JP4211952B2 - Composite particles for abrasives and slurry abrasives - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abrasive used when polishing a glass material, a metal material, a semiconductor device, or the like, and is suitable for the flat precision finishing of the surface of these materials and the improvement of the polishing rate.
[0002]
[Prior art]
Inorganic glass materials and filters used for optical disks, magnetic disks, glass substrates for flat panel displays, watch plates, camera lenses, various lenses for optical components, etc. There are crystal materials such as. These glass substrates are required to polish the surface with high accuracy.
[0003]
Therefore, for example, for precision polishing of a glass material, it is common to use a material in which fine particles of silica or cerium oxide are dispersed in a liquid as a slurry.
[0004]
Polishing with a silica abrasive has less surface roughness and scratches on the polished surface, and the polished surface is excellent. However, there is a drawback that the polishing rate is slow. Therefore, in order to increase the polishing rate compared with the silica abrasive, an abrasive mainly composed of cerium oxide has been developed and proposed in Japanese Patent Application Laid-Open No. 3-146585. The dispersion form of the particles used for the abrasive as the abrasive grains is often a tufted aggregate form other than colloidal silica.
[0005]
This tuft-like aggregated particle has a primary particle diameter of 0.01 to 0.1 μm, and several hundred to several thousand of these primary particles gather to form 0.2 to 0.5 μm secondary particles. Further, the secondary particles are aggregated to form an aggregate of several μm. These agglomerated particles are held in the voids of a polishing pad of several tens of μm. The agglomerated particles are supplied from the polishing pad during the polishing process, are crushed and become finer particles, and contribute to a highly accurate polishing process while increasing the active specific surface area.
[0006]
However, such aggregated particles have the following problems. Thus, it is difficult to produce agglomerated particles that are crushed and atomized by grinding with high reproducibility. If not pulverized or atomized by grinding, it may cause scratches. In addition, abrasives using particles with low specific gravity as silica, such as silica, have relatively little precipitation in the slurry, but if a material with high specific gravity is used as the abrasive, the particles will precipitate. And has the disadvantage of condensing.
[0007]
Usually, the abrasive is used while being circulated. Therefore, when the abrasive grains are settled, the abrasive grains become a large mass, which damages the polished surface and causes scratches. Further, if the particles settle in the pipe or the container, the abrasive grains cannot be maintained at a predetermined concentration, and the polishing rate decreases with time, and the amount of polishing cannot be controlled accurately, making process management difficult.
[0008]
Further, there is a step of flattening the device in an intermediate step of manufacturing a semiconductor device. As one of the planarization techniques, there is a polishing method called CMP. This method is an abbreviation for Chemical-Mechanical-Polishing, and is a polishing method in which the mechanical action of abrasive grains and the chemical action of a dispersion medium of working fluid abrasive grains are combined.
[0009]
By this method, for example, the entire surface of the device can be formed with a uniform thickness by polishing the interlayer insulating film. As a typical example of CMP that has been conventionally performed, a method is used in which a polishing material is manufactured by dispersing silica in a weak alkaline solution as an abrasive grain on a silicon wafer for LSI, and polishing to a smooth and distortion-free mirror surface. . The fine particle silica described above is used in the CMP method currently in practical use. Since these silica abrasives have a low polishing rate as in the case of glass polishing, recently, particles in the form of tufted aggregates of cerium oxide have been developed.
[0010]
However, an abrasive using such cerium oxide as an abrasive grain has a drawback that the settling property of the abrasive grain is large in the slurry as described above.
[0011]
Furthermore, it is important to prevent contamination caused by impurities in various materials used for manufacturing semiconductor devices. In particular, impurities including alkali metal ions such as sodium and potassium that cause a decrease in yield and radioactive elements that are sources of α rays must be avoided. Therefore, abrasives produced by firing and pulverizing natural minerals contain these impurities, and are therefore unsuitable for materials related to semiconductor devices.
[0012]
[Problems to be solved by the invention]
The object of the present invention relates to polishing of glass materials and semiconductor devices, does not contain contaminants, maintains the same surface processing state as conventional silica abrasives, and improves the polishing rate compared to silica abrasives, thereby improving productivity. It is to provide an abrasive that contributes to improvement.
[0013]
As a mechanical method for increasing the polishing rate, a method of increasing the polishing pressure or the rotation speed is conceivable. However, scratches such as scratches are likely to enter the polishing surface, which adversely affects the surface accuracy of the polishing surface. In order to avoid this, it is necessary to develop a technique for increasing the polishing rate without reducing the polishing accuracy.
[0014]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the composite particles for abrasives are characterized in that child particles comprising zirconium oxide / cerium oxide solid solution are supported on the surface of the mother particles.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The average particle diameter of the mother particles is preferably in the range of 0.3 to 30 μm, more preferably in the range of 0.2 to 5 μm.
[0016]
The average particle diameter of the child particles is preferably in the range of 0.001 to 5 μm, more preferably in the range of 0.002 to 0.5 μm, although it depends on that of the mother particles. When the average particle diameter is within this range, composite particles having good support on the mother particles and good coverage can be obtained. The amount of the child particles supported on the surface of the mother particles is preferably 5 to 70% by weight, more preferably 10 to 40% by weight. If it is less than 5% by weight, the coverage is lowered and a sufficient polishing rate cannot be obtained, and if it exceeds 70% by weight, many particles fall off from the mother particles.
[0017]
The specific gravity of the composite particles obtained in this manner depends on that of the child particles and the mother particles. However, the effect of greatly reducing specific gravity is great, and when the slurry is used, the settling property is small and excellent dispersibility is exhibited.
[0018]
In order to adjust the slurry-like abrasive using the composite particles of the present invention, the composite particles are 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. % Range. When the addition amount is less than 0.5% by weight, the abrasive concentration is too dilute and the polishing rate is lowered. Further, if it is added in excess of 30% by weight, the polishing rate when converted per unit weight of the abrasive grains is lowered, and the polishing efficiency is lowered.
[0019]
Matrix particles of the present invention is nylon, polyethylene, polypropylene, polystyrene, polyurethane, styrene-acryl copolymer, polymethyl methacrylate, epoxy, phenolic, melamine, cellulose, polyolefins, silicones, may be used silicon oxide, child particles it can be used an acid zirconium-cerium oxide solid solution.
[0020]
By using a polishing material in which the composite particles with the child particles supported on the surface of the base particles are added as abrasive grains and dispersed as a slurry, it is free of contaminants and is used for polishing glass materials and semiconductor devices. The surface processing state equivalent to that of the abrasive can be maintained, and the polishing rate can be improved as compared with the silica abrasive.
[0021]
[Characteristic evaluation method]
(1) Measurement of particle diameter The particle diameter described here was measured by observing the primary particle diameter of abrasive grains and the size of aggregates with a transmission electron microscope.
[0022]
(2) Polishing conditions [for glass disc]
Material to be polished: Glass substrate (φ100 blue plate glass)
Polishing device: Wrapping machine polishing cloth: Synthetic suede cloth Weight: 30 g / cm ²
Surface plate rotation speed: 30 rpm
Work rotation speed: 30 rpm
Polishing time: 5 hours in total (sampling interval every 30 minutes)
[0023]
[For silicone wafers]
Material to be polished: 4-inch silicone wafer polishing device: Wrapping machine polishing cloth: Polyurethane foam load: 100 g / cm ²
Surface plate rotation speed: 60 rpm
Work rotation speed: 30 rpm
Polishing time: Total 20 minutes (sample ring interval 5 minutes)
[0024]
(3) Polishing rate [for glass disc]
During polishing, the weight before and after polishing was measured every 30 minutes between samplings, the weight loss before and after was converted into thickness, and the average polishing rate was obtained by dividing by the polishing time.
[0025]
[For silicone wafers]
During polishing, the weight before and after polishing was measured every 5 minutes between samplings, the weight loss before and after was converted into thickness, and the average polishing rate was obtained by dividing by the polishing time.
[0026]
(4) Scratch observation The disk is etched with a 1% HF solution for 2 minutes, washed with pure water, dried, and then observed with a condenser lamp. Count the number of scratches at that time.
[0027]
【Example】
Comparative Example 1
434 g of cerium nitrate (Ce (NO3) 3 .6H2 O) is dissolved in 2000 ml of pure water. To this, 60 g of 31 wt% aqueous hydrogen peroxide and 200 g of 28 wt% aqueous ammonia were added dropwise with stirring to obtain hydrous cerium oxide gel.
[0028]
Next, this gel was heat-treated at 150 ° C. for 24 hours in an autoclave, and the resulting slurry was filtered and washed 5 times with pure water, and further filtered and washed 3 times with acetone to obtain a cake. Next, this cake was pulverized with an attritor for 3 hours and dried at 60 ° C. using a rotary evaporator to obtain cerium oxide particles having an average particle diameter of 0.01 μm. This is a child particle.
[0029]
On the other hand, 50 g of anhydrous laurolactam was mixed with 200 ml of liquid paraffin (dispersing agent) and 1 g of sodium stearate (dispersing aid). Next, the mixture is heated at 140 ° C. in a nitrogen atmosphere to dissolve laurolactam, and 0.2 ml of phosphorus trichloride is added as a polymerization accelerator, and the mixture is stirred for about 1 hour to carry out polymerization. Obtained. Further, the particles were separated by filtration, washed with boiling benzene, and dried under reduced pressure at 80 ° C. to obtain particles made of nylon 12 resin having an average particle size of 5 μm. This is the mother particle.
Next, 5 parts by weight of the child particles and 20 parts by weight of the mother particles were mixed and mixed using an automatic mortar to support the child particles on the surface of the mother particles to obtain composite particles. And the said composite particle was added so that it might become a 3 weight% density | concentration in a pure water, and the slurry-like abrasive | polishing material was adjusted. The specific gravity of the composite particles was 1.6, and the specific gravity was greatly reduced as compared with 7.13 of cerium oxide. When the slurry was made into a slurry, the settling property was small and excellent dispersibility was shown.
[0030]
Using the abrasive thus obtained, the polishing effect of the glass disk was examined. The polishing rate of this abrasive was 4.3 μm / hr, and no scratches were observed.
[0031]
Comparative Example 2
The same as in Comparative Example 1 except that a commercially available colloidal silica (particle diameter 0.04 μm) was added as an abrasive grain for the abrasive to a concentration of 10% by weight to prepare a slurry abrasive. Polished. The polishing rate of this abrasive was 1.2 μm / hr, and no scratches were observed.
[0032]
Example 1
59.48 ml of an aqueous solution of cerium chloride (CeCl3) and 83.04 g of an aqueous solution of zirconium oxychloride (ZrOCl2) were mixed so that the atomic ratio of Ce to Zr (Ce / Zr) was 40/60. After adding and mixing 1.15 g of hydrogen oxide water, pure water was added to make 200 ml. On the other hand, 48.57 ml of 28 wt% ammonia water was measured so that the atomic ratio (NH3 / Cl) of NH3 to Cl contained in CeCl3 and ZrOCl2 was 1.5, and pure water was added thereto. The total volume was 200 ml. The two solutions were added dropwise with stirring, and the entire amount was put into a beaker to obtain a coprecipitated gel of hydrous cerium oxide and hydrous zirconium oxide. In the same manner as in the cerium oxide of Comparative Example 1, heat treatment, filtration with pure water, washing with water, acetone treatment, and drying were performed in an autoclave to obtain cerium oxide / zirconium oxide solid solution particles having a particle diameter of 0.01 μm.
[0033]
The solid solution particles were used as child particles on nylon 12 mother particles as in Comparative Example 1 to obtain composite particles.
[0034]
The above-mentioned particles were added as abrasive grains for the abrasive to a concentration of 5% by weight in pure water to prepare a slurry-like abrasive. The polishing effect of the silicon wafer was examined using the polishing material thus obtained.
[0035]
The polishing rate of this abrasive was 5.2 μm / hr, and no scratches were observed.
[0036]
Comparative Example 3
Polishing was carried out in the same manner as in Example 1 except that a commercially available colloidal silica (particle size: 0.04 μm) was added as an abrasive grain for the abrasive so as to have a concentration of 10%, and a slurry-like abrasive was prepared. . The polishing rate of this abrasive was 2.5 μm / hr, and no scratches were observed.
[0037]
【The invention's effect】
The present invention relates to the polishing of glass materials and semiconductor devices by using a polishing material in which a composite polishing material in which child particles are supported on the surface of base particles is added as abrasive grains and dispersed as a slurry. In addition, it is possible to maintain the surface processing state equivalent to the current silica abrasive and to improve the polishing rate as compared with the silica abrasive.

Claims (5)

A composite particle for abrasives, wherein a child particle comprising a solid solution of zirconium oxide and cerium oxide is supported on the surface of a mother particle.  2. The composite particle for an abrasive according to claim 1, wherein the average particle diameter of the base particles is in the range of 0.3 to 30 μm.  The composite particle for abrasives according to claim 1, wherein the average particle diameter of the child particles is in the range of 0.001 to 5 μm.  The base particle is selected from nylon, polyethylene, polypropylene, polystyrene, polyurethane, styrene-acrylic copolymer, polymethyl methacrylate, epoxy, phenol, melamine, cellulose, polyolefin, silicone, and silicon oxide. The composite particle for abrasive | polishing materials in any one of 1-3. A composite abrasive particle for abrasive according to any one of claims 1 to 4 , which is dispersed as suspended particles in a liquid, and a slurry-like abrasive.