Abstract:
An apparatus for recycling a grinding slurry capable of effectively removing unwanted components at a reduced cost. Slurry used in a grinding treatment is at first recovered as recovery slurry. The recovery slurry is then recycled so as to obtain recycled slurry. One or more cyclone separators are provided and used for sizing the used slurry to obtain slurry particles having a predetermined particle size. The slurry having the predetermined particle size is supplied as recovery slurry. When the recovery slurry is recycled to produce recycled slurry, one or more supersonic wave generators are used for irradiating supersonic waves to the recovery slurry.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    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.  
           [0002]    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.  
           [0003]    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.  
           [0004]    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.  
           [0005]    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).  
           [0006]    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.  
           [0007]    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.  
           [0008]    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.  
           [0009]    However, the above conventional apparatus has been found to have the following problem. Namely, since there is a relatively large load on a filter  15  (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  31  (a rear stage filter) will become short.  
         SUMMARY OF THE INVENTION  
         [0010]    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.  
           [0011]    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.  
           [0012]    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.  
           [0013]    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.  
           [0014]    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.  
           [0015]    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.  
           [0016]    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 predetermined particle size. Moreover, the apparatus includes recycling means capable of recycling the second sizing slurry, so as to obtain recycled slurry which can be used again in the grinding treatment. At this time, it is desired to provide one or more dispersing means (for example, supersonic wave generator) for dispersing the above discharge slurry. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is an explanatory view schematically showing a conventional apparatus for recycling grinding slurry used for grind chemical machine.  
         [0018]    [0018]FIG. 2 is an explanatory view schematically showing an improved apparatus for recycling grinding slurry used for grind chemical machine, formed according to one embodiment of the present invention.  
         [0019]    [0019]FIG. 3 is also an explanatory view schematically showing an improved apparatus for recycling grinding slurry used for grind chemical machine, formed according to another embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    In the following, a conventional apparatus for recycling grinding slurry will be described with reference to FIG. 1. Namely, when slurry used for grinding a chemical machine is to be recycled, a commonly used apparatus is as shown in FIG. 1.  
         [0021]    At first, an amount of a slurry is supplied to a grinding table  11  of a CMP apparatus, Then, a chemical machine such as a wafer is ground on the grinding table  11  o f the CMP apparatus. During the grinding treatment, an amount of slurry dropping from the grinding table  11  of the CMP apparatus is allowed to at first stay in a slurry container  12 . Then, the slurry staying in the slurry container  12  is recovered as used slurry by means of a pump  13 . Subsequently, the used slurry is caused to pass through a filter  15  by way of a valve  14 . The filter  15  is provided to separate unwanted large particles from the used slurry. Namely, the filter  15  is a filter element having relatively large mesh eyes. Separated slurry will thus become filtered slurry which arrives at a tank  18  through a valve  16  and a valve  17 , and at the same arrives at a tank  20  by way of the valve  16  and another valve  19 .  
         [0022]    Furthermore, the valves  21 ,  22  and  23  are connected with the valve  16 . In particular, the valve  23  is connected to both of the valves  26  and  27  through a composition analyzer  24  and a pump  25 . The valves  26  and  27  are respectively disposed in the open areas of tanks  18  and  20  by means of respective pipes. Further disposed on the open areas of the tanks  18  and  20  are valves  28  and  29 , respectively. The valves  28  and  29  are then connected to a filter  31  through a pump  30 . In this way, an amount of slurry serving as grinding slurry can be supplied from the filter  31  to the grinding table  11  of the CMP apparatus.  
         [0023]    By properly opening and closing the valves  16 ,  17  and  19 , the above filtered slurry is recovered as a recovery slurry so as to be moved selectively into the tank  18  or the tank  20 . Once the recovery slurry is recovered into the tank  18  or the tank  20 , the valve  16  is closed. Afterwards, the pump  25  is driven. Upon driving the pump  25 , the recovery slurry is drawn up from the tank  18  and the tank  20 . In this way, the recovery slurry can be again circulated into the tank  18  by way of the composition analyzer  24  and the valve  23  as well as the valve  17 . Further, the recovery slurry is also circulated into the tank  20  by way of the composition analyzer  24  and the valve  23  as well as the valve  19 . At this time, the valve  21  and the valve  22  are in their opened positions. Therefore, a fresh slurry and a pure water may be supplied to the slurry recycling apparatus through the valves  21  and  22  (the fresh slurry has a higher concentration than the recovery slurry).  
         [0024]    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 in circulation is measured by the above composition analyzer. Subsequently, once the concentration of the slurry in circulation becomes equal to a predetermined concentration, the valves  21  and  22  are closed, and the pump  25  is stopped.  
         [0025]    After treating in the above-described manner, the recovery slurry will thus become recycled slurry having a predetermined concentration. Then, when the recycled slurry is used for performing a grinding treatment, recycled slurry supply valves (the valves  28  and  29 ) for supplying the recycled slurry to the grinding table of the CMP apparatus are opened and the pump  30  is driven. By virtue of this, the recycled slurry can be drawn up from the tank  18  and/or the tank  20 . Subsequently, the recycled slurry is filtered in the filter  31 , and is supplied as grinding slurry to the grinding table  11  of the CMP apparatus. In fact, the filter  31  is provided to separate unwanted small particles failed to be caught up in the filter  15 . This means that the filter  31  is a filter element having smaller mesh eyes.  
         [0026]    During wafer grinding treatment, when a slurry is to be recovered and recycled, a used slurry is recovered into either the tank  18  or the tank  20 , with the recovering and recycling as well as its supplying towards the grinding table all carried out in a batch treatment manner.  
         [0027]    Next, referring to FIG. 2, description will be given to one embodiment of an improved apparatus formed according to the present invention for recycling grinding slurry used for a chemical machine. However, in the drawing of FIG. 2, elements identical to those of the recycling apparatus shown in FIG. 1 will be represented by the same reference numerals.  
         [0028]    The illustrated apparatus for recycling grinding slurry used for a chemical machine is equipped with a grinding table  11  for grinding a chemical machine such as a wafer. As will be described in the following, slurry is supplied to the grinding table  11  so as to carry out a grinding treatment for grinding a chemical machine. During the grinding treatment, the slurry dropping from the grinding table  11  is allowed to at first stay in the slurry container  12 . The slurry accumulated in the slurry container  12  is recovered as used slurry by virtue of a pump  13 . The used slurry is then supplied to a cyclone separator  41  by way of a valve  14 .  
         [0029]    The cyclone separator  41  is connected to a tank  18  through a valve  16  and a valve  17 . Further, the cyclone separator  41  is also connected to the tank  20  through the valves  16  and  19 . Moreover, the cyclone separator  41  is also connected to a drain. In fact, the used slurry is sized in the cyclone separator  41  so that only particle of a predetermined size are recovered. Subsequently, the used slurry is selectively recovered into the tank  18  or the tank  20  as described later. On the other hand, the slurry particles having other sizes than that predetermined in the cyclone separator  41  are discharged as a waste liquid to the drain,  
         [0030]    As shown in the drawing, in an area between the valve  16  and the valve  17 , the valve  16  is connected with the valves  21 ,  22  and  23 . Specifically, the valve  23  is connected through the composition analyzer  24  to a supersonic wave oscillator  42 . A pump  25  is connected between the supersonic oscillator  42  and the composition analyzer  24 . The pump  25  is also connected to both the valve  26  and the valve  27 . Pipes extending from the valves  26  and  27  are introduced into the tanks  18  and  20 .  
         [0031]    Valves  28  and  29  are disposed in the vicinity of the tanks  18  and  20 . The valves  28  and  29  are also connected to a filter  31  by way of a pump  30 . The slurry having passed through the filter  31  is supplied as grinding slurry to the grinding table  11 .  
         [0032]    By properly opening and closing the valve  16  and the valve  17  as well as the valve  19 , the used slurry can be selectively recovered as a recovery slurry into the tank  18  or the tank  20 . Once the recovery slurry is recovered into the tank  18  and the tank  20 , the valve  16  is closed and then the pump  25  is driven. With the driving of the pump  25 , the recovery slurry is drawn up from the tank  18  and the tank  20 . The recovery slurry drawn up in this manner is circulated back into the tank  18  through the supersonic wave oscillator  42 , the composition analyzer  24  and the valve  17 . Meanwhile, the drawn-up recovery slurry is also circulated back into the tank  20  by way of the supersonic wave oscillator  42 , the composition analyzer  24  and the valve  19 . The recovery slurry in circulation is irradiated by a supersonic wave from the supersonic wave oscillator  42 . The slurry irradiated by the supersonic wave is then easily dispersed so that its aggregated state can be desirably broken down. After that, the valve  21  and  22  are opened so that pure water and fresh slurry may be supplied to the recycling apparatus.  
         [0033]    In this way, pure water and a fresh slurry may be supplied continuously to the recycling apparatus, while the concentration of the slurry in circulation is measured by the composition analyzer  24 . When the concentration of the slurry in circulation becomes equal to a predetermined desired concentration, the valves  21  and  22  are closed. At this time, the pump  25  is stopped.  
         [0034]    By treating in the above-described manner, after the recovery slurry has been recycled so that the recycled slurry has been obtained, and when the recycled slurry is used for carrying out a grinding treatment, the valve  28  and/or valve  29  are opened and the pump  30  is driven. By virtue of this, the recycled slurry will be drawn up from the tank  18  and/or the tank  20 . The recycled slurry is then filtered by the filter  31  and supplied as grinding slurry to the grinding table  11 . The filter  31  is provided to separate unwanted small particles failed to be separated in the cyclone separator  41 . Therefore, the filter  31  is a filter element and it is thus required to be formed with many mesh eyes of small size capable of separating unwanted small particles.  
         [0035]    In the above-described slurry recycling apparatus, when a wafer is being ground and slurry is being recovered and recycled, the used slurry is recovered into either the tank  18  or the tank  20 . Here, the recovering of the slurry and the recycling of the slurry, as well as the supplying of the slurry to the grinding table are all performed in a batch treatment manner.  
         [0036]    Next, referring to FIG. 3, a description will be given to another embodiment of an improved apparatus formed according to the present invention for recycling grinding slurry used for a chemical machine. However, in the drawing of FIG. 3, elements identical to those of the recycling apparatus shown in FIG. 2 will be represented by the same reference numerals.  
         [0037]    As shown in FIG. 3, an apparatus formed according to the present embodiment for recycling the grinding slurry used for a chemical machine, has a further cyclone separator  43  which is different from the above cyclone separator  41 . Here, the cyclone separator  43  is connected with the above cyclone separator  41 . Used slurry is supplied to the cyclone separator  43  by way of the valve  14 . In fact, the cyclone separator  43  is used for sizing the used slurry so as to obtain certain slurry particles having a predetermined particle size. The slurry particles (having the predetermined particle size) sized by the cyclone separator  43  are then recovered as a recovery slurry into the tank  18  and/or the tank  20  through the valves  44  and  45 , respectively. On the other hand, the slurry particles having different particle size from that predetermined in the cyclone separator  43  are at first recovered to a buffer tank  46 . At this time, a supersonic wave is irradiated to the slurry staying in the buffer tank  46  from the supersonic wave oscillator  47 , The slurry staying in the buffer tank  46  is dispersed thereby.  
         [0038]    Subsequently, the slurry staying within the buffer tank  46  is drawn up by virtue of a liquid transporting pump  48 . The slurry drawn up in this manner is then supplied through the valve  49  to the cyclone separator  41 . At this time, the slurry is again sized in the cyclone separator  41  in the same manner as described with reference to FIG. 2. The sizing slurry particles are then selectively recovered into the tank  18  or the tank  20 .  
         [0039]    Afterwards, as described with reference to FIG. 2, the recovery slurry staying in the tank  18  and/or the tank  20  can be used as recycled slurry. Therefore, the recycled slurry is thus supplied as grinding slurry to the grinding table  11 , by virtue of the pump  30 .  
         [0040]    As described above, according to the present invention, since one or more than one cyclones are employed to size the particles of used slurry, and since a recycling treatment is carried out after the sizing step, it is possible to reduce the cost associated with the filters. In addition, since the particle size of recycled slurry is in a stabilized condition, it is possible to obtain an extended life time for the filters.