Liquid purification or separation – Structural installation – Closed circulating system
Reexamination Certificate
2001-04-05
2003-04-15
Reifsnyder, David A. (Department: 1723)
Liquid purification or separation
Structural installation
Closed circulating system
C210S194000, C210S195100, C210S243000, C210S252000, C210S512100, C210S512200, C210S748080
Reexamination Certificate
active
06547961
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for recycling a grinding slurry, particularly to a grinding slurry recycling apparatus which can be used at a time when a chemical machine is being ground.
In the following, description will be given to explain a conventional apparatus for recycling grinding slurry. Usually, an apparatus described below has been commonly employed for recycling slurry used for a process of grinding a chemical machine.
At first, an amount of slurry is supplied to a grinding table of a CMP apparatus. Then, a chemical machine such as a wafer is ground on the grinding table of the CMP apparatus. During the grinding treatment, an amount of slurry dropping from the grinding table of the CMP apparatus is allowed to at first stay in a slurry container. Then, the slurry staying in the slurry container is recovered as used slurry by means of a first pump. Afterwards, the used slurry is caused to pass through a first filter by way of a first valve. The first filter is provided to separate unwanted large particles from the used slurry. Namely, the first filter is a filter element having relatively large mesh eyes. Separated slurry will thus become filtered slurry which arrives at a first tank through a second valve and a third valve, and at the same time arrives at a second tank by way of the second valve and a fourth valve.
Furthermore, a fifth valve and a sixth valve as well as a seventh valve are connected with the second valve. In particular, the seventh valve is connected to both an eighth valve and a ninth valve through a composition analyzer and a second pump. The above eighth valve and the ninth valve are respectively disposed in the open areas of the first and second tanks by means of respective pipes. Further disposed on the open areas of the first and second tanks are a tenth valve and an eleventh valve, respectively. The tenth valve and the eleventh valve are then connected to a second filter through a third pump. In this way, an amount of slurry serving as grinding slurry can be supplied from the second filter to the grinding table of the CMP apparatus.
By properly opening and closing second, third and fourth valves, the filtered slurry is recovered as recovery slurry so as to be moved selectively into the first tank or the second tank. Once the recovery slurry is recovered into the first tank or the second tank, the second valve is closed. Afterwards, the second pump is driven. Upon driving the second pump, the recovery slurry is drawn up from the first tank and the second tank. In this way, the recovery slurry can be again circulated into the above first tank by way of the composition analyzer and the above seventh valve as well as the above third valve. Further, the recovery slurry is also circulated into the second tank by way of the composition analyzer and the above fourth valve. At this time, the fifth valve and the sixth valve are in their opened positions. Subsequently, a fresh slurry and a pure water are supplied to the slurry recycling apparatus through the fifth valve and the sixth valve (the fresh slurry has a higher concentration than the recovery slurry).
In this way, the pure water and the fresh slurry are supplied to the slurry recycling apparatus, while at the same time the concentration of the slurry being circulated is measured by the above composition analyzer. Subsequently, once the concentration of the slurry in circulation becomes equal to a predetermined concentration, the fifth valve and the sixth valve are closed, while the second pump is stopped.
After treating in the above-described manner, the recovery slurry will thus become a recycled slurry having a predetermined concentration. Then, when the recycled slurry is used for performing a grinding treatment, recycled slurry supply valves (the tenth valve and the eleventh valve) for supplying the recycled slurry to the grinding table of the CMP apparatus are opened and the third pump is driven. By virtue of this, the recycled slurry can be drawn up from the first tank and/or the second tank. Subsequently, the recycled slurry is filtered in the second filter, and is supplied as grinding slurry to the grinding table of the CMP apparatus. In fact, the above second filter is provided to separate unwanted small particles failed to be caught up in the above first filter. This means that the above second filter is a filter element having smaller mesh eyes.
In the above slurry recycling apparatus, during wafer grinding treatment, when used slurry is to be recovered and recycled, the used slurry is recovered into either the first tank or the second tank. The recovering, the recycling, and the supplying towards the grinding table carry out in a batch treatment manner.
However, the above conventional apparatus has been found to have the following problem. Namely, since there is a relatively large load on a filter
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(a front stage filter) which is provided for catching up unwanted large particles such as grinding chips, the front stage filter has only a short life time. In order to solve this problem, although it is allowed to dispose a plurality of filters in several different stages, this will cause an increase in the cost of the filters, thus making the recycling apparatus too expensive. On the other hand, if the front stage filter is replaced by a filter having larger mesh eyes, the life time of the filter
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(a rear stage filter) will become short.
SUMMARY OF THE INVENTION
The present invention has been suggested in order to eliminate the above-described problems. It is an object of the invention to provide an apparatus for recycling grinding slurry which is used for a chemical machine, making it possible to extend the life time of both the front stage filter and the rear stage filter.
It is another object of the present invention to provide an improved apparatus for recycling a grinding slurry, which is capable of effectively removing unwanted components at a reduced cost.
A grinding slurry recycling apparatus according to the present invention is an apparatus for recovering, as recovery slurry, used slurry used in a grinding treatment, and for recycling the recovery slurry. The recycling slurry is used as the grinding slurry. Specifically, the grinding slurry recycling apparatus of the present invention, comprises a cyclone separator for sizing the particles of the used slurry to obtain sizing slurry particles having a predetermined particle size, and for supplying, as recovery slurry, the sizing slurry having the predetermined particle size. The grinding slurry recycling apparatus further comprises recycling means for recycling the recovery slurry, so as to obtain recycled slurry.
Furthermore, the recycling means includes dispersing means for dispersing the recovery slurry. Moreover, the dispersing means is for example a supersonic wave generator capable of irradiating a supersonic wave to the recovery slurry.
In addition, the recycling means further includes a recycled slurry producing means capable of producing mixed slurry as a recycled slurry by adding and mixing a fresh slurry and a pure water into the sizing slurry. Further, when the concentration of the mixed slurry becomes equal to a predetermined concentration, the mixing of the fresh slurry and the pure water into the recovery slurry is stopped.
Alternatively, the grinding slurry recycling apparatus comprises a first cyclone separator for sizing the particles of the recovery slurry so as to obtain sizing slurry particles having a predetermined particle size. The first cyclone separator supplies, as the recovery slurry, first sizing slurry having the predetermined particle size, and discharges, as discharge slurry, an amount of slurry not containing the first sizing slurry.
The apparatus further comprises supplying means for supplying the discharge slurry, and a second cyclone separator for sizing the particles of the discharge slurry to obtain sizing slurry particles having a predetermined particle size, and for supplying, as the recovery slurry, a second sizing slurry having the pre
Kondo Ikuyo
Kondo Nobuki
Uto Mitsuyoshi
Kondo Ikuyo
NEC Electronics Corporation
Reifsnyder David A.
Sughrue & Mion, PLLC
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