JP4233485B2 - Flocculant manufacturing apparatus and flocculant manufacturing method - Google Patents

Description

  The present invention relates to a flocculant, a production apparatus thereof, and a production method.

  At present, reducing industrial waste and separating and reusing industrial waste are important themes from an ecological point of view and are corporate issues in the 21st century. Among these industrial wastes, there are various fluids containing the objects to be removed.

  These are expressed in various words such as sewage, drainage, and waste liquid. Hereinafter, a substance that is a substance to be removed in a fluid such as water or chemicals will be referred to as drainage. These wastewater is treated as industrial waste by removing the object to be removed with an expensive filtration processing device, etc., and draining the wastewater into a clean fluid and reusing it, or separating the object to be removed or unfiltered. ing. In particular, water is returned to the natural world such as rivers and seas by being filtered to be in a clean state that satisfies environmental standards, or reused.

  However, it is very difficult to adopt these apparatuses due to problems such as equipment costs such as filtration processing, running costs, and the like, which is also an environmental problem.

  As can be seen from this, the wastewater treatment technique is an important problem from the viewpoint of environmental pollution and from the viewpoint of recycling, and a system with low initial cost and low running cost is urgently desired.

  As an example, wastewater treatment in the semiconductor field will be described below. In general, when grinding or polishing metals, semiconductors, ceramics, etc., fluid such as water is taken into consideration to prevent temperature rise of jigs due to friction, improve lubricity, adhesion of grinding scraps or cutting scraps to plate-like bodies, etc. Is showered on a polishing (grinding) jig or plate.

  Specifically, a method of flowing pure water when dicing a semiconductor wafer or back grinding is used. In the dicing machine, in order to prevent the temperature of the dicing blade from rising and to prevent dicing debris from adhering to the wafer, a flow of pure water is created on the semiconductor wafer, or the water is discharged so that the pure water hits the blade. A nozzle is installed and showered. Also, when the wafer thickness is reduced by back grinding, pure water is flowed for the same reason.

  Waste water mixed with grinding or polishing waste discharged from the dicing equipment and back grinding equipment described above is filtered to clean water and returned to nature, or reused, and concentrated waste water is recovered. Yes.

  In the current semiconductor manufacturing, there are two methods for treating wastewater mixed with removal objects (scraps) mainly composed of Si: a coagulation sedimentation method, and a combination of filter filtration and a centrifugal separator.

  In the former coagulation-precipitation method, PAC (polyaluminum chloride) or Al2 (SO4) 3 (sulfuric acid band) or the like is mixed in the waste water as a coagulant to generate a reaction product with Si and remove this reaction product. The wastewater was filtered.

  In the latter method, which combines filter filtration and centrifugation, the wastewater is filtered, the concentrated wastewater is centrifuged and the silicon waste is recovered as sludge, and the clean water produced by filtering the wastewater is returned to nature. It was released or reused.

  For example, as shown in FIG. 17, waste water generated during dicing is collected in a raw water tank 201 and sent to a filter device 203 by a pump 202. Since the filter device 203 is equipped 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.

  On the other hand, the filter device 203 is regularly 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 of the recovered water tank 205. The waste water 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 centrifuge 209 via the pump 208 and separated into sludge and sludge by the centrifuge 209. Sludge composed of Si waste is collected in the sludge collection tank 210, and the separation liquid is collected in the separation liquid tank 211. Further, the drainage of the separation liquid tank 211 in which the separation liquid is collected is transported to the raw water tank 201 via the pump 212.

  These methods occur, for example, when grinding or polishing a solid or plate-like body mainly made of a metal material such as Cu, Fe, or Al, or a solid or plate-like body made of an inorganic substance such as ceramic. It was also used when collecting waste.

  On the other hand, CMP (Chemical-Mechanical Polishing) has appeared as a new semiconductor process technology. This CMP technology provides (1) realization of a flat device surface shape and (2) realization of an embedded structure made of a material different from that of the substrate.

  In (1), a fine pattern using a lithography technique is formed with high accuracy. Further, the combined use of the Si wafer bonding technique brings about the possibility of realizing a three-dimensional IC.

  (2) enables an embedded structure. Conventionally, a tungsten (W) embedding technique has been adopted for IC multilayer wiring. In this method, W was buried in the groove of the interlayer film by the CVD method, and the surface was etched back to flatten it, but recently it has been flattened by CMP. Applications of this embedding technique include damascene process and element isolation.

  These CMP techniques and applications are described in detail in “CMP Science” published by Science Forum.

  The CMP mechanism will be briefly described with reference to FIG. The semiconductor wafer 252 is placed on the polishing cloth 251 on the rotating surface plate 250, and is rubbed while flowing an abrasive (slurry) 253, polished, and chemically etched, thereby eliminating irregularities on the surface of the wafer 252. It is flattened by a chemical reaction by the solvent in the abrasive 253 and a mechanical polishing action between 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 adjuster, and is generally called a slurry. Yes. While flowing the slurry 253, the wafer 252 is rotated against the polishing cloth 251 and rubbed with a certain pressure. Reference numeral 254 denotes a dressing unit that maintains the polishing ability of the polishing pad 251 and always makes the surface of the polishing pad 251 dressed. Reference numerals 202, 208 and 212 denote motors, and 255 to 257 denote belts.

  The mechanism described above is constructed as a system, for example, as shown in FIG. This system roughly comprises a wafer cassette loading / unloading station 260, a wafer transfer mechanism 261, the polishing mechanism 262 described in FIG. 18, the wafer cleaning mechanism 263, and a system control for controlling these.

  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 rotating surface plate 250 provided in the polishing mechanism unit 262, and the wafer is planarized using CMP technology. . When the planarization 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. The cleaned wafer is accommodated in a wafer cassette 266.

  For example, the amount of slurry used in one process is about 500 cc to 1 liter / wafer. Further, pure water is caused to flow through the polishing mechanism 262 and the wafer cleaning mechanism 263. Since these wastewaters are finally combined together at the drain, wastewater of about 5 to 10 liters / wafer 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 the flattening of the metal and the flattening of the interlayer insulating film, and 5 to 10 liters of seven times drainage is completed until one wafer is completed. 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 have been treated by a coagulation precipitation method for colloidal solutions (see Patent Document 1 below).
Japanese Patent Laid-Open No. 2003-290779

However, in the coagulation-precipitation method, chemicals are added as coagulants, but it is very difficult to specify the amount of chemicals that react completely. In addition, flocs, which are the reaction product of chemicals and objects to be removed, are generated as if they were floating substances such as algae. The conditions for forming this floc are severe pH conditions, and a stirrer, a pH measuring device, a flocculant injection device, a control device for controlling these, and the like are required. In addition, a large sedimentation tank is required to settle the floc stably. For example, if the wastewater treatment capacity is 3 cubic meters (m ³ ) / 1 hour, a tank with a diameter of 3 meters and a depth of 4 meters (approximately 15 tons of sedimentation tank) is required. It becomes a large-scale system that requires a site of about 11 meters.

On the other hand, as shown in FIG. 17, in the method of combining the filter filtration of 5 cubic meters (m ³ ) / 1 hour and the centrifuge, the filter F (referred to as a UF module and made of polysulfone fiber) is used in the filtration device 203. In other words, water can be reused. However, four filters F are attached to the filtering device 203. From the life of the filter F, it has been necessary to replace a high-priced filter of about 500,000 yen / piece at least once a year. Therefore, there is a problem that the running cost is very large because the electric cost of the motor is very high and the replacement cost of the pump P and the filter F is high.

  Furthermore, in CMP, an amount of waste water that cannot be compared with dicing is discharged. The slurry is colloidally distributed in the fluid and does not settle easily due to Brownian motion. Moreover, the particle size of the abrasive grains mixed in the slurry is extremely fine, 10 to 200 nm. Therefore, when a slurry consisting of fine abrasive grains is filtered with a filter, the abrasive grains enter the pores of the filter, causing immediate clogging and frequent clogging. It was.

  Furthermore, aluminum contained in PAC (polyaluminum chloride) currently used as an aggregating agent may cause neurological diseases such as Alzheimer's disease. And what is substituted for the flocculant which has such a danger is requested | required.

  Accordingly, an object of the present invention is to provide a flocculant excellent in safety and economy as a recycle of CMP waste water as a flocculant, a manufacturing apparatus and a manufacturing method therefor.

The flocculant production apparatus of the present invention comprises an addition means for adding a halogen ion or a compound containing a halogen ion to a fluid containing particulate silica extracted from a concentrated CMP waste water , It is characterized by comprising generation means for introducing an iron ion eluted from an electrode pair and generating an aggregating agent that combines the silica and the iron ion.

In the method for producing a flocculant of the present invention, a halogen ion or a compound containing a halogen ion is added to a fluid containing particulate silica extracted from a concentrated CMP waste water, and an electrode pair containing iron is immersed in the fluid. Then, by applying a voltage to the electrode pair, iron ions are eluted from the electrode pair, and the iron ions and the silica are combined to produce a flocculant.

  Therefore, the above-mentioned means can provide a flocculant composed of a compound in which a metal and silica are bonded.

  According to the present invention, the following effects can be achieved.

  That is, a flocculant composed of a compound in which a metal and silica are bonded can be provided. The aggregating agent in which silica and metal are bonded has an aggregating effect equivalent to or higher than that of the above-described PAC. Furthermore, the flocculant of the present invention can be produced with a simple and low-cost apparatus and method.

<First embodiment>
In this embodiment, a flocculant and an apparatus and method for producing the same are described. First, an apparatus for producing the flocculant of this embodiment will be described with reference to FIG. FIG. 1A is a schematic view of a manufacturing apparatus 10A that manufactures a flocculant, and FIG. 1B is a schematic view of another form of manufacturing apparatus 10B.

  Referring to FIG. 1A, a flocculant manufacturing apparatus 10A includes a flocculant obtained by introducing a metal belonging to Group 8 of the periodic table or a metal ion into a fluid containing silica and combining the silica and the metal ion. It is the structure which has a production | generation means to produce | generate. Here, an electrode pair is employed as the generating means. Hereinafter, the flocculant manufacturing apparatus 10A of this embodiment will be described together with its operation.

  The tank 11 stores a fluid W that performs processing according to this embodiment. Here, as the fluid W, a fluid containing silica is employed. For example, silica is contained in the wastewater generated from the CMP process or the like. Further, if it is a fluid containing silicon such as silica, it is possible to adopt a fluid other than the waste water generated from the CMP process.

  The electrode pair 12 including the first electrode 12A and the second electrode 12B has a function of treating a fluid by electrochemical treatment. The electrochemical treatment here refers to, for example, an agglomeration effect caused by metal ions melted from an electrode. Here, one electrode pair 12 is illustrated, but a configuration in which a large number of electrode pairs 12 are immersed in a fluid may be employed. Moreover, as the shape of each electrode, various shapes such as a rod shape and a plate shape can be adopted. It is preferable that the distance between the first electrode 12A and the second electrode 12B be close as long as no short circuit occurs. By narrowing this interval, the electric power used for the electrochemical treatment of the fluid can be reduced. Furthermore, as the first electrode 12A, a conductor including the eighth group or the eighth group of the periodic table, or the same group or a conductor including the same group can be employed. For example, iron (Fe) or iron-coated one can be used as the first electrode 12A. The first electrode 12A and the second electrode 12B are electrically connected to a power source 12C that supplies a direct current. Furthermore, a switching means for switching the electrode pair 12 is provided in the power source. Further, monitoring means for monitoring the current passing through the electrode pair 12 or the voltage applied thereto may be added. The operation of the electrode pair 12 can be controlled according to the output of the monitoring means. Further, a cooler may be installed in order to suppress the temperature rise of the fluid due to electrolysis of the electrode pair. Specifically, the cooler can control the temperature of the fluid by means for cooling the tank 11 or means for allowing the fluid to flow into the cooling device.

  The stirring device 14 has a function of stirring the fluid W stored in the tank 11. Here, the fluid W is agitated by a mechanism in which the propeller connected to the motor rotates in the fluid. The stirring device may be a device having another mechanism as long as it has a stirring action.

  Reference numeral P1 indicates a path for supplying the tank W1 with the fluid W1 that is the water to be treated of this embodiment. As described above, the drainage discharged from the CMP process may pass through the path P1. Furthermore, CMP wastewater that has been subjected to some pretreatment such as concentration may be introduced into the tank 11 from P1.

  Reference symbol P2 is a path through which a pH adjusting agent or a conductivity adjusting agent is introduced. These modifiers may be introduced from separate routes. Here, the PH adjusting agent refers to an adjusting agent that dissolves in the fluid W1 inside the tank 11 and exhibits acidity. For example, in addition to chemicals such as hydrochloric acid and sulfuric acid, solids and powders that are dissolved in water and exhibit acidity can be employed as the PH adjuster. The fine particles contained in the fluid may lose its fluidity when the pH of the fluid is inclined to alkalinity. Therefore, by making the pH of the fluid acidic with a PH adjuster, production of a flocculant with stable performance, Alternatively, stable aggregation can be performed.

  As the conductivity adjusting agent, a halogen ion or a compound containing a halogen ion can be employed. Specifically, sodium chloride can be adopted as the conductivity adjusting agent and can be supplied to the fluid W in a state dissolved in a solvent such as water, a powder state, or a solid state. As described above, by adding the conductivity adjusting agent to the fluid W, the conductivity of the fluid W can be improved. Therefore, a predetermined current can flow through the electrode pair 12 via the fluid W. Further, a monitoring means for monitoring the pH of the fluid may be provided, and the amount of the PH adjusting agent to be added may be determined according to the output of the monitoring means. Furthermore, a means for measuring the temperature of the fluid stored in the tank 11 may be provided to prevent an excessive temperature rise of the fluid W.

  Next, the operation of the electrode pair 12 having the above configuration will be described. First, the fluid W1 is introduced into the tank 11 from P1. Then, the electrode pair 12 is operated by turning on the power supply 12C. The first electrode 12A is connected to the positive electrode of the power source 12C to become an anode electrode, and the second electrode 12B is connected to the negative electrode of the power source 12C to form a cathode electrode. Thereby, the fluid W is subjected to electrolytic treatment as an electrochemical method. Since the first electrode 12A constituting the anode is composed of the conductor as described above, iron (II) ions are eluted from the first electrode 12A into the fluid, so that iron (III ) Oxidized to ions. Then, it chemically reacts with silica, which is one of the objects to be removed contained in the fluid, to produce a polymer compound of iron silica. The polymer compound which is an aggregate of iron silica is formed to be slightly larger than the original silica particles. Here, the amount of metal eluted from the electrode pair 12 is preferably 4 to 5 times as much as the removal target contained in the fluid in terms of molar ratio. Specifically, it is preferable to introduce a larger amount of metal ions than the amount of ions that bind to the object to be removed contained in the fluid.

  Moreover, the high molecular compound of iron silica itself functions as a flocculant. Further, silica is an object to be removed contained in the CMP waste water. Therefore, by aggregating the iron silica, there is an advantage that the silica that is one of the objects to be removed can be agglomerated to facilitate the waste water treatment, and further, an iron silica aggregating agent can be generated. By producing the iron silica flocculant, abrasive grains and grinding scraps other than silica contained in the CMP waste water can be agglomerated to facilitate generation of the flocculant or waste water treatment by agglomeration.

  The iron-silica flocculant has a stronger aggregating action when it is produced by the combination of iron (III) ions and silica than by the combination of iron (II) ions and silica. However, the amount of iron (III) ions eluted by the electrolytic treatment of iron is very small, and most of them are eluted as iron (II) ions and exist in the tank 11. Therefore, it is possible to generate iron (III) ions by adding an oxidizing agent and oxidize iron (II) ions to generate iron silica flocculants. As the oxidizing agent, hydrogen peroxide or ozone is preferable. Furthermore, according to experiments conducted by the inventors of the present application, it is possible to generate sufficient iron (III) ions by adding 3 mL of 30% hydrogen peroxide to the 200 cc CMP waste water having a silica amount of 1200 mg / L. Met. As a method of adding ozone, there is a method of supplying ozone generated from an ozone generator or the like as bubbles into the fluid W in the tank 11, or a method of flowing a fluid containing ozone into the tank 11.

  The timing for adding the oxidizing agent is preferably after iron (II) ions are introduced or eluted. Specifically, during or after the PH adjustment described later is preferable. Further, hydrogen peroxide and ozone are contained in the waste water in the semiconductor manufacturing process. Therefore, the wastewater generated in the semiconductor manufacturing process can be efficiently treated and the coagulant reduced at the same time by allowing wastewater containing hydrogen peroxide and ozone to flow into the flocculant manufacturing equipment where CMP wastewater is stored as an oxidizing agent. It becomes possible to produce at a cost. Also, hydrogen peroxide used in other manufacturing processes can be diverted. Iron (III) ions are generated by oxidizing an iron (II) ion with hydrogen peroxide as an oxidizing agent. Therefore, it is possible to adjust the amount of iron (III) ions produced by adjusting the amount of oxidizing agent that reacts with iron (II) ions. Therefore, the flocculant generated from iron (II) ion and the flocculant generated from iron (III) ion by converting at least a part of iron (II) ion to iron (III) ion by the oxidizing agent It is possible to adjust the ratio. In addition, it is possible to change the molar ratio of iron and silica constituting the flocculant to be generated by adjusting the addition amount of iron ions. From the above, it is possible to control the flocculation performance of the iron silica flocculant, and it is possible to produce a flocculant suitable for the wastewater to be treated. Moreover, when a strong coagulant | flocculant is added to organic waste_water | drain etc., organic waste_water | drain raises a bubble and the fall of a coagulation | floating action has been a problem. However, since the present flocculant can control the type of iron ions bound to silica and the molar ratio of iron to silica, it is possible to adjust the flocculating ability of the flocculant. Therefore, the problem can be solved by using the present flocculant.

  Along with the electrochemical treatment, both regulators are added via P2. By adding the conductivity adjusting agent to the fluid W1, the electrical treatment by the electrode pair 12 can be reliably performed. Further, by adding a PH adjuster, it is possible to prevent the objects to be removed mixed in the fluid W from aggregating to form flocs themselves. That is, by adjusting the fluid W to be more acidic than neutral, the particles contained in the fluid can be separated from each other. Furthermore, according to experiments conducted by the inventors of the present application, an iron silica flocculant can be satisfactorily produced even when the pH is in the range of 2.5 to 2. In addition, the optimum pH for generating iron (III) ions by the oxidant is around 2.8, and it is preferable to be under acidic conditions. Therefore, the formation of iron (III) ions and the formation of iron silica flocculants are prevented. It can be carried out under almost the same acidic region. Therefore, it is preferable to add a pH adjusting agent at least to the extent that the CMP waste water becomes neutral when the agglomeration by the electrolytic treatment is performed on the CMP waste water that is originally alkaline. However, the PH of the fluid W does not necessarily have to be acidic, and if there is no risk of floc formation, agglomeration without PH adjustment can be performed. In addition, the pH of the fluid may be adjusted after the above aggregation treatment.

  Considering the case where the water to be treated that has undergone the agglomeration treatment is discharged, the fluid that has undergone the agglomeration treatment is preferably neutral. This is to meet the pH drainage standard. Moreover, in order to perform a suitable coagulation process, it is suitable to adjust the pH of the fluid to neutral.

  When the electrochemical treatment proceeds, the fluid in the tank becomes alkaline due to the generation of hydroxyl groups (OH). Therefore, the action of the above-described pH adjusting means is also important in order to prevent fluid alkalinization due to this phenomenon.

  After a while from the start of the above process, the polarity of the electrode pair 12 is switched. Specifically, the first electrode 12A is a cathode and the second electrode 12B is an anode. This switching can also be performed periodically by setting a predetermined time in advance. Further, the switching can be performed by monitoring the current passing through the electrode pair 12 or the voltage applied to the electrode pair 12. By switching the electrodes, it is possible to suppress the inhibition of conduction due to the removal object attached to the cathode electrode. Specifically, by switching the electrode to the anode, the metal on the electrode surface is eluted, and the layer of the object to be removed adhered to the surface is peeled off. Therefore, in order to continuously perform the aggregation treatment, it is preferable to perform the electrochemical treatment while switching the polarity of the electrodes. Further, while the electrolytic treatment is being performed, the fluid W is stirred by the stirring device 14. As a result, the objects to be removed contained in the fluid stored in the tank 11 can be uniformly aggregated.

  By performing the electrical treatment, the objects to be removed contained in the fluid W are aggregated. That is, the object to be removed contained in the fluid can be removed by this aggregation. Furthermore, when a substance containing silicon such as silica is contained as an object to be removed, a polymer compound that functions as a flocculant can be generated. Furthermore, even when the fluid W contains a non-aggregating substance other than silica, it can be removed by the aggregating effect of the aggregating agent produced by the above method. In addition, the object to be removed contained in the CMP wastewater may contain harmful substances such as copper in addition to silica, but even in this case, the harmful substances such as copper can be shared by forming a flocculant. Can be sunk and removed.

  The CMP waste water is mixed with extremely fine silica having a particle size of about 100 nanometers. Therefore, the flocculant produced from such fine silica is also fine. A flocculant having a fine diameter generally has high aggregating performance. Furthermore, it is considered that a decrease in aggregation ability due to aggregation of the aggregating agent itself can be suppressed. Here, the particle size distribution of the flocculant produced by this embodiment is, for example, in the range of 1 μm to 500 μm. The particle size distribution of the flocculant has a shape having one peak or a plurality of peaks.

  With reference to FIG. 1 (B), the coagulant | flocculant manufacturing apparatus 10B of another form is demonstrated. The flocculant manufacturing apparatus 10B shown in this figure is configured to include means for adding a substance containing metal to the fluid W in place of the electrode pair 12 described above. Specifically, a fluid containing metal is introduced into the tank 11 from the path P3. Specifically, as the metal contained in the introduced fluid, the same metal as that constituting the electrode pair 12 described above can be employed. For example, a fluid containing an ionized metal (for example, iron) can be adopted as the fluid. As an example, a fluid containing iron chloride may be introduced from the path P3. It is also possible to produce an aggregating agent optimum for the intended use by adjusting the amount of iron (III) ions to be introduced.

  As described above, the flocculant manufacturing apparatus described with reference to FIG. 1 can perform the agglomeration treatment of the fluid containing the object to be removed, and also the high concentration composed of silica and metal ions contained in the fluid. Molecular compounds can be produced. Therefore, when waste water containing silica such as CMP waste water is adopted as the fluid W, a high-performance flocculant can be generated simultaneously with the waste water treatment. From this, the above-mentioned flocculant manufacturing apparatus can be regarded as an aggregating apparatus. Moreover, the flocculant manufactured by the method mentioned above can be used in wide fields, such as a waterworks and a sewer.

  With reference to FIG. 2, an example of the waste water treatment apparatus using the flocculant manufacturing apparatus 10 mentioned above is demonstrated. Referring to the figure, CMP waste water containing a silicon component such as silica is discharged from CMP apparatus 15. The path P1 indicates the path of the CMP drainage. In the path P <b> 1, the CMP waste water discharged from the CMP waste water is conveyed to the flocculant manufacturing apparatus 10. A CMP waste water treatment device 17 is provided in the middle of the path P1.

  In the CMP apparatus 15, the CMP waste water is discharged by performing the CMP process. As an example, the concentration of silica contained in the CMP waste water is 1000 ppm to 2000 ppm. Furthermore, in addition to silica, an object to be removed such as metal is contained.

  The CMP wastewater treatment device 17 performs pretreatment of the CMP wastewater sent to the flocculant manufacturing device 10. Specifically, CMP waste water is concentrated and impurities are removed. As a specific method for concentrating the CMP waste water, concentrating by sunlight, concentrating by heating, concentrating by a filtering device, concentrating by coagulating precipitation, or the like can be considered. In this embodiment, a method using a filtration device described in a second embodiment to be described later can also be employed. By concentrating the CMP waste water using the CMP waste water treatment device 17, the flocculant manufacturing device 10 can generate a flocculant having a high concentration. Here, it is also possible to configure the whole without the CMP waste water treatment device 17.

  In the flocculant manufacturing apparatus 10, the flocculant is generated from the CMP waste water. Since the details of the flocculant manufacturing apparatus 10 have been described with reference to FIG. 1, the description thereof is omitted here. With the flocculant produced by this apparatus, it is possible to treat CMP wastewater in an amount of about 100 to 1000 times the amount of the flocculant.

  The path P3 is a path through which the flocculant generated by the flocculant manufacturing apparatus 10 passes. The flocculant passing through this path may be in a liquid state that has been subjected to a flocculant treatment by the flocculant production apparatus 10 or may be in a state in which a treatment such as concentration has been performed. Further, the flocculant may be in a solid or powdery solid state.

  In the solid-liquid separator 16, the waste water is purified using the flocculant generated by the flocculant manufacturing apparatus 10. As an example of the to-be-processed water processed with this apparatus, the CMP waste water which passes the path | route P4 is mentioned. The flocculant used here is produced by electrolytically treating a part of the CMP waste water. Therefore, in this embodiment, it is possible to perform solid-liquid separation of the remaining CMP wastewater itself using the flocculant generated from a part of the CMP wastewater. This is one advantage of this embodiment. That is, in the past, the CMP waste water was treated using a separately prepared treatment agent or the like, but in this embodiment, the CMP waste water treatment can be performed without using the treatment agent. Furthermore, the flocculant produced | generated from CMP waste_water | drain can also be handled as a valuable material.

  As a specific mechanism of the solid-liquid separator 16, a mechanism for performing membrane filtration, a mechanism for performing coagulation sedimentation, and the like can be generally employed. Furthermore, the filtration apparatus described in the second embodiment to be described later can also be used here. In any mechanism, by using the flocculant of this embodiment, the object to be removed contained in the fluid is aggregated, and the object to be removed can be efficiently removed. Furthermore, by using the flocculant of this embodiment, there is an advantage that toxic substances such as heavy metals contained in the object to be removed can be aggregated. Furthermore, the solid-liquid separator 16 generates agglomerates composed of CMP waste water. The dehydrated aggregate can be used as an adsorbent or a heat insulating material. Moreover, the treated water processed with this apparatus may be discharged | emitted out of the system, and may be reused.

  The path P5 is a path through which wastewater other than CMP wastewater flows into the solid-liquid separator 16. For example, wastewater discharged from equipment other than the CMP apparatus at the semiconductor manufacturing factory can be introduced into the solid-liquid separator 16 from the path P5. Thereby, the waste water discharged from the semiconductor manufacturing factory can be treated using the flocculant generated from the CMP waste water. Moreover, waste water other than the waste water discharged from the semiconductor manufacturing factory can be flowed to the path P5.

  The path P6 is a path through which the oxidant flows into the tank 11, and has a function as an oxidant addition means. Here, hydrogen peroxide or ozone is employed as the oxidizing agent, and a fluid containing the oxidizing agent is allowed to flow into the tank 11. Further, ozone gas may be diffused into the fluid W to dissolve ozone. Further, wastewater containing hydrogen peroxide or ozone generated in the semiconductor manufacturing process, or hydrogen peroxide or ozone used in another manufacturing process may flow into the tank 11 through the path P6. Iron (II) ions can be oxidized by the oxidizing agent to generate iron (III) ions. This makes it possible to generate an oxidizing agent in which iron (III) ions and silica are bonded. Moreover, the kind of iron ion couple | bonded with a silica can be controlled by adjusting the quantity of the oxidizing agent which flows in from the path | route P6. Therefore, it is possible to adjust the aggregation ability of the flocculant.

  In the present embodiment, the method for treating wastewater using a flocculant produced by CMP wastewater has been described. However, various methods other than the above can be adopted as the wastewater treatment method. For example, by treating all of the CMP waste water generated from the CMP apparatus with the flocculant manufacturing apparatus 10, all of the CMP waste water can be reused as the flocculant. In this case, the CMP waste water may be concentrated by the CMP waste water treatment device 17.

  Next, with reference to FIG. 3 to FIG. 7, characteristics of the flocculant manufactured by the above flocculant manufacturing apparatus will be described.

  With reference to the graph of FIG. 3, the coagulant effect of the coagulant | flocculant manufactured with the coagulant | flocculant manufacturing apparatus 10 of this form is confirmed. The vertical axis of the graph in FIG. 3 indicates the concentration of silica contained in the supernatant of the CMP wastewater, and the horizontal axis indicates the amount of the flocculant to be added. Here, several 500 ml of CMP waste water was prepared, and a coagulant was added to each waste water in amounts of 10, 30, and 50 ml / L to perform the coagulation sedimentation treatment. From the graph in the figure, it can be seen that as the amount of the flocculant added increases, the concentration of silica in the wastewater decreases. Therefore, the coagulation effect with respect to the CMP waste water of the coagulant | flocculant produced | generated by this form was confirmed.

  With reference to the graph of FIG. 4, the performance of the flocculant of this form is compared with a commercially available thing. Here, the aggregating performance of a commercially available aggregating agent made of polyiron and the aggregating agent produced according to the present embodiment were compared. The vertical axis of the graph in FIG. 4 indicates the aggregation rate of the aggregates measured using a graduated cylinder, and the horizontal axis indicates the elapsed time since the flocculant was added. With reference to the figure, it was confirmed that the flocculant produced | generated by this form has the aggregation performance equivalent to or more than a commercially available thing.

  With reference to the graph of FIG. 5, an investigation was made on PH, which is an important factor for coagulation precipitation. Here, agglomeration treatment was performed on several types of CMP wastewater having different pHs using the aggregating agent of the present application, and the amount of silica and iron remaining in the supernatant was measured. In the graph of FIG. 5, the left vertical axis indicates the concentration of iron remaining in the supernatant, the right vertical axis indicates the silica component remaining in the supernatant, and the horizontal axis indicates the pH of the drainage. Referring to this graph, it can be seen that the residual iron concentration is 0 mg / L in the range of PH from 4 to 7, and the amount thereof is very small. Further, considering that the iron emission standard is 10 mg / L, it can be seen that the flocculant of the present application can be applied even to wastewater having a pH of 4 or less or 7 or more. Further, the concentration of the residual silica showed a very low value in the range of PH from 4 to 8. Although the other PH regions showed relatively high residual silica concentrations, there is no problem with emissions. From the above, it was confirmed that the flocculant of the present application can be used in a wide PH range. Preferably, it was confirmed that the coagulant effect of the coagulant of this embodiment is high when the pH is in the range of 4 to 7.

  With reference to the graph of FIG. 6, the sedimentation effect of the flocculant of this form is confirmed. Here, sedimentation refers to a phenomenon in which the flocculant aggregates with the object to be removed contained in the fluid and precipitates. The treated water used here is waste water containing copper. The vertical axis of this graph indicates the concentration of copper contained in the supernatant, and the horizontal axis indicates the amount of flocculant added. Referring to the figure, it can be seen that as the amount of the flocculant added increases, the concentration of copper remaining in the supernatant decreases. Furthermore, it can be seen that when the amount of the flocculant to be added is 1000 mg / L or more, there is almost no copper remaining in the supernatant. From the above, the flocculant of this embodiment has a function of removing harmful metals such as copper from the fluid.

  With reference to the graph of FIG. 7, when processing wastewater containing copper, the concentration of copper and iron remaining in the supernatant and the pH of the wastewater were examined. The vertical axis on the left side of this graph indicates the amount of remaining copper, the vertical axis on the right side indicates the amount of remaining iron, and the horizontal axis indicates the pH of drainage. Here, the addition amount of the flocculant was fixed at 1000 mg / L. From this graph, it was confirmed that the higher the pH of the wastewater, the lower the concentration of residual iron and copper.

  With reference to the graph of FIG. 7 (B), the waste water containing the slurry used for CMP was examined over time for the sedimentation rate using the flocculant of this embodiment. Here, 500 mL of waste water having a silica concentration of 1200 mg / L was used. Moreover, the coagulant | flocculant which made the iron (II) ion produced | generated by this form or an iron (III) ion as a main component, and the commercially available flocculant were used for the coagulant | flocculant. As the flocculant mainly composed of iron (III) ions, a flocculant produced by adding 3 mL of hydrogen peroxide in the presence of iron (II) ions in a silica-containing solution was used. First, referring to the same figure, the aggregating ability of a flocculant mainly composed of iron (II) ions and a commercially available flocculant are compared. As a result, it was confirmed that the settling rate and settling rate of silica with the flocculant showed almost the same value. Thus, it was confirmed that the flocculant mainly composed of iron (II) ions has the same flocculating ability as that of the commercially available flocculant.

  Next, the aggregating ability of the aggregating agent mainly composed of iron (III) ions and the aggregating agent mainly composed of iron (II) ions will be compared. Referring to the figure, silica that could not be precipitated with a flocculant mainly composed of iron (II) ions is precipitated by using a flocculant mainly composed of iron (III) ions. Was confirmed. Furthermore, by comparing the sedimentation rates at the same time, it was confirmed that the coagulant containing iron (III) ions as the main component has a faster coagulation rate.

<Second Embodiment>
In this embodiment, a filtration mechanism applicable to the CMP waste water treatment apparatus 17 or the solid-liquid separation apparatus 16 shown in FIG. 2 in the first embodiment will be described.

  First, the definition of terms used in the description of this embodiment will be clarified.

  The colloidal solution refers to a state in which fine particles having a diameter of 1 nm to 1 μm are dispersed in a medium. These fine particles have a Brownian motion and have a property of passing through a normal filter paper but not through a semipermeable membrane. In addition, the property of very slow aggregation speed is thought to reduce the chance of approach because electrostatic repulsion is acting between the fine particles.

  The sol is used almost synonymously with the colloidal solution. Unlike the gel, the sol is dispersed in a liquid and exhibits fluidity, and the fine particles are actively performing Brownian motion.

  A gel is a state in which colloidal particles have lost their independent motility and are aggregated and solidified. For example, agar and gelatin are dispersed into a sol when dissolved in warm water, but when cooled, they lose their fluidity and become a gel. Gels include hydrogels with a high liquid content and slightly dry xerogels.

  Factors for gelation include removing the water of the dispersion medium and drying, adding electrolyte salt to silica slurry (pH 9-10) to adjust pH to pH 6-7, cooling to lose fluidity Etc.

  Slurry refers to a colloidal solution or sol used for polishing by mixing particles with liquid and chemicals. The above-mentioned abrasive used for CMP is called 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. Silica-based abrasives are most often used, and colloidal silica is widely used. Colloidal silica is a dispersion in which ultrafine silica particles having a colloidal size of 7 to 300 nm are uniformly dispersed without being precipitated in water or an organic solvent, and is also called silica sol. Since the colloidal silica has monodispersed particles in water, the colloidal silica hardly settles even when left for more than one year due to the repulsive force of the colloidal particles. Ammonia is added to the CMP slurry applied to the oxide film.

  First, the present embodiment is to provide a fluid processing system for removing an object to be removed by filtration from waste water in a state where the object to be removed is contained in a fluid as a colloidal solution or a sol.

  An object to be removed is a colloidal solution (sol) containing a large amount of fine particles having a particle size distribution of 3 nm to 2 μm. For example, a semiconductor generated by grinding with abrasive grains such as silica, alumina or ceria used for CMP and abrasive grains. Material waste, metal waste and / or insulating film material waste. In this example, a slurry for polishing an ILD1300 oxide film manufactured by Rodel Nitta was used as the CMP slurry. This slurry is an ammonia-based slurry whose main component is silica having a pH of 10 and an abrasive grain distribution of 10 to 350 nm. Due to the strong alkalinity, the slurry is highly dispersible and difficult to gel.

  Referring to FIG. 8 and subsequent figures, the filter device used in this embodiment removes a fluid (drainage) mixed with an object to be removed of a colloidal solution (sol) with a filter made of a gel film formed from the object to be removed. It is.

  More specifically, a gel film to be a second filter 2 formed from a CMP slurry that is an object to be removed of a colloidal solution is formed on the surface of the first filter 1 made of organic polymer. It is immersed in the fluid 3 in the tank, and the waste water containing the object to be removed is filtered. The object to be removed is characterized in that a large sol particle aggregated from the initial particle is formed in advance by electrochemical treatment with the electrode 12 to facilitate gelation.

  The first filter 1 can be either organic polymer type or ceramic type in principle, as long as a gel film can be attached. Here, a polyolefin polymer film having an average pore diameter of 0.25 μm and a thickness of 0.1 mm was employed. A surface photograph of the filter membrane made of polyolefin is shown in FIG.

  Further, the first filter 1 has a flat membrane structure provided on both surfaces 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.

  Next, the second filter 2 is a gel film that is attached to the entire surface of the first filter 1 and is immediately gelled by sucking the sol particles aggregated to be removed. In general, since the gel film is jelly-like, it is considered that there is no function as a filter. However, in this embodiment, the function of the second filter 2 can be provided by selecting the gel film generation conditions. This generation condition will be described in detail later.

  Now, with reference to FIGS. 8 and 9A, the second filter 2 that is the gel film of the object to be removed is formed by the above-described colloidal solution (sol) of the object to be removed, and the filtration for removing the object to be removed is described with reference to FIGS. explain.

  The fluid (drainage) in which the object to be removed of the colloidal solution (sol) is mixed is aggregated by electrochemical treatment to form large sol particles. That is, even the large sol particles do not lose the fluidity of the sol and are not gelled, but are placed in a state in which they are easily gelled. In FIG. 8, large sol particles are represented as two sol particles combined, but this number is not related. Usually, the sol particles having a size of about 20 nm are aggregated to form an aggregated sol particle having a size of about 100 nm.

  The first filter 1 has a large number of filter holes 1A, and the gel film of the object to be removed formed in layers on the opening of the filter hole 1A and the surface of the first filter 1 is the second filter 2. is there. On the surface of the first filter 1, there are aggregated particles of an object to be removed that are easily aggregated and gelled. The aggregated particles are sucked through the first filter 1 by the suction pressure from the pump, and the fluid 3 Since moisture is absorbed, the gel is formed immediately after drying (dehydration), and the second filter 2 is formed on the surface of the first filter 1.

  Since the second filter 2 is formed from the aggregated particles of the object to be removed, the film thickness immediately becomes a predetermined film thickness, and filtration of the aggregated particles of the object to be removed of the colloidal solution is started using the second filter 2. . Therefore, if the filtration is continued while sucking with the pump 6, the gel film of aggregated particles is laminated on the surface of the second filter 2 to become thick, and the second filter 2 is clogged and cannot be continuously filtered. During this time, the agglomerated particles of the object to be removed adhere to the surface of the second filter 2 while being gelled, and the wastewater passes through the first filter 1 and is taken out as filtered water.

  In FIG. 9 (A), there is drainage of the colloidal solution mixed with the object to be removed on one side of the first filter 1, and the first filter 1 has passed through the first filter 1 on the opposite side of the first filter 1. Filtered water is generated. The drainage is sucked and flows in the direction of the arrow, and as a result of the suction, the aggregated particles in the colloid solution lose their electrostatic repulsion as they approach the first filter 1 and are gelled to form a gel film in which several aggregated particles are bonded. The second filter 2 is formed by being adsorbed on the surface of the first filter 1. By the action of the second filter 2, the object to be removed in the colloidal solution is gelled while the waste water is filtered. Filtrated water is sucked from the opposite surface of the first filter 1.

  By slowly sucking the colloidal solution drainage through the second filter 2 in this way, the water in the drainage can be taken out as filtered water, and the object to be removed is dried and gelled and laminated on the surface of the second filter 2. Then, the aggregated particles of the removal target are captured as a gel film.

  Next, the generation conditions of the second filter 2 will be described with reference to FIG. FIG. 10 shows the generation conditions of the second filter 2 and the subsequent filtration amount.

  Next, the filtration conditions of the second filter 2 will be described. The amount of purified water filtered at the time of filtration varies greatly depending on the production conditions of the second filter 2, and if the purification conditions of the second filter 2 are not properly selected, the gel membrane cannot be filtered almost due to the characteristics of the second filter 2. Becomes clear. This is consistent with the fact that conventionally it has been said that filtration of colloidal solutions is difficult.

The characteristics shown in FIG. 10B 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, and 50 cc of a stock solution of slurry 22 for polishing ILD1300 oxide film manufactured by Rodel Nitta Co. and a flocculant are added to generate a gel film by changing the suction pressure. Subsequently, the remaining slurry 22 is discarded, 100 cc of purified water 23 is added, and filtration is performed at a very low suction pressure. Thereby, the filtration characteristic of the gel film used as the 2nd filter 2 can be investigated. At this time, the first filter 1 having a diameter of 47 mm is used, and its area is 1734 mm ² .

  In FIG. 10B, in the gel film generation step, film formation was performed 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 as strong as -55 cmHg, the filtration amount is as large as 16 cc in 2 hours, and becomes 12.5 cc, 7.5 cc, 6 cc, and 4.5 cc in order.

  Next, it replaces with purified water and performs filtration with this gel membrane. The suction pressure at this time is set to -10 cmHg constant. A gel film formed at a suction pressure of −55 cmHg can only filter 0.75 cc / hour. A gel film formed at a suction pressure of −30 cmHg has a filtration rate of about 1 cc / hour. However, the filtration amount is 2.25 cc / hour for a gel membrane with a suction pressure of −10 cmHg, 3.25 cc / hour for a gel membrane with a suction pressure of −5 cmHg, and 3.1 cc / hour for a gel membrane with a suction pressure of −2 cmHg. The gel film formed with the suction pressure can be stably filtered even in the filtration process. From this experimental result, if the suction pressure is set so that the filtration amount of about 3 cc / hour is set in the gel film generation step of the second filter 2, the filtration amount in the subsequent filtration step is the largest. it is obvious.

  The reason for this is that if the suction pressure is strong, the gel film to be formed has a low degree of swelling, becomes dense and hard, and the gel film is formed in a contracted state with little moisture content, so that purified water penetrates. This is probably because the passage is almost gone.

  On the other hand, if the suction pressure is weakened, the gel film to be formed has a high degree of swelling, a low density and is soft, and the gel film is formed with a large amount of water swelled and purified water penetrates. Many passages can be secured. It can be easily understood if you think about the situation where powder snow falls slowly. A feature of this embodiment is that filtration is realized by using a gel film having a high degree of swelling formed with this weak suction pressure and utilizing the property of moisture permeating into the gel film.

  The filter shown in FIG. 9 (A) shows one side of the filter shown in FIG. 8, and is a schematic diagram for explaining how the gel film actually adheres.

  The first filter 1 is immersed vertically in the colloidal solution drainage, and the drainage is a colloidal solution in which the objects to be removed are dispersed. By the electrochemical treatment by the electrode 12 described above, a polymer compound that is an aggregate of iron silica is formed. The iron-silica polymer compound functions as an aggregating agent, whereby the object to be removed S2 is aggregated to produce aggregated particles S1. When the drainage is sucked by the pump 6 through the first filter 1 with a weak suction pressure, the aggregated particles of the objects to be removed are bonded to each other on the surface of the first filter 1 to be gelled, and the surface of the first filter 1 To be adsorbed. Aggregated aggregated particles S1 indicated by white circles are adsorbed and stacked on the surface of the first filter 1 to form a second filter 2 made of a gel film, which is larger than the filter hole 1A of the first filter 1. The agglomerated particles S1 having a diameter smaller than that of the filter hole 1A pass through the first filter 1. However, in the step of forming the second filter 2, the filtered water is circulated again into the drainage, so that there is no problem. As described above, the second filter 2 is formed by taking about 120 minutes. In this film forming step, the gelled aggregated particles S1 are laminated while forming gaps of various shapes because they are sucked with a very weak suction pressure, and a second soft gel film having a very high degree of swelling is formed. Filter 2 is obtained. The water in the wastewater penetrates through the gel film having a high degree of swelling and is sucked and passes through the first filter 1 to be taken out as filtered water. Finally, the wastewater is filtered.

  That is, in this embodiment, the second filter 2 is formed with 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. The gel film is contracted by dehydration, and the gel film in contact with the drainage is infiltrated with water, replenished and swollen, and the second filter 2 is infiltrated only with water and filtered.

  In addition, 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 adheres uniformly to the entire surface of the first filter 1 and forms a gap in the second filter 2 so as to adhere softly. Specifically, the air flow rate is set to 1.8 liters / minute, but it is selected depending on the film quality of the second filter 2.

  Next, in the filtration step, gelled aggregated particles S1 indicated by white circles are gradually stacked on the surface of the second filter 2 while being adsorbed by a weak suction pressure. At this time, purified water permeates the second filter 2 and the gelled aggregated particles S1 indicated by the white circles to be further laminated, and is taken out from the first filter 1 as filtered water. In other words, in the case of CMP, for example, in the case of CMP, abrasives such as silica, alumina or ceria and scraps of semiconductor material generated by grinding with abrasive grains, metal scraps and / or insulating film material scraps, etc., are treated as gels. Gradually stacked on the surface of the second filter 2 and captured, and water can permeate the gel membrane and be taken out from the first filter 1 as filtered water.

  However, if the filtration is continued for a long time as shown in FIG. 10 (B), the gel film is thickly attached to the surface of the second filter 2, so that the above-mentioned gap eventually becomes clogged, and the filtered water cannot be taken out. . For this reason, it is necessary to remove the laminated gel film in order to regenerate the filtration capacity.

  Next, a more specific filter device will be described with reference to FIG.

  In FIG. 11, 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 mixed with the object to be removed into the tank 50. For example, in the semiconductor field, wastewater (raw water) mixed with a removal object of a colloidal solution flowing out from a dicing apparatus, a back grinding apparatus, a mirror polishing apparatus or a CMP apparatus is introduced. This waste water will be described as waste water mixed with abrasive grains flowing from the CMP apparatus and scraps polished or ground by the abrasive grains.

  In the raw water 52 stored in the raw water tank 50, a plurality of filter devices 53 in which a second filter is formed are installed. Below this filter device 53, there is provided an air diffuser tube 54, such as a bubbling device used in a fish tank, for example, with a small hole in the pipe, and its position so as to pass through the surface of the filter device 53. 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. 55 is an air pump. Here, the filter device 53 refers to the first filter 1, the frame 4, the hollow portion 5, and the second filter 2 shown in FIG. 8.

  The pipe 56 fixed to the filter device 53 corresponds to the pipe 8 in FIG. The pipe 56 is connected to a magnet pump 57 through which the filtered fluid filtered by the filter device 53 flows and sucks through the valve V1. The pipe 58 is connected from the magnet pump 57 to the valve V3 and the valve V4 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 a flow rate is controlled by a flow meter 61. The air flow rate from the air pump 55 is controlled by the control valve CV2.

  The raw water 52 supplied from the pipe 51 is stored in the raw water tank 50 and filtered by the filter device 53. Bubbles pass through the surface of the second filter 2 attached to the filter device, and a parallel flow is generated by the rising force or rupture of the bubbles, and the gelled object to be adsorbed on the second filter 2 is moved. The filter device 53 is uniformly adsorbed on the entire surface and is maintained so that its filtering ability does not decrease.

  Here, the filter device 53 described above, specifically, the filter device 53 immersed in the raw water tank 50 will be described with reference to FIGS.

  A reference numeral 30 illustrated in FIG. 12A is a frame having a frame-like shape, and corresponds to the frame 4 in FIG. Filter films 31 and 32 to be the first filter 1 are bonded and fixed to both surfaces of the frame 30. A pipe 34 (corresponding to the pipe 8 in FIG. 8) is sucked into the inner space 33 (corresponding to the hollow part 5 in FIG. 8) surrounded by the frame 30 and the filter membranes 31 and 32, so that the filter Filtered by membranes 31 and 32. And filtered water is taken out through the pipe 34 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 from other than the filter membrane.

  Since the filter films 31 and 32 in FIG. 12A are thin resin films, if they are sucked, they may warp inward, leading to destruction. Therefore, in order to make this space as small as possible and increase the filtration capacity, it is necessary to make this space 33 large. FIG. 12B shows a solution to this. In FIG. 12B, only nine spaces 33 are shown, but many spaces 33 are actually formed. The filter membrane 31 actually employed is a polyolefin-based polymer membrane having a thickness of about 0.1 mm, and a thin filter membrane is formed in a bag shape as shown in FIG. In B), it is indicated by FT. A frame 30 in which a pipe 34 is integrated is inserted into the bag-like filter FT, and the frame 30 and the filter FT are bonded together. Reference numeral RG denotes pressing means that presses the frame on which the filter FT is bonded from both sides. The filter FT is exposed from the opening OP of the pressing means. Details will be described again with reference to FIG.

  FIG. 12C shows the filter device 53 itself having a cylindrical shape. The frame attached to the pipe 34 has a cylindrical shape, and openings OP1 and OP2 are provided on the side surfaces. Since the side surfaces corresponding to the opening OP1 and the opening OP2 are removed, 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.

  Further, with reference to FIG. 13, the filter device 53 of FIG. First, a portion 30a corresponding to the frame 30 in FIG. 12B will be described with reference to FIGS. 13A and 13B. The portion 30a is shaped like a cardboard as far as it is seen. Thin resin sheets SHT1 and SHT2 having a thickness of about 0.2 mm are overlapped, and 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 space 33 has a shape in which many straws having the rectangular cross section are arranged and integrated. Since the portion 30a maintains the filter films FT on both sides at regular intervals, it is hereinafter referred to as a spacer.

  Many holes HL having a diameter of 1 mm are formed on the surfaces 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.

  The filter film FT is bonded to both surfaces SHT1 and SHT2 of the spacer 30a. Both surfaces SHT1 and SHT2 of the spacer 30a have 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 drainage does not pass, there will be a part where the object to be removed is not captured. In order to prevent this phenomenon, at least two filter films FT are bonded together. The filter film FT1 on the frontmost side is a filter film that captures an object to be removed, and a filter film having a larger hole than the hole 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 bonded. Therefore, since the filter film FT2 is provided between the portions where the holes HL of the spacer 30a are not formed, 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 entire front and back surfaces SH1 and SH2. For the convenience of the drawings, the filter films SHT1 and SHT2 are represented as rectangular sheets, but are actually formed in a bag shape.

  Next, how the bag-like filter films SHT1, SHT2, the spacer 30a, and the pressing means RG are attached will be described with reference to FIGS. 13A, 13C, and 13D. To do.

  FIG. 13A is a completed view, and FIG. 13C is cut from the head of the pipe 34 in the extending direction (longitudinal direction) of the pipe 34 as indicated by the line AA in FIG. 13A. FIG. 13D is a cross-sectional view of the filter device 35 cut in the horizontal direction as indicated by the line BB.

  As can be seen from FIGS. 13 (A), 13 (C), and 13 (D), the spacer 30a inserted into the bag-like filter film FT includes pressing means on the four sides including the filter film FT. It is sandwiched between RG. Then, the three side edges and the remaining one side bound in a bag shape are fixed with an adhesive AD1 applied to the pressing means RG. Further, a space SP is formed between the remaining one side (bag opening) and the pressing means RG, and the filtered water generated in the space 33 is sucked into the pipe 34 through the space SP. In addition, the adhesive AD2 is provided over the entire circumference of the opening OP of the presser fitting RG so that the adhesive AD2 is completely sealed and fluid cannot enter from other than the filter.

  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 film FT and the hole HL of the spacer 30a toward the space 33, and from the space 33 via the pipe 34. The structure is such that filtered water can be transported to the outside.

The filter device 53 used here adopts the structure shown in FIG. 13, and the size of the frame (holding metal fitting RG) to which the filter membrane is attached is A4 size. Specifically, the length is about 19 cm, and the width is about 28. .8 cm, thickness: 5 to 10 mm. Actually, since the filter device 53 is provided on both sides of the frame, the area is twice the above (area: 0.109 m ² ). However, the number and size of the filter devices are freely selected depending on the size of the raw water tank 50, and are determined from the required filtration amount.

  Next, an actual filtration method will be specifically described using the filter device shown in FIG. First, the waste water mixed with the material to be removed of the colloidal solution is put into the raw water tank 50 through the pipe 51. Here, the object to be removed is agglomerated by electrolytic treatment of the electrode 12. Thereafter, 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 drainage is performed while suctioning with a weak suction pressure by the pump 57 through the pipe 56. Circulate. The circulation path is a filter device 53, a pipe 56, a valve V 1, a pump 57, a pipe 58, a control valve CV 1, a flow meter 61, an optical sensor 62, and a valve V 3, and waste water is sucked from the tank 50 and returned to the tank 50.

  By circulating, the second filter 2 is formed on the first filter 1 (31 in FIG. 9) of the filter device 53, so that the object to be removed of the target colloidal solution is finally captured. Become.

  That is, when the drainage is sucked by the pump 57 through the first filter 1 with a weak suction pressure, the aggregated particles of the removal target are easily gelled and adsorbed on the surface of the first filter 1. Aggregated particles that have gelled are larger than the filter holes 1A of the first filter 1 and are adsorbed and stacked on the surface of the first filter 1 to form a second filter 2 made of a gel film. The agglomerated particles pass through the first filter 1, but the water in the wastewater is sucked through the gel membrane as a passage and taken out as purified water together with the film formation of the second filter 2, and the wastewater is filtered. .

  The concentration of the agglomerated particles contained in the filtered water is monitored by the optical sensor 62, and it is confirmed that the agglomerated particles are lower than the desired mixing rate, and filtration is started. When the filtration is started, the valve V3 is closed by a detection signal from the optical sensor 62, the valve V4 is opened, and the above-described circulation path is closed. Therefore, purified water is taken out from the valve V4. Air bubbles constantly supplied from the air pump 55 are adjusted from the air diffusion pipe 54 by the control valve CV2 and supplied to the surface of the filter device 53.

  If the filtration is continued continuously, the water in the waste water of the raw water tank 50 is taken out of the tank 50 as purified water, so that the concentration of the object to be removed in the waste water increases. That is, the colloidal solution is concentrated to increase the viscosity. For this purpose, the raw water tank 50 is replenished with drainage from the pipe 51 to suppress an increase in the concentration of drainage and increase the efficiency of filtration. However, the gel film is thickly attached to the surface of the second filter 2 of the filter device 53, and eventually the second filter 2 becomes clogged and becomes unable to be filtered.

  When the second filter 2 of the filter device 53 is clogged, the filtration capacity 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.

  The regeneration process will be further described in detail with reference to the schematic diagram shown in FIG. FIG. 14A shows the state of the filter device 53 in the filtration process. Since the hollow portion 5 of the first filter 1 has a negative pressure compared to the outside due to a weak suction pressure, the first filter 1 has a shape recessed inward. Accordingly, the second filter 2 adsorbed on the surface is similarly recessed inward. The same applies to the gel film that is gradually adsorbed on the surface of the second filter 2.

  However, referring to FIG. 14B, in the regeneration process, the weak suction pressure is stopped and returns to almost 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 in the same manner. As a result, since the suction pressure that first adsorbs the gel film disappears, the gel film loses the adsorbing force to the filter device 53 and simultaneously receives a force that expands outward. Thereby, the adsorbed gel film starts to be detached from the filter device 53 by its own weight. Furthermore, in order to advance this separation, it is preferable to increase the amount of bubbles from the air diffuser 54 by about twice. According to the experiment, the separation 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 is detached like an avalanche and settles on the bottom surface of the raw water tank 50. Thereafter, the second filter 2 may be formed again by circulating the waste water through the circulation path described above. In this regeneration step, the second filter 2 returns to the original state, returns to a state where the drainage can be filtered, and again filters the drainage.

  Furthermore, when the filtered water is caused to flow back into the hollow portion 5 in this regeneration step, firstly, the first filter 1 is helped to return to its original state, and the hydrostatic pressure of the filtered water is applied to further expand the outside. Second, the filtered water oozes out from the inside of the first filter 1 through the filter hole 1A 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. Facilitates the release of the gel film.

  If filtration is continued while regenerating the second filter 2 as described above, the concentration of the material to be removed from the waste water in the raw water tank 50 increases, and the waste water eventually has a considerable viscosity. Therefore, when the concentration of the object to be removed from the wastewater exceeds a predetermined concentration, the filtering operation is stopped and left to settle. 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 heat-dried to remove water contained therein and further compressed. This can greatly reduce the amount of slurry that is treated as industrial waste.

With reference to FIG. 15, the driving | running condition of the filter apparatus shown in FIG. 11 is demonstrated. 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 flow rate after regeneration is also set to be 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 a pressure gauge 59. Pout and re-Pout are pressures in the pipe 58 and are measured by the pressure gauge 60. The flow rate and the reflow rate are measured by the flow meter 61 and represent the filtration amount sucked from the filter device 53.

  In FIG. 15, the left Y-axis indicates the pressure (unit: MPa), and the negative pressure increases as the X-axis is approached. The right Y-axis indicates the flow rate (unit: cc / min). The X axis indicates the elapsed time (unit: minutes) from the film formation.

  As a point of this embodiment, the flow rate and reflow rate are controlled to be maintained at 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, Pin forms the second filter 2 with a gel film that is softly adsorbed with a very weak suction pressure of −0.001 MPa to −0.005 MPa.

  Next, in the filtration step, Pin is gradually increased from −0.005 MPa, and filtration is continued while ensuring a constant flow rate. Filtration is continued for about 1000 minutes, and the regeneration process is performed when the flow rate begins to decrease. This is because the gel film is thickly attached to the surface of the second filter 2 to cause clogging.

  Further, when the second filter 2 is regenerated, filtration is continued again at a constant reflow rate while gradually increasing the re-Pin. The regeneration and refiltration of the second filter 2 is continued until the raw water 52 has a predetermined concentration, specifically, the concentration is 5 to 10 times.

  Further, unlike the operation method described above, a method of performing filtration while fixing the suction pressure to −0.005 MPa, which has a large filtration flow rate, can also be employed. In this case, the filtration flow rate gradually decreases as the second filter 2 is clogged, but there is an advantage that the filtration time can be increased and the control of the pump 57 is simplified. Therefore, the regeneration of the second filter 2 may be performed when the filtration flow rate decreases below a certain value.

  FIG. 16A shows the particle size distribution of abrasive grains contained in the CMP slurry. A distribution curve indicated by a solid line indicates a particle size distribution of abrasive grains contained in the CMP slurry. A distribution curve indicated by a broken line indicates a particle size distribution of an abrasive flow used for dry CMP.

  With reference to the distribution curve shown by the solid line, this abrasive grain is 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 76 nm and the maximum particle size was 340 nm. These large particles are agglomerated particles made up of a plurality of particles therein. The average particle diameter is about 150 nm, and the distribution has a peak in the vicinity of 130 to 150 nm.

  Referring to the distribution curve indicated by the broken line, the abrasive grains used for dry CMP show a distribution curve having a peak at 20 nm to 30 nm. From this, it can be seen that the particles are extremely fine compared to the abrasive grains of the CMP slurry. In this embodiment, the waste water treatment is performed by agglomerating the fine abrasive grains by electrochemical treatment and filtering with a gel film.

  Specifically, the abrasive grains for CMP are mainly silica-based, alumina-based, cerium oxide-based, and diamond-based. Other than these, chromium oxide-based, iron oxide-based, manganese oxide-based, BaCO4-based, antimony oxide-based, zirconia-based There is a yttria system. Silica is used for planarization of semiconductor interlayer insulating films, P-Si, SOI, etc., and Al / glass disks. Alumina is used for polishing hard disks, general metals, and planarization of Si oxide films. Further, 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.

  Furthermore, it is called an oxide sol. This sol is a monolith in which colloidal sized particles consisting of metal oxide or partial hydroxide, such as silica, alumina, zirconia, etc., are uniformly dispersed in water or liquid. It is used for planarization of interlayer insulating films and metals of semiconductor devices, and is also being studied for information disks such as aluminum disks.

  FIG. 16B shows data indicating that CMP waste water is filtered and abrasive grains are captured. In the experiment, the above-mentioned slurry stock solution was diluted 50 times, 500 times, and 5000 times with pure water and prepared as a test solution. As described in the prior art, these three types of test solutions were prepared assuming that the drainage is about 50 to 5000 times because the wafer is cleaned with pure water in the CMP process.

  When the light transmittance of these three types of test solutions is examined with light having a wavelength of 400 nm, the test solution of 50 times is 22.5%, the test solution of 500 times is 86.5%, and the test solution of 5000 times. Is 98.3%. In principle, if abrasive grains are not included in the drainage, light is not scattered and should take a value close to 100%.

  When the filter on which the second filter film 13 was formed was immersed in these three types of test solutions and filtered, the transmittance after filtration was 99.8%. 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. Incidentally, the transmittance data of the 50-fold diluted test solution is not shown in the drawing because the value is small.

From the above results, when the removal object of the colloidal solution discharged from the CMP apparatus is filtered with the second filter 2 made of the gel film of the filter apparatus 53 provided in the filter apparatus of this embodiment, the transmittance is 99.8%. It was found that it can be filtered to the extent.

It is the schematic diagram (A) explaining the flocculant manufacturing apparatus of this invention, and a schematic diagram (B). It is a figure explaining the structure of the waste water treatment apparatus actualized of this invention. It is a figure explaining the characteristic of the flocculant of this invention. It is a figure explaining the characteristic of the flocculant of this invention. It is a figure explaining the characteristic of the flocculant of this invention. It is a figure explaining the characteristic of the flocculant of this invention. It is a figure (A) and (B) explaining the characteristic of the flocculant of this invention. It is a figure explaining the filter apparatus which the waste water treatment equipment of the present invention has. FIG. 4A is a diagram for explaining the operation principle of the filter device of the present invention, and FIG. 5B is an enlarged view of the first filter. It is sectional drawing (A) explaining the film-forming conditions of the 2nd filter apparatus of this invention, and a characteristic view (B). It is a figure explaining the filter apparatus which actualized this invention. FIG. 3 is a perspective view (A), a perspective view (B), and a perspective view (C) illustrating a filter device of the present invention. FIG. 4 is a perspective view (A), a perspective view (B), a cross-sectional view (C), and a cross-sectional view (D) for explaining a more specific filter device of the present invention. It is sectional drawing (A) and sectional drawing (B) explaining reproduction | regeneration of the filter apparatus of this invention. It is a characteristic view explaining the driving | running state of the filter apparatus of this invention. It is the characteristic view (A) and characteristic view (B) explaining the filtration characteristic of this invention. It is a figure explaining the conventional filtration system. It is a figure explaining a CMP apparatus. It is a figure explaining the system of CMP apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st filter 1A Filter hole 2 2nd filter 4 Frame 5 Hollow part 6 Pump 7 Filtrate 10A, 10B Coagulant manufacturing apparatus 11 Tank 12 Electrode pair 12A 1st electrode 12B 2nd electrode 12C Power supply P1-P6 Path 13 through which fluid passes Filter device 14 Peeling water tank 15 CMP device 16 Solid-liquid separator 17 CMP wastewater treatment device 50 Raw water tank 52 Raw water 53 Filter device 57 Pump 61 Flow meter 62 Optical sensor 50 Raw water tank

Claims (9)

An addition means for adding halogen ions or a compound containing halogen ions to a fluid containing particulate silica extracted from the concentrated CMP waste water ;
An apparatus for producing a flocculant, comprising: a generation unit that introduces iron ions eluted from an electrode pair into the fluid to generate a flocculant that combines the silica and the iron ions.   The flocculant manufacturing apparatus according to claim 1, wherein the flocculant is generated while switching the polarity of the electrode pair. 3. The flocculant manufacturing apparatus according to claim 1 , wherein the amount of the iron ions eluted from the electrode pair is larger than the amount of the iron ions bound to the silica contained in the fluid. The flocculant manufacturing apparatus according to any one of claims 1 to 3, wherein at least a part of the iron ions are trivalent ions of iron. The flocculant manufacturing apparatus according to any one of claims 1 to 4, further comprising an oxidizing agent adding unit that adds an oxidizing agent that oxidizes the iron ions.   The flocculant manufacturing apparatus according to claim 5, wherein the oxidizing agent is hydrogen peroxide or ozone. The flocculant manufacturing apparatus according to claim 5 or 6 , wherein an addition amount of the oxidizing agent is adjusted so that the iron ions and the iron ions oxidized by the oxidizing agent are mixed. The flocculant manufacturing apparatus according to any one of claims 1 to 7, further comprising addition means for adding a substance exhibiting acidity to the fluid. In a fluid containing particulate silica extracted from concentrated CMP wastewater, a halogen ion or a compound containing a halogen ion is added and an electrode pair containing iron is immersed, and a voltage is applied to the electrode pair. Then, the iron ion is eluted from the electrode pair, and the iron ion and the silica are combined to produce a flocculant.

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