, for example, the diameter of all substantially spherical secondary aggregated silica particles at a plurality of locations, as shown in a transmission electron microscope (TEM) photograph. Is measured, and these values are averaged. Incidentally, in the method based on the TEM photograph, it may be difficult to distinguish the true aggregated particles and the aggregated particles due to drying at the time of preparing the sample, but here, the particle concentration is reduced to the limit and isopropyl alcohol is used for the dilution. Use avoids these misconceptions. Specifically, for example, the colloidal silica of the sample,
0.1% silica concentration using isopropyl alcohol
Using a solution diluted to 10,000 times,
(Transmission electron microscope) Take a picture
Select four places where 0 or more silica particles are present,
Each part is photographed at a magnification of 40,000. From these photographic images, the diameters of all the particles that do not cover the end face are measured, and the average value is determined to be the geometric average particle diameter (X1).

On the other hand, the equivalent diameter determined from the surface area of the silica particles is calculated as follows. In general, a method is known in which molecules or ions of a known size are adsorbed on a sample surface, and the specific surface area of the particles is determined from the amount of adsorption. In the BET method, nitrogen gas is adsorbed in the gas phase as an adsorbent, and in the Sears method, Na ions are adsorbed in the liquid phase as an adsorbent. The Sears method is described in G. W. Sears, Jr. ”An
alytical Chemistry ", 28, 1981-1983 (1956).

The specific surface area means the total particle surface area of a unit mass of powder. When the powder is pulverized, a new surface is formed. As the pulverization proceeds and the particles become finer, the specific surface area of the powder also increases. growing. Here, assuming that the powder is composed of n spheres having a diameter x and a density ρ, the total particle surface area is nπ
x ^2, since the powder mass becomes ρnπx ^3/6, the following (1)
An equation relationship is derived. Specific surface area S (m ² / g) = 6 / {density ρ (g / cm ³ ) × diameter x (cm)} (1) When this is applied to colloidal silica, the density ρ is 2.2 g / cm ³ . Therefore, if the unit is rewritten with the unit aligned, it becomes the following equation (2). Diameter x (nm) = 2720 / specific surface area S (m ² / g) (2) Thus, the equivalent diameter x can be calculated from the specific surface area of the colloidal silica measured by the BET method and the Sears method.

The particle size and specific surface area of colloidal silica are described in "THE CHEMISTRY OF SILICA Solubility,
Polymerization, Colloid and Surface Properties an
d Biochemistry ”(P344-354, by RALPH K. ILER, A Wile
y-Interscience Publication JOHN WILEY & SONS P).

The geometric mean particle diameter (X
The ratio Y of 1) and the equivalent diameter (X2) calculated from the specific surface area is 1 when the particles are perfectly spherical, but the silica particles obtained by integrating the aggregated particles of the present invention have a substantially spherical shape. Although the particles are particles, the specific surface area is larger than that of a true sphere due to the unevenness of the surface, and the equivalent diameter calculated from the above equation (2) is a small value. Therefore, the value of Y increases from 1 as the degree of irregularities on the surface of the particle increases. The commonly available monodispersed colloidal silica has a Y value of 1.05 to 1.11, while the agglomerated / integrated colloidal silica particles of the present invention have a Y value of:
1.3 or more and 2.5 or less, more preferably 1.3
The range is from 5 to 2.2.

The geometric mean particle size of the aggregated and integrated colloidal silica particles of the present invention is determined by the particle size of the monodispersed colloidal silica silica particles as a starting material and the number of particles to be aggregated. As a polishing application of the material, the monodispersed colloidal silica particles serving as a starting material have a silica particle of 5 to 50 nm, and the secondary aggregated colloidal of the present invention obtained by aggregating and integrating several to a dozen or more of them. The geometric mean particle size of the silica particles is 20 to 200 nm,
Preferably it is 30 to 100 nm.

The aggregated and integrated colloidal silica particles of the present invention are prepared by adding a flocculant of silica particles to monodisperse colloidal silica to form substantially spherical aggregated secondary particles, and then adding active silicic acid. By integrating the aggregated particles.

First, as a raw material of the monodispersed colloidal silica used in the present invention, an aqueous solution of alkali silicate is used, and an aqueous solution of sodium silicate usually called water glass (water glass No. 1 to 4) is preferably used. . It is relatively inexpensive and can be easily obtained. In addition, when used for a product for a semiconductor in which the presence of Na ions is not preferable, an aqueous solution of potassium silicate is suitable for a target of high purification.

As the monodispersed colloidal silica used in the present invention, it is possible to use colloidal silica obtained by ion-exchanging such an aqueous alkali silicate solution. In the production process of colloidal silica by this ion exchange method, first, an aqueous solution of an alkali silicate is diluted with water to a silica concentration of 3 to 10%, and then contacted with an H-type strongly acidic cation exchange resin to remove alkali.
It is anion-exchanged by contact with a strong basic anion exchange resin to form active silicic acid. Various proposals have already been made regarding the type and various conditions of the ion exchange resin, and any of those known methods can be applied. Next, colloid particles are grown according to a conventional method. That is, the pH of this aqueous solution of activated silicic acid is
The alkali agent is added so that the temperature is 8 or more.
Or a build-up method in which active silicic acid is added to a seed sol having a pH of 8 or more at 60 to 240 ° C., or a method in which active silicic acid is added to a diluted aqueous solution of alkali silicate. Any of these methods may be used. As the alkali agent used here, alkali metal hydroxides such as NaOH and KOH, and organic bases such as amines and quaternary ammonium hydroxides can be used. Also, their aqueous alkali silicate solutions can be used.

Using these methods, silica particles having a particle size of 5
It is grown to have a thickness of about 50 nm. Although the dispersion state of the silica particles is monodisperse, secondary aggregation may be present, and the silica particles can be used properly depending on the application. The shape of the monodispersed silica particles is a true sphere, but may include a secondary agglomerated non-spherical shape and may be properly used depending on the application. Instead of using the colloidal silica obtained by the ion exchange method, a commercially available colloidal silica can be used as the starting material. In this case, a commercially available product is used after being diluted to a silica concentration of 3 to 20%.

A coagulant for silica particles is added to a dilute aqueous solution of colloidal silica containing monodisperse colloidal silica as described above to form aggregated secondary particles. As the coagulant used in the present invention, polyaluminum chloride, aluminum compounds such as aluminum sulfate, basic iron chloride, iron compounds such as iron sulfate, alkaline earth metal compounds such as lime and dolomite, Water-soluble inorganic compounds such as
Alternatively, cationic polymers such as polyamines such as polyethyleneamine, and quaternary ammonium salts such as tetramethylammonium hydroxide may be used. These are all adsorption-type flocculants based on electric charge, and if added in an appropriate amount, can form aggregated secondary particles of a plurality of silica particles without causing the entire colloid to gel, and stabilize the secondary particles. A good colloidal state can be obtained. The amount added varies depending on the coagulant. For example, in the case of polyaluminum chloride, the order of ppm is sufficient, and excessive addition causes generation of precipitates and gelation of the entire colloid. In the case of polyamines and quaternary ammonium salts, addition in the order of% is an appropriate amount range. Further, these flocculants have an optimum pH range, and it is preferable to adjust the pH of the colloidal silica prior to addition in order to obtain good flocculation performance.
For example, the optimum pH range of polyaluminum chloride is pH7 ~
9 and pH 9 for tetramethylammonium hydroxide.
~ 11. Polyaluminum chloride is particularly preferable as a coagulant used in the present invention because it is inexpensive, has a large effect in a small amount, and can be used in an alkaline region.

Next, activated silica is added to the obtained aggregated secondary particles to integrate the aggregated secondary particles. The integration of the aggregated secondary particles means that the pH of the aqueous dispersion of the aggregated secondary particles is maintained at 60 to 240 ° C., preferably 90 to 240 ° C. while adding an alkaline agent so as to maintain the pH at 8 or more, preferably at pH 9 to 10. 10
In a state of being heated to 0 ° C., silica is deposited on the surface of the aggregated secondary particles by adding active silicic acid over a period of time corresponding to the added amount corresponding to the target particle diameter, and the aggregated particles are added. For further growth and reinforcement.
The method of growing the aggregated secondary particles in this way, compared with the case of growing the original colloidal silica as it is,
A large particle size can be obtained in a short time. As the alkali agent used here, the same one as described above can be used.

Next, it is concentrated and purified by an ultrafiltration membrane so that the concentration of silica becomes 10 to 60%. However, since this step also has the effect of washing out excess ions, if necessary, pure water is added even after reaching the target concentration to further wash out and remove, thereby increasing the removal rate of excess ions. You can also do work.

The separation to which the ultrafiltration membrane is applied has a target particle size of 1 nm to several microns. However, since the target is also for a dissolved high molecular substance, in the nanometer range, the filtration accuracy is expressed by a fraction molecular weight. . In the concentration of the colloidal silica according to the present invention, an ultrafiltration membrane having a cut-off molecular weight of 15,000 or less is used. When a film in this range is used, particles of 1 nm or more can be separated. More preferably, the molecular weight cut off is 30.
An ultrafiltration membrane of 00-15000 is used. If the membrane is less than 3,000, the filtration resistance is too large, and the treatment time becomes longer, which is uneconomical. The material of the membrane is polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon, etc., and any of them can be used. However, a membrane made of polysulfone is easy to use because of heat resistance and filtration speed. The shape of the membrane can be any type such as a spiral type, a tubular type and a hollow fiber type, and any type can be used, but the hollow fiber type is compact and easy to use.

Further, before or after the concentration by the ultrafiltration membrane, a purification step using an ion exchange resin can be added if necessary. That is, the alkali used in the particle growth step can be removed by contacting with an H-type strongly acidic cation exchange resin, and by contacting with an OH-type strongly basic anion exchange resin to be deanionized and purified, Further purification can be achieved.

Further, the present invention is a polishing composition for electronic materials containing the secondary aggregated colloidal silica of the present invention thus obtained. The secondary agglomerated colloidal silica of the present invention is a monodisperse colloidal silica in which several to a dozen or more primary particles are agglomerated and integrated, and the surface thereof has an irregular shape, and is a so-called rag-shaped particle. It is a relatively large particle having an average particle diameter of 20 nm to 200 nm. Since the particles have such a special shape and are relatively large agglomerated particles, they exhibit excellent polishing characteristics when used for polishing for electronic materials.

The abrasive composition for an electronic material of the present invention is an aqueous dispersion of colloidal silica particles containing the secondary aggregated colloidal silica in a proportion of 1 to 15% by weight, preferably 1 to 10% by weight. The abrasive composition for electronic materials of the present invention, further depending on the type of material to be polished and the polishing conditions,
Other colloids such as alumina sol, cerium oxide sol, zirconium oxide sol and the like can also be added,
Those fine particle powders can also be added. In order to improve the wettability of the polished surface or the pad, a surfactant or a water-soluble polymer can be added. Similarly, oxidizing agents, chelating agents, corrosion inhibitors, bactericides and the like can be added as needed. The polishing target material to which the polishing slurry of the present invention can be used is various electronic materials, and is particularly useful for polishing a silicon wafer, a compound semiconductor wafer, a semiconductor device wafer, a magnetic disk substrate, or a quartz substrate.

[0028]

The present invention will be described in more detail with reference to the following examples. In the examples, "%" is based on weight.

Example 1: JIS was added to 5450 g of deionized water.
No. 3 sodium silicate (SiO_Two : 29.0%, Na _TwoO:
9.7%, H_TwoO: 61.3%)
Mixed together and mixed with SiO _TwoDiluted sodium silicate containing 4.5%
Created. Regenerate this diluted sodium silicate with hydrochloric acid in advance
Through a column of strong H-type cation exchange resin
Activated silicic acid with pH 3.8 and silica concentration 3.8%
7250 g were obtained. Under stirring 330g of activated silica
Add 10% NaOH to pH 8.0 and bring to 95 ° C.
After heating and maintaining this temperature for 1 hour, the remaining activated silica 6
920 g were added over 8 hours. Keep 95 ° C during addition.
Then, add 10% NaOH for 30 minutes to maintain the pH at 10.
Was added. After addition of activated silica, keep at 95 ° C for 1 hour.
Was. In this way, the primary particles of colloidal silica are formed.
Was completed. The particle size of silica at this point is shown in the TEM image
At 20 nm according to the BET method,
The id solution was pale and transparent. Then, 1N-
HCl was added dropwise to adjust the pH to 8.5, and Al was used as a flocculant.
_TwoO_Three1% polyaluminum chloride aqueous solution (Japan
Chemical Industry Co., Ltd. poly aluminum chloride (Al_TwoO_Three1
30% of a 10-fold diluted solution (0% by weight). For addition
The colloid liquid became more white and translucent.

Next, 10% Na was added to the colloid solution while stirring.
OH was added to bring the pH back to 10, and again activated silica was added.
0 g was added over 2 hours. Keep 95 ° C during the addition,
10% NaOH was added every 30 minutes to keep the pH at 10. After completion of the addition, the mixture was heated to 95 ° C. and maintained at this temperature for 1 hour, and then allowed to cool to 50 ° C. In this way, the aggregated silica particles were integrated to obtain a secondary aggregated colloidal silica dispersion of the present invention. The obtained secondary aggregated colloidal silica dispersion was subjected to pressure filtration by pump circulation using a hollow fiber type ultrafiltration membrane having a molecular weight cutoff of 6000 (Microza UF module SIP-1013 manufactured by Asahi Kasei Corporation). Then, about 900 g of secondary aggregated colloidal silica having a silica concentration of 30% was obtained. This colloidal silica is T
According to the EM image, secondary particles formed by agglomeration of several primary particles were formed, the surface of the particles was uneven, and the average value (X1) of the geometric particle diameter was 40 nm. In addition, nitrogen adsorption BET
The particle diameter (X2) by the method is 21 nm, and the ratio Y
(X1 / X2) was 1.90.

The measurement of the geometric average particle diameter by a transmission electron microscope (TEM) was performed as follows.
First, the sample was diluted with isopropyl alcohol to a silica concentration of 0.1%, and a TEM photograph of the diluted solution was taken at 10,000 times. Next, four portions where 10 or more particles were present were selected from the visual field, and those portions were photographed at a magnification of 40,000. From these photographs, the diameters of all particles that did not cover the edges of the screen were measured and averaged. The total number of particles measured is 50
Was around. FIG. 1 shows a TEM photograph of the aggregated particles obtained in Example 1 at a magnification of 40,000.

Example 2: JI in 13.0 kg of deionized water
S3 sodium silicate (SiO_Two: 28.8%, Na _TwoO:
9.7%, H_Two(O: 61.5%)
Mixed together and mixed with SiO _TwoDiluted sodium silicate containing 4.5%
Created. Regenerate this diluted sodium silicate with hydrochloric acid in advance
Through a column of strong H-type cation exchange resin
Activated silicic acid with pH 3.8 and silica concentration 3.8%
18 kg were obtained. Under agitation to 1.0 kg of activated silica
Add 10% tetramethylammonium hydroxide to pH
To 10 and heated to 95 ° C. and kept at this temperature for 1 hour
Thereafter, the remaining 14 kg of active silicic acid was added over 8 hours.
Maintain 95 ° C during the addition and maintain 10% pH at 10
Add tetramethylammonium hydroxide every 30 minutes
Was. After the addition of activated silicic acid, the temperature was maintained at 95 ° C for 1 hour,
It was allowed to cool to 0 ° C. Next, a hollow fiber having a cut-off molecular weight of 6000
Type ultrafiltration membrane (Microza UF module manufactured by Asahi Kasei Corporation)
By pump circulating liquid using
The solution was filtered under pressure and concentrated to a silica concentration of 10%. this
Thus, primary particles of colloidal silica were formed.
The particle size of the colloidal silica is shown in the TEM image.
20 nm according to the method and 18 nm according to the Sears method.
PH was 9.8.

1N- is added to 5000 g of the colloidal silica.
HCl was added dropwise to adjust the pH to 8.7, and Al was used as a flocculant.
1% concentration of aqueous polyaluminum chloride solution at ₂ O ₃ (Nippon Chemical Industrial Co., Ltd. polyaluminum chloride (Al ₂ O _3; 1
60% of a 10-fold diluted solution (0%) was added. P after addition
H became 7.9, and the colloid liquid became dark and translucent. After adding 3 kg of activated silicic acid thereto, 10% tetramethylammonium hydroxide was added to adjust the pH to 10, and the temperature was maintained at 160 ° C. and 620 kPa for 1 hour. After allowing to cool, pressure filtration was performed by pump circulation using the same ultrafilter as described above, and concentrated to a silica concentration of 40%. In this way, the aggregated silica particles were integrated to obtain a secondary aggregated colloidal silica dispersion of the present invention. According to the TEM image, most of the colloidal silica was agglomerated secondary particles having a few primary particles. The particle surface had irregularities, and the average value (X1) of the geometric particle diameter was 40 nm. The particle size (X
2) is 19 nm and the ratio Y (X1 / X2) is 2.
It was 11.

Example 3 Commercially available colloidal silica ("Silica Doll 40L" manufactured by Nippon Chemical Industry Co., Ltd., SiO2; 4)
0% by weight, the particle size of silica was 20 according to the TEM image.
nm, 21 nm according to the BET method, and pH 9.
9) To 5 kg, add 15 kg of deionized water to dilute to a SiO ₂ concentration of 10%, and add 1N-HCl dropwise while stirring to adjust the pH.
8.7 and a 1% aqueous solution of polyaluminum chloride as Al ₂ O ₃ (10-fold diluted solution of polyaluminum chloride (Al ₂ O ₃ ; 10%) manufactured by Nippon Chemical Industry Co., Ltd.) as a coagulant. 250 g were added. After the addition, the pH became 7.9, and the colloidal liquid became deeper in white color to obtain translucent aggregated colloidal silica.

Separately, a commercially available aqueous solution of potassium silicate (“A potassium silicate” manufactured by Nippon Chemical Industry Co., Ltd.) was added to 149 kg of deionized water.
SiO ₂ ; 26.5%, K ₂ O; 13.5%) 26.4k
g was added and mixed uniformly to prepare a diluted potassium silicate containing 4.0% of SiO ₂ . The diluted potassium silicate was passed through a column of a strongly acidic cation exchange resin regenerated with hydrochloric acid in advance to remove alkali, thereby obtaining 200 kg of activated silica having a silica concentration of 3.5% and a pH of 2.8. The agglomerated colloidal silica is heated to 98 ° C. with stirring to maintain this temperature,
Activated silicic acid and 10% KOH are mixed with SiO ₂ / K ₂ O at a molar ratio of 4
Simultaneous addition was performed at a rate of 0. Activated silicic acid 200kg
And 3268 g of 10% KOH were added in about 7 hours. After completion of the addition, the mixture was kept at 95 ° C. for 1 hour and allowed to cool. Next, a hollow fiber type ultrafiltration membrane having a molecular weight cut off of 10,000 (Asahi Kasei Corporation)
Pressure filtration was performed by pump circulation using a Microza UF module (SLP-3053 manufactured by Fuji Electric Co., Ltd.), and concentrated to a silica concentration of 30%. In this way, the aggregated silica particles were integrated to obtain a secondary aggregated colloidal silica dispersion of the present invention.

According to a TEM image, this colloidal silica constitutes secondary particles in which several primary particles are aggregated, the particle surface has irregularities, and the average geometric particle diameter (X1) is 4
It was 5 nm. The particle diameter (X2) measured by the nitrogen adsorption BET method was 33 nm, and the ratio Y (X1 / X2) was 1.36. TEM of 10,000 times and 40,000 times of the secondary aggregated colloidal silica particles obtained in Example 3
The photographs are shown in FIGS. 2 and 3, respectively.

Example 4: Using the colloidal silica of the present invention obtained in Examples 1 to 3 and a commercially available colloidal silica,
Polishing compositions shown in Table 1 were prepared.

[0038]

[Table 1]

Using these polishing compositions 1 to 4, a polishing test of a silicon single crystal (silicon rectangular mirror wafer, orientation: <100> ± 1 °) was performed under the following polishing conditions. Table 2 shows the results. <Polishing Conditions> Polishing machine; single-side polishing machine polishing pad; Rodel Co. SUBA400 platen rotational speed; 150 rpm rotation speed; 100 rpm working pressure; 230 g / cm ² Polishing time: 10 minutes polishing liquid supply amount; 20 ml / min < Evaluation of Polishing Performance> Polishing Rate: The silicon after processing was washed and dried, and the polishing rate was determined from the weight loss before and after processing. Polishing marks: The presence or absence of polishing marks was visually determined in a dark room.

[0040]

[Table 2]

As shown in Table 2, the polishing rate of the abrasive composition (No. 1 to 3) using the colloidal silica of the present invention was 17 to 34% as compared with that using the commercially available colloidal silica. An improvement was obtained.

[Brief description of the drawings]

FIG. 1 is an electron micrograph at a magnification of 40,000 times of the secondary aggregated colloidal silica of the present invention obtained in Example 1.

FIG. 2 is an electron micrograph of the secondary aggregated colloidal silica of the present invention obtained in Example 3 at a magnification of 10,000.

FIG. 3 is an electron micrograph at a magnification of 40,000 times of the secondary aggregated colloidal silica of the present invention obtained in Example 3.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiro Izumi 9-11-1, Kameido, Koto-ku, Tokyo Nippon Kagaku Kogyo Co., Ltd. F term (reference) 3C058 AA07 CA01 DA02 4G072 AA28 BB05 BB07 CC13 DD06 DD07 EE01 GG01 MM40 TT01 TT06 UU01 UU30

Claims (7)

[Claims] 1. A geometric mean particle diameter (X) determined from an electron beam transmission projection image of colloidal silica silica particles.
The ratio Y (X1 / X2) between 1) and the equivalent particle diameter (X2) calculated from the surface area of the silica particles is in the range of 1.3 to 2.5, and the geometric average particle diameter is 20 to 20
Secondary aggregated colloidal silica having a range of 0 nm. 2. The secondary aggregated colloidal silica according to claim 1, wherein the method for measuring the surface area of the silica particles is a Sears method. 3. The secondary aggregated colloidal silica according to claim 1, wherein the method for measuring the surface area of the silica particles is a nitrogen adsorption BET method. 4. The method according to claim 1, wherein the geometric mean particle diameter (X1) obtained from the transmission projection image by the electron beam is an average value of the diameter of the particles obtained from the projection image of the transmission electron microscope. Item 2. The secondary aggregated colloidal silica according to Item 1. 5. A secondary particle, characterized in that a coagulant of silica particles is added to monodisperse colloidal silica to form substantially spherical aggregated secondary particles, and then activated silica is added to integrate the aggregated particles. A method for producing aggregated colloidal silica. 6. A geometric mean particle size (X) determined from a transmission projection image of colloidal silica silica particles by an electron beam.
The ratio Y (X1 / X2) between 1) and the equivalent particle diameter (X2) calculated from the surface area of the silica particles is in the range of 1.3 to 2.5, and the geometric average particle diameter is 20 to 20
An abrasive composition for electronic materials, comprising secondary aggregated colloidal silica in a range of 0 nm. 7. A silicon wafer, a compound semiconductor wafer,
The polishing composition according to claim 6, which is used for a semiconductor device wafer, a magnetic disk substrate, or a quartz substrate.