JP2000026840A - Abrasive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive which, with respect to abrasion of a glass stock and a semiconductor device, contains no contaminants, provides an im proved abrasion speed as compared to a silica abrasive, while maintaining a surface processed state equal to that obtained using a silica abrasive, shows reduced adhesion of a abrasive grains on the abraded surface and can contribute to the improvement of productivity, by using a ceric oxide powder having spe cific properties. SOLUTION: This abrasive comprises a cerium oxide powder in which a number average particle diameter of a primary particle is 0.01-0.5 μm and the half-value width 2θ( deg.) of an angle 28.6 deg. (111 face) of diffraction in X-ray diffraction is 0.7-0.15 deg.. In order to prepare a slurry of the abrasive using the cerium oxide as an abrasive grain, the cerium oxide is preperably contained 0.5-30 wt.%, preferably 1-10 wt.% to a whole amount of the abradant. A stock powder of the cerium oxide can be prepared by various methods. In a hydrothermal method, a base such as ammonia water or the like is added to an aqueous solution of a cerium salt to neutralize the solution and a precipitation is deposited, followed by heating the resulting product in a pressure vessel to crystallize the product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive used for polishing a glass material, a metal material or a semiconductor device.

[0002]

2. Description of the Related Art Inorganic glass used for optical disk substrates, magnetic disks, glass substrates for flat panel displays, timepieces, camera lenses, various lenses for optical parts, etc., as examples where the material surface must be precisely polished. There are crystalline materials such as materials and filters. These glass substrates are required to have their surfaces polished with high precision. For this reason, for example, in the precision polishing of a glass material, it is common to use, as a polishing material, fine particles of silica or cerium oxide dispersed in a liquid in a slurry state.

[0003] Polishing with a silica abrasive has less surface roughness and scratches on the polished surface, and the condition of the polished surface is excellent. However, there is a disadvantage that the polishing rate is low. Therefore, in order to increase the polishing rate over silica abrasives, magnesium chloride is contained in an amount of 0.1 to 20.0% by weight, and the number average particle diameter is 0.1.
An abrasive mainly composed of cerium oxide having a thickness of 10 to 10 μm has been developed and proposed in Japanese Patent Application Laid-Open No. 3-146585.

Further, there is a step of flattening a device in an intermediate step of manufacturing a semiconductor device. As one of the flattening techniques, there is a polishing method called CMP. This method is based on Chemical-Mechanical-Pol.
It is an abbreviation of ising, and is a polishing method in which the mechanical action of the abrasive grains and the chemical action of the dispersion medium of the working fluid abrasive grains are combined. According to this method, for example, the entire surface of the device can be formed to a uniform thickness by polishing the interlayer insulating film. As a typical example of conventional CMP, a method is used in which an abrasive is produced by dispersing silica as abrasive grains in a weakly alkaline solution on a silicon wafer for LSI, and polishing is performed on a mirror surface which is smooth and has no distortion. .

[0005] The above-mentioned fine particle silica is used in the CMP method currently put into practical use. These silica abrasives, like the polishing of glass, have a low polishing rate,
Cerium oxide having a number average particle diameter of 0.1 μm or less
A slurry dispersed at a concentration of 0 g / l has been developed and proposed in JP-A-8-134435.

Conventionally developed abrasive grains are in the form of secondary aggregates in a lump, and even when dispersed in water,
There is a case where the abrasive grains are not easily dispersed but exist in a lump state, and the abrasive grains are settled, and scratches are formed during polishing. In a production line, in order to keep the process clean, it is important to remove abrasive grains generated from the slurry after CMP and to prevent heavy metal contamination. For this purpose, there is a wafer cleaning step after CMP, and the cleaning method includes scrubber cleaning as physical cleaning, acid treatment as chemical cleaning, and dilute H.
F treatment, alkali treatment and the like are used.

Further, it is important for various materials used in the manufacture of semiconductor devices to prevent contamination due to impurity contamination. In particular, contamination with alkali metal ions such as sodium and potassium, which cause a reduction in yield, and impurities including radioactive elements which generate α rays must be avoided. Therefore, abrasives produced by firing and pulverizing natural minerals are not suitable for semiconductor device-related materials because they contain these impurities.

[0008]

SUMMARY OF THE INVENTION An object of the present invention relates to polishing of glass materials and semiconductor devices, etc., which does not contain contaminants, maintains the same surface processing state as conventional silica abrasives, An object of the present invention is to provide an abrasive which improves a polishing rate, has less abrasive grains attached to a polishing surface, and contributes to an improvement in productivity.

As a mechanical method for increasing the polishing rate, a method of increasing the polishing pressure or the rotation speed may be considered. However, scratches such as scratches are liable to be formed on the polished surface.
If scrubber cleaning or chemical cleaning is strengthened to eliminate the adhesion of abrasive grains on the polished surface after MP, the surface accuracy of the polished surface will be adversely affected. In order to avoid these problems, it is necessary to increase the polishing rate without lowering the polishing accuracy and to develop an abrasive material with less adhesion of abrasive grains.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above object, as a polishing step of flattening the surface of a glass material, a semiconductor device, or the like, "the primary particles have a number average particle diameter of 0%". .01 to 0.5 μm, and the half-value width 2θ of the diffraction angle of X-ray diffraction of 28.6 ° (111 plane)
A polishing material characterized by containing a cerium oxide powder whose (゜) is 0.7 to 0.15 ゜. Has been found to be preferred.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The cerium oxide powder of the present invention has a primary particle having a number average particle diameter of 0.01 to 0.5 μm and an X-ray diffraction angle of 28.6 ° (111 plane). It is assumed that the half width 2θ (゜) is 0.7 to 0.15 °.

The cerium oxide powder is in the form of particles, and the primary particles have a number average particle diameter of 0.01 to 0.5 μm.
m, preferably 0.02 to 0.3 μm. If the number average particle size is less than 0.01 μm, scratches such as scratches on the polished surface are small, but the polishing rate is too slow and productivity is deteriorated. If the number average particle size exceeds 0.5 μm, the polishing rate is increased, but the polished surface is liable to be scratched or damaged.

The diffraction angle of X-ray diffraction is 28.6 ° (11
The half width 2θ (゜) of one surface is 0.7 to 0.15 °, preferably 0.5 to 0.2 °. In a region where the half width exceeds 0.7, the crystallinity is insufficient and the region is near amorphous, and the polishing rate is too low. If it is less than 0.15 °, the crystallinity is sufficient, but the grains grow too much and the polishing rate is increased, but scratches such as scratches on the polished surface increase.

Usually, the abrasive grains such as silica and cerium oxide used for polishing have a number average particle diameter of 0.002 to 0.002.
Although it is 0.5 μm, studies on control of crystallinity are insufficient. Since the polishing rate is not determined only by the particle diameter, and the crystallinity of the particles is also an important factor, when cerium oxide whose crystallinity is not controlled is used as abrasive grains, the polishing rate is not only stable. This may cause scratches and other scratches.

The cerium oxide of the present invention is used as abrasive grains,
In order to adjust the slurry-like abrasive, cerium oxide is preferably contained in an amount of 0.5 to 30% by weight, more preferably 1 to 10% by weight, based on the total amount of the abrasive. If the addition amount is less than 0.5% by weight, the abrasive grain concentration is too low and the polishing rate is reduced. Addition of more than 30% by weight or more is not preferable because the polishing rate in terms of the unit weight of the abrasive grains decreases and the polishing efficiency decreases.

By the way, as the raw material powder of cerium oxide used in the present invention, those produced by various methods can be used. For example, in the hydrothermal method, a base such as aqueous ammonia is added to an aqueous solution of a cerium salt to neutralize the solution, precipitate a precipitate, and then heat and crystallize in a pressure vessel. The alkoxide method hydrolyzes an alcohol solution of a cerium alkoxide compound. In the gas phase method, cerium oxide powder is instantaneously melted in ultra-high temperature using high-frequency induction thermal plasma to obtain cerium oxide powder. In addition, the firing method is a method in which an organic compound of cerium such as cerium carbonate or cerium oxalate is fired to blow off a carbonate group or an oxalate group, or an aqueous solution of cerium chloride or cerium nitrate is immersed in a precursor such as wood pulp to form a precursor. And the like.

In the method for producing cerium oxide powder of the present invention, the above-mentioned cerium oxide raw material can be used. However, in order to adopt a production method in which cerium oxide is calcined in an oxidizing atmosphere to adjust the particle diameter and crystallinity, The number average particle diameter of the primary particles is 0.5 μm or less, and the half value width 2θ (゜) at a diffraction angle of 28.6 ° (111 plane) of X-ray diffraction is 0.15.
原料 The raw material powder that is not less than is required.

The cerium oxide of the present invention can be incorporated into the abrasive as abrasive grains in the form of particles as they are.

[0019]

[Measurement methods and evaluation methods of physical properties] (1) Particle size Transmission electron microscope (H-7100 manufactured by Hitachi, Ltd.)
FA type), and the powder was observed and expressed as a number average particle diameter of primary particles.

(2) X-ray half width wide angle X-ray diffractometer (RU-200 manufactured by Rigaku Corporation)
It measured using B). Using a CuKα ray as an X-ray source, the measurement range (2θ) was scanned from 20 to 80 °, and a cubic diffraction pattern of the cerium oxide powder was measured. The diffraction angles (2θ) had main peaks at 28.6 °, 47.5 °, and 56.4 °.

A substance having a corresponding interplanar spacing and relative intensity was selected from the JSPDS standard diffraction data and matched with the characteristic peak of cubic cerium oxide. A half-width of 28.6 ° (111 plane, lattice constant of 3.1234 Å) showing the strongest peak was measured and represented as the half-width of the present invention.

(3) Polishing conditions Material to be polished: 4 inch non-patterned insulating film silicone wafer Polishing device: Lapping machine Polishing cloth: IC-1000 manufactured by Rodel Nitta Co., Ltd. Weight: 200 g / cm ² Number of rotations of platen: 60 rpm Polishing Time: 2 minutes (4) Polishing rate The difference in thickness before and after polishing was measured using a high-accuracy digital length measuring machine (manufactured by Tokyo Seimitsu Co., Ltd.), and the polishing rate was converted to per minute.

(5) Scratch Abrasion scratches were taken with a three-dimensional surface structure analysis microscope (Zygo Cor).
Evaluation was performed from Surface Profile of the polished surface using NV-100-Zoom manufactured by POR Corporation. The evaluation criterion was determined by polishing a 4-inch non-patterned insulating silicon wafer as a material to be polished, and determining the number of polishing scratches on a 2-inch square portion of the surface.

(6) Abrasive Grain Adhesion The degree of adhesion of abrasive grains was measured by a three-dimensional surface structure analysis microscope (Nyv-100 manufactured by Zygo Corporation).
-Zoom) by Surface Map
Polished material without pattern Polished material 4 inch Non-patterned insulation film Silicon wafer 0.7mm × 0.52mm
The number of aggregates attached to the surface was observed. Evaluation criteria is 1
00 or more were “large”, 99 to 10 were “medium”, 9-1 were “small”, and “none”.

[0025]

EXAMPLE 1 19.7 g of a 31% by weight aqueous hydrogen peroxide solution was added to 148.7 ml of a 1.6 mol / l cerium chloride (CeCl ₃ ) aqueous solution.
Was added, and pure water was added to bring the total volume to 200 ml. On the other hand, a 28 wt% aqueous ammonia, the atomic ratio of Cl contained in the NH ₃ and CeCl ₃ (NH ₃ / Cl) are weighed 65.6ml to be 1.5, this was added pure water total amount To 200 ml. Then, the two solutions were dropped and stirred little by little into a beaker to which 50 ml of pure water had been added to precipitate a cerium oxide-containing gel. Next, this precipitated gel was heated in an autoclave at 150 ° C. for 24 hours to obtain 500 ml of a slurry, which was filtered and washed five times with pure water. Then pulverize with an attritor mill, and add 2
Cerium oxide powder was obtained by washing with 00 ml of ethyl alcohol, stirring, filtering and drying under reduced pressure.

The cerium oxide powder thus obtained is dispersed as abrasive grains in 5% pure water, and the pH is adjusted to 10.5 to 1
The polishing effect was examined using the abrasive adjusted to 1.0.

Example 2 19.7 g of a 31% by weight aqueous hydrogen peroxide solution was added to 148.7 ml of a 1.6 mol / l cerium chloride (CeCl ₃ ) aqueous solution.
Was added, and pure water was added to bring the total volume to 200 ml. On the other hand, a 28 wt% aqueous ammonia, the atomic ratio of Cl contained in the NH ₃ and CeCl ₃ (NH ₃ / Cl) are weighed 65.6ml to be 1.5, this was added pure water total amount To 200 ml. Then, the two solutions were dropped and stirred little by little into a beaker to which 50 ml of pure water had been added to precipitate a cerium oxide-containing gel. Next, this precipitated gel was subjected to heat treatment at 150 ° C. for 24 hours in an autoclave to obtain 500 ml of a slurry, which was filtered and washed five times with pure water, filtered, and dried under reduced pressure. This powder was placed in an alumina crucible and placed in an electric furnace in air at 5 ° C./min and 600 ° C. for 3 hours.
It was kept for a time and fired. Then, the mixture was pulverized with an attritor mill, further washed with 200 ml of ethyl alcohol, stirred, filtered, and dried under reduced pressure to obtain a cerium oxide powder.

The cerium oxide powder thus obtained is dispersed as abrasive grains in 5% pure water, and the pH is adjusted to 10.5 to 1
The polishing effect was examined using the abrasive adjusted to 1.0.

EXAMPLE 3 19.7 g of a 31% by weight aqueous hydrogen peroxide solution was added to 148.7 ml of an aqueous 1.6 mol / l cerium chloride (CeCl ₃ ) solution.
Was added, and pure water was added to bring the total volume to 200 ml. On the other hand, a 28 wt% aqueous ammonia, the atomic ratio of Cl contained in the NH ₃ and CeCl ₃ (NH ₃ / Cl) are weighed 65.6ml to be 1.5, this was added pure water total amount To 200 ml. Then, the two solutions were dropped and stirred little by little into a beaker to which 50 ml of pure water had been added to precipitate a cerium oxide-containing gel. Next, this precipitated gel was subjected to heat treatment at 150 ° C. for 24 hours in an autoclave to obtain 500 ml of a slurry, which was filtered and washed five times with pure water, filtered, and dried under reduced pressure. This powder was placed in an alumina crucible, and calcined in an electric furnace at 5 ° C./min and 1000 ° C. for 3 hours in air. Then, the mixture was pulverized with an attritor mill, further washed with 200 ml of ethyl alcohol, stirred, filtered, and dried under reduced pressure to obtain a cerium oxide powder.

The cerium oxide powder thus obtained was dispersed as abrasive grains in 5% pure water, and the pH was adjusted to 10.5 to 1
The polishing effect was examined using the abrasive adjusted to 1.0.

Comparative Example 1 19.7 g of a 31% by weight aqueous hydrogen peroxide solution was added to 148.7 ml of an aqueous 1.6 mol / l cerium chloride (CeCl ₃ ) solution.
Was added, and pure water was added to bring the total volume to 200 ml. On the other hand, a 28 wt% aqueous ammonia, the atomic ratio of Cl contained in the NH ₃ and CeCl ₃ (NH ₃ / Cl) are weighed 65.6ml to be 1.5, this was added pure water total amount To 200 ml. Then, the two solutions were dropped and stirred little by little into a beaker to which 50 ml of pure water had been added to precipitate a cerium oxide-containing gel. Next, this precipitated gel was heated in an autoclave at 110 ° C. for 10 hours to obtain 500 ml of a slurry, which was filtered and washed five times with pure water. Then pulverize with an attritor mill, and add 2
Cerium oxide powder was obtained by washing with 00 ml of ethyl alcohol, stirring, filtering and drying under reduced pressure.

The cerium oxide powder thus obtained was dispersed as abrasive grains in 5% pure water, and the pH was adjusted to 10.5 to 1
The polishing effect was examined using the abrasive adjusted to 1.0.

Comparative Example 2 19.7 g of a 31% by weight aqueous hydrogen peroxide solution was added to 148.7 ml of a 1.6 mol / l cerium chloride (CeCl ₃ ) aqueous solution.
Was added, and pure water was added to bring the total volume to 200 ml. On the other hand, a 28 wt% aqueous ammonia, the atomic ratio of Cl contained in the NH ₃ and CeCl ₃ (NH ₃ / Cl) are weighed 65.6ml to be 1.5, this was added pure water total amount To 200 ml. Then, the two solutions were dropped and stirred little by little into a beaker to which 50 ml of pure water had been added to precipitate a cerium oxide-containing gel. Next, this precipitated gel was subjected to heat treatment at 150 ° C. for 24 hours in an autoclave to obtain 500 ml of a slurry, which was filtered and washed five times with pure water, filtered, and dried under reduced pressure. This powder was placed in an alumina crucible, and calcined in an electric furnace at 5 ° C./min and 1200 ° C. for 3 hours in air. Then, the mixture was pulverized with an attritor mill, further washed with 200 ml of ethyl alcohol, stirred, filtered, and dried under reduced pressure to obtain a cerium oxide powder.

The cerium oxide powder thus obtained is dispersed as abrasive grains in 5% pure water, and the pH is adjusted to 10.5 to 1
The polishing effect was examined using the abrasive adjusted to 1.0.

Comparative Example 3 800 g of wood pulp was immersed in 1,000 ml of 1.6 mol / l cerium chloride (CeCl ₃ ) aqueous solution for 24 hours. The wet pulp is put into quartz glass, and fired at a heating rate of 5 ° C./min while sending a small amount of air in a cylindrical firing furnace. Burn the pulp at 500-600 ° C.
Thereafter, the temperature is further raised to 1000 ° C., maintained for 3 hours, and allowed to cool to room temperature after firing. The powder in which cerium chloride was incinerated was filtered and washed five times with pure water. Then, the mixture was pulverized with an attritor mill, and further washed with 1000 ml of ethyl alcohol, stirred, filtered, and dried under reduced pressure to obtain a cerium oxide powder.

The cerium oxide powder thus obtained was dispersed as abrasive grains in 5% pure water, and the pH was adjusted to 10.5 to 1
The polishing effect was examined using the abrasive adjusted to 1.0.

Table 1 compares the measurement results of the powders of Examples 1 to 3 and Comparative Examples 1 to 3.

[0038]

[Table 1]

[0039]

According to the present invention, the primary particles have a number average particle diameter of 0.01 to 0.5 μm and a half-value width 2θ (゜) at an X-ray diffraction angle of 28.6 ° (111 plane). ) Is 0.7-
The use of abrasives in which cerium oxide powder, which is 0.15%, is dispersed and slurry is used as abrasive grains, and for polishing glass materials and semiconductor devices, is free of contaminants and is equivalent to the current silica abrasives. The surface processing state is maintained, the adhesion of the abrasive grains on the polished surface is small, and the polishing rate can be improved more than the silica abrasive.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C058 AA02 AA07 AC04 CA01 CA04 CA06 CB03 CB06 CB10 DA02 4G076 AA02 AB04 AC02 BA15 BA42 BA43 BA46 BC02 BC07 BC08 BD02 BD04 CA05 CA15 CA26 CA33 DA30

Claims (2)

[Claims] The number average particle diameter of the primary particles is 0.01 to 1.
A cerium oxide powder having a half-width 2θ (価) of 0.5 μm and a diffraction angle of 28.6 ° (111 plane) of X-ray diffraction of 0.7 to 0.15 °. Abrasive material. 2. The abrasive according to claim 1, wherein the cerium oxide is dispersed as a slurry in the liquid.