JP2002016027A - Abrasive material recovering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive material recovery device for efficiently recovering abrasive particles from waste water which contains abrasive material and is discharged out in a CMP process, which is employed in a semiconductor manufacturing factory or the like. SOLUTION: An abrasive material recovering device for recovering abrasive material from waste water discharged out in a CMP process is equipped with a film-separating means, to which waste water discharged out in a CMP process is introduced and a cleaning means which rinses a concentrated water obtained by the film separating means with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for collecting abrasives. More specifically, the present invention relates to a CMP (Chemical Mechanical Polishing) used in a semiconductor manufacturing plant or the like.
cal Mechanical Polishing) from the polishing process wastewater containing the abrasive discharged from the process,
The present invention relates to an abrasive collection device for efficiently collecting and reusing abrasive particles.

[0002]

2. Description of the Related Art An insulating film formed on a semiconductor wafer,
The surface of a coating such as a metal thin film is required to be a highly flat surface, and as a means for performing polishing, a polishing slurry is interposed between a polishing member such as a polishing pad and a semiconductor wafer. CMP is employed. CM
Examples of the abrasive used in P include silica fine particles having a good dispersibility and uniform particle diameter, ceria having a high polishing rate,
Alumina having high hardness and stable is used. These abrasives are provided by a manufacturer as a slurry in which particles having a predetermined particle size and concentration are dispersed in water, and are diluted to a predetermined concentration when supplied to a CMP machine according to each site. Usually, this slurry contains pH adjusters such as potassium hydroxide, ammonia, organic acids, and amines, surfactants as dispersants, and oxidizing agents such as hydrogen peroxide, potassium iodate, and iron (III) nitrate. Or the like is added in advance, or separately added during polishing. These polishing slurries are expensive and expensive,
From the viewpoint of reducing the amount of industrial waste, it is desirable to reuse it. However, the polishing process wastewater has a reduced abrasive concentration due to dilution. In addition, semiconductor wafers, coating materials, polishing pad debris, fine particles in which the abrasive is broken, and particles generated by agglomeration of the abrasive particles. Solid impurities with a large diameter are mixed. Therefore, if such polishing process wastewater is reused without any treatment as an abrasive, the polishing rate decreases due to a decrease in the concentration of the abrasive, and scratches on the wafer surface are generated. Further, since the additive chemical is used, the polishing process wastewater contains the residual additive chemical, and further contains impurities made of metal ions generated by polishing. Therefore, when the recovered slurry is reused, these impurities hinder concentration adjustment, making concentration management difficult. For these reasons, the polishing wastewater cannot be circulated and reused as it is. Therefore, when reusing, it is necessary to remove impurities such as coarse solids and salts from the polishing wastewater, and to perform a concentration treatment to re-prepare a polishing slurry having a predetermined composition. Conventionally, development of various technologies for wastewater treatment in a CMP process has been attempted. For example, a method has been proposed in which wastewater from the CMP process is treated with a microfiltration membrane to remove coarse solids, then treated with an ultrafiltration membrane, a chemical is added, the concentration is adjusted, and the slurry is reused as an abrasive slurry. ing. Even by such a method, it is possible to remove coarse solids, and it is possible to suppress generation of scratches on the wafer surface. However, since the concentration of the polishing agent and the pH are adjusted by adding a new agent while the added chemicals and salts remain, these impurities hinder the concentration adjustment, and the result is that the concentration adjustment cannot be performed well. Has become. In addition, adverse effects on the product such as contamination are caused. In particular, when the particle size distribution of the abrasive in the slurry is controlled uniformly by using an organic dispersant to maintain the particle size distribution within a predetermined range, the effect on the particle size is large. Therefore, it is important to remove these residual drugs and salts.

[0003]

SUMMARY OF THE INVENTION The present invention efficiently recovers and reuses abrasive particles from a polishing process wastewater containing an abrasive discharged from a CMP process used in a semiconductor manufacturing plant or the like. The purpose of the present invention is to provide an apparatus for collecting abrasives for the purpose.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a membrane separation means for introducing wastewater from the CMP step, and a concentrated water obtained by membrane separation. Combining the washing means to wash the water, diluting and redispersing the concentrated water by adding water, and then performing the operation of concentrating by membrane separation and washing with water to effectively remove impurities such as salts and organic matter in the wastewater of the CMP process. And found that a slurry of high-purity abrasive particles could be recovered, and based on this finding, completed the present invention.
That is, the present invention provides (1) an apparatus for recovering an abrasive from wastewater from a CMP step, comprising: a membrane separation means for introducing the wastewater from the CMP step; and a washing means for washing the concentrated water obtained by the membrane separation means with water. 2. The abrasive recovery device according to claim 1, comprising: a polishing agent recovery device, (2) a concentration adjustment device into which a liquid from the cleaning device is introduced, and
(3) An apparatus for recovering an abrasive according to item 1, comprising a filtration treatment means for removing coarse solids before the membrane separation means or between the membrane separation means and the concentration adjustment means. . Further, as a preferred embodiment of the present invention, (4) the apparatus for collecting abrasives according to item 1, wherein the membrane separation means comprises a ceramic membrane mainly composed of columnar β-type silicon nitride crystals.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process system diagram of one embodiment of the abrasive recovery apparatus of the present invention. The abrasive recovery device of this aspect includes a CMP machine unit, a pre-filtration unit, a concentration unit, and a concentration adjustment unit. The CMP machine section includes a slurry supply tank 1 for diluting a new slurry to a predetermined concentration and storing the slurry, a CMP machine 2 for polishing a wafer with the slurry supplied from the slurry supply tank, and a waste slurry tank 3 for storing a waste slurry after polishing. Having. The pre-filtration unit includes a slurry receiving tank 4 for storing waste slurry from the CMP machine unit, a filter 5 for filtering and removing coarse solids in the waste slurry supplied from the slurry receiving tank, and a filter for removing coarse solids. It has a filtered water tank 6 for storing the removed filtered water. The concentrating unit has a membrane separation means 7 for concentrating the filtered water from the pre-filtration unit. The concentration adjusting unit includes a concentration adjusting tank 9 in which the dispersant diluted in the dispersant dilution tank 8 is added to the filtered water supplied from the pre-filtration unit, and reaggregated coarse particles in the slurry sent from the concentration adjusting tank. And a slurry stirring tank 11 for storing the recovered slurry.

[0006] The slurry discharged from the CMP machine and containing abrasive having an average particle size of about 0.05 to 0.5 µm is
Once received in the slurry receiving tank 4 and then filtered by a filter 5 as a filtering means for removing coarse solids at the preceding stage of the membrane separation means, polishing pad debris having a large particle size of about 0.7 to 1.5 μm. And other impurities are removed.
By removing large particle size impurities in the waste slurry,
The load on the membrane separation means can be reduced. When a microfiltration membrane (MF) having a pore size larger than the abrasive and smaller than the polishing debris is used as the filter, a cake layer is formed on the membrane surface, so that even the abrasive having a small particle diameter is captured. The result is severe clogging. Therefore,
A microfiltration membrane having an aperture larger than the polishing pad debris is suitable, and a microfiltration membrane having a pore size of 10 to 100 μm is preferable.
A microfiltration membrane having a pore size of 25 to 75 μm is more preferred. The material of the microfiltration membrane is not particularly limited, and examples thereof include polypropylene, polycarbonate, cellulose triacetate, polyamide, polyvinyl chloride, and polyvinylidene fluoride. In particular, it is possible to suitably use a microfiltration membrane having any of these materials and having a multi-layered filtration element whose pores become finer from the primary side to the secondary side.

There are no particular restrictions on the conditions for the filtration treatment using the microfiltration membrane, but it is preferable to filter the entire amount of the waste slurry at a pressure of 0.01 to 0.5 MPa. In operation, when the pressure difference between the inlet and the outlet becomes 0.01 MPa or more, it is preferable to perform backwashing or replace the membrane. Also,
By providing filters in two or more stages and providing a filter with a large pore size in the first stage and a filter with a small pore size in the second stage, the life of the membrane can be extended. In the apparatus of the present embodiment, the filter 5 is provided before the membrane separation means.
Is provided to remove the coarse solids, but a filtration treatment means for removing the coarse solids may be provided after the membrane separation means, that is, between the membrane separation means and the concentration adjusting means.
If the filter as the filtration means is provided at the subsequent stage of the membrane separation means, the liquid whose membrane has been concentrated and whose absolute amount has been reduced is targeted, so that the life of the filter can be extended.

[0008] The filtered water treated by the filter 5 which is the filtration means at the former stage is stored in a filtered water tank 6 and then sent to a concentrating section comprising a membrane separation means 7. Although there is no particular limitation on the membrane used for the membrane separation means, a monolithic ceramic film obtained by sintering alumina oxide, a ceramic film mainly made of columnar β-type silicon nitride crystal obtained by sintering silicon nitride, and the like are preferably used. Can be. A ceramic film mainly composed of columnar β-type silicon nitride crystals is formed from a mixture of silicon nitride powder and other additive powders, heat-treated at a high temperature to form a porous body, and further treated with acid and alkali. And dissolving and removing additives other than silicon nitride. A ceramic film composed of a microstructure in which columnar β-type silicon nitride crystals are intertwined has a high porosity,
An element having a high strength and a single-layer honeycomb structure can be obtained. In the CMP process wastewater using an organic dispersant, in order to prevent clogging with the dispersant and slurry,
It is particularly preferable to use a silicon nitride ceramic film having a high porosity and a high flux even at a low flow rate. There is no particular limitation on the pore size of the silicon nitride ceramic film used,
An ultrafiltration membrane (UF) or microfiltration membrane (MF) having a pore size of 0.01 to 0.5 μm can be suitably used. Although there is no particular limitation on the degree of concentration in the membrane separation means, it is usually preferable to set the concentration conditions so that the concentration of the abrasive in the concentrated water is 5 to 50% by weight. In addition, the processing conditions are set to 0.
A batch-type or semi-batch type concentration method using a cross flow in which concentrated water is circulated to the filtered water tank 6 via the concentrated water pipe 12 at a pressure of 01 to 0.5 Mpa is preferable. The permeated water separated by the membrane separation means can be discharged to the outside of the system for drainage treatment. However, it is preferable that a part of the permeated water be stored in a pit and used as backwash water at the time of membrane cleaning.

The washing means for washing the concentrated water obtained by the membrane separation means in the apparatus of the present embodiment is constituted by means for supplying washing water to the filtered water tank and means for diluting the concentrated water with the washing water in the filtered water tank. Have been. Washing can be performed by adding washing water to concentrated water, diluting and redispersing, and then concentrating by membrane separation.Using ultrapure water for washing effectively removes impurities such as salts and organic substances. And a slurry of a high-purity abrasive can be obtained. The degree of concentration of the concentrated water is measured by a Coriolis type densitometer,
Monitoring is performed by a level meter or the like, and the concentrated water concentrated to a predetermined concentration is diluted by supplying the washing water by the washing water supply means and stirring. The concentrated water diluted by the washing water can be circulated between the membrane separation means 7 and the filtered water tank 6 to perform the concentration and the water washing simultaneously. By this water washing, impurities such as salts, organic substances, and fine polishing debris are removed by the membrane separation means. If the amount of washing water used for water washing is too small, a sufficient washing effect cannot be obtained, and if it is excessively large, the amount of water used increases and the cost of recovery treatment increases.
Normally, it is preferable to use about 10 to 100 times by volume of the washing water with respect to the concentrated water, and perform the washing twice. Ultrapure water is usually used as the washing water, but it is preferable to use ultrapure water to which an appropriate amount of a dispersant has been added in order to prevent agglomeration of the abrasive. In the apparatus of the present invention, the cleaning means is not limited to the configuration including the filtered water tank, but may be provided with a concentrated water tank for storing concentrated water at a stage preceding the concentration adjusting tank to supply the cleaning water to constitute the cleaning means. Can also.

After the washing, the slurry concentrated to a predetermined concentration is introduced from the washing means into a concentration adjusting tank 9 at a subsequent stage as a concentration adjusting means, and a dispersant diluted with ultrapure water is supplied to the slurry to a predetermined concentration. Adjusted. According to the apparatus of the present invention, since salts, organic substances, and the like are removed by washing, the concentration can be easily adjusted, and impurities such as salts and organic substances are extremely small, and it is possible to recover as a slurry equivalent to a new article. . The density can be detected using a Coriolis type densitometer or the like. The slurry adjusted to a predetermined concentration is used to remove abrasives coarsened by re-agglomeration in a filter 10 as a filtration processing means provided at the latter stage of the concentration adjustment tank, and after adjusting to a desired particle size distribution, It is stored in the stirring tank 11 and taken out as a recovered slurry. As the filter used here, the same filter as the microfiltration membrane used as the filtration treatment means in the preceding stage of the membrane separation means can be used. The number of filters is not limited to one, but may be two or more. In the apparatus of the present invention, the slurry stirring tank 11 is not always necessary, and the slurry can be returned to the slurry supply tank 1 of the CMP machine directly and recycled.

[0011]

According to the abrasive recovery apparatus of the present invention, C
A recovered slurry that can be easily reused as an abrasive slurry can be efficiently obtained from the MP process wastewater. Moreover, since the concentration is adjusted after removing impurities by washing with water, a slurry having the same performance as a new slurry can be recovered. Therefore, according to the apparatus of the present invention, the amount of expensive abrasive slurry used in the wafer CMP process can be reduced, and the slurry cost can be reduced. Further, since the amount of discharged wastewater is reduced, the load on the wastewater treatment system and the like can be reduced, and the amount of industrial waste treated can be reduced.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of one embodiment of an abrasive recovery apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slurry supply tank 2 CMP machine 3 Waste slurry tank 4 Slurry receiving tank 5 Filter 6 Filtration water tank 7 Membrane separation means 8 Dispersant dilution tank 9 Concentration adjustment tank 10 Filter 11 Slurry stirring tank 12 Concentrated water piping

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C02F 1/44 C02F 1/44 EF term (reference) 3C047 GG14 GG17 3C058 AA07 AC04 CA01 CB03 CB06 DA12 4D006 GA06 GA07 JA56A KA02 KA63 KA72 KB14 KD04 KD14 KD17 KE07Q KE07R MA22 MB02 MC03 MC03X NA39 NA54 PA04 PB08 PB15 PB70 PC01

Claims (3)

[Claims] An apparatus for recovering an abrasive from wastewater from a CMP process, comprising: a membrane separation means into which wastewater from the CMP process is introduced;
A polishing means for washing the concentrated water obtained by the membrane separation means with water. 2. The apparatus according to claim 1, further comprising a concentration adjusting means for introducing a liquid from the cleaning means. 3. The polishing material recovery apparatus according to claim 1, further comprising a filtration treatment means for removing coarse solids before the membrane separation means or between the membrane separation means and the concentration adjustment means.