JP2016084243A - Method for producing silica composite particle dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silica composite particle dispersion that not only enables polishing of an Si wafer and a hard-to-work material but also achieves high surface accuracy (low scratch and the like) and can be suitably used for polishing the surface of a semiconductor device because it is free from impurities.SOLUTION: A method for producing a silica composite particle dispersion includes the steps as given below: a step of adding a metal salt of cerium while stirring a silica sol having silica fine particles having an average particle size of 40 to 600 nm, a minor axis/major axis ratio of 0.95 to 1.0, a content of each element of Na and the like of 20 ppm or less and a content of each element of U and Th of 1 ppm or less dispersed therein in a temperature range of 5 to 98°C and a pH range of 7.0 to 9.0 to produce a precursor particle dispersion; a step of drying the precursor particle dispersion, firing at 400 to 1,200°C and then crushing/pulverizing to produce a powder; and a step of subjecting the powder dispersed in water to centrifugal separation treatment at 11,000 G or more for 10 minutes or more and recovering a supernatant liquid to produce a silica composite particle dispersion.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a silica-based composite particle dispersion.

In semiconductor devices such as semiconductor substrates and wiring boards, flatness, seams, scratches, adhesion of abrasive grains, contamination of impurities, etc. affect semiconductor characteristics, so the surfaces and end faces of these components are extremely accurate. Polishing is required.
Conventionally, as a polishing method for such a member, after performing a relatively rough primary polishing process, and then performing a precise secondary polishing process, a smooth surface or a highly accurate surface with few scratches such as scratches can be obtained. The way to get done.
Conventionally, for example, the following methods have been proposed for the abrasive used for the secondary polishing as the finish polishing.

  For example, Patent Document 1 discloses that an aqueous solution of cerium nitrate and a base are stirred and mixed at a quantitative ratio of pH 5 to 10, followed by rapid heating to 70 to 100 ° C. and aging at that temperature. A method for producing cerium oxide ultrafine particles comprising a cerium oxide single crystal having a characteristic particle size of 10 to 80 nm is described. And by such a manufacturing method, it is possible to provide cerium oxide ultrafine particles that not only have an average particle size of 10 to 80 nm, but also have a uniform particle size and the same shape as possible. It is described.

  Further, Non-Patent Document 1 is a method for producing ceria-coated silica similar to the production method described in Patent Document 1, and does not have a firing-dispersing step in the production method described in Patent Document 1. A manufacturing method is described.

  Furthermore, Patent Document 2 discloses that the surface of the amorphous silica particles A has at least one selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium. A silica-based composite particle characterized by having a crystalline oxide layer B containing an element is described. As a preferred embodiment, an amorphous oxide layer containing an element such as aluminum on the surface of the amorphous silica particles A, which is different from the amorphous silica layer A crystalline oxide layer having C and further containing one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium Silica-based composite particles characterized by having B are described. And since such a silica type composite particle has the crystalline oxide layer B on the surface of the amorphous silica particle A, it can improve a grinding | polishing speed and pre-process on a silica particle. By suppressing the sintering of particles during firing, the dispersibility in the polishing slurry can be improved, and further, the amount of cerium oxide used can be greatly reduced without containing cerium oxide. Therefore, it is described that it is possible to provide an abrasive that is inexpensive and has high polishing performance. Further, it is described that those having an amorphous oxide layer C between the silica-based particles A and the oxide layer B are particularly excellent in the effect of suppressing the sintering of particles and the effect of improving the polishing rate.

Japanese Patent No. 2746861 JP 2013-119131 A

Seung-Ho Lee, Zhenyu Lu, S .; V. Babu and Egon Matijevic, “Chemical mechanical polishing of thermal oxide films using sir te sir te s i s e s s e s e s e n e s e s e n i e s e s e e n e s e n e s e n e i e n e s e i e n e e m e n e s e i e m e n e n i e n e n i e n i e n i e n i e n i e n i e n i e n i e n i e n i e n i e n i n e n e n i.

  However, when the present inventors actually manufactured and studied the ultrafine cerium oxide particles described in Patent Document 1, the polishing rate was low, and the surface of the polishing base material had defects (decrease in surface accuracy (increased scratches). It has been found that the residual of the abrasive on the surface of the polishing substrate is likely to occur. This is because the ceria particles are only crystallized from the liquid phase and remain on the surface of the polishing substrate due to the low crystallinity of the ceria particles compared to the firing method. The present inventor presumes that the particle shape becomes distorted due to the combination of these, which is the main factor of the increase in scratches.

  In addition, since the ceria-coated silica described in Non-Patent Document 1 is not fired, it is considered that the actual polishing rate is low, and there is a concern that particles remain on the surface of the polishing substrate.

  Furthermore, when polishing using the silica-based composite particles having the oxide layer C described in Patent Document 2, impurities such as aluminum remain on the surface of the semiconductor device, which may adversely affect the semiconductor device. The inventor found out.

  An object of the present invention is to solve the above problems. That is, the present invention can polish Si wafers and difficult-to-work materials at high speed, and at the same time, can achieve high surface accuracy (low scratch, etc.) and does not contain impurities. An object of the present invention is to provide a method for producing a silica-based composite particle dispersion that can be preferably used for polishing the surface of a semiconductor device.

The inventor has intensively studied in order to solve the above problems, and has completed the present invention.
The present invention includes the following (1) to (6).
(1) A method for producing a silica-based composite particle dispersion, comprising the following steps 1 to 3.
Step 1: The average particle diameter measured by the laser diffraction scattering method is 40 to 600 nm, the minor axis / major axis ratio measured by the image analysis method is 0.95 to 1.0, Na, Ag, Al, Ca, Cr, Stirring a silica sol formed by dispersing silica fine particles in which the content of each element of Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 20 ppm or less and the content of each element of U and Th is 1 ppm or less in a solvent A step of adding a cerium metal salt continuously or intermittently to obtain a precursor particle dispersion while maintaining a temperature range of 5 to 98 ° C. and a pH range of 7.0 to 9.0.
Process 2: The process of drying the said precursor particle dispersion liquid, baking at 400-1200 degreeC, and then crushing and grind | pulverizing and obtaining powder.
Step 3: A step of subjecting the powder in a state of being dispersed in water to a centrifugation treatment at 11,000 G or more for 10 minutes or more to collect the supernatant and obtain a silica-based composite particle dispersion.
(2) In the step 1, the temperature range of the silica sol is set to 48 to 52 ° C., a precursor particle dispersion is prepared, and the precursor particle dispersion is aged at a temperature of 90 to 98 ° C. The manufacturing method of the silica type composite particle dispersion liquid as described in (1).
(3) The method for producing a silica-based composite particle dispersion as described in (1) or (2) above, wherein the addition of the cerium metal salt in Step 1 is carried out over 0.5 to 24 hours.
(4) In the step 1, the silica system according to any one of (1) to (3) above, wherein an alkali is added to maintain the pH range of the silica sol at 7.0 to 9.0. A method for producing a composite particle dispersion.
(5) The silica according to any one of (1) to (4) above, wherein, in the step 2, the pH of the precursor particle dispersion before drying is 6.0 to 7.0. Method for producing a composite particle dispersion.
(6) A method for producing silica-based composite particles, wherein silica-based composite particles obtained by the production method according to any one of (1) to (5) above are further dried to obtain silica-based composite particles.

  According to the present invention, even a Si wafer or a difficult-to-process material can be polished at high speed, and at the same time, high surface accuracy (low scratch, etc.) can be achieved, and further, no impurities are contained. It is possible to provide a method for producing a silica-based composite particle dispersion that can be preferably used for polishing the surface of a semiconductor device.

  A method for producing the silica-based composite particle dispersion of the present invention (hereinafter also referred to as the production method of the present invention) will be described.

<Production raw materials>
In the method for producing a silica-based composite particle dispersion of the present invention, a silica sol obtained by dispersing silica fine particles in a solvent and a metal salt of cerium are used as raw materials.
1) Silica sol The silica sol used as a raw material is obtained by dispersing amorphous silica fine particles in a solvent.

The silica fine particles are mainly composed of amorphous silica, and may contain other impurities such as crystalline silica or an impurity element that contains silicon and does not become a margin for use.
In the silica fine particles, the content of each element of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 20 ppm or less, and preferably 10 ppm or less, More preferably, it is 5 ppm or less, and further preferably 1 ppm or less. In addition, the content of each element of U and Th is 1 ppm or less, and silica fine particles prepared using water glass as a raw material are generally derived from Na, Ag, Al, Ca, Cr, Cu, Fe, K, water glass. Each element of Mg, Ni, Ti, Zn, Zr, U, and Th is contained in a total of about several thousand ppm. In the case of a silica sol in which such silica fine particles are dispersed in a solvent, ion exchange treatment is performed to perform Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, and It is possible to reduce the Th content, but even in that case, several ppm to several hundred ppm Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr and U And Th remain. On the other hand, in the case of silica sol in which silica fine particles synthesized using alkoxysilane as a raw material are dispersed in a solvent, usually, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, The content of each element of Zr, U and Th is 20 ppm or less.
The content of each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, and Th in the silica fine particles is a value obtained by measurement using ICP. .

  Here, the main component means that the content is 90% by mass or more. That is, in the silica fine particles, the content of amorphous silica is 90% by mass or more. This content is preferably 95% by mass or more, more preferably 98% by mass or more, and more preferably 100% by mass, that is, the silica fine particles are more preferably substantially composed of amorphous silica. . Here, “becomes substantially” means that impurities and damages inevitably included from the raw materials and the manufacturing process can be included, but other than that are not included. In the following description of the present invention, “main component” and “substantially” are used in this sense.

The average particle diameter of the silica fine particles is 40 to 600 nm, preferably 60 to 200 nm.
When the average particle diameter of the silica fine particles is in the range of 40 to 600 nm, scratches are reduced. When the average particle diameter of the silica fine particles is less than 40 nm, the polishing rate is insufficient, or problems are caused in the stability of the particles. Similarly, when the average particle diameter exceeds 600 nm, scratches tend to occur.

  The average particle diameter of the silica fine particles means a value obtained by measurement by the following method. After dispersing silica fine particles in water to obtain an aqueous dispersion containing 1% by mass in solid content, this aqueous dispersion is mixed with a known laser diffraction / scattering device (for example, Microtrack UPA device manufactured by Nikkiso Co., Ltd.). Is used to measure the integrated particle size distribution by the laser diffraction / scattering method, and the average particle size (median diameter) is determined from the particle size distribution.

  A spherical fine particle is used as a raw material. Specifically, silica fine particles having a minor axis / major axis ratio in the range of 0.95 to 1 are used.

  The silica fine particles are pulverized for 10 minutes using a mortar and, for example, when an X-ray diffraction pattern is obtained with a conventionally known X-ray diffractometer (for example, RINT1400, manufactured by Rigaku Corporation), the silica fine particles are amorphous. I can confirm.

2) Cerium metal salt Examples of the cerium metal salt used as a raw material in the method for producing a silica-based composite particle dispersion of the present invention include cerium nitrate, cerium carbonate, cerium sulfate, and cerium chloride. Can be mentioned.

<Production method of the present invention>
The production method of the present invention will be described.
The production method of the present invention includes steps 1 to 3 described below.

<Step 1>
In step 1, the average particle diameter measured by the laser diffraction scattering method is 40 to 600 nm, the short diameter / major diameter ratio measured by the image analysis method is 0.95 to 1.0, Na, Ag, Al, Ca, Cr Silica sol obtained by dispersing silica fine particles in which the content of each element of Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 20 ppm or less and the content of each element of U and Th is 1 ppm or less in a solvent Is a process of obtaining a precursor particle dispersion by continuously or intermittently adding a metal salt of cerium while maintaining a temperature range of 5 to 98 ° C. and a pH range of 7.0 to 9.0 under stirring conditions. .

In step 1, a silica sol in which silica fine particles are dispersed in a solvent is prepared.
As described above, it is preferable to use a silica sol produced by hydrolysis of alkoxysilane as such a silica sol. Further, for example, a conventionally known silica sol obtained by acid treatment may be used. In this case, the content of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr in the silica fine particles decreases, and specifically, it can be 20 ppm or less. is there. The present inventor has found that the stability of the composite particles is increased and the generation of scratches is suppressed.

  The dispersion medium in the silica sol preferably contains water, and it is preferable to use a water sol.

The solid concentration in the silica sol is preferably 20 to 40% by mass in terms of SiO ₂ . When this solid content concentration is too low, the silica concentration in the production process becomes low, and the productivity may deteriorate.

  The pH of the silica sol is adjusted to a range of 7.0 to 9.5. This is because when the pH is less than 7.0 or the pH exceeds 9.5, the stability is further lowered.

  Further, impurities can be extracted with a cation exchange resin or an anion exchange resin, mineral acid, organic acid, or the like, and silica sol can be deionized using an ultrafiltration membrane or the like, if necessary. A silica sol from which impurity ions and the like are removed by deionization is preferable from the viewpoint that the sol is stable for a longer period of time and that contamination of the substrate is further prevented.

  In step 1, a cerium metal salt is added to the silica sol as described above.

As the metal salt of cerium, cerium chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide and the like can be used.
Of these, ceric nitrate is preferred. Crystalline cerium oxides are formed from a solution that becomes supersaturated at the same time as neutralization, and they quickly adhere to the silica fine particles by an agglomeration and deposition mechanism.

  The amount of the cerium metal salt added to the silica sol is such that the mass ratio between the silica fine particles and the crystalline ceria in the silica-based composite particles obtained by the production method of the present invention falls within the specific range described later.

  After adding the cerium metal salt to the silica sol, the temperature at the time of stirring is 5 to 98 ° C, preferably 50 to 95 ° C. If the temperature is too low, the reaction of mixing with a hydroxide or forming a low oxide and crystallizing is remarkably slow, which is not preferable. On the other hand, if this temperature is too high, scale and the like are easily generated on the reactor wall surface, which is not preferable.

  Moreover, the time at the time of stirring is 0.5 to 24 hours, and it is preferable that it is 0.5 to 18 hours. If this time is too short, crystalline cerium oxide cannot be sufficiently formed, which is not preferable. Conversely, even if this time is too long, the formation of crystalline cerium oxide is uneconomical because the reaction does not proceed any further.

  By such step 1, a dispersion liquid (precursor particle dispersion liquid) containing particles (precursor particles) which are precursors of the composite particles of the present invention is obtained.

  The precursor particle dispersion obtained in step 1 may be further diluted or concentrated using pure water, ion-exchanged water, or the like, and used for the next step 2.

  The solid concentration in the precursor particle dispersion is preferably 5 to 27% by mass.

  The precursor particle dispersion may be deionized using a cation exchange resin, an anion exchange resin, an ultrafiltration membrane, or the like.

  More preferably, in Step 1, the temperature range of the silica sol is 48 to 52 ° C., and the pH range is maintained at 7.0 to 9.0, while the metal salt of cerium is added continuously or intermittently, It is carried out by preparing a body particle dispersion and further aging the precursor particle dispersion at a temperature of 90 to 98 ° C. When Step 1 is performed under such conditions, it is possible to prevent cerium oxide having a low crystallinity from uniformly attaching to the surface of the silica fine particles and forming an aggregate of cerium oxides.

  In step 1, in order to maintain the pH range of the silica sol at 7.0 to 9.0, it is preferable to adjust the pH by adding an alkali as desired. A publicly known alkali can be used as an example of such an alkali. Specific examples include aqueous ammonia, alkali hydroxide, alkaline earth metal, and aqueous amines, but are not limited thereto.

<Step 2>
In step 2, the precursor particle dispersion is dried, baked at 400 to 1200 ° C., and then crushed and pulverized to obtain a powder.

  The method for drying is not particularly limited. For example, it can be dried using a conventionally known dryer.

  After drying, the firing temperature is 400 to 1200 ° C, and preferably 800 to 1100 ° C. When fired in such a temperature range, crystallization of ceria proceeds sufficiently, and silica fine particles and crystalline ceria are firmly bonded. If this temperature is too high, ceria crystals grow abnormally, the amorphous silica constituting the silica fine particles crystallizes, and fusion between the ceria proceeds, making it difficult to crush as ceria-coated silica particles. there is a possibility.

  In the step 2, it is recommended that the pH of the precursor particle dispersion before drying is further preferably 6.0 to 7.0. It is because surface activity can be suppressed when the pH of the precursor particle dispersion before drying is 6.0 to 7.0.

  In step 2, the powder is pulverized and pulverized after the above baking. The method for crushing and pulverizing is not particularly limited, but conventionally known wet pulverization is preferable. When wet pulverization is performed, the powder is dispersed in the liquid. However, the “powder” obtained in step 2 may be dispersed in the liquid as described above.

<Step 3>
In step 3, the powder in a state of being dispersed in water is subjected to a centrifugation treatment at 11,000 G or more for 10 minutes or more, and the supernatant is recovered to obtain a silica-based composite particle dispersion.

  First, powder in a state of being dispersed in water is prepared. Examples of the water include pure water, ultrapure water, and ion exchange water. The mass of water with respect to the powder is not particularly limited as long as the powder can be dispersed, but it is preferable that the solid content concentration of the powder is 10 to 30% by mass. When wet pulverization is performed in Step 2 and the powder is already dispersed in water, it can be directly used in Step 3.

Next, the powder in a state of being dispersed in water is classified by centrifugation, and the supernatant is recovered.
The centrifugal acceleration in the centrifugal separation process is 11,000 G or more. Further, the treatment time is 10 minutes or more, preferably 15 minutes or more.
After centrifugation, the supernatant is collected. The recovered supernatant is a silica-based composite particle dispersion.

  In step 3, it is necessary to provide a centrifugal separation process that satisfies the above conditions. When centrifugal acceleration or processing time does not meet the above conditions, coarse particles remain in the silica-based composite particle dispersion, and scratches occur when used as an abrasive using the silica-based composite particle dispersion. Cause.

  In the present invention, silica-based composite particles can be obtained by further drying the silica-based composite particle dispersion obtained by the above production method. A drying method is not specifically limited, For example, it can dry using a conventionally well-known dryer.

<Silica-based composite particles obtained by the method for producing a silica-based composite particle dispersion of the present invention>
The silica-based composite particles contained in the silica-based composite particle dispersion obtained by the production method of the present invention (hereinafter also referred to as “the composite particle dispersion of the present invention”) are specifically composed of silica-ceria composite oxide. This is a silica-based composite particle.
Hereinafter, such silica-based composite particles are also referred to as “composite particles of the present invention”. The “composite particles of the present invention” can be obtained by drying the composite particle dispersion of the present invention.
The composite particles of the present invention are, for example, a mixture of spherical particles and substantially spherical particles. According to the analysis results described later, it can be said that the composite particles of the present invention have particulate crystalline ceria bound to the surface of the silica fine particles.

  The size of the crystalline ceria in the composite particle of the present invention is preferably 10 to 30 nm, and more preferably 15 to 25 nm. The size of the crystalline ceria is measured using a scanning electron microscope (for example, model number “S-5500” manufactured by Hitachi, Ltd.).

When the composite particles of the present invention are pulverized for 10 minutes using a mortar and an X-ray diffraction pattern is obtained by, for example, a conventionally known X-ray diffraction apparatus (for example, RINT1400, manufactured by Rigaku Corporation), only the ceria crystal phase is obtained. Is detected.
Ceriaite is an example of the ceria crystal phase.

When the composite particles of the present invention are subjected to X-ray diffraction, only the ceria crystal phase is detected as described above. This indicates that even if the composite particle of the present invention contains a crystal phase other than ceria, it is only a minute amount that is out of the detection range of X-ray diffraction.
The definition of “principal component” is as described above.

  The crystallite diameter of the (111) plane of crystalline ceria, measured by X-ray diffraction, is preferably 10 to 25 nm, and more preferably 12 to 16 nm.

The crystallite diameter of the (111) plane of crystalline ceria means a value obtained by the method described below.
First, the composite particles of the present invention are pulverized for 10 minutes using a mortar, and an X-ray diffraction pattern is obtained by, for example, a conventionally known X-ray diffractometer (for example, RINT1400, manufactured by Rigaku Corporation). Then, the half width of the peak of the (111) plane near 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the crystallite diameter is obtained by the following Scherrer equation.
D = Kλ / βcos θ
D: Crystallite diameter (angstrom)
K: Scherrer constant λ: X-ray wavelength (1.7789 Å Cu lamp)
β: Half width (rad)
θ: Reflection angle

  In the composite particles of the present invention, silica fine particles and crystalline ceria are bonded.

In the composite particles of the present invention, the mass ratio between the silica fine particles and the crystalline ceria is 100: 11 to 230, preferably 100: 20 to 150.
If the amount of crystalline ceria with respect to the silica fine particles is too small, the silica fine particles are bonded to each other, and the particle shape becomes distorted due to the generation of coarse particles and the bonding between the particles, and crushing becomes difficult. In this case, the abrasive obtained from the composite particles of the present invention may cause defects (decrease in surface accuracy such as an increase in scratches) on the surface of the polishing substrate. Further, if the amount of crystalline ceria with respect to the silica fine particles is too large, not only is the cost high, but also the resource risk increases. Furthermore, the fusion of the crystalline ceria particle-coated silica particles progresses, becomes coarse, becomes difficult to disintegrate, and may cause defects (scratches) on the surface of the polishing substrate.

Composite particles of the present invention obtained by the process of the present invention, the specific surface area typically is preferably 10 to 200 m ² / g, more preferably 15~80m ² / g, 20~ More preferably, it is 70 m ² / g.

A method for measuring the specific surface area (BET specific surface area) will be described.
First, a dried sample (0.2 g) is put in a measurement cell, degassed in a nitrogen gas stream at 250 ° C. for 40 minutes, and then the sample is a mixed gas of 30% by volume of nitrogen and 70% by volume of helium. Liquid nitrogen temperature is maintained in a stream of air, and nitrogen is adsorbed to the sample by equilibrium. Next, the temperature of the sample is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured using a calibration curve prepared in advance.
Such a BET specific surface area measurement method (nitrogen adsorption method) can be performed using, for example, a conventionally known surface area measurement device.
In the present invention, the specific surface area means a value obtained by such a method unless otherwise specified.

  The average particle size of the composite particles of the present invention obtained by the production method of the present invention is usually preferably 600 nm or less. Typically, it is more preferably 40 nm to 600 nm, more preferably 150 to 300 nm, and further preferably 170 to 260 nm.

The average particle size of the composite particles of the present invention means a value obtained by measurement by the following method.
After diluting the composite particle dispersion of the present invention with water to obtain an aqueous dispersion containing 1% by mass in solid content concentration, a known laser diffraction / scattering device (for example, Microdevices manufactured by Nikkiso Co., Ltd. The integrated particle size distribution is measured by a laser diffraction / scattering method using a track UPA apparatus), and the average particle diameter (median diameter) is obtained from the particle size distribution.

  Thus, in the composite particles of the present invention, ceria crystallites having a size of about 20 nm as observed with an electron microscope and a crystallite diameter of X-ray diffraction of preferably 10 to 25 nm are bonded to the surface of silica particles. However, it is fused and has an uneven surface shape.

<Slurry for polishing>
The polishing slurry will be described.
A polishing slurry can be obtained using the composite particle dispersion of the present invention or the composite particles of the present invention. Hereinafter, it is also referred to as “the polishing slurry of the present invention”.

  The polishing slurry of the present invention is excellent in effects such as a high polishing rate when polishing a semiconductor substrate and the like, and few scratches (scratches) on the polishing surface during polishing.

  The polishing slurry of the present invention contains water and / or an organic solvent as a dispersion solvent. When inorganic oxide fine particles having the same size as the coated ceria are used, Ra is further improved.

  As the dispersion solvent, for example, water such as pure water, ultrapure water, or ion exchange water is preferably used. Furthermore, the polishing slurry of the present invention may optionally contain one or more selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster, and a pH buffer as an additive.

  Examples of the dispersion solvent for the polishing slurry of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-but Glycol ether acetates such as ciethyl acetate; Esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; Aromatic hydrocarbons such as benzene, toluene and xylene; Hexane, heptane and isooctane Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl Organic solvents such as pyrrolidones such as -2-pyrrolidone can be used. These may be used by mixing with water.

  The solid content concentration of the composite particles of the present invention contained in the polishing slurry of the present invention is preferably in the range of 0.3 to 50% by mass. If this solid content concentration is too low, the polishing rate may decrease. Conversely, even if the solid content concentration is too high, the polishing rate is rarely improved further, which can be uneconomical. Ra is improved by including the inorganic oxide particles in the polishing slurry of the present invention in an amount of 5 to 20% by mass based on the ceria-coated particles (composite particles of the present invention).

  Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples.

  First, details of each measurement method and test method in Examples and Comparative Examples will be described.

[X-ray diffraction method, measurement of crystallite diameter]
In accordance with the method described above, the silica-based composite particle dispersions obtained in Examples and Comparative Examples were dried, and the obtained powder was pulverized in a mortar for 10 minutes, and an X-ray diffractometer (manufactured by Rigaku Denki Co., Ltd.) , RINT 1400) to obtain an X-ray diffraction pattern to identify the crystal form.
Further, as described above, the half width of the peak of the (111) plane in the vicinity of 2θ = 28 degrees in the obtained X-ray diffraction pattern was measured, and the crystallite diameter was determined by the Scherrer equation.

[Measurement method of specific surface area]
The silica-based composite particle dispersions obtained in the examples and comparative examples were adjusted to pH 3.5 using HNO3, then placed in a dryer adjusted to 110 ° C. overnight and dried. And after that, it stood to cool in a desiccator.
Next, about 8 ml of the dried sample was collected in a mortar and ground with a pestle for 1 minute.
Next, about 1/2 of the pulverized sample was collected in a magnetic crucible (15 ml), fired in an electric furnace at 500 ° C. for 1 hour, and then allowed to cool in a desiccator.

  The specific surface area of the sample thus obtained was measured by the BET specific surface area measurement method (nitrogen adsorption method). The specific method is as described above.

<Average particle size>
About the silica type composite particle dispersion liquid obtained by the Example and the comparative example, the average particle diameter (median diameter) of the silica type composite particle was measured by the above-mentioned method. As a laser diffraction / scattering device, a Microtrack UPA device manufactured by Nikkiso Co., Ltd. was used.

<Short diameter / Long diameter ratio>
In the photograph projection drawing obtained by photographing a silica sol at a magnification of 250,000 times (or 500,000 times) with a scanning electron microscope (manufactured by Hitachi, Ltd., model number “S-5500”), the maximum axis of the particle is the major axis. The length was measured, and the value was defined as the long diameter (DL). Further, a point that bisects the major axis on the major axis was determined, two points where a straight line perpendicular to the major axis intersected with the outer edge of the particle were determined, and a distance between the two points was measured to obtain a minor axis (DS). And ratio (DS / DL) was calculated | required. This measurement was performed on any 50 particles, and the average value was defined as the minor axis / major axis ratio.

[Polishing test method]
A slurry (polishing slurry) containing the silica-based composite particle dispersion obtained in each of Examples and Comparative Examples was prepared. Here, the solid content concentration was 9% by mass.
Next, an aluminosilicate glass substrate for a hard disk was prepared as a substrate to be polished. This substrate has a donut shape, an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm. This substrate was pre-polished and had a surface roughness (Ra) of 0.3 nm.
Next, this substrate to be polished is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), a polishing pad (“Polytex φ12” manufactured by Nano Factor Co., Ltd.) is used, a substrate load of 0.18 MPa, and a table rotation speed of 30 rpm The polishing slurry was supplied for 10 minutes at a rate of 20 g / min.
And the grinding | polishing speed | rate was calculated by calculating | requiring the weight change of the to-be-polished base material before and behind grinding | polishing.
Moreover, the smoothness (surface roughness Ra) of the surface of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Co., Ltd.).

<Example 1>
Preparation of << Silica sol (60 nm) >> 12,090 g of ethanol and 6,3.93.9 g of normal ethyl silicate were mixed to obtain a mixed solution a.
Next, 6,120 g of ultrapure water and 444.9 g of 29% ammonia water were mixed to obtain a mixed solution b.
Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed and used as bedding water.
And it adjusted to 75 degreeC, stirring floor water, and added simultaneously so that the addition of the liquid mixture a and the liquid mixture b might be completed here in 10 hours, respectively. When the addition is completed, the liquid temperature is kept at 75 ° C. for 3 hours and ripened, then the solid content concentration is adjusted, the SiO ₂ solid content concentration is 19% by mass, and the average particle diameter measured by the laser diffraction / scattering method 9,646.3 g of 60 nm silica sol was obtained.

Preparation of << Silica sol (100 nm) >> 2,733.3 g of methanol and 1,822.2 g of normal ethyl silicate were mixed to obtain a mixed solution a.
Next, 1,860.7 g of ultrapure water and 40.6 g of 29% ammonia water were mixed to obtain a mixed solution b.
Next, 592.1 g of ultrapure water and 1,208.9 g of methanol were mixed and used as a bedding water, and 922.1 g of 60 nm silica sol obtained in the previous step was added.
Then, the water containing the silica sol was adjusted to 65 ° C. while stirring, and the mixed solution a and the mixed solution b were simultaneously added so that the addition was completed in 18 hours. When the addition is completed, the liquid temperature is kept at 65 ° C. for 3 hours to ripen, and the solid content concentration is adjusted. (SiO ₂ solid content concentration 19% by mass, average particle measured by laser diffraction / scattering method) A high-purity silica sol having a diameter of 100 nm, a minor axis / major axis ratio of 0.98 by observation with a transmission electron micrograph, and an alkali and alkaline earth metal content of 1 ppm or less by ICP measurement was obtained.
The solid content concentration of this high-purity silica sol was adjusted to obtain 3,600 g of high-purity silica sol with a SiO ₂ solid content concentration of 19% by mass.
114 g of cation exchange (SK-1BH manufactured by Mitsubishi Chemical Corporation) was gradually added to 1,053 g of this high-purity silica sol and stirred for 30 minutes to separate the resin.
The pH at this time was 1.8. Next, 30 g of an anion exchange resin (SANUPC manufactured by Mitsubishi Chemical Corporation) was gradually added to separate the resin.
The pH at this time was 4.2.
Ultrapure water was added to the obtained silica sol to obtain a liquid A having a SiO ₂ solid content concentration of 3% by mass.

Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (manufactured by Kanto Chemical Co., Inc., 4N high-purity reagent) to obtain 2.5 mass% B liquid in terms of CeO ₂ .

Next, the liquid A (6,000 g) was heated to 50 ° C. and stirred, while the liquid B (2,153 g, 100 parts by mass of SiO ₂ ) was 29.9 parts by mass of CeO _2. Was added over 18 hours. During this time, the liquid temperature was maintained at 50 ° C., and 3% ammonia water was added as necessary to maintain pH 7.85.
And when addition of B liquid was complete | finished, the liquid temperature was raised to 93 degreeC and ageing | curing | ripening was performed for 4 hours. After aging, the product was allowed to cool by allowing it to stand indoors, and after cooling to room temperature, washing was performed while supplying ion-exchanged water with an outer membrane. The precursor particle dispersion obtained after the washing was finished had a solid content concentration of 7% by mass, a pH of 9.1 (at 25 ° C.), and an electric conductivity of 67 μs / cm (at 25 ° C.). .

  Next, 5 mass% acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 7, and after drying in a dryer at 100 ° C. for 16 hours, using a muffle furnace at 1090 ° C. for 2 hours. Firing was performed to obtain a powder.

  After adding 375 g of ion-exchanged water to 125 g of the obtained powder and further adjusting the pH to about 9 using a 3% ammonia aqueous solution, φ0.22 mm high-purity silica beads (manufactured by Daiken Chemical Industry Co., Ltd.) Wet crushing and pulverization were performed to obtain 540 g of a powder dispersion having a solid content concentration of 20% by mass.

  This powder dispersion is centrifuged at 11,000 G for 15 minutes using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number “CR21G”), and the supernatant is recovered to obtain a silica-based composite particle dispersion. Got.

  The obtained silica-based composite particle dispersion contains silica-based composite particles made of silica / ceria composite oxide. When this silica-based composite particle was measured by an X-ray diffraction method, a Ceriaite diffraction pattern was observed.

  Next, the silica-based composite particle dispersion was concentrated with a rotary evaporator and then diluted with ion-exchanged water to adjust the concentration to obtain a 9% by mass polishing slurry, and a polishing test was performed. Moreover, the average particle diameter of the silica type composite particle contained in polishing slurry was measured. The results are shown in Table 1.

<Example 2>
The condition of the addition amount of the liquid B is 8,453 g (CeO ₂ is equivalent to 117.4 parts by mass with respect to 100 parts by mass of SiO ₂ ). A silica-based composite particle dispersion containing a composite oxide was prepared. And operation similar to Example 1 was performed and the same measurement was performed. The results are shown in Table 1.

<Comparative Example 1>
In Comparative Example 1, the silica sol of 100 nm used in the examples (SiO ₂ solid content concentration 19% by mass, average particle diameter 76 nm in terms of BET specific surface area, the short diameter / long diameter ratio by TEM image observation = 0.98, ICP measurement The content of alkali and alkaline earth metal was 1 ppm or less.

  And when this silica sol was measured by the X-ray diffraction method, an amorphous diffraction pattern was observed.

Next, the silica sol was diluted with ion exchange water to obtain a polishing slurry of 9% by mass, and a polishing test was performed. Further, the specific surface area and average particle diameter were measured in the same manner as in Example 1. The results are shown in Table 1.
Compared to Example 1, the average particle size was small and the polishing rate was considerably low.

<Comparative Example 2>
The silica sol used in Comparative Example 1 was dried and calcined in the same manner as in Examples 1 and 2 without using cerium (III) nitrate hexahydrate in Comparative Example 2.
Next, in the same manner as in Examples 1 and 2, when the fired sample of the obtained silica particles was measured by X-ray diffraction, an amorphous diffraction pattern was observed.
Next, 375 g of ion-exchanged water was added to 125 g of the calcined sample of silica particles, and the pH was adjusted to about 9 using a 3% aqueous ammonia solution, and then high-purity silica beads of φ0.22 mm (manufactured by Daiken Chemical Industries, Ltd.) ) Was subjected to wet crushing and pulverization to obtain 540 g of a 20% by mass slurry.

Next, the slurry was concentrated with a rotary evaporator, then diluted with ion-exchanged water, the concentration was adjusted to obtain a 9% by mass polishing slurry, and a polishing test was performed. Further, the specific surface area and average particle diameter were measured in the same manner as in Example 1. The results are shown in Table 1.
Compared to Example 1, the average particle size is very large, but this is probably because the silica particles did not have ceria on the surface, and the sintering of the silica particles progressed slightly during firing.
On the other hand, the polishing rate was low, and the surface roughness was very large, resulting in poor surface accuracy.

<Comparative Example 3>
The precursor particle dispersion prepared under the same conditions as in Example 2 was adjusted to pH 7 by adding 5% by mass acetic acid and dried in a dryer at 100 ° C. for 16 hours. Obtained.

  When the obtained precursor particle dry powder was measured by the X-ray diffraction method, a slight Ceriaite diffraction pattern was observed.

  After adding 375 g of ion-exchanged water to 125 g of the obtained precursor particle dry powder and further adjusting the pH to about 9 using a 3% aqueous ammonia solution, φ0.22 mm high-purity silica beads (manufactured by Daiken Chemical Industries, Ltd.) ) Was subjected to wet crushing and pulverization to obtain 540 g of a 20% by mass slurry.

  Next, the slurry was concentrated with a rotary evaporator, diluted with ion-exchanged water, the concentration was adjusted to obtain a 9% by weight polishing slurry, and a polishing test was performed. Moreover, the average particle diameter of the precursor particle | grains contained in polishing slurry was measured. The results are shown in Table 1.

Compared to Example 2, the average particle diameter is not so different, but the polishing rate is very low, the surface roughness is high, and the surface accuracy is deteriorated.
This is presumably because the ceria on the surface of the abrasive particles has a low crystallinity, so that the abrasive particles adhered and remained on the surface of the substrate.

Since the composite particle of the present invention does not contain impurities, it can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.

Claims (6)

The manufacturing method of the silica type composite particle dispersion characterized by including the following process 1-process 3.
Step 1: The average particle diameter measured by the laser diffraction scattering method is 40 to 600 nm, the minor axis / major axis ratio measured by the image analysis method is 0.95 to 1.0, Na, Ag, Al, Ca, Cr, Stirring a silica sol formed by dispersing silica fine particles in which the content of each element of Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 20 ppm or less and the content of each element of U and Th is 1 ppm or less in a solvent A step of adding a cerium metal salt continuously or intermittently to obtain a precursor particle dispersion while maintaining a temperature range of 5 to 98 ° C. and a pH range of 7.0 to 9.0.
Process 2: The process of drying the said precursor particle dispersion liquid, baking at 400-1200 degreeC, and then crushing and grind | pulverizing and obtaining powder.
Step 3: A step of subjecting the powder in a state of being dispersed in water to a centrifugation treatment at 11,000 G or more for 10 minutes or more to collect the supernatant and obtain a silica-based composite particle dispersion.   In the step 1, the temperature range of the silica sol is set to 48 to 52 ° C, a precursor particle dispersion is prepared, and the precursor particle dispersion is aged at a temperature of 90 to 98 ° C. The manufacturing method of the silica type composite particle dispersion liquid of description.   The method for producing a silica-based composite particle dispersion according to claim 1 or 2, wherein the metal salt of cerium in Step 1 is added over 0.5 to 24 hours.   4. The silica-based composite particle dispersion according to claim 1, wherein an alkali is added in the step 1 in order to maintain the pH range of the silica sol at 7.0 to 9.0. 5. Manufacturing method.   The silica-based composite particle dispersion according to any one of claims 1 to 4, wherein, in the step 2, the pH of the precursor particle dispersion before drying is set to 6.0 to 7.0. Liquid manufacturing method.   The manufacturing method of the silica type composite particle which further dries the silica type composite particle dispersion liquid obtained by the manufacturing method in any one of Claims 1-5, and obtains a silica type composite particle.