JP2000080348A - Method of treating silicon wafer polishing waste liquid and abrasive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of effectively regenerating, with high purity, a used abrasive which is contained in a silicon wafer polishing waste liquid including melted Al2O3 and ZrSiO4 as major components and an abrasive regenerated thereby. SOLUTION: A silicon wafer polishing waste liquid is separated into a solid abrasive and a solution by means of a vacuum type drum filter 1 and the solid component including a mixture of Al2O3 and ZrSiO4 as major components is dispersed in water in a dispersing bath 2 to remove rough foreign matters by a screen 3. The solid component is then separated into the abrasive and silicon by a wet screen 5 which are again dispersed in water to remove iron by an iron removing apparatus 7 followed by being dryed by a drying apparatus 8 and the particle size's being adjusted by a vibrative screen 9 to give an inexpensive abrasive having reliable quality in a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating used abrasives from a silicon wafer polishing waste liquid mainly composed of a molten Al2O3 component and a ZrSiO4 component, and to a regenerated abrasive.

[0002]

2. Description of the Related Art Generally, waste liquid after polishing a silicon wafer is:
As a mushy solid, fused alumina (A
l2O3) and zircon (ZrSiO4), iron (Fe) from a polisher, and silicon (Si) from a wafer. In the treatment of this waste liquid, solid-liquid separation was conventionally performed using a number of large sedimentation tanks, the supernatant liquid was filtered and reused, and the solid content was discarded. However, such a process not only wastes effective resources but also has a problem in environmental conservation.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and includes a molten Al2O3 component and ZrSiO
The present invention relates to a processing method for treating waste liquid after polishing a silicon wafer with an abrasive mainly composed of a mixture of four components to efficiently regenerate the abrasive with high purity, and a regenerated abrasive.

[0004]

According to the present invention, there is provided a method for treating a silicon wafer polishing slurry waste liquid, comprising the steps of: using a vacuum drum filter to remove a silicon wafer polishing waste liquid mainly composed of a molten Al2O3 component and a ZrSiO4 component. Solid-liquid separation into an abrasive component and a solution, the solid content of the molten Al2O3 component and the ZrSiO4 component dispersed in water and coarse foreign substances removed by sieving, then separated into an abrasive and silicon by a wet classifier, and again After dispersing the solids in water,
It is characterized in that iron is removed by magnetic force and then dried to regenerate the abrasive.

[0005] The regenerated abrasive contains about 60 to 55% (hereinafter referred to as% by weight) of fused alumina (Al2O3),
Zircon (ZrSiO4) is about 40 to 45%, and has such a purity that it can be reused as an abrasive in a silicon wafer polishing process. In particular, a molten alumina (Al2O3) component, zircon (ZrSiO)
4) A wide range of uses of the abrasive can be expected by appropriately adding the components and setting an arbitrary composition ratio.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, a silicon wafer polishing waste liquid mainly composed of a mixture of a molten Al2O3 component and a ZrSiO4 component is solid-liquid separated into an abrasive component and a solution by a vacuum drum filter. And the molten Al
The solid content of the mixture of the 2O3 component and the ZrSiO4 component is dispersed in water, coarse foreign substances are removed by sieving, then the abrasive and silicon are separated by a wet classifier, and the solid content is again dispersed in water. To remove iron, and then dry to regenerate the abrasive. The use of a vacuum drum filter allows solid-liquid separation into an abrasive component and a solution, and a raw material having an excellent effect as an abrasive mainly composed of a mixture of a molten Al 2 O 3 component and a ZrSiO 4 component. It becomes a powder. Then, a solid content mainly composed of a mixture of the molten Al2O3 component and the ZrSiO4 component is dispersed in water, and the use of a sieve has an effect of removing coarse foreign substances. Then
Using a wet classifier has the effect of separating the abrasive powder and the silicon component. Then, after again dispersing the solid content in water, by removing iron by magnetic force and drying,
There is an effect of obtaining high-purity abrasive powder.

According to a second aspect of the present invention, the vacuum drum filter has a filter medium having a pore diameter in a range of 3 μm to 10 μm. When the pore size of the filter medium of the vacuum drum filter is in the range of 3 μm to 10 μm, the solid material having a different particle size in the abrasive waste liquid can be accurately extracted. If the particle size is less than 3 μm, it is not preferable because the fine particle powder adheres to the surface of the filter and significantly reduces the function of the filter medium.
The above is not preferable because the fine particle powder accumulates inside the filter medium, causing clogging and reducing the filtration speed.

According to a third aspect of the present invention, there is provided a polishing composition comprising a mixture of a regenerated molten Al2O3 component and a ZrSiO4 component, and a molten Al2O3 component and a ZrS
Among the iO4 components, the total of one or two is 1.0 to 30.
It is configured to perform addition and mixing within the range of 0% by weight. It is to be noted that the addition of the above-mentioned additive components in an amount within the range and a mixing treatment have a good effect of obtaining an abrasive having a wide particle size range. As the operation of the additive component, the addition of the molten Al2O3 component has the effect of correcting the component ratio of the regenerated abrasive to a desired value, expanding the particle size range, and enhancing the polishing effect. The addition of the ZrSiO4 component has the effect of correcting the component ratio of the regenerated abrasive to a desired value, broadening the particle size range and enhancing the polishing effect. still,
If it is less than 1.0% by weight, the effect of correcting the desired abrasive component is poor, which is not preferable. On the other hand, if it is 30.0% by weight or more, an inexpensive regenerated abrasive becomes expensive, which is not preferable.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
2, 3, 4, (Table 1), (Table 2), (Table 3),
This will be described using (Table 4). FIG. 1 illustrates a method for treating a silicon wafer polishing waste liquid according to the present invention. In FIG. 1, the waste liquid after polishing the silicon wafer (polishing waste liquid) is usually composed of a water-soluble lubricating oil, a molten Al2O3 component and a ZrSiO4 component as an abrasive, an iron component of polishing dust from a polishing machine, and a silicon wafer. A muddy liquid containing silicon and other trace components. In the present invention, this polishing waste liquid is solid-liquid separated by the vacuum drum filter 1. As shown in Table 1, the average pore diameter of the filter medium of the vacuum drum filter 1 cannot be specified unconditionally because the filtration rate varies depending on the concentration of the waste liquid. However, in terms of environmental standards, the solid content in the filtrate exceeds 200 ppm. And cannot be discarded. Table 1
As shown in, for example, in the case of a filter medium having a pore size of 3 μm, the solid content concentration in the waste liquid is about 2 times that of the undiluted waste liquid, and the lower limit of the suitable range is obtained. The upper limit of the preferred range is about 1/3 of the range.
That is, when the average pore diameter of the filter is in the range of 3 μm to 10 μm, the filter can be separated into the abrasive component and the solution, and the workability is enhanced, which is practical. The separated solution can be circulated and reused as a polishing liquid in the silicon wafer polishing step as it is.

Next, the solid content is mixed with water in the dispersion tank 2, stirred and diluted and dispersed. Thereafter, coarse foreign substances are removed using the sieve 3. The diluted dispersion is then pump 4
Through a wet classifier 5 to separate into an abrasive component and a silicon component. This means that the abrasive component having a particle size distribution of about 12 μm and the silicon having an average particle diameter of 1 μm or less can be separated by specific gravity. The separated silicon is extracted together with the water and sent to the wastewater treatment device 6. Next, iron is removed through an iron removing machine 7 using a permanent magnet having a magnetic force of about 3500 to 10000 gauss.

Thereafter, the slurry is dried at a temperature of 200 ° C. using a dryer 8 (spray dryer) to obtain an abrasive powder. If necessary, a regenerated abrasive having a required particle diameter can be obtained by using the vibrating sieve 9 as a classification of the particle size of the abrasive. The component is about 55-60% alumina, about 40- zircon.
45%, and the obtained abrasive powder has such a purity that it can be reused as a silicon wafer abrasive as it is. The mixed abrasive of the regenerated alumina component and zircon component is an abrasive which is not inferior to any new abrasive.

In the present invention, the abrasive regenerated from the waste liquid can be used as it is as an abrasive for various ceramics.
A 2O3 component and a ZrSiO4 component are added and mixed, and can be used as an abrasive having a wide range of various particle sizes.

[0013]

[Table 1]

[0014]

Embodiment 1 Next, a specific example of the present invention will be described. A method for treating silicon wafer polishing waste liquid in this embodiment will be described. First, 200 liters of waste liquid after polishing a silicon wafer was used as a vacuum drum filter 1 under the trade name P
Vacuum degree is 600-6 using C separator (made by Kanebo)
40 mmHg, average pore size 2.0 μm to 15.0 for filter media
Solid-liquid separation was carried out into an abrasive component and a solution using a powder having a size in the range of μm. The solids adhering to the drum were scraped off with a screver. Solids content is about 13.8kg, moisture content is about 12%
The color was gray and the average particle size was 12.0 μm. (The filtrate can be circulated and reused as it is in the silicon wafer polishing step.) The solid separated from the solid and liquid was diluted and dispersed in the dispersion tank 2 by injecting about 100 liters of water to reduce the viscosity. Thereafter, foreign substances such as coarse sample pieces were removed by using a 400 mesh nylon sieve 3. Next, the mixture was subjected to a super classifier (trade name, manufactured by Murata Industry Co., Ltd.) as a wet classifier 5 via a pump 4 to separate an abrasive component and a silicon component. Table 1 shows the results of experiments in which the pore size of the filter medium of the vacuum drum filter was changed. As is clear from Table 1, the filter medium having an average pore diameter of 3.0 μm to 10.0 μm had a good yield and was very good. Especially 5 μm
The product obtained the most stable quality.

Next, in order to remove the iron component contained in the abrasive, the iron is passed twice through an iron remover using a permanent magnet having a magnetic force of about 3500 gauss with an iron remover 7 (trade name: Magclean, manufactured by Kanetec). After removing iron, about 1.5kg of iron
Has been removed. (The removal rate of iron was about 99.8%.) Then, the abrasive powder was dried at a temperature of 200 ° C. using a dryer 8 and a hot air circulation type spray dryer (manufactured by Okawara) to dry the abrasive powder to 1% or less. Agent was obtained. In addition, a sample having an average particle diameter of 12.7 μm was prepared by using a vibrating sieve 9 (manufactured by Nitto Kagaku) as a polishing agent if necessary.

The reclaimed abrasive obtained in the above example was replaced with FP
Quantitative analysis was performed by the method. An X-ray fluorescence analyzer (SXF-1200 manufactured by Shimadzu Corporation) was used as an analyzer. The sample is pressed with a total pressure of 300 tons using an aluminum ring and fluorescent X
The line spectrum was measured. Table 2 shows the estimated quantitative analysis results of the main detection elements by the FP method based on the obtained fluorescent X-ray spectrum. The content is shown in terms of simple oxide.

[0017]

[Table 2]

Further, X-ray diffraction, particle size distribution, and microscopic observation were performed. As a result, X-ray diffraction is shown in FIG. 2A, the particle size distribution is shown in FIG. 3A, and the result of microscopic observation is shown in FIG. As a comparative example, FIGS. 2 (b), 3 (b), and 4 (b) are shown so that a new unused abrasive can be compared. The analysis conditions were as follows: X-ray diffraction: X-ray diffractometer XD-1 manufactured by Shimadzu Corporation, and the measurement conditions were as follows. X-ray tube Target: Cu Tube voltage: 35 (kV) Tube current: 15 (mA) Slit Divergence slit: 1 (deg) Air scattering prevention slit: 1 (deg) Detection slit: 0.30 (mm)

Measurement of particle size distribution: The measurement conditions were as follows using a Shimadzu laser diffraction type particle size distribution analyzer (SALD-2000). Sampling manual Refractive index 3.00 to 0.20i Number of measurements 2 Measurement interval (seconds) 2 Average number 64 Measurement absorbance range (maximum value) 0.200, (minimum value) 0.2
010

Microscope observation: The magnification was × 200 using a microscope manufactured by Olympus Corporation.

As is clear from Table 2, the results of the quantitative analysis
The recycled abrasive had almost no change as compared with a new unused abrasive, and had a high purity. Also, as is clear from FIGS. 2, 3 and 4, the reclaimed abrasive is not inferior in all of X-ray diffraction, particle size distribution, and microscopic observation results as compared with a new unused abrasive. In the X-ray peak pattern, a corundum crystal alumina and zircon beak is clearly precipitated. In addition, the particle size distribution and the particle shape showed almost no change, indicating that the abrasive had characteristics that could be sufficiently reused as a wafer abrasive as it was.

Next, a polishing test was carried out using the above-mentioned recycled abrasive and a new unused abrasive. As a test method, suspend the abrasive in water and wrapping oil, grind the object to be polished using a lapping machine, perform a performance test (grinding speed, surface roughness, scratch) in the following manner, and check the results. Table 3
It was shown to.

Grinding speed--A 30 inch silicon wafer was used as the object to be polished, a machine made by Fujikoshi Co., Ltd. was used as a lapping machine, and a 3 inch φ work was weighted at 100 g / cm ² .
Polishing was performed at a rotation speed of 60 rpm and a slurry injection amount of 100 ml / min. The composition of the polishing slurry is 450 g of lapping oil and 2250 ml of water with respect to 600 g of the abrasive. Surface roughness—The silicon wafer after polishing of the object to be polished was measured with a roughness meter (Tokyo Seimitsu). Scratch—The scratched surface of the silicon wafer after polishing of the object to be polished was examined using a 40 × optical microscope.

As is clear from the results shown in Table 3, it was confirmed that the reclaimed abrasive had no inferiority in the polishing performance such as the grinding speed, the surface roughness and the scratches as compared with the new unused abrasive.

[0025]

[Table 3]

[0026]

Example 2 A regenerated product of a mixture of the molten Al2O3 component and the ZrSiO4 component obtained in Example 1 had an average of 40 μm and a molten Al2O3 component having an average particle size of 40 μm with respect to the abrasive (12 μm average particle size) component. Z with particle size
Abrasive 1 regenerated as addition and mixing treatment of rSiO4 component
0 kg, 1 kg of molten Al2O3 component and ZrSiO
5 kg of the four components were added and mixed with a ball mill. The particle size of the mixed powder was 12 to 40 µm. Also, for 10 kg of the regenerated abrasive, a molten A having an average particle diameter of 80 μm was used.
5 kg of 12O3 component was added and mixed with a ball mill. The particle size of the mixed powder was 12 to 80 μm. The particle size of the abrasive can be freely changed by adding and mixing a molten Al2O3 component or a ZrSiO4 component having different particle diameters. The performance test (grinding speed, surface roughness, scratch) of the abrasive thus obtained was carried out in the same manner as in Example 1, and the results are shown in Table 4. As is clear from the results shown in Table 4, a new molten Al2O
By adding and mixing the three components or the molten Al2O3 component and the ZrSiO4 component, a wide range of abrasives having different particle sizes can be obtained, and it has been confirmed that they can be sufficiently used in grinding speed, surface roughness, scratching and other polishing performance. did it.

[0027]

[Table 4]

[0028]

As is apparent from the above, according to the present invention, a silicon wafer polishing waste liquid mainly composed of a mixture of a molten Al2O3 component and a ZrSiO4 component is solid-liquid separated into an abrasive component and a solution by a vacuum drum filter. Molten Al2O
A solid content mainly composed of a mixture of the three components and the ZrSiO4 component is dispersed in water, and coarse foreign substances are removed by sieving.
Abrasives and silicon were separated by a wet classifier, and again, after solids were dispersed in water, iron was removed by magnetic force.
According to the method for treating a silicon wafer polishing waste liquid by drying and regenerating an abrasive, there is an effective effect of obtaining a new stable abrasive from waste. Further, when the pore size of the filter medium of the vacuum drum filter is in the range of 3 μm to 10 μm, there is an effect that the solid content having a different particle size in the abrasive waste liquid is accurately extracted. Further, a new molten Al2O3 component or Zr is added to the abrasive component of the mixture of the regenerated molten Al2O3 component and the ZrSiO4 component.
By adding and mixing the SiO4 component within the range, the particle size can be controlled, and there is an effective effect of obtaining an abrasive having a wide application range. And the obtained abrasive has the effect of being an inexpensive and stable quality abrasive. In addition, there is a great industrial advantage because the amount of abrasive waste that needs to be disposed of can be significantly reduced, and it is also excellent as an environmental protection technology. Furthermore, it is possible to reduce wasteful costs required for waste disposal. Can also be.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a method for treating a wafer polishing waste liquid according to the present invention.

FIG. 2 is an X-ray diffraction diagram of a recycled abrasive (a) and a new unused abrasive (b)

FIG. 3 is a particle size distribution diagram of a recycled abrasive (a) and a particle size distribution diagram of a new unused abrasive (b)

FIG. 4 is a micrograph of a recycled abrasive (a) and a micrograph of a new unused abrasive (b).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum type drum filter 2 Dispersion tank 3 Sieve 4 Pump 5 Wet classifier 6 Drainage treatment 7 Iron removal machine 8 Dryer 9 Vibrating sieve

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 3, 1999 (1999.3.3)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

Microscope observation: The magnification was × 2000 using a microscope manufactured by Olympus Corporation.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

[0027]

[Table 4]

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiromitsu Taki 7078 Shimanouchi, Oaza, Miyazaki-shi, Miyazaki F-term (reference) 3C047 AA18 AA27 GG13 4D071 AA06 AB70 BA03 DA20

Claims (3)

[Claims] 1. A silicon wafer polishing waste liquid mainly composed of a mixture of a molten Al2O3 component and a ZrSiO4 component is solid-liquid separated into an abrasive component and a solution by a vacuum drum filter, and the mixture of the molten Al2O3 component and a ZrSiO4 component is mainly formed. Solid matter to be dispersed in water to remove coarse foreign matter by sieving, then separated into abrasive and silicon by a wet classifier, again, after solid matter is dispersed in water, iron is removed by magnetic force, then A method for treating a silicon wafer polishing waste liquid, comprising drying and regenerating an abrasive. 2. The method according to claim 1, wherein the pore size of the filter medium of the vacuum drum filter is in the range of 3 μm to 10 μm. 3. An abrasive component 100 of a mixture of a molten Al2O3 component and a ZrSiO4 component regenerated by the method according to claim 1, wherein the molten Al2O3 component is ZrSiO.
An abrasive characterized in that one or more of the four components are added and mixed within a range of 1.0 to 30.0 weight percent.