JP2004321997A - Filter apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter apparatus equipped with a mechanism capable of efficiently recovering a substance to be removed precipitated in a tank. <P>SOLUTION: This filter apparatus 20 has a tank 50 for housing a fluid containing the substance to be removed, a filter device 53 immersed in the tank 50 and a recovery tank 15 communicating with the lower part of the tank 50 through a valve V to permit the sedimentation of the substance to be removed. The recovery tank 15 can be separated from the tank 50 and is constituted so as to recover the substance to be removed precipitated in the recovery tank 15 by bringing the valve V to a shut-off state to separate the recovery tank 15 from the tank 50. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a filtration device, and more particularly, to a filtration device provided with a mechanism capable of efficiently collecting a substance to be removed settling in a tank.
[0002]
[Prior art]
At present, reduction of industrial waste, separation and reuse of industrial waste, or prevention of discharge of industrial waste to the natural world are important themes from an ecological point of view, and are business issues in the 21st century. In this industrial waste, there are various fluids containing the substances to be removed.
[0003]
These are expressed in various terms such as sewage, drainage, and waste liquid. Hereinafter, a substance in which a substance to be removed is contained in a fluid such as water or a chemical will be referred to as drainage. These wastewaters are used to remove the object to be removed by an expensive filtration device or the like, and the wastewater is reused as clean fluid. ing. In particular, water is returned to the natural world, such as a river or sea, in a clean state that meets environmental standards by filtration, or is reused.
[0004]
However, it is very difficult to employ these devices due to problems such as equipment costs such as filtration processing and running costs, which is also an environmental problem.
[0005]
As can be seen from this, wastewater treatment technology is an important problem from the viewpoint of environmental pollution and recycling, and a system with low initial cost and low running cost is urgently desired.
[0006]
As an example, wastewater treatment in the semiconductor field will be described below. Generally, when grinding or polishing a plate-like body such as a metal, a semiconductor, and a ceramic, preventing a temperature rise of a polishing (grinding) jig or the like due to friction, improving lubricity, attaching grinding chips or cutting chips to the plate-like body. Therefore, a fluid such as water is showered on a polishing (grinding) jig or a plate-like body.
[0007]
Specifically, a method of flowing pure water when dicing or back grinding a semiconductor wafer which is a plate-like body of a semiconductor material has been adopted. In the dicing machine, to prevent the temperature of the dicing blade from rising, and to prevent dicing debris from adhering to the wafer, create a flow of pure water on the semiconductor wafer or discharge water so that the pure water hits the blade. Nozzles are installed and showered. Also, when reducing the wafer thickness by back grinding, pure water is flown for the same reason.
[0008]
The wastewater mixed with grinding dust or polishing waste discharged from the above-mentioned dicing device or back grinding device is filtered and returned to the natural world as clean water, or reused, and the concentrated wastewater is collected and recovered. I have.
[0009]
In the current semiconductor manufacturing, there are two methods of treating wastewater mixed with an object to be removed (dust) mainly composed of Si, a coagulation sedimentation method, and a method combining a filter filtration and a centrifugal separator.
[0010]
In the former coagulation sedimentation method, PAC (polyaluminum chloride) or Al2 (SO4) 3 (sulfuric acid band) or the like is mixed in the wastewater as a coagulant to generate a reaction product with Si and remove this reaction product. The wastewater was filtered.
[0011]
In the latter method, which combines filter filtration and centrifugation, the wastewater is filtered, the concentrated wastewater is centrifuged to collect silicon waste as sludge, and the clean water created by filtering the wastewater is returned to nature. Released or reused.
[0012]
For example, as shown in FIG. 13, wastewater generated during dicing is collected in a raw water tank 201 and sent to a filtration device 203 by a pump 202. Since the filtering device 203 is provided with a ceramic or organic filter F, the filtered water is sent to the recovered water tank 205 via the pipe 204 and reused. Or released to nature.
[0013]
On the other hand, the filtering device 203 is periodically cleaned because the filter F is clogged. For example, the valve B1 on the raw water tank 201 side is closed, the valve B3 and the valve B2 for sending cleaning water from the raw water tank are opened, and the filter F is back-washed with the water in the recovered water tank 205. The wastewater mixed with the high-concentration Si waste generated thereby is returned to the raw water tank 201. The concentrated water in the concentrated water tank 206 is transported to the centrifugal separator 209 via the pump 208, and is separated by the centrifugal separator 209 into sludge (sludge) and a separated liquid. The sludge composed of Si waste is collected in a sludge collection tank 210, and the separated liquid is collected in a separated liquid tank 211. Further, the drainage of the separated liquid tank 211 in which the separated liquid is collected is transported to the raw water tank 201 via the pump 212.
[0014]
These methods occur, for example, when grinding or polishing a solid or a plate-like body made of a metal material such as Cu, Fe, or Al as a main material, or a solid or plate-like body made of an inorganic substance such as ceramic. It was also used when collecting waste.
[0015]
On the other hand, CMP (Chemical-Mechanical Polishing) has emerged as a new semiconductor process technology. The CMP technology provides (1) realization of a flat device surface shape and (2) realization of an embedded structure of a material different from a substrate.
[0016]
(1) is to form a fine pattern with high accuracy using a lithography technique. In addition, the possibility of realizing a three-dimensional IC is brought about by the combined use of the bonding technique of the Si wafer and the like.
[0017]
{Circle around (2)} enables an embedded structure. 2. Description of the Related Art Conventionally, tungsten (W) embedding technology has been adopted for multilayer wiring of an IC. In this method, W is buried in a groove of an interlayer film by a CVD method, and the surface is etched back to be planarized. However, recently, the surface is planarized by CMP. Applications of this embedding technique include a damascene process and element isolation. These CMP technologies and applications are described in detail in "Science of CMP" published by Science Forum.
[0018]
Subsequently, the mechanism of the CMP will be briefly described. As shown in FIG. 14, a semiconductor wafer 252 is placed on a polishing cloth 251 on a rotary platen 250, rubbed while flowing an abrasive (slurry) 253, polished, and chemically etched to form irregularities on the surface of the wafer 252. Is lost. The surface is flattened by the chemical reaction of the solvent in the abrasive 253 and the mechanical polishing action of the polishing cloth and the abrasive grains in the abrasive. As the polishing cloth 251, for example, foamed polyurethane, non-woven fabric, or the like is used, and the abrasive is a mixture of abrasive grains such as silica and alumina in water containing a pH adjusting material, and is generally called a slurry. I have. While the slurry 253 is flowing, a constant pressure is applied to the polishing pad 251 while rotating the wafer 252 to rub it. Reference numeral 254 denotes a dressing unit for maintaining the polishing ability of the polishing pad 251 and for keeping the surface of the polishing pad 251 in a dressed state. Reference numerals 202, 208, and 212 denote motors, and reference numerals 255 to 257 denote belts.
[0019]
The above-described mechanism is configured as a system, for example, as shown in FIG. This system is roughly divided into a wafer cassette loading / unloading station 260, a wafer transfer mechanism unit 261, a polishing mechanism unit 262 described in FIG. 14, a wafer cleaning mechanism unit 263, and a system control for controlling these units.
[0020]
First, the cassette 264 containing the wafer is placed in the wafer cassette loading / unloading station 260, and the wafer in the cassette 264 is taken out. Subsequently, the wafer is held by a wafer transfer mechanism unit 261, for example, a manipulator 265, placed on a rotary platen 250 provided in a polishing mechanism unit 262, and the wafer is flattened using a CMP technique. . When the flattening operation is completed, the wafer is transferred to the wafer cleaning mechanism 263 by the manipulator 266 and cleaned in order to clean the slurry. Then, the washed wafer is stored in a wafer cassette 266.
[0021]
For example, the amount of slurry used in one process is about 500 cc to 1 liter / wafer. Further, pure water flows through the polishing mechanism 262 and the wafer cleaning mechanism 263. Since these drains are finally combined at the drain, about 5 to 10 liters / wafer of drainage is discharged in one flattening operation. For example, in the case of a three-layer metal, about seven times of flattening work is performed by metal flattening and interlayer insulating film flattening, and five to ten liters of drainage is required until one wafer is completed. Is discharged. Therefore, it can be seen that when a CMP apparatus is used, a considerable amount of slurry diluted with pure water is discharged. These wastewaters were treated by the coagulation sedimentation method.
[0022]
[Patent Document 1]
JP 2001-157894 A
[Problems to be solved by the invention]
However, in the coagulation sedimentation method, a chemical is fed as a coagulant. However, it is very difficult to specify the amount of a completely reacting chemical, and a large amount of the chemical is inevitably introduced and unreacted chemical remains. Conversely, if the amount of the chemical is small, all the objects to be removed are not aggregated and settled, and the objects to be removed remain without being separated. In particular, when the amount of the drug is large, the drug remains in the supernatant. When this is reused, since chemicals remain in the filtration fluid, there is a problem that it cannot be reused for those who dislike the chemical reaction.
[0024]
Flock, which is a reaction product between a chemical and a substance to be removed, is generated as a floating substance like an algae. Conditions for forming this floc are strict pH conditions, and require a stirrer, a pH measuring device, a coagulant injection device, and a control device for controlling these. In addition, a large sedimentation tank is required to stably settle flocs. For example, a wastewater treatment capacity of 3 cubic meters (m ³ ) per hour would require a tank with a diameter of about 3 meters and a depth of about 4 meters (about 15 tons of sedimentation tank). It will be a large system that requires a site of about × 11 meters.
[0025]
In addition, there are flocks floating without settling in the sedimentation tank, which may flow out of the tank to the outside, and it was difficult to collect all of them. That is, there are problems such as the size of the equipment, the high initial cost of this system, the difficulty in reusing water, and the high running cost resulting from the use of chemicals.
[0026]
On the other hand, as shown in FIG. 13, in a method in which a filter filtration of 5 cubic meters (m ³ ) / 1 hour is combined with a centrifugal separator, a filter F (called a UF module, which is made of polysulfone-based fiber) , Or a ceramic filter), the water can be reused. However, four filters F are attached to the filtering device 203, and it is necessary to replace a high-priced filter of about 500,000 yen / filter at least once a year from the life of the filter F. In addition, since the filter F is a pressurized filtration method, the filter 202 has a large load on the motor 202 because the filter F is a pressurized filtration method, and the pump 202 has a high capacity. In addition, about 排水 of the wastewater passing through the filter F has been returned to the raw water tank 201. Further, since the wastewater containing the substance to be removed is transported by the pump 202, the inner wall of the pump 202 is cut off, and the life of the pump 2 is very short.
[0027]
To summarize these points, there is a problem that the running cost is very large because the electricity cost of the motor is extremely high and the replacement cost of the pump P and the filter F is high.
[0028]
Furthermore, in CMP, an incomparable amount of wastewater is discharged compared with dicing. The slurry is colloidally distributed in the fluid and hardly sediments due to Brownian motion. Moreover, the particle size of the abrasive particles mixed into the slurry is extremely fine, from 10 to 200 nm. Therefore, when a slurry composed of fine abrasive particles is filtered with a filter, the abrasive particles enter the pores of the filter, causing immediate clogging and frequent clogging. Was.
[0029]
As can be seen from the above explanation, in order to remove as much as possible substances harmful to the global environment, or to reuse filtration fluids and separated removal objects, various filtration devices for wastewater are used. , The system becomes large-scale, and the initial cost and running cost are enormous after all. Therefore, the conventional sewage treatment apparatus has not been a system that can be adopted at all.
[0030]
Furthermore, in order to collect the object to be removed settled at the bottom of the tank, the filtering operation is temporarily stopped, and the liquid in the tank is taken out to the outside. Therefore, this operation has caused a decrease in filtration efficiency.
[0031]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and has a tank in which a fluid containing an object to be removed is stored, a filter device immersed in the tank, and a valve that communicates with a lower portion of the tank via a valve to remove the object to be removed. A collecting tank in which the substance settles, wherein the collecting tank is separable from the tank, and the valve set in a closed state is separated from the tank to separate the collecting tank from the tank. It is characterized by collecting the removed matter.
[0032]
Further, the present invention provides a tank containing a fluid containing a colloidal substance to be removed, a first filter immersed in the tank, and a second filter comprising a gel film adsorbed on the surface of the first filter. A filter device to be formed, and a recovery tank that communicates with a lower portion of the tank via a valve and in which the object to be removed settles, wherein the recovery tank is separable from the tank, and the valve is closed. By separating the recovery tank from the tank, the object to be removed precipitated in the recovery tank is recovered.
[0033]
Therefore, in the present invention, a separable collection tank is provided below the tank for performing filtration, so that only the separation of the collection tank can collect the precipitated material to be removed. In addition, it is possible to collect the precipitate to be removed without stopping the filtration operation.
[0034]
Generally, in order to remove particles having a size of 200 nm or less, such as abrasive particles mixed in a CMP slurry, a filter film having pores smaller than the particles is generally used. However, in the present invention, a gel film made of an object to be removed is used as a filter, and a number of gaps formed in the filter are used as a passage for a fluid. Further, in the present invention, since the filter itself is an aggregate of the particles of the object to be removed, the object to be clogged can be separated from the filter, and the filtration performance can be maintained. Further, according to the present invention, even if the filter of the gel membrane is clogged by continuing the filtration, the filter can be regenerated and the filtration can be continued to realize long-time filtration.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
With reference to FIG. 1, the configuration and the like of the filtration device 20 of the present invention will be described. FIG. 1A is a schematic configuration diagram of a filtering device 20 according to the present invention, and FIG. 1B is an enlarged cross-sectional view of a filtering device 53.
[0036]
The filter device 20 of the present invention includes a tank 50 in which a fluid containing an object to be removed is stored, a filter device 53 immersed in the tank 50, and a valve V that communicates with a lower portion of the tank 50 to remove the object. And a collecting tank 15 in which the sediment can be separated from the tank 50. By removing the collecting tank 15 from the tank 50 with the valve V shut off, the removed substance settled in the collecting tank 15 can be removed. It is configured to collect things. Details of the filtering device 20 having such a configuration will be described below.
[0037]
First, an outline of the filtration device 20 will be described with reference to FIG. Reference numeral 50 denotes a raw water tank. Above the tank 50, a pipe 51 is provided as drainage supply means. The pipe 51 introduces the fluid containing the substance to be removed into the tank 50. For example, in the field of semiconductors, it is a place where wastewater (raw water) mixed with an object to be removed of a colloid solution flowing out of a dicing apparatus, a back grinding apparatus, a mirror polishing apparatus, or a CMP apparatus is introduced. This wastewater will be described as wastewater mixed with abrasive grains flowing from a CMP apparatus and debris polished or ground by the abrasive grains. Further, as shown in the figure, the fluid temporarily stored in the drainage receiving tank 17 may be introduced into the raw water tank 50 via the pipe 51.
[0038]
In the raw water 52 stored in the raw water tank 50, a plurality of filter devices 53 each having a second filter are provided. A diffuser 54 is provided below the filter device 53, such as a small hole in a pipe, or a bubbling device used for a fish tank. Has been adjusted. The air diffuser 54 is arranged over the entire bottom of the filter device 53 so that air bubbles can be uniformly supplied to the entire surface of the filter device 53.
[0039]
The bottom of the raw water tank 50 has a tapered shape, and the recovery tank 15 communicates with the lowermost part of the bottom. Since the bottom of the raw water tank 50 has such a tapered shape, the object to be removed that has settled downward can be efficiently moved to the collection tank 15. The raw water tank 50 is preferably made of a resin such as vinyl chloride. In addition, the steeper the slope of the taper shape, the greater the effect of collecting the settled object to be removed in the collection tank 15. That is, as the inclination of the taper shape is steeper, the object to be removed does not adhere to the inner wall of the raw water tank 50 at the tapered portion, and the object to be removed moves to the recovery tank 15 below.
[0040]
The air diffuser S is provided near the tapered inner wall of the raw water tank 50, and is connected to the air pump 55 via the ventilation pipe 40. The air diffuser 54 has a function of generating air bubbles inside the raw water 52. It is activated when the object to be removed accumulated in the collection tank 15 is collected. That is, the object to be removed attached to the flat wall of the raw water tank 50 is separated by the bubbles generated from the air diffuser 54 and moved to the raw water tank 50.
[0041]
The recovery tank 15 is provided in communication with the lower part of the raw water tank 50. The recovery tank 15 and the raw water tank 50 communicate with each other via a valve V in the middle. That is, by opening the valve V, the recovery tank 15 and the raw water tank 50 are in a state of communication. Then, by closing the valve V, the recovery tank 15 and the raw water tank 50 are shut off.
[0042]
The recovery tank 15 is provided with a supply unit K and a discharge unit H each having a valve interposed. The supply unit K is used when a large amount of the object to be removed is settled in the collection tank 15, and the gas or the liquid is injected into the collection tank 15 from the collection unit K to include the object to be removed from the discharge unit H. Drained fluid can be discharged. Further, by opening the valve interposed in the discharge part H, it is possible to collect the fluid including the substance to be removed.
[0043]
During operation of the filter device 53, the valve V is open. Therefore, when the raw water 52 is introduced into the raw water tank 50, the inside of the recovery tank 15 is also filled with the raw water 52. Further, the collection tank 15 may be formed of a transparent material in order to visually confirm the amount of the object to be removed settled inside. The collection tank 15 has a mechanism that can be separated from the filtration device 20.
[0044]
The transfer means D is, for example, a trolley having wheels, and a recovery tank 15 is placed on the upper part thereof.
[0045]
55 is an air pump. The air pump 55 and the air diffuser 54 are connected by a pipe-shaped ventilation pipe 40. Further, a communicating recovery tank 15 is provided below the raw water tank 50.
[0046]
The pump 57 is connected to the filter device 53 via a pipe 56. That is, the fluid filtered by the filter device 53 is discharged to the outside by the suction force generated by the pump 57.
[0047]
The separating water tank 70 is connected to the pipe 56 for extracting the filtrate from the filter device 53, and stores the filtered water filtered by the filter device 53.
[0048]
With reference to FIG. 1 (A) and FIG. 1 (B), the operation of the filtering device 20 having the above configuration will be described.
[0049]
First, the raw water 52 is introduced into the raw water tank 50. Then, the raw water 52 is passed through the filter device 53 by using the suction force of the pump 55 to form the second filter 2 which is a self-forming film on the filtration surface of the first filter 1. At this stage, the filtered water may be returned to the raw water 52 because the fluid passing through the pipe 56 has not been sufficiently filtered. At this stage, the valve V is in the open state, and the raw water is also introduced into the recovery tank 15.
[0050]
Next, the process proceeds to the step of filtering the raw water 52 using the filter device 53 having the second filter 2 formed sufficiently. At this stage, the filtered water obtained from the filter device 53 has sufficient transparency. Therefore, the filtered water is discharged out of the filtration device 20. A part of the filtered water is stored in the separating water tank 70.
[0051]
As the filtration step proceeds, the second filter 2 gradually becomes clogged, and the amount of filtered water obtained decreases. Then, the process proceeds to the step of peeling the second filter 2. First, the pump 55 that applies a suction force to the filter device 53 is stopped. Then, the filtered water stored in the separating water tank 70 is returned to the filter device 53 via the pipe 56. When the filtered water flows back into the hollow portion 5 of the filter device 53, the pressure acting from inside to outside acts on the filter device 53. Due to this pressure, the second filter 2 is separated from the first filter 1 and moves downward. Further, a large amount of air bubbles may be generated from the air diffuser 54 in order to promote the movement of the second filter 2.
[0052]
Referring to FIG. 1B, the separated second filter travels to the recovery tank 15 along the bottom of the tapered raw water tank 50. As described above, the raw water tank 50 is made of a material having excellent water repellency. Therefore, the residue of the second filter made of the gel-like material to be removed is solidified by its surface tension. Then, the solidified object to be removed moves along the inner wall of the raw water tank 50 having a tapered shape and moves to the collection tank 15.
[0053]
When the object to be removed has accumulated to a certain extent in the collection tank 15, the object to be removed is collected. First, air bubbles are generated from the air diffuser S, and the object to be removed attached to the inner wall of the raw water tank 50 is settled in the recovery tank 15. Next, with the valve V closed, the raw water tank 50 and the recovery tank 15 are separated. Next, the recovery tank 15 is separated from the filtration device 20, and the raw water 52 containing a large amount of the substance to be removed stored therein is discharged. Thereafter, the collection tank 15 is attached to the filtration device 20 and the valve V is opened, so that the raw water in the raw water tank 50 flows into the collection tank 15, and the collection tank 15 is filled with the raw water 52 again. The transfer means D is used to move the collection tank 15 when discharging the raw water in the collection tank 15. Further, the work of collecting the object to be removed can be performed in a state where the filter device 53 is operated.
[0054]
With reference to FIG. 2, a further embodied filtering device will be described. The same components as those of the filtration device shown in FIG. 1 are denoted by the same reference numerals.
[0055]
In FIG. 2, 50 is a raw water tank. Above the tank 50, a pipe 51 is provided as drainage supply means. The pipe 51 introduces the fluid containing the substance to be removed into the tank 50. For example, in the field of semiconductors, it is a place where wastewater (raw water) mixed with an object to be removed of a colloid solution flowing out of a dicing apparatus, a back grinding apparatus, a mirror polishing apparatus, or a CMP apparatus is introduced. This wastewater will be described as wastewater mixed with abrasive grains flowing from a CMP apparatus and debris polished or ground by the abrasive grains.
[0056]
An adjustment valve 41 and a stop valve 42 are interposed in the ventilation pipe 40 connecting the air pump 55 and the air diffusion pipe 54. The adjustment valve 41 is set to allow a desired amount of gas flow. For example, a needle valve or the like can be employed as the adjustment valve. The stop valve 42 is a valve for opening and shutting off the gas flowing inside the ventilation pipe 40. Specifically, as the stop valve 42, for example, a valve using a solenoid can be used. As described above, by using the adjustment valve 41A and the stop valve 42 in combination, a desired amount of gas is supplied to the air diffuser 54 simply by opening and closing the stop valve 42 while keeping the output of the air pump 55 fixed. Can be supplied.
[0057]
Further, the ventilation pipe 40 is provided with a plurality of paths that are branched and arranged in the middle of the ventilation pipe 40. Specifically, the first path 40A, the second path 40B, and the third path 40C are branched and arranged in parallel. The above-described adjustment valve 41 and stop valve 42 are interposed in each path.
[0058]
A first adjustment valve 41A and a first stop valve 42A are interposed in the first path 40A. The first adjustment valve 41A is adjusted so that an appropriate amount of gas passes when the filter device 53 performs a filtering operation or the like. The first stop valve 42A is opened in a filtration step of filtering with the filter device 53, a step of forming a gel-like second filter, or the like. When the first stop valve 42A is in the open state, the second stop valve 42B and the third stop valve 42C are in the shut-off state. With the first adjustment valve 41A adjusted in this way, it becomes possible to supply an appropriate amount of gas from the air diffuser 54 at the time of filtration. Therefore, the raw water in the raw water tank 50 is stirred by the bubbles rising from the air diffuser 54, so that the filtration can be performed smoothly.
[0059]
A second adjustment valve 41B and a second stop valve 42B are interposed in the second path 40B. The second adjusting valve 41B is set so that a larger amount of gas passes than the first adjusting valve 41A described above. The second stop valve 42B is opened in a step (regeneration step) of separating the gel-like second filter constituting the filter device 53 from the first filter. When a large amount of gas is supplied from the air diffuser into the raw water, the second filter can be detached. When the second stop valve 42B is open, the first stop valve 42A and the third stop valve 42C are shut off.
[0060]
A third adjustment valve 41C and a third stop valve 42C are interposed in the third path 40C. The third adjustment valve 41C is set so that a smaller amount of gas flows than the first adjustment valve 41A and the second adjustment valve 41B described above. The third stop valve 42C is opened when the operation of the entire filtration device 20 is stopped. When the third stop valve 42C is in the open state, the first stop valve 42A and the second stop valve 42B are in the shut-off state. As described above, when the entire filtering device 20 is in a state of stopping the filtration operation, the filter device 20 is in the open state, so that the air diffuser 54 can be prevented from being clogged.
[0061]
The pipe 56 is connected to a magnet pump 57 through which the filtered fluid filtered by the filter device 53 flows and which performs suction through the valve V1. The pipe 58 is connected to the valves V3 and V4 from the magnet pump 57 via the control valve CV1. A first pressure gauge 59 is provided after the valve V1 of the pipe 56 to measure the suction pressure Pin. Further, a flow meter F and a second pressure gauge 60 are provided after the control valve CV1 of the pipe 58, and the flow rate is controlled by a flow meter 61 to a constant flow rate. The air flow rate from the air pump 55 is controlled by the control valve CV2.
[0062]
In the raw water 52 stored in the raw water tank 50, a plurality of filter devices 53 each having a second filter are provided. Below the filter device 53, an air diffuser 54 is provided over the entire bottom of the filter device 53, such as a small hole in a pipe or a bubbling device used for a fish tank. Its position is adjusted so that it passes through the surface. 55 is an air pump. The air is supplied from the air pump 55 and is guided to the air diffuser 54 via the air flow meter 69. In addition, the above-described first path 40A, second path 40B, and third path 40C are provided in the ventilation pipe 40 connecting the air diffusion pipe 54 and the air pump 55. Further, the first stop valve 42A, the second stop valve 42B, and the third stop valve 42C provided in each path are electrically connected to the control unit 68.
[0063]
The pipe 56 fixed to the filter device 53 is connected to a magnet pump 57 through which the filtration fluid filtered by the filter device 53 flows and suctions through the valve V1. The pipe 58 is connected from the magnet pump 57 to the valves V3 and V4 via the first control valve CV1. A first pressure gauge 59 is provided after the valve V1 of the pipe 56 to measure the suction pressure Pin. Further, a flow meter 61 and a second pressure gauge 60 are provided after the first control valve CV1 of the pipe 58, and the flow meter 61 controls the flow rate so as to be a constant filtration flow rate.
[0064]
The pipe 58 is connected to the optical sensor 62, and is led from the optical sensor 62 to branched pipes 63 and 64. Valves V3 and V4, which can be opened and closed by a detection signal from the optical sensor 62, are inserted into the pipes 63 and 64. The pipe 63 returns filtered water to the tank 50, and the pipe 64 takes filtered water out. I have. The optical sensor 62 monitors the concentration of the fine particles contained in the filtered water, and starts filtering after confirming that the fine particles are lower than the desired mixing ratio. When the filtration is started, the valve V3 is closed by the detection signal from the optical sensor 62, the valve V4 is opened, and the purified water is taken out.
[0065]
Further, the separating tank 70 is connected to the pipe 58 by the valve V5 and has a function of storing filtered water. When a certain amount is exceeded, the tank 70 overflows and is returned to the tank 50 by the pipe 71. A valve V2 is provided at the bottom thereof, and is connected to the pipe 56. The separating water tank 70 is provided at a position about 10 to 20 cm higher than the liquid level of the tank 50, and is used in the regeneration process of the second filter.
[0066]
Further, the tank 50 is provided with a pH controller 65 and a heating / cooling device 66, and particularly adjusts the pH of the CMP waste water to about 6 to 7 or adjusts the temperature of the waste water to promote gelation. In order to prevent the drainage from overflowing from the tank 50, the level is monitored by a liquid level gauge 67 and the inflow of the drainage is adjusted.
[0067]
Further, a control device 68 for controlling the operation of the filtration device is provided, and as shown by a dotted line in the figure, a control valve CV1, flow meters 61 and 69, a pump 57, pressure gauges 59 and 60, an optical sensor 62, etc. It is controlled for each process.
[0068]
In the above-described filtration device, in the film forming process of the second filter, the filtration process, the regeneration process of the second filter, the re-filtration process, and the maintenance process, each valve and the like are opened and closed under the control of the control device 68, and the pump 57 And other operations are controlled. The operation of each process will be described below. FIG. 3 shows the operation states of the pump 57, the optical sensor 62, the air pump 55, and each valve in each step.
[0069]
First, the wastewater mixed with the substance to be removed of the colloid solution is put into the raw water tank 50 through the pipe 51. In the tank 50, the filter devices 53 of the first filter 1 alone, on which the second filter 2 is not formed, are immersed at intervals so that a desired filtration flow rate can be obtained. Specifically, about 10 to about 40 filter devices 53 are suspended by the support means (not shown). Of course, the number varies depending on the filtration area of one filter device 53, but the total required filtration area of the filter device 53 is determined from the size of the tank 50.
[0070]
Next, the process proceeds to the film forming process of the second filter 2. The wastewater in the tank 50 is circulated while sucking at a slight suction pressure by the pump 57 via the pipe 56. The circulation path includes the filter device 53, the pipe 56, the valve V1, the pump 57, the pipe 58, the control valve CV1, the flow meter 61, the optical sensor 62, and the valve V3. The drain water is sucked from the tank 50 and returned to the tank 50. From the air diffuser 54, air bubbles supplied from the air pump 55 through the first path 40 </ b> A rise and are supplied to the surface of the filter device 53. That is, the first stop valve 42A is opened, and a desired amount of gas is supplied to the diffuser 54 by the first adjustment valve 41A. At this time, the other valves V2, V4, V5, V6, and D are closed.
[0071]
By circulating the waste water, the second filter 2 is formed on the first filter of the filter device 53, and finally, the object to be removed of the target colloid solution is captured. (The specific principle will be described later.) That is, when the drainage is suctioned by the pump 57 through the first filter 1 with a weak suction pressure, the fine particles of the object to be removed are gelled as approaching the first filter 1. And is adsorbed on the surface of the first filter 1. The gelled fine particles, which are larger than the filter holes 11 of the first filter 1, are gradually adsorbed on the surface of the first filter 1 and are laminated to form the second filter 2 made of a gel film. The gelled fine particles having a smaller diameter than the filter hole 11 pass through the first filter 1, and the water in the drainage is sucked through the gap as a passage along with the formation of the second filter 2, so that the first filter 1 is removed. , And is taken out as purified water, and the wastewater is filtered.
[0072]
At this time, the concentration of the fine particles contained in the filtered water is monitored by the optical sensor 62, and it is confirmed that the fine particles are lower than the desired mixing ratio.
[0073]
Subsequently, when the film formation of the second filter 2 is completed, the process proceeds to a filtration step. When the filtration is started, the valve V3 is closed by the detection signal from the optical sensor 62, the valve V4 is opened, the circulation path is closed, and filtered water is taken out from the valve V4. In this step, the flow rate is controlled by the controller 68 so that the flow rate is controlled by the flow meter 61, and the operation is performed so as to prevent the second filter 2 from being clogged as much as possible and to maintain the filtration time as long as possible. As shown in FIG. 9, the suction pressure Pin of the pump 57 is gradually increased, and the filtration flow rate is kept constant. The other parts have the same operating conditions as the film forming process. Also in this step, the gas supplied to the diffuser 54 is supplied via the first path 40A.
[0074]
If the second filter 2 is broken for any reason, the entry of fine particles is detected by the optical sensor 62, the valve V4 is closed, and the valve V3 is opened to return the filtered water to the tank 50. That is, the process returns to the film forming process to repair the second filter 2, and returns to the normal condition to return to the filtering process.
[0075]
When the filtration is continuously performed, the water in the wastewater from the raw water tank 50 is taken out of the tank 50 as filtered water, so that the concentration of the substance to be removed in the wastewater increases. That is, the colloid solution is concentrated to increase the viscosity. For this purpose, the raw water tank 50 is replenished with drainage from the pipe 51, thereby suppressing an increase in the concentration of the drainage and increasing the filtration efficiency. However, the gel film thickly adheres to the surface of the second filter 2 of the filter device 53, and eventually the second filter 2 is clogged and cannot be filtered.
[0076]
When the gel film of the second filter 2 is thickly adsorbed on the surface of the first filter 1, it is detected by the flow meter 61 as a decrease in the filtration flow rate, and the control device 68 switches from the filtration step to the second filter regeneration step. Transition.
[0077]
First, in the regeneration step, the pump 57 is stopped, and the negative suction pressure applied to the filter device 53 is released. At the same time, the valve V2 is opened and the filtered water previously stored in the separating water tank 70 flows backward through the pipe 56 via the valve V1 and is sent to the hollow portion 5 of the filter device 53.
[0078]
Accordingly, in the regeneration step, the weak suction pressure is stopped and almost returns to the atmospheric pressure, so that the first filter 1 of the filter device 53 returns from the state depressed by the suction pressure to the original state. As a result, the second filter 2 and the gel film adsorbed on the surface thereof also return. As a result, first, the suction pressure for adsorbing the gel film is eliminated, so that the gel film loses the adsorbing force to the filter device 53 and receives a force expanding outward. Further, since the separating water tank 70 is provided at a position higher than the liquid level of the tank 50, the reverse flow of the filtered water from the separating water tank 70 applies a hydrostatic pressure due to the difference in height thereof, and the first filter 1 and the second filter The second filter 2 is applied with a force expanding outward. Thereby, the adsorbed gel film starts to be separated from the filter device 53 by its own weight and hydrostatic pressure. According to the experiment, detachment starts from the lower end of the filter device 53, and the gel film of the second filter 2 attached to the surface of the first filter 1 detaches like an avalanche and settles on the bottom surface of the raw water tank 50. . Subsequently, it is preferable that the wastewater is circulated through the above-described circulation path to form the second filter 2. In this regeneration step, the second filter 2 returns to the original state, returns to a state where the drainage can be filtered, and filters the drainage again. At this time, the valve V2 is closed, the valve V5 is opened, and the filtered water is stored in the separating water tank 70 to prepare for the next regeneration step.
[0079]
Further, in order to promote this separation, it is preferable to increase the amount of bubbles from the air diffuser 54 to about twice. Specifically, the second stop valve 42B is opened, and the first stop valve 42A and the third stop valve 42C are closed.
[0080]
Thereafter, a re-filtration step is started, and the filtration of waste water is started again. The operating conditions are the same as in the filtration step. If the filtration is continued many times while regenerating the second filter 2 in this manner, the concentration of the substance to be removed from the wastewater in the raw water tank 50 increases, and the wastewater eventually has a considerable viscosity. Therefore, when the concentration of the substance to be removed from the wastewater exceeds a predetermined concentration, the filtering operation is stopped and the process proceeds to the maintenance process.
[0081]
The maintenance process includes a step of discharging the filtered water in the pipes 56 and 58 and the separating water tank 70, and a step of discharging the drainage in the tank 50 and the gel stored in the bottom. In the previous step, the pump 57 and the air pump 55 are stopped, the control valve CV1, the valves V1, V2, V5 are opened, and the filtered water in the pipes 56, 58 and the separating tank 70 is discharged to the pipe 56. From the valve D.
[0082]
Further, in a later step, the concentrated slurry is settled at the bottom of the tank 50 by being left for coagulation and sedimentation, and the concentrated slurry of the gel is recovered by opening the valve V6. The recovered concentrated slurry is thermally dried to evaporate water contained therein and further compress the amount. This can significantly reduce the amount of slurry treated as industrial waste. The supernatant drainage is likewise discharged from valve V6 and returned to tank 50 again in the subsequent filtration step.
[0083]
Here, the above-described filter device 53, specifically, the filter device 53 immersed in the raw water tank 50 will be described with reference to FIGS.
[0084]
Reference numeral 30 shown in FIG. 4A is a frame having a frame-like shape, and filter films 31 and 32 serving as first filters are attached and fixed to both surfaces of the frame 30. Then, the pipe 34 is sucked into the inner space 33 surrounded by the frame 30 and the filter films 31 and 32, so that the inner space 33 is filtered by the filter films 31 and 32. Then, filtered water is taken out via a pipe 34 which is sealed and attached to the frame 30. Of course, the filter membranes 31 and 32 and the frame 30 are completely sealed so that drainage does not enter the space 33 except from the filter membrane.
[0085]
Since the filter films 31 and 32 in FIG. 4A are thin resin films, they may warp inward when sucked and may be broken. Therefore, in order to make this space as small as possible and to increase the filtration capacity, it is necessary to make this space 33 large. FIG. 4B shows a solution to this problem. Although only nine spaces 33 are shown in FIG. 4 (B), many spaces 33 are actually formed. The actually employed filter film 31 is a polyolefin-based polymer film having a thickness of about 0.1 mm, and as shown in FIG. 4B, a thin filter film is formed in a bag shape. In B), it was indicated by FT. The frame 30 in which the pipe 34 is integrated is inserted into the bag-shaped filter FT, and the frame 30 and the filter FT are bonded to each other. Reference numeral RG denotes a pressing unit that presses the frame to which the filter FT is attached from both sides. The filter FT is exposed from the opening OP of the holding means. The details will be described again with reference to FIG.
[0086]
FIG. 4C shows the filter device 53 itself having a cylindrical shape. The frame attached to the pipe 34 has a cylindrical shape, and has openings OP1 and OP2 on the side surface. Since the side surfaces corresponding to the openings OP1 and OP2 have been removed, the support means SUS for supporting the filter film 31 is provided between the openings. Then, the filter film 31 is bonded to the side surface.
[0087]
Further, referring to FIG. 5, the filter device 53 of FIG. 4B will be described in detail. First, a portion 30a corresponding to the frame 30 in FIG. 4B will be described with reference to FIGS. 5A and 5B. The portion 30a is shaped like a cardboard as seen. Thin resin sheets SHT1 and SHT2 having a thickness of about 0.2 mm overlap each other, a plurality of sections SC are provided in the vertical direction therebetween, and a space 33 is provided surrounded by the resin sheets SHT1, SHT2 and sections SC. The cross section of the space 33 is a rectangle having a length of 3 mm and a width of 4 mm. In other words, the cross section has a shape in which a number of straws having the rectangular cross section are arranged and integrated. The portion 30a maintains the filter films FT on both sides at a constant interval, and is hereinafter referred to as a spacer.
[0088]
Many holes HL having a diameter of 1 mm are formed in the surface of the thin resin sheets SHT1 and SHT2 constituting the spacer 30a, and a filter film FT is bonded to the surface. Therefore, the filtered water filtered by the filter membrane FT passes through the hole HL and the space 33, and finally exits from the pipe 34.
[0089]
Further, the filter film FT is bonded to both surfaces SHT1 and SHT2 of the spacer 30a. On both surfaces SHT1 and SHT2 of the spacer 30a, there is a portion where the hole HL is not formed, and when the filter film FT1 is directly attached thereto, the filter film FT1 corresponding to the portion where the hole HL is not formed is filtered. Since there is no function and the drainage does not pass, there is a portion where the object to be removed is not captured. In order to prevent this phenomenon, at least two filter films FT are attached. The filter film FT1 on the foremost side is a filter film for capturing an object to be removed, and a filter film having holes larger than the holes of the filter film FT1 is provided from the filter film FT1 toward the surface SHT1 of the spacer 30a. Here, one filter film FT2 is attached. Therefore, even in a portion where the hole HL of the spacer 30a is not formed, since the filter film FT2 is provided therebetween, the entire surface of the filter film FT1 has a filtering function, and an object to be removed is present on the entire surface of the filter film FT1. The second filter film is captured and formed on the front and back surfaces SH1 and SH2. Although the filter films SHT1 and SHT2 are shown as rectangular sheets for the sake of convenience in the drawing, they are actually formed in a bag shape as shown in FIG. 4B.
[0090]
Next, how the bag-shaped filter films SHT1, SHT2, the spacer 30a, and the holding means RG are attached will be described with reference to FIGS. 5 (A), 5 (C), and 5 (D). .
[0091]
FIG. 5 (A) is a completed view, and FIG. 5 (C) is cut from the head of the pipe 34 in the extending direction (longitudinal direction) of the pipe 34 as indicated by line AA in FIG. 5 (A). FIG. 5D is a cross-sectional view of the filter device 35 cut in the horizontal direction as indicated by line BB.
[0092]
As can be seen from FIGS. 5 (A), 5 (C), and 5 (D), the spacer 30a inserted into the bag-shaped filter film FT has four sides including the filter film FT. It is sandwiched between RG. The three sides and the remaining one side bound in a bag shape are fixed by the adhesive AD1 applied to the holding means RG. Further, a space SP is formed between the remaining one side (opening portion of the bag) and the holding means RG, and the filtered water generated in the space 33 is sucked into the pipe 34 via the space SP. In addition, the adhesive AD2 is provided over the entire periphery of the opening OP of the holding bracket RG, is completely sealed, and has a structure in which fluid cannot enter from anything other than the filter.
[0093]
Therefore, the space 33 and the pipe 34 communicate with each other. When the pipe 34 is sucked, the fluid passes through the hole of the filter membrane FT and the hole HL of the spacer 30 a toward the space 33, and passes from the space 33 to the pipe 34. To transport filtered water to the outside.
[0094]
The filter device 53 used here adopts the structure shown in FIG. 5, and the size of the frame (holding bracket RG) to which the filter membrane is attached is A4 size. Specifically, the length: about 19 cm and the width: about 28 0.8 cm, thickness: 5 to 10 mm. Actually, since the filter device 53 is provided on both sides of the frame, the area becomes twice as large as described above (area: 0.109 m ² ). However, the number and size of the filter devices are freely selected according to the size of the raw water tank 50, and are determined from the required filtration amount.
[0095]
Next, the principle of filtering raw water using the gel-like second filter will be described. First, the definitions of terms used in the following description will be clarified.
[0096]
A colloid solution refers to a state in which fine particles having a diameter of 1 nm to 1 μm are dispersed in a medium. These particles have Brownian motion, and have the property of passing through ordinary filter paper but not through semipermeable membranes. In addition, it is considered that the property that the coagulation speed is extremely low reduces the chance of approach because the electrostatic repulsion acts between the fine particles.
[0097]
The sol is used almost synonymously with the colloid solution. Unlike the gel, the sol is dispersed in a liquid and exhibits fluidity, and the fine particles are actively browning.
[0098]
Gel refers to a state in which colloid particles have lost independent motility and have aggregated and solidified. For example, when agar or gelatin is dissolved in warm water, it disperses into a sol, but when cooled, it loses fluidity and becomes a gel. Gels include hydrogels with high liquid content and slightly dry xerogels.
[0099]
The gelation may be caused by removing water as a dispersion medium and drying the slurry, adding an electrolyte salt to a silica slurry (pH 9 to 10) to adjust the pH to 6 to 7, or cooling to lose fluidity. And so on.
[0100]
A slurry refers to a colloidal solution or sol that mixes particles, liquids and chemicals and is used for polishing. The abrasive used for the above-mentioned CMP is called a CMP slurry. As the CMP slurry, a silica-based abrasive, an aluminum oxide (alumina) -based abrasive, a cerium oxide (ceria) -based abrasive, and the like are known. Most frequently used is a silica-based abrasive, of which colloidal silica is widely used. Colloidal silica is a dispersion in which ultrafine silica particles having a colloid size of 7 to 300 nm are uniformly dispersed without sedimentation in water or an organic solvent, and are also referred to as silica sol. Since the colloidal silica particles are monodispersed in water, the colloid particles hardly settle even after being left for one year or more due to mutual repulsion of the colloid particles.
[0101]
An object of the present invention is to provide a method for removing an object to be removed by removing the object from filtration in a state where the object is contained in a fluid as a colloid solution or a sol.
[0102]
The object to be removed is a colloid solution (sol) containing a large amount of fine particles having a particle size distribution of 3 nm to 2 μm. For example, abrasives such as silica, alumina or ceria used for CMP and semiconductors generated by the abrasives are used. Material waste, metal waste and / or insulating film material waste. In this example, a slurry for polishing W2000 tungsten manufactured by Cabot Corporation was used as the CMP slurry. This slurry is mainly composed of silica having a pH of 2.5 and an abrasive distribution of 10 to 200 nm.
[0103]
The basic principle of the present invention will be described with reference to FIG. The present invention is to remove a fluid (drain) mixed with an object to be removed of a colloid solution (sol) using a filter made of a gel film formed from the object to be removed.
[0104]
More specifically, a gel film to be a second filter 2 formed from a CMP slurry, which is an object to be removed of a colloid solution, is formed on the surface of a first filter 1 made of an organic polymer. It is immersed in the fluid 3 in the tank, and the wastewater containing the substance to be removed is filtered.
[0105]
The first filter 1 may be of an organic polymer type or a ceramic type in principle, provided that a gel film can be attached thereto. Here, a polyolefin polymer film having an average pore diameter of 0.25 μm and a thickness of 0.1 mm was employed. FIG. 2B is a photograph of the surface of the polyolefin-based filter film.
[0106]
Further, the first filter 1 has a flat membrane structure provided on both sides of the frame 4, is immersed so as to be perpendicular to the fluid, and is configured to be sucked by the pump 6 from the hollow portion 5 of the frame 4. The filtrate 7 can be taken out.
[0107]
Next, the second filter 2 is a gel film which is attached to the entire surface of the first filter 1 and is formed by sucking the sol of the object to be removed and gelling. Generally, it is considered that the gel film does not function as a filter because it is in a jelly state. However, in the present invention, the function of the second filter 2 can be provided by selecting the conditions for forming the gel film. This generation condition will be described later in detail.
[0108]
Then, the second filter 2 which is a gel film of the object to be removed is formed from the above-mentioned colloid solution (sol) of the object to be removed, and the filtration for removing the object to be removed is described with reference to FIGS. 6 and 7A. explain.
[0109]
1 is a first filter, and 11 is a filter hole. The film formed in a layer on the opening of the filter hole 11 and the surface of the first filter 1 is a gel film of the object 13 to be removed. The object to be removed 13 is sucked through the first filter 1 by the suction pressure from the pump, and is dried (dehydrated) because the moisture of the fluid 3 is sucked up. A large gel film that binds and cannot pass through the filter hole 11 is formed on the surface of the first filter 1. This gel film forms the second filter 2.
[0110]
Eventually, when the second filter 2 has a predetermined thickness, the second filter 2 forms a gap through which the gel of the substance to be removed does not pass, and the second filter 2 is used to filter the substance to be removed of the colloid solution. Is started. Therefore, if the filtration is continued while being sucked by the pump 6, the gel film is gradually laminated on the surface of the second filter 2 and becomes thicker, and the second filter 2 is eventually clogged and the filtration cannot be continued. During this time, the colloid solution to be removed adheres to the surface of the second filter 2 while being gelled, and the water of the colloid solution passes through the first filter 1 and is taken out as filtered water.
[0111]
In FIG. 7 (A), one side of the first filter 1 has drainage of the colloid solution mixed with the substance to be removed, and the other side of the first filter 1 has passed through the first filter 1. Filtration water has been produced. The wastewater is sucked and flows in the direction of the arrow, and the fine particles in the colloidal solution lose their electrostatic repulsion as they approach the first filter 1 due to the suction, and are gelled. The second filter 2 is formed by being adsorbed on the surface of the filter 1. By the operation of the second filter 2, the waste in the colloid solution is gelled while the wastewater is filtered. Filtered water is sucked from the opposite surface of the first filter 1.
[0112]
By slowly sucking the wastewater of the colloid solution through the second filter 2 in this manner, the water in the wastewater can be taken out as filtered water, and the material to be removed is dried and gelled, and is laminated on the surface of the second filter 2. Then, the object to be removed is captured as a gel film.
[0113]
Next, a generation condition of the second filter 2 will be described with reference to FIG. FIG. 8 shows the generation conditions of the second filter 2 and the subsequent filtration amount.
[0114]
The method of the present invention comprises the steps of producing and filtering the second filter 2 first. The amount of purified water to be filtered during filtration greatly differs depending on the conditions for forming the second filter 2. It is apparent that almost no filtration can be performed with the gel membrane second filter 2 unless the purification conditions for the second filter 2 are properly selected. It becomes. This is consistent with the fact that filtration of colloidal solutions was previously not possible.
[0115]
The characteristics shown in FIG. 8B are experimentally obtained by the method shown in FIG. That is, the first filter 1 is provided at the bottom of the cylindrical container 21, 50 cc of a stock solution of a slurry 22 for polishing W2000 tungsten manufactured by Cabot Corporation is charged, and a suction pressure is changed to generate a gel film. Subsequently, the remaining slurry 22 is discarded, 100 cc of purified water 23 is added, and filtration is performed at an extremely low suction pressure. Thereby, the filtration characteristics of the gel membrane serving as the second filter 2 can be examined. In this case, the first filter 1 used had a diameter of 47 mm and its area was 1734 mm ² .
[0116]
In FIG. 8B, in the step of forming the gel film, the film was formed for 120 minutes while changing the suction pressure to −55 cmHg, −30 cmHg, −10 cmHg, −5 cmHg, and −2 cmHg, and the properties of the gel film were examined. As a result, when the suction pressure is set to a high value of -55 cmHg, the filtration amount is the largest at 16 cc in 2 hours, and becomes 12.5 cc, 7.5 cc, 6 cc and 4.5 cc in this order.
[0117]
Next, the gel membrane is replaced with purified water and filtered. At this time, the suction pressure is set to a constant value of −10 cmHg. A gel film formed at a suction pressure of -55 cmHg can filter only 0.75 cc / hour. For a gel film formed at a suction pressure of -30 cmHg, the filtration rate is about 1 cc / hour. However, the filtration amount is 2.25 cc / hour for a gel film with a suction pressure of −10 cmHg, 3.25 cc / hour for a gel film with a suction pressure of −5 cmHg, and 3.1 cc / hour for a gel film with a suction pressure of −2 cmHg. The gel film formed by the suction pressure can be stably filtered even in the filtration step. From the results of this experiment, it can be seen that if the suction pressure is set so that the filtration amount is about 3 cc / hour in the gel membrane generation step of the second filter 2, the filtration amount in the subsequent filtration step will be the largest. it is obvious.
[0118]
The reason for this is that if the suction pressure is high, the gel film to be formed has a low degree of swelling, becomes dense and hard, and the gel film is formed in a state of shrinkage with a low water content, so that purified water permeates. It is considered that the passage is almost eliminated.
[0119]
On the other hand, when the suction pressure is reduced, the gel film to be formed has a high degree of swelling, has a low density and becomes soft, and is formed while the gel film is swollen with a large amount of water, and the purified water penetrates. Many passages can be secured. It can be easily understood just by considering the situation where powder snow falls slowly. The feature of the present invention lies in that filtration is realized by using a gel membrane having a high degree of swelling formed by this weak suction pressure and utilizing the property of water permeation into the gel membrane.
[0120]
The characteristics of the gel film will be described with reference to FIG. FIG. 9A shows the relationship between the amount of sol contained in the gel membrane and the amount of filtration. The amount of sol removed is determined from the amount of sol captured by the first filter 1 from the amount of filtration at the time of gel film formation from purified water having a slurry concentration of 3%. This amount of sol is considered to be the amount that has gelled and adhered as the second filter 2 due to drying by suction. This reveals that the amount of the sol is smaller as the second filter 2 is formed into a film by weak suction. That is, the amount of sol consumed at a filtration rate of 3 cc / hour is extremely small at 0.15 cc, and the smaller the amount of sol contained in the second filter 2, the greater the filtration amount. This suggests an important point of the present invention, in which the formation of the second filter 2 having as small an amount of sol as possible enables the filtration of the wastewater of the colloid solution.
[0121]
FIG. 9B shows the degree of swelling, that is, the density of the sol in the gel film, based on the sol removal amount and the volume of the gel film described above. From the experimental result that the film thickness of the second filter 2 when the suction pressure is −30 mmHg is 6 mm and the film thickness of the second filter 2 is 4 mm when the suction pressure is −10 mmHg, the degree of swelling is 27 to 30. It has increased. In other words, it indicates that the degree of swelling decreases as the suction pressure increases, and the density of the sol amount in the second filter 2 increases. More importantly, the lower the suction pressure, the thinner the film thickness of the second filter 2 and the greater the degree of swelling, and the filtration of the second filter 2 formed by weakening the suction pressure shown in FIG. It supports that the amount of filtration at the time is large and that filtration can be performed for a long time.
[0122]
Therefore, in the present invention, it is clear that a major point at which the drainage of the colloidal solution of fine particles having a particle size of 0.15 μm or less can be filtered largely depends on the film forming conditions of the second filter 2.
[0123]
The filter shown in FIG. 7A shows one side of the filter in FIG. 6, and is a schematic diagram for explaining how a gel film actually adheres.
[0124]
The first filter 1 is immersed vertically in the colloid solution drainage, and the drainage is a colloid solution in which the object 13 is dispersed. The object 13 to be removed is indicated by a small black circle. When the wastewater is sucked by the pump 6 through the first filter 1 with a weak suction pressure, the fine particles of the object to be removed are gelled and adsorbed on the surface of the first filter 1 as approaching the first filter 1. . The gelled fine particles 14 indicated by white circles, which are larger than the filter holes 11 of the first filter 1, are gradually adsorbed on the surface of the first filter 1 and are laminated to form the second filter 2 made of a gel film. The gelled fine particles 14 having a smaller diameter than the filter hole 11 pass through the first filter 1, but there is no problem in the step of forming the second filter 2 because the filtered water is circulated again to the waste water. Then, as described above, the second filter 2 is formed over about 120 minutes. In this film forming step, the gelled fine particles 14 are stacked while forming gaps of various shapes because they are sucked by an extremely weak suction pressure, and the second filter of a soft gel film having a very low degree of swelling is formed. It becomes 2. The water in the waste water permeates the gel membrane having a high degree of swelling, is sucked, passes through the first filter 1, is taken out as filtered water, and finally the waste water is filtered.
[0125]
That is, in the present invention, the second filter 2 is formed from a gel film having a high degree of swelling, and the moisture contained in the gel film in contact with the first filter 1 is sucked from the first filter 1 with a weak suction pressure. Dehydration is performed to shrink the gel film, and the gel film is repeatedly permeated with water from the gel film in contact with the wastewater, supplied, and swelled, whereby only the water is permeated through the second filter 2 and filtered.
[0126]
Further, air bubbles 12 are sent to the first filter 1 from the bottom surface of the drainage, and a parallel flow is formed in the drainage along the surface of the first filter 1. This is because the second filter 2 uniformly adheres to the entire surface of the first filter 1 and because a gap is formed in the second filter 2 so that the second filter 2 adheres softly. Specifically, the air flow rate is set at 1.8 liter / min, but is selected depending on the film quality of the second filter 2.
[0127]
Next, in the filtration step, the gelled fine particles 14 indicated by white circles are gradually laminated on the surface of the second filter 2 while being adsorbed by a weak suction pressure. At this time, the purified water penetrates the second filter 2 and the gelled fine particles 14 indicated by white circles to be further laminated, and is taken out as filtered water from the first filter 1. That is, in the case of CMP, for example, in the case of CMP, abrasive particles such as silica, alumina or ceria, and processing chips such as semiconductor material chips, metal chips and / or insulating film material chips generated by being cut by the abrasive grains are gelled. Water is gradually accumulated on the surface of the second filter 2 and captured, and the water permeates the gel membrane and can be taken out of the first filter 1 as filtered water.
[0128]
However, if the filtration is continued for a long time as shown in FIG. 8B, a thick gel film is adhered to the surface of the second filter 2 so that the above-mentioned gap is eventually clogged, and the filtered water cannot be taken out. . Therefore, it is necessary to remove the laminated gel membrane in order to regenerate the filtration ability.
[0129]
Subsequently, an actual filtration method using the filtration device shown in FIG. 2 will be specifically described.
[0130]
First, the wastewater mixed with the substance to be removed of the colloid solution is put into the raw water tank 50 through the pipe 51. The filter device 53 of only the first filter 1 in which the second filter 2 is not formed is immersed in the tank 50, and the drainage is circulated while being suctioned by the pump 57 through the pipe 56 with a weak suction pressure. . The circulation path includes the filter device 53, the pipe 56, the valve V1, the pump 57, the pipe 58, the control valve CV1, the flow meter 61, the optical sensor 62, and the valve V3. The drain water is sucked from the tank 50 and returned to the tank 50.
[0131]
By circulating, the second filter 2 is formed on the first filter of the filter device 53, and finally, the object to be removed of the target colloid solution is captured.
[0132]
That is, when the drainage is sucked by the pump 57 through the first filter 1 with a weak suction pressure, the fine particles of the object to be removed are gelled as approaching the first filter 1 and adsorbed on the surface of the first filter 1. Is done. The gelled fine particles, which are larger than the filter holes 11 of the first filter 1, are gradually adsorbed on the surface of the first filter 1 and are laminated to form the second filter 2 made of a gel film. The gelled fine particles having a smaller diameter than the filter hole 11 pass through the first filter 1, and the water in the drainage is sucked through the gap as a passage along with the formation of the second filter 2, so that the first filter 1 is removed. , And is taken out as purified water, and the wastewater is filtered.
[0133]
The concentration of the fine particles contained in the filtered water is monitored by the optical sensor 62, and the filtration is started after confirming that the fine particles are lower than the desired mixing ratio. When the filtration is started, the valve V3 is closed by the detection signal from the optical sensor 62, the valve V4 is opened, and the circulation path is closed. Therefore, purified water is taken out from the valve V4. Air bubbles constantly supplied from the air pump 55 from the air diffuser 54 are adjusted by the control valve CV2 and supplied to the surface of the filter device 53.
[0134]
When the filtration is continuously performed, the water in the wastewater from the raw water tank 50 is taken out of the tank 50 as purified water, and the concentration of the substance to be removed in the wastewater increases. That is, the colloid solution is concentrated to increase the viscosity. For this purpose, the raw water tank 50 is replenished with drainage from the pipe 51, thereby suppressing an increase in the concentration of the drainage and increasing the filtration efficiency. However, the gel film thickly adheres to the surface of the second filter 2 of the filter device 53, and eventually the second filter 2 is clogged and cannot be filtered.
[0135]
When the second filter 2 of the filter device 53 is clogged, the filtering capability of the second filter 2 is regenerated. That is, the pump 57 is stopped, and the negative suction pressure applied to the filter device 53 is released.
[0136]
The regeneration step will be described in further detail with reference to the schematic diagram shown in FIG. FIG. 10A shows a state of the filter device 53 in the filtration step. Since the hollow portion 5 of the first filter 1 has a negative pressure compared with the outside due to the weak suction pressure, the first filter 1 has a shape depressed inward. Therefore, the second filter 2 adsorbed on the surface also has a shape depressed inward. The same applies to the gel film gradually adsorbed on the surface of the second filter 2.
[0137]
However, referring to FIG. 10 (B), in the regeneration step, the weak suction pressure is stopped and almost returns to the atmospheric pressure, so that the first filter 1 of the filter device 53 returns to the original state. As a result, the second filter 2 and the gel film adsorbed on the surface thereof also return. As a result, first, the suction pressure for adsorbing the gel film is eliminated, so that the gel film loses the adsorbing force to the filter device 53 and receives a force expanding outward. As a result, the adsorbed gel film starts to separate from the filter device 53 by its own weight. Further, in order to promote this separation, it is preferable to increase the amount of bubbles from the air diffuser 54 to about twice. According to the experiment, detachment starts from the lower end of the filter device 53, and the gel film of the second filter 2 on the surface of the first filter 1 detaches like an avalanche, and settles on the bottom surface of the raw water tank 50. Thereafter, the second filter 2 may circulate the wastewater in the above-described circulation path and perform film formation again. In this regeneration step, the second filter 2 returns to the original state, returns to a state where the drainage can be filtered, and filters the drainage again.
[0138]
Further, when the filtered water is caused to flow back into the hollow portion 5 in this regeneration step, firstly, the first filter 1 is assisted to return to the original state, and the hydrostatic pressure of the filtered water is applied to apply a force to expand outward. Secondly, the filtered water seeps from the inside of the first filter 1 through the filter hole 11 to the boundary between the first filter 1 and the second filter 2 and from the surface of the first filter 1 to the second filter 2. Promotes detachment of the gel film.
[0139]
If the filtration is continued while regenerating the second filter 2 as described above, the concentration of the substance to be removed from the wastewater in the raw water tank 50 increases, and the wastewater eventually has a considerable viscosity. Therefore, when the concentration of the substance to be removed from the wastewater exceeds a predetermined concentration, the filtration operation is stopped and the wastewater is left for sedimentation. Then, the concentrated slurry is stored at the bottom of the tank 50, and the concentrated slurry of the gel is recovered by opening the valve 64. The recovered concentrated slurry is compressed or thermally dried to remove water contained therein and further compress the amount. This can significantly reduce the amount of slurry treated as industrial waste.
[0140]
With reference to FIG. 11, an operation state of the filtration device shown in FIG. 2 will be described. The operating conditions are those using one side (area: 0.109 m ² ) of the A4 size filter device 53 described above. As described above, the initial flow rate is set to ³ cc / hour (0.08 m ³ / day) with good filtration efficiency, and the post-regeneration flow rate is set the same. The air blow rate is 1.8 L / min during film formation and filtration, and 3 L / min during regeneration. Pin and Re-Pin are suction pressures and are measured by the pressure gauge 59. Pout and re-Pout are the pressure in pipe 58 and are measured by manometer 60. The flow rate and the re-flow rate are measured by the flow meter 61, and represent the amount of filtration sucked from the filter device 53.
[0141]
In FIG. 11, the left Y-axis indicates the pressure (unit: MPa), and indicates that the negative pressure increases as approaching the X-axis. The right Y-axis shows the flow rate (unit: cc / min). The X-axis indicates the elapsed time (unit: minute) from the film formation.
[0142]
The point of the present invention is that the flow rate and the re-flow rate are controlled so as to maintain 3 cc / hour in the film formation step, the filtration step, and the filtration step after regeneration of the second filter 2. For this reason, in the film forming process, the second filter 2 is formed of a gel film that is softly adsorbed with an extremely weak suction pressure of -0.001 MPa to -0.005 MPa.
[0143]
Next, in the filtration step, Pin is gradually increased from -0.005 MPa, and filtration is continued while maintaining a constant flow rate. Filtration lasts about 1000 minutes, and when the flow rate begins to decrease, a regeneration step is performed. This is because the gel film adheres thickly to the surface of the second filter 2 to cause clogging.
[0144]
Further, when the regeneration of the second filter 2 is performed, the filtration is continued again at a constant reflow rate while gradually increasing the re-Pin. The regeneration and re-filtration of the second filter 2 is continued until the raw water 52 has a predetermined concentration, specifically, a concentration of 5 to 10 times.
[0145]
Also, different from the above-described operation method, a method of performing filtration while fixing the suction pressure at −0.005 MPa, which has a large filtration flow rate, can be adopted. In this case, the filtration flow rate gradually decreases with the clogging of the second filter 2, but there is an advantage that the filtration time can be increased and the control of the pump 57 can be simplified. Therefore, regeneration of the second filter 2 may be performed when the filtration flow rate is reduced to a certain value or less.
[0146]
FIG. 12A shows the particle size distribution of abrasive grains contained in the slurry for CMP. These abrasive grains are used for CMP of an interlayer insulating film made of Si oxide, and the material is made of Si oxide, which is generally called silica. The minimum particle size was about 0.076 μm, and the maximum particle size was 0.34 μm. The large particles are agglomerated particles formed by collecting a plurality of particles therein. The average particle size is about 0.1448 μm, and the distribution has a peak in the vicinity of 0.13 to 0.15 μm. In addition, KOH or NH3 is generally used as a slurry modifier. Also, the pH is between about 10 and 11.
[0147]
Specifically, abrasives for CMP mainly include silica-based, alumina-based, cerium oxide-based, and diamond-based abrasives, as well as chromium oxide-based, iron oxide-based, manganese oxide-based, BaCO4-based, antimony oxide-based, zirconia-based abrasive grains. , There is a yttria system. Silica is used for flattening an interlayer insulating film of a semiconductor, P-Si, SOI, and the like, and flattening an Al-glass disk. Alumina is used for polishing a hard disk, flattening a metal, a silicon oxide film and the like. Cerium oxide is used for polishing glass and Si oxide, and chromium oxide is used for mirror polishing of steel. Manganese oxide and BaCO4 are used for polishing tungsten wiring.
[0148]
Further, the sol is called an oxide sol, and is a mono-particle in which colloidal fine particles composed of a metal oxide or a partial hydroxide, such as silica, alumina, and zirconia, are uniformly dispersed in water or a liquid. It is used for flattening an interlayer insulating film and metal of a semiconductor device, and is also being studied for an information disk such as an aluminum disk.
[0149]
FIG. 12B is data showing that the CMP wastewater is filtered and the abrasive grains are captured. In the experiment, the stock solution of the above-mentioned slurry was diluted 50 times, 500 times, and 5000 times with pure water to prepare a test solution. These three types of test liquids were prepared on the assumption that the drainage would be about 50 to 5000 times because the wafer was washed with pure water in the CMP step as described in the conventional example.
[0150]
When the light transmittance of these three types of test solutions is examined with light having a wavelength of 400 nm, a 50-fold test solution is 22.5%, a 500-fold test solution is 86.5%, and a 5000-fold test solution is Is 98.3%. In principle, if the drainage does not contain abrasive grains, the light is not scattered, and the value should be as close to 100% as possible.
[0151]
When the filter on which the second filter membrane 13 was formed was immersed and filtered in these three types of test liquids, the transmittance after filtration was 99.8% for all three types. That is, since the value of the light transmittance after filtration is larger than the light transmittance before filtration, the abrasive grains can be captured. The transmittance data of the 50-fold diluted test solution does not appear in the drawing because its value is small.
[0152]
From the above results, when the removal of the colloid solution discharged from the CMP apparatus was filtered by the second filter 2 made of the gel film of the filter apparatus 53 provided in the filtration apparatus of the present invention, the transmittance was 99.8%. It turned out that it was possible to filter to the extent.
[0153]
In the above description, the method of filtering a fluid using the second filter which is a gel-like self-forming film has been described, but the self-forming film is not limited to the gel-like one. The configuration of the present application can also be applied to a filtering device and a filtering method using another type of self-forming film (precoat filter).
[0154]
【The invention's effect】
In the present invention, by providing the recovery tank 15 communicating below the raw water tank 50 for performing filtration, the object to be removed concentrated in the filtration step can be precipitated in the recovery tank 15. Further, since the recovery tank 15 is detachable from the filtration device, it is possible to recover the object to be removed settled in the recovery tank 15 while performing the filtering operation.
[0155]
Further, the raw water tank 50 is made of a material having excellent water repellency. Therefore, the gel-like material to be removed is moved to the collection tank 15 as a lump due to the surface tension. Therefore, it is possible to prevent the gel-like material to be removed from adhering to the inner wall of the raw water tank 50.
[0156]
Further, in order to mainly remove fine particles having a size of 0.15 μm or less, such as abrasive grains mixed in a slurry of CMP, a filter film having pores smaller than the fine particles is generally used. However, the present invention has realized a filtering device capable of forming a gel film filter and filtering an object to be removed of a colloid solution without using a filter film having small pores of 0.15 μm or less.
[Brief description of the drawings]
FIG. 1 is a configuration diagram (A) illustrating a filtration device of the present invention, and an enlarged cross-sectional view (B) of a raw water tank.
FIG. 2 is a diagram illustrating a filtration device embodied in the present invention.
FIG. 3 is a diagram illustrating an operation state of a filtration device according to a further embodiment of the present invention.
FIG. 4 is a diagram illustrating a filter device of the present invention.
FIG. 5 is a diagram illustrating a filter device according to a further embodiment of the present invention.
FIG. 6 is a diagram illustrating a filter of the present invention.
FIG. 7 is a diagram illustrating the operation principle of the filter of the present invention.
8A is a sectional view and FIG. 8B is a characteristic diagram for explaining film forming conditions of a second filter of the present invention.
FIG. 9 is a diagram illustrating characteristics of a second filter according to the present invention.
FIG. 10 is a diagram illustrating regeneration of the filter device of the present invention.
FIG. 11 is a diagram illustrating an operation state of the filtration device of the present invention.
FIG. 12 is a diagram illustrating the filtration characteristics of the present invention.
FIG. 13 is a diagram illustrating a conventional filtration system.
FIG. 14 is a diagram illustrating a CMP apparatus.
FIG. 15 is a diagram illustrating a system of a CMP apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st filter 2 2nd filter 4 Frame 5 Hollow part 6 Pump 7 Filtrate 11 Filter hole 40 Vent pipe 50 Raw water tank 52 Raw water 53 Filter device 57 Pump 61 Flow meter 62 Optical sensor

Claims (12)

A tank in which a fluid containing an object to be removed is stored, a filter device immersed in the tank, and a collection tank in which the object to be removed precipitates in communication with a lower portion of the tank through a valve,
The collection tank is separable from the tank, and the valve is shut off to separate the collection tank from the tank, thereby collecting the object to be removed precipitated in the collection tank. apparatus. The filtration device according to claim 1, wherein the tank has the tapered bottom, and the collection tank is connected to a lowermost portion of the bottom. The filtering device according to claim 1, wherein the recovery tank is mounted on a transfer unit. The filter device is formed of a first filter and a second filter made of the object to be removed deposited on the surface thereof, and the second filter separated from the first filter is settled in the collection tank. The filtration device according to claim 1, wherein the filtration is performed. 2. The filtering device according to claim 1, further comprising a diffuser for generating air bubbles from below the filter device, wherein the air bubbles cause the object to be removed attached to the inner wall of the tank to settle in the recovery tank. . A filter device formed of a tank containing a fluid containing a colloidal substance to be removed, a first filter immersed in the tank, and a second filter made of a gel film adsorbed on the surface of the first filter; A collection tank in which the object to be removed settles in communication with the lower part of the tank via a valve;
The collection tank is separable from the tank, and the valve is shut off to separate the collection tank from the tank, thereby collecting the object to be removed precipitated in the collection tank. apparatus. The filtration device according to claim 6, wherein the tank has the tapered bottom portion, and the recovery tank is connected to a lowermost portion of the bottom portion. The filtering device according to claim 6, wherein the collection tank is mounted on a transfer unit. The filtration device according to claim 5, wherein the gel-like second filter separated from the first filter precipitates in the collection tank. 7. The filtering device according to claim 6, wherein the inner wall of the tank is made of a material having good water repellency. The filtering device according to claim 6, wherein an inner wall of the tank is made of a resin. 7. The filtering device according to claim 6, further comprising a diffuser for generating air bubbles from below the filter device, wherein the air bubbles cause the object to be removed attached to the inner wall of the tank to settle in the recovery tank. .

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