JP4632635B2 - Waste processing system for semiconductor materials - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drainage filtration method.
[0002]
[Prior art]
At present, reducing industrial waste, separating and reusing industrial waste, or preventing industrial waste from being released into the natural world are important themes from an ecological perspective, and are corporate issues toward the 21st century. It is. Among these industrial wastes, there are various fluids containing the objects to be removed.
[0003]
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.
[0004]
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 an environmental problem.
[0005]
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.
[0006]
As an example, wastewater treatment in the semiconductor field will be described below. In general, when grinding or polishing a plate such as metal, semiconductor, ceramic, etc., prevention of temperature rise of a polishing (grinding) jig due to friction, improvement of lubricity, adhesion of grinding or cutting waste to the plate 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 a semiconductor wafer, which is a plate of semiconductor material, is diced or back-ground. 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.
[0008]
Waste water mixed with grinding or polishing waste discharged from the dicing equipment or back grinding equipment described above is filtered to clean water and returned to nature, or reused, and concentrated waste water is recovered. Yes.
[0009]
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.
[0010]
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.
[0011]
In the latter method, which combines filter filtration and centrifugation, the wastewater is filtered, the concentrated wastewater is centrifuged, and silicon waste is recovered as sludge. It was released or reused.
[0012]
For example, as shown in FIG. 18, waste water generated during dicing is collected in a raw water tank 201 and sent to a filtration device 203 by a pump 202. Since the filter 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.
[0013]
On the other hand, since the filtering device 203 applies pressure to the waste water and supplies it to the filter F, since the filter F is clogged, it is periodically cleaned. 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.
[0014]
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.
[0015]
On the other hand, CMP (Chemical-Mechanical Polishing) has appeared as a new semiconductor process technology. This CMP is a technique for polishing irregularities on the upper surface of an interlayer insulating film for the purpose of planarizing the upper surface of the interlayer insulating film covering the wiring in order to realize an ideal multilayer wiring structure of a semiconductor device.
[0016]
By this CMP technique, firstly a flat device surface shape can be realized. As a result, a fine pattern using a lithography technique can be formed with high accuracy, and the possibility of realizing a three-dimensional IC is brought about by the combined use of a Si wafer attaching technique.
[0017]
Second, an embedded structure of a material different from that of the substrate can be realized. As a result, there is an advantage that a wiring embedding structure can be easily realized. Conventionally, a tungsten (W) embedding technique in which W is embedded in a trench of an interlayer film by a CVD method and flattened by etching back the surface is adopted in a multilayer wiring of an IC, but recently, planarization by CMP is more preferable. CMP is in the spotlight because the process can be simplified.
[0018]
These CMP techniques and applications are described in detail in “CMP Science” published by Science Forum.
[0019]
Next, the CMP mechanism will be briefly described. As shown in FIG. 19, a semiconductor wafer 252 is placed on a polishing cloth 251 on a rotating surface plate 250, and is rubbed while flowing an abrasive (slurry) 253, polished, and subjected to chemical etching. Is lost. 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. The polishing material is a mixture of abrasive grains such as silica and alumina in water containing a pH adjusting material, 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. M1 to M3 are motors, and 255 to 257 are belts.
[0020]
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. 19, the wafer cleaning mechanism 263, and a system control for controlling these.
[0021]
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.
[0022]
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. Discharged.
[0023]
Therefore, when a CMP apparatus is used, a considerable amount of slurry diluted with pure water is discharged, and a method that can efficiently treat the wastewater is regarded as a problem. At present, these wastewaters are treated by a conventional method that combines the coagulation sedimentation method and the filter filtration and the centrifugal separation shown in FIG.
[0024]
[Problems to be solved by the invention]
However, in the coagulation precipitation method, a chemical is input as the coagulant. However, it is very difficult to specify the amount of a chemical that completely reacts, and a large amount of chemical is inevitably added, and an unreacted chemical remains. Conversely, if the amount of chemicals is small, all the objects to be removed are not agglomerated and settled, and the objects to be removed remain without being separated. In particular, when the amount of the chemical is large, the chemical remains in the supernatant. When this is reused, since chemicals remain in the filtered fluid, there is a problem that it cannot be reused for those who dislike chemical reactions.
[0025]
For example, in the case of dicing, the waste water consists of silicon scrap and distilled water, and the water filtered by the coagulation sedimentation method causes chemicals to remain. There was a problem that could not be reused.
[0026]
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 the flocs are severe PH conditions, and a stirrer, a PH measuring device, a flocculant injecting device, and a control device for controlling them 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 (m3) / hour, a tank with a diameter of about 3 meters and a depth of about 4 meters (about 15 tons of sedimentation tank) is required. It becomes a large-scale system that requires a site of about 11 meters.
[0027]
Moreover, there are some flocs that do not settle in the settling tank and are floating, and these may flow out of the tank, and it is difficult to collect all of them. In other words, there are problems such as the size of the equipment, the high initial cost of this system, the difficulty of reusing water, and the high running cost generated from the use of chemicals.
[0028]
On the other hand, in the method of combining the filter filtration of 5 cubic meters (m3) / 1 hour and the centrifugal separator as shown in FIG. In addition, since a ceramic filter is used, 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. Moreover, the pump 202 in front of the filtration device 203 has a large motor load because the filter F is a pressure filtration method, and the pump 202 has a high capacity. Further, about 2/3 of the waste water passing through the filter F was returned to the raw water tank 201. Furthermore, since the waste water containing the object to be removed is transported by the pump 202, the inner wall of the pump 202 is shaved and the life of the pump 2 is very short.
[0029]
To sum up these points, the electric cost of the motor is very high, and the replacement cost of the pump P and filter F is high.
[0030]
Furthermore, in CMP, an amount of waste water that cannot be compared with dicing is discharged. In addition, the particle size of the abrasive grains mixed in the slurry is very fine, 0.2 μm, 0.1 μm, 0.1 μm or less. Therefore, when the fine abrasive grains are filtered with a filter, the abrasive grains enter the hole of the filter, causing clogging immediately, and clogging occurs frequently, so that there is a problem that a large amount of waste water cannot be treated.
[0031]
As can be seen from the above description, wastewater filtration devices are used in various ways to remove as much of the substances that harm the global environment as possible, or to reuse filtration fluids and separated objects. The system becomes a large-scale system, and the initial cost and running cost are enormous. Therefore, the sewage treatment apparatus so far has not been a system that can be adopted.
[0032]
[Means for Solving the Problems]
  The present invention has been made in view of the above problems,
  An apparatus for slicing a crystal ingot into a wafer, an apparatus for back grinding a semiconductor wafer, an apparatus for dicing a semiconductor wafer, or an apparatus for polishing by CMP;
Transports wastewater containing solids that are processing waste generated from an apparatus for slicing the crystal ingot into a wafer, an apparatus for back grinding the semiconductor wafer, an apparatus for dicing the semiconductor wafer, or an apparatus for polishing by CMP. Pipe to
  A raw water tank for storing the waste water discharged from the pipe;
  In a semiconductor material processing waste processing system having at least a filtration device in which a filter membrane is immersed in waste water stored in the raw water tank,
  By pressing or sucking the waste water through the filter membrane, the solid matter is laminated on the filter membrane, and the water flow of the waste water is separated so that the solid matter on the surface layer of the laminate composed of the solid matter is separated. Or applying an external force consisting of bubbles generated from a bubbling device located below the filter membrane to refresh the surface of the laminate,
The problem is solved by passing water from between the solids constituting the laminate and filtering the waste water.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
An object of the present invention is to remove an object to be removed from a fluid (drainage) mixed with an object to be removed such as a semiconductor, a metal, an inorganic substance, or an organic substance using a filter made of a solid material different from the object to be removed. is there.
[0045]
Another object of the present invention is to mix a solid matter in a fluid, pass the fluid through a first filter, and form a second filter containing the solid matter on the first filter surface, The object is to remove an object to be removed contained in the fluid.
[0046]
Another object of the present invention is to prepare a filter containing a solid material different from the object to be removed contained in the fluid, and to remove the object to be removed in the fluid using the filter.
[0047]
Still another object of the present invention is to introduce a fluid containing an object to be removed and a solid material different from the object to be removed into a tank having a first filter, and pass the fluid through the first filter. Thus, the second filter containing the solid matter is formed on the surface of the first filter, and the object to be removed in the fluid is removed.
[0048]
First, in the present invention, the object to be removed refers to a solid substance contained in the wastewater to be filtered, and the solid substance is collected from the solid substance like sand in order to filter the wastewater containing the object to be removed. It refers to the constituent material of the filter membrane. For example, as a solid material, since it is laminated on the first filter membrane, the laminated membrane has higher filtration accuracy than the filtration accuracy of the first filter membrane, and can be applied individually by applying external force. It is desirable to be separated.
[0049]
Specifically, the object to be removed is a large amount of particles having a size of about 0.3 μm, 0.2 μm, 0.1 μm or less, and is generated, for example, by abrasive grains used for CMP or abrasive grains. Semiconductor material waste, metal waste and / or insulating film material waste.
[0050]
More specifically, the object to be removed is waste generated when slicing a crystal ingot into a wafer, dicing a semiconductor wafer, back grinding, etc., mainly semiconductor materials, insulating materials, metal materials This includes organic substances such as Si, oxidized Si, Al, SiGe, sealing resin, and other insulating film materials and metal materials. In the compound semiconductor, a compound material such as GaAs is applicable.
[0051]
Recently, dicing has been adopted in the manufacture of CSP (chip scale package), so that semiconductor materials, ceramic materials, and sealing resins generated during dicing are also objects to be removed.
[0052]
Further, there are many places where the removal object is generated even outside the semiconductor field. For example, in the industry using glass, liquid crystal panels, panels of EL display devices, and the like perform dicing of the glass substrate, polishing of the side surfaces of the substrate, etc., and thus the glass waste generated here corresponds to the object to be removed. In addition, electric power companies and steel companies use coal as fuel, which corresponds to powder generated from coal. Further, powder mixed in smoke emitted from the chimney corresponds to the object to be removed. This is also the case for powders generated from processing minerals, gemstones, and tombstones. Furthermore, it corresponds to metal scrap generated when processing with a lathe or the like, ceramic scrap generated by dicing, polishing, etc. of a ceramic substrate.
[0053]
These scraps are generated by processing such as polishing, grinding, or pulverization, and are taken into a fluid such as water or chemicals to remove the scraps, and are generated as waste water.
[0054]
Further, the solid substance is a substance distributed in a wider range (up to about 500 μm) than the particle size distribution (up to about 0.14 μm) of the object to be removed (CMP abrasive grains). For example, a semiconductor material such as Si, alumina Insulating substances such as metals, cutting scraps such as metals, polishing scraps or crushed scraps, and solid substances having the above particle size distribution, such as diatomaceous earth and zeolite.
[0055]
Now, embodiments of the present invention will be described with reference to the drawings.
[0056]
In the present embodiment, water is employed as the fluid, and the case where dicing waste of the semiconductor wafer is included in the water will be described in detail.
[0057]
One feature of the present invention resides in the filter. First, the structure of the filter, the forming method, and the operation thereof will be described.
[0058]
The structure of the filter is as follows. Reference numeral 10 in FIG. 1a denotes a first filter membrane, and 11 denotes a filter hole. The film formed in a layered manner on the opening of the filter hole 11 and the surface of the first filter film 10 is an aggregate of solid substances 12. The solid material 12 is divided into a large solid material 12A that cannot pass through the filter hole 11 and a small solid material 12B that can pass through the filter hole 11. In the figure, those indicated by black circles are small solids 12B that can pass through.
[0059]
The filter membrane that can be used here can be either organic polymer type or ceramic type in principle. However, here, a polyolefin polymer film having an average pore diameter of 0.25 μm and a thickness of 0.1 mm was employed. Also, a photograph of the surface of the filter membrane made of polyolefin is shown in FIG. 1b.
[0060]
Next, a method for forming a filter will be described. Above the first filter membrane 10 in FIG. 1 a is water mixed with solid matter, and below the first filter membrane 10 is produced filtered water filtered by the first filter membrane 10. Yes. In order to flow water in the direction of the arrow and filter the water using the filter membrane 10, the water is naturally dropped or pressurized and moves downward in the figure. Further, water is sucked from the side where the filtered water is present. Further, the first filter film 10 is arranged horizontally, but may be placed vertically.
[0061]
As described above, as a result of pressurizing or sucking water through the filter membrane, water passes through the first filter membrane 10. At that time, a large solid material 12 </ b> A that cannot pass through the filter hole 11 is captured on the surface of the first filter film 10.
[0062]
The solid matter generated by machining such as grinding, polishing, or pulverization is distributed within a certain range (particle size), and the shape of each solid matter is different. As an example, FIG. 2a shows the particle size distribution of Si dicing waste, and the electron micrograph is shown in FIG. 2b. As described above, the particle diameter is distributed in the range of 0.1 to 200 μm, and the shape of the waste is also various.
[0063]
Solids are randomly located in the water in which the first filter membrane 10 is immersed. A large solid to a small solid is irregularly moved to the filter hole 11. The large solid matter 12A captured at random becomes the first layer of the second filter film 13, and this layer forms a filter hole smaller than the filter hole 11, and from the large solid matter 12A through this small filter hole. Even small solids 12B are captured. At this time, since the shapes of the solids are different from each other, gaps of various shapes are formed between the solids and the solids, and the water moves through the gaps, and finally the water is filtered. This is very similar to the good drainage of sandy beaches.
[0064]
Further, the operation of the filter will be described. The second filter film 13 gradually grows while randomly capturing small solids 12B from large solids 12A, and traps the small solids 12B while securing a water (fluid) passage. FIG. 3 shows this state. Moreover, since the second filter film 13 remains in the form of a layer and the solid matter can easily move like sand, air bubbles are passed near the layer, a water flow is applied, and sound waves and ultrasonic waves are applied. The surface layer of the second filter film 13 can be easily moved to the drainage side by giving, mechanical vibration, or rubbing with a squeegee or the like. Even if the filtration capability of the second filter membrane 13 is reduced, the structure that is individually separated like sand is a factor that can easily restore the capability by applying an external force to the second filter membrane 13. Become. In other words, the cause of the decrease in the filter capacity is mainly clogging, and the solid matter on the surface layer of the second filter film 13 causing the clogging is moved again into the fluid. It is possible to eliminate clogging repeatedly and to maintain the filtration capacity.
[0065]
In FIG. 2a, the particle size distribution of the apparatus in which the particle size distribution is smaller than 0.1 μm cannot be detected. Therefore, the distribution of cutting waste smaller than 0.1 μm is not shown. However, when observing FIG. 2b, in fact, smaller ones are included. According to the experiment, it was found that when the water mixed with the cutting waste was filtered, the cutting waste was formed on the first filter film and captured up to 0.1 μm or less.
[0066]
For example, if it is intended to remove cutting scraps of up to 0.1 μm, it is a general idea to employ a filter in which holes smaller than this size are formed. However, it can be understood from the above description that even when a filter hole having a size between these is used, cutting scraps of 0.1 μm or less can be captured while a large particle size and a small particle size are distributed.
[0067]
Conversely, if the solid has a single particle size peak of 0.1 μm, and the distribution is distributed in a very narrow range of several μm, the filter will soon become clogged. As can be seen from FIG. 2a, the dicing scrap of Si, which is a solid substance, has two peaks of a large particle size and a small particle size, and is distributed in a range of ˜200 μm, so that the filtration capacity is improved. Has been. Further, as shown in FIG. 2b, when observed with an electron microscope or the like, it can be seen that the shapes of the solid matter are various. In other words, since there are at least two particle size peaks and the solids have a wide variety of shapes, various gaps are formed between the solids, thereby forming a water passage, which reduces clogging and is less than 0.1 μm. It is considered that a filter that can capture debris has been realized.
[0068]
However, if the distribution of solid matter is shifted to the right or left in the figure, the pore diameter of the first filter may be changed according to the distribution. For example, a hole diameter larger than 0.25 μm may be adopted as long as it shifts to the right. In general, if the pore size is increased, the amount of solids passing through the filter membrane increases. However, if the time for circulating the filtered water is lengthened, most of the solid can finally be trapped by the second filter membrane 12B. Naturally, if the pore size of the filter is reduced, the time until a small solid can be captured becomes shorter.
[0069]
As described above, when a solid material having a particle size distribution of 0.1 μm to 200 μm is formed as the second filter film 13 on the surface of the first filter film 10, even a solid material of 0.1 μm or less can be removed. I understand. The maximum particle size is not limited to 200 μm and may be larger. For example, filtration is possible even with solids distributed at ˜500 μm.
[0070]
Therefore, as shown in FIG. 4, after forming a filter made of a solid material, it is understood that even the object to be removed can be removed by passing the waste water in which the objects to be removed 14 and 15 are mixed into the drain side fluid.
[0071]
Next, a second filter film 13 made of the solid substance 12 (or the solid substance and the object to be removed) is formed in the same tank, and subsequently filtered using the second filter film 13; There is a method in which the filter 13 is formed in a separate tank and the filter is transferred and filtered.
[0072]
5 and 6 correspond to the former method. That is, in FIG. 5, the first filter film 10 is sandwiched between the first storage tank 70a and the second storage tank 70b, and the second filter film 13 is formed on the surface of the first filter film 10. Thereafter, a fluid containing an object to be removed is added and filtered.
[0073]
In FIG. 5a, the first filter membrane 10 is attached to a position where the storage tank 70 is divided into a first storage tank 70a and a second storage tank 70b, and solids 12 (for example, from the pipe 72 to the first storage tank 70a). A fluid 73 containing Si dicing waste) is poured, spontaneously falls, pressurizes the fluid in the first storage tank 70a or sucks the pipe 74, and moves the fluid to the second storage tank 70b. . At this time, the solid material 12 is captured on the first filter film 10 and the second filter film 13 is formed. Thereafter, as shown in FIG. 5b, the fluid 73 'mixed with the objects 14 and 15 to be removed is supplied to the first storage tank 70a through the pipe 72, and the filtration is started as it is.
[0074]
In FIG. 5a ′, the fluid 73 stored in the first storage tank 70a is mixed with the solid substance 12 and the objects 14 and 15 to be removed, and the second filter film 13 is combined with the solid substance 12 and the object to be removed. It consists of removed products 14 and 15. In this case, a fluid 73 in which the object to be removed and solid matter are mixed may flow from the pipe 72, or a fluid in which the object to be removed is mixed flows from the pipe 72, and from the outside of the storage tank 70. You may throw a solid substance into the 1st storage tank 70a. Then, as shown in FIG. 5b, the fluid 73 'mixed with the objects 14 and 15 to be removed is supplied to the first storage tank 70a through the pipe 72, and the filtration is started as it is.
[0075]
FIG. 6 a shows that a fluid 73 containing solid matter (for example, Si dicing waste) 12 is poured into a first tank 75 through a pipe 76, and the filtration device 35 to which the first filter membrane 10 is attached is provided with the fluid 73. Shows a method of sucking the fluid through the pipe 34 attached to the filtration device 35 when completely immersed. As a result of this suction, the solid material 12 is captured by the first filter film 10 and a second filter film 13 is formed. Then, as shown in FIG. 6 b, the fluid in which the objects to be removed 14 and 15 are mixed is supplied to the first tank 75 through the pipe 76, and the objects to be removed 14 and 15 can be captured by the second filter film 13. It is a method of performing filtration after confirming this.
[0076]
In FIG. 6 a ′, the fluid 73 stored in the first tank 75 is mixed with the solid material 12 and the objects to be removed 14, 15, and the second filter film 13 has the solid material 12 and the material to be removed 14. , 15. In this case, a fluid 73 in which the object to be removed and the solid matter are mixed may flow from the pipe 76, or a fluid in which the object to be removed is mixed flows from the pipe 76 from the outside of the first tank 75. A solid material may be added. Then, as shown in FIG. 6 b, the fluid 73 ′ mixed with the objects to be removed 14 and 15 is supplied to the first tank 75 through the pipe 76, and the objects to be removed 14 and 15 can be captured by the second filter film 13. Then, after confirming that the fluid 73 ′ containing the object to be removed is added, filtration is performed.
[0077]
7 and 8 correspond to the latter method. In this method, a filter containing solid matter or a solid matter and an object to be removed is prepared in a separate tank in advance, and this filter is transferred to a tank containing a fluid containing the object to be removed, and the object to be removed is filtered.
[0078]
In FIG. 7a, the first filter membrane 10 is attached to a position where the storage tank 70 is divided into a first storage tank 70a and a second storage tank 70b, and solids 12 (for example, from the pipe 72 to the first storage tank 70a). A fluid 73 containing Si dicing waste) is poured, spontaneously falls, pressurizes the fluid in the first storage tank 70a or sucks the pipe 74, and moves the fluid to the second storage tank 70b. .
[0079]
At this time, the solid material 12 is captured on the first filter film 10 and the second filter film 13 is formed. And when it becomes a predetermined film thickness, it takes out from the storage tank 70 and prepares the filter as shown in FIG. 7b. Then, this filter is bonded to the filter device 35 as shown in FIG. 7C, the filter device 35 is immersed in another tank 75 as shown in FIG. 7d, and the pipe 34 is sucked and filtered. In FIGS. 5 and 6, since the second filter is formed in the tank in which the waste water enters, filtration cannot be performed until the second filter is formed. However, since the filter is prepared here, the filtration is immediately performed. Has the advantage of starting. Moreover, even if the formation place of the 2nd filter 13 and the tank in which waste_water | drain drains are separated in distance, it has the merit which can carry a filter easily.
[0080]
Here, in FIG. 7a, the object to be removed may be mixed into the fluid 73 of the first storage tank 70a to form a second filter composed of a solid substance and the object to be removed.
[0081]
FIG. 8 shows a method for preparing the filter device 35. In FIG. 8a, the fluid containing only the solid matter 12 is passed through the first filter membrane 10 attached to the filtration device 35, and the second filter membrane 13 is formed on the first filter membrane 10 in advance. As shown in FIG. 8b, a filtering device 35 is prepared, and the filtering device 35 is immersed in a second tank 76 as shown in FIG. 8C to filter the fluid mixed with the object to be removed.
[0082]
The structure of the filtration device 35 will be described in detail with reference to FIGS. 9 and 10, and a method is adopted in which a suction pump is provided in the pipe 34 and fluid is sucked through the pipe 34 to form the second filter film 13. Yes.
[0083]
As described above, since the filtering device 35 in which the second filter 13 is formed in advance is prepared, it can be easily carried to the second tank 76 located at a distance, and the second There is an advantage that filtration can be started immediately without forming a second filter in the tank.
[0084]
As described above, in the method of configuring a filter with a solid material, the method of configuring a filter with a solid material and an object to be removed, and the method of preparing a filter formed by any one of the former methods in advance, the first filter film The pore diameter is set during the particle size distribution of the solid (Si dicing waste). For example, when the hole diameter is 0.25 μm, solids (Si dicing scraps) and objects to be removed (abrasive grains) of 0.25 μm or less pass through. However, solids (Si dicing scraps) of 0.25 μm or more and objects to be removed (abrasive grains) are captured, and the second filter made of solids and / or objects to be removed is formed on the surface of the first filter film 10. A filter film 13 is formed. As the second filter film 13 grows, solids and objects to be removed can be captured gradually with a thickness of 0.25 μm or less, particularly near 0.1 μm or smaller.
Next, a more specific example of the filtering device 35 will be described with reference to FIGS. The filtration device 35 is of a type that is immersed in a tank (raw water tank) and sucked.
[0085]
Reference numeral 30 shown in FIG. 9A is a frame shaped like a frame, and filter films 31 and 32 are bonded to both sides of the frame. Then, in the space 33 surrounded by the frame 30 and the filter membranes 31 and 32, the filtered water filtered by the filter membrane is generated by sucking the pipe 34. And filtered water is taken out through the pipe 34 sealed and attached to the frame 30. Of course, the filter membranes 31, 32 and the frame 30 are completely sealed so that drainage does not enter the space from other than the filter membrane.
[0086]
Since the filter film 31 of FIG. 9a is a thin resin film, if it is sucked, it may warp inward and may be destroyed. Therefore, it is necessary to make this space as small as possible. On the other hand, in order to increase the filtration capacity, it is necessary to form a lot of this space, and an improved one is shown in FIG. 9b. In FIG. 9b, only nine spaces 33 are shown, but many spaces are actually formed. The filter membranes 31 and 32 actually employed are polyolefin polymer membranes having a thickness of about 0.1 mm, and a thin filter membrane is formed in a bag shape as shown in FIG. It was. 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 film 31 is bonded from both sides. The filter films 31 and 32 are exposed from the opening OP of the pressing means. Details will be described with reference to FIG.
[0087]
FIG. 9C shows the cylindrical shape of the filtration device 35 itself. The frame attached to the pipe 34 is cylindrical, and openings OP1 and OP2 are provided on the side surfaces. Since the side surfaces corresponding to the openings OP1 and OP2 are removed, support means SUS for supporting the filter film 31 is provided between the openings. A filter film is bonded to the side surface.
[0088]
Further, the improved filter device 35 will be described in detail with reference to FIG. First, the portion corresponding to the frame 30 in FIG. 9b corresponds to 30a in FIG. 10b.
[0089]
Reference numeral 30a has a shape like a cardboard. A plurality of sections SC are provided in the vertical direction between thin resin sheets SHT1 and SHT2 of about 0.2 mm, and a space 33 is provided surrounded by the resin sheets SHT1, SHT2 and section SC. The horizontal 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 straw 33 has a shape in which many straws having the rectangular cross section are arranged and integrated. Reference numeral 30a keeps the filter films FT on both sides at a constant interval, and is hereinafter referred to as a spacer.
[0090]
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.
[0091]
The filter film FT is bonded to both surfaces SHT1 and SHT2 of the spacer 30a. The sheets SHT1 and SHT2 have a portion where the hole HL is not formed. When the filter film FT1 is directly attached thereto, the filter film FT1 corresponding to the portion where the hole HL is not formed has a filtering function. Since there is no drainage and no drainage passes, there are parts where the objects to be removed are not captured. In order to prevent this phenomenon, at least two filter films FT are bonded together. The filter film FT1 on the foremost side is a filter film that captures an object to be removed. A filter film having a larger hole than that 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 in actuality, they are formed in a bag shape as shown in FIG. 9b.
[0092]
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. 10a, 10C, and 10d.
[0093]
FIG. 10A is a completed view, and FIG. 10C shows a view cut in the extending direction (longitudinal direction) of the pipe 34 from the head of the pipe 34, as shown by line AA in FIG. 10A. It is sectional drawing at the time of cut | disconnecting the filtration apparatus 35 to a horizontal direction as shown to a BB line.
[0094]
As is clear from FIGS. 10a, 10C, and 10d, the spacer 30a inserted into the bag-like filter film FT is sandwiched by the pressing means RG, including the filter film FT. 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.
[0095]
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.
[0096]
FIG. 11 conceptually shows the operation of the above filtering device 35. Here, if the pipe 34 side is sucked by a pump or the like, water flows and is filtered as shown by an arrow without hatching.
[0097]
First, the filtering device 35 is immersed in a tank in which a fluid mixed with the solid material 16 is stored and sucked through the pipe 34. And the fluid passes like white arrows. The small solid material 16B passes through, but the large solid material 16A is captured by the first filter films 31 and 32, and the small solid material 16B is gradually captured. When the solid content becomes lower than the predetermined mixing rate, the second filter film 36 is completed.
[0098]
Subsequently, as shown in FIG. 12, the filtration device 35 on which the second filter film 36 is formed is disposed in the drainage 37 mixed with the object to be removed. Then, by sucking the pipe 34, the object to be removed is captured by the second filter film 36. At this time, since the solid matter 16 is gathered in the second filter film 36, the second filter film 36 can be removed by applying an external force to the second filter film 36, or the second filter 36 can be removed. Or remove the surface layer. Further, since the abrasive grains 14 and the object to be removed (ground object) 15 are aggregates of solids, they can be easily separated from the second filter film 36 by applying an external force, and the drainage 37 Can be moved to.
[0099]
This removal or separation can be easily realized by bubble rising force, water flow, sound wave, ultrasonic vibration, mechanical vibration, rubbing the surface using a squeegee, or a stirrer. Further, the immersed filtration device 35 itself is structured to be movable in the waste water (raw water), and a water flow is generated on the surface layer of the second filter membrane 36 to remove the second filter 36 and the objects 14 and 15 to be removed. Also good. For example, in FIG. 12, you may move to the left and right like the arrow Y by using the bottom face of the filtration apparatus 35 as a fulcrum. In this case, since the filtration device itself is movable, a water flow is generated, and the surface layer of the second filter 36 can be removed. When the bubble generating device 54 described later is also employed, if the movable structure is employed, the bubbles can reach the entire filtration surface, and the removed matter can be efficiently moved to the drainage side.
[0100]
In addition, if the cylindrical filtration device shown in FIG. 9C is adopted, the filtration device itself can be rotated about the center line CL, and drainage can be performed more than the method of moving the plate-like filter of FIG. Resistance can be reduced. By this rotation, a water flow is generated on the surface of the filter membrane, and the object to be removed from the second filter membrane surface layer can be moved to the drainage side, and the filtration ability can be maintained.
[0101]
In FIG. 12, as a method for removing the surface layer of the second filter film, the rise of bubbles was used. Bubbles rise in the direction of the hatched arrow, and the rising force of the bubbles and the bursting of the bubbles directly apply external force to the object to be removed and the solid, and the water flow generated by the rising force of the bubbles and the bursting of the bubbles is generated. An external force is applied to the object to be removed or solid matter. By this external force, the filtration capacity of the second filter membrane 36 is constantly refreshed and maintained at a substantially constant value.
[0102]
The point of the present invention is to maintain the filtration capacity. That is, even if clogging occurs in the second filter film 36 and the filtration capacity thereof is reduced, external force is applied to the solid material 16 and the objects to be removed 14 and 15 constituting the second filter film 36 like the bubbles. Therefore, the solid material 16 and the objects to be removed 14 and 15 constituting the second filter membrane 36 can be moved to the drainage side, and the filtration ability can be maintained for a long time.
[0103]
This seems to make the thickness of the second filter substantially constant by applying an external force. Also, it is as if each object to be removed is plugged at the entrance of the filtered water, the plug is removed by external force, filtered water enters from the removed place, and once the plug is formed, it is repeatedly removed by external force. It is like that. In addition, by adjusting the size of the bubbles, the amount of the bubbles, and the time for which the bubbles are applied, there is a merit that the filtering ability can be always maintained.
[0104]
In addition, as long as the filtration capability can be maintained, an external force may be applied constantly or intermittently.
[0105]
Further, as can be said in all the embodiments, the filter membrane needs to be completely immersed in raw water. This is because when the second filter membrane is exposed to air for a long time, the membrane dries and peels off or collapses. Further, if there is even a small amount of the filter that is in contact with air, the filter membrane sucks air, so that the filtration ability is lowered.
[0106]
As described above, in view of the principle of the present invention, as long as the second filter film 36 is formed on the first filter films 31 and 32, the first filter films 31 and 32 are made of sheet-like polymers. It may be a membrane or ceramic, and may be a suction type or a pressure type. However, when actually employed, the first filter films 31 and 32 are polymer films and are preferably of a suction type. The reason is described below.
[0107]
First, when a sheet-like ceramic filter is made, the cost rises considerably. If a crack occurs, a leak occurs and filtration becomes impossible. Moreover, when it is a pressurization type | mold, it is necessary to pressurize waste_water | drain. For example, taking the tank 50 of FIG. 13 as an example, in order to apply pressure, the upper part of the tank must be a closed type rather than an open type. However, it is difficult to generate air bubbles in the sealed type. On the other hand, for polymer membranes, sheets of various sizes and bag-like filters can be obtained at low cost. Moreover, since it is flexible, cracks do not occur, and it is easy to form irregularities on the sheet. By forming the unevenness, the second filter film bites into the sheet, and peeling in the waste water can be suppressed. Moreover, if it is a suction type, the tank may remain open.
[0108]
In addition, it is difficult to form the second filter film if it is a pressure type. In FIG. 12, if the pressure in the space 33 is assumed to be 1, the drainage needs to apply a pressure of 1 or more. Therefore, a load is applied to the filter membrane, and the captured object to be removed is fixed at a high pressure, so that the object to be removed is unlikely to move.
Now, an embodiment of a suction type mechanism using the above-described polymer film as a filter film will be described with reference to FIG. Even in this structure, three methods are possible to form the second filter film.
[0109]
That is, in the first method, the raw water tank 50 is equipped with the filtration device 53 to which the first filter membrane is attached. Further, solids are mixed in the fluid in the raw water tank 50. Then, the pipe 56 is sucked to form a second filter membrane, and after the second filter membrane is completed, the waste water mixed with the object to be removed is supplied to the raw water tank 50 through the pipe 51 and filtration is started. .
[0110]
In the second method, the raw water tank 50 is fitted with the filtration device 53 to which the first filter membrane is attached. Furthermore, the waste water in the raw water tank 50 is mixed with solids and objects to be removed. Then, the pipe 56 is sucked to form a second filter film. After the completion of the second filter membrane, the waste water mixed with the object to be removed is supplied through the pipe 51, and filtration is started.
[0111]
The third method is a method in which a filtration device in which the second filter membrane is formed on the first filter membrane is prepared in another tank without using the raw water tank 50, and this is installed in the raw water tank 50. Then, the waste water mixed with the object to be removed is supplied from the pipe 51, and when the waste water completely immerses the filtration device 35, the filtration is started.
[0112]
Here, dicing waste was used as the solid material constituting the second filter film.
[0113]
Reference numeral 50 in FIG. 13 denotes a raw water tank. Above the tank 50, a pipe 51 is provided as drainage supply means. This pipe 51 is a place where a fluid mixed with an object to be removed passes. For example, in the semiconductor field, waste water (raw water) mixed with an object to be removed flowing out from a dicing apparatus, a back grinding apparatus, a mirror polishing apparatus, or a CMP apparatus passes. 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.
[0114]
In the raw water 52 stored in the raw water tank 50, a plurality of filtration devices 53 on which a second filter membrane is formed are installed. Below this filtering device 53 is provided a bubble generating device 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 membrane. Has been adjusted. 55 is an air blow.
[0115]
The pipe 56 fixed to the filtration device 53 corresponds to the pipe 34 in FIG. Through this pipe 56, the filtered fluid filtered by the filtering device 53 passes, and through the first valve 58, a pipe 59 that goes to the raw water tank 50 side and a pipe 60 that goes to the reuse (or drained) side. Selected to be transported. A second valve 61, a third valve 62, a fourth valve 63, and a fifth valve 64 are attached to the side wall and the bottom surface of the raw water tank 50. Also, what is attached to the tip of the pipe 65 is a filter device 66 provided separately.
[0116]
The raw water 52 supplied from the pipe 51 is stored in the raw water tank 50 and filtered by the filtering device 53. The surface of the filter membrane attached to this filtration device is maintained so that bubbles pass through and the removal target trapped in the filter membrane is moved by the rising force or rupture of the bubbles, and the filtration capacity is not always reduced. .
[0117]
In addition, when a filtration device with a second filter membrane is newly installed, stopped for a long time due to a holiday, or when a substance to be removed is mixed in the pipe 56 in a larger amount than a predetermined mixing rate, the valve 58 The filter fluid is designed to circulate to the raw water tank 50 through the pipe 59. Other than that, the valve 58 is switched to the pipe 60, and the filtered fluid is reused or transferred to the waste water treatment side.
[0118]
When the filtration device 53 to which the second filter membrane is attached is newly attached to the raw water tank 50, the circulation time varies depending on the size of the filter membrane and the suction speed, but is circulated for about 1 hour. Even if a part of the second filter film is broken, it is self-repaired in this time and becomes a film that can capture silicon debris of 0.1 μm or less. However, it has been found that 30 minutes may be used if the filter membrane has a small size. Therefore, if the circulation time is known, it may be set by a timer, and the first valve 58 may be automatically switched when a predetermined time has elapsed.
[0119]
Here, the structure of FIG. 10 is employ | adopted for the filtration apparatus, and the magnitude | size of the frame (holding metal fitting RG) which attaches a filter membrane is length: about 100 cm, width: about 50 cm, and thickness: 5-10 mm.
[0120]
If the object to be removed is higher than a predetermined mixing rate (concentration), it is determined that the filtered fluid is abnormal water, and the circulation starts automatically, or the pump 57 is stopped and the filtration is stopped. Further, when circulating, the supply of fluid from the pipe 51 to the tank 50 may be stopped in consideration of the fact that drainage overflows from the tank 50. Such a case is briefly described below.
[0121]
The first case is a case where the filtration device 35 is newly attached.
[0122]
Since the second filter membrane may be damaged in the transportation process or the like, the object to be removed is captured and repaired by circulating the second filter membrane. The second filter film is grown until the target particle diameter is captured by the second filter film (until the object to be removed reaches a predetermined first mixing ratio). Then, after reaching the first predetermined value, the filtered fluid is transferred to the pipe 60 via the first valve 58.
[0123]
The second case is a case where filtration is stopped on holiday, long vacation, maintenance, etc., and filtration is started again.
[0124]
Since the second filter membrane is composed of an object to be removed and is in the waste water, if the filtration is stopped for a long time, a part of the membrane surface layer may collapse. Circulation is used to repair this membrane collapse. In the experiment, the second filter film made of a solid material is firmly attached to the first filter film, and the surface thereof is covered with an object to be removed, so that there is almost no collapse of the film. However, it is circulating here just in case. When the filtered fluid reaches the first predetermined value, the first valve 58 is switched and transferred to the pipe 60. The bubbles are generated at least when the first predetermined value is reached and filtration is started.
[0125]
The third case is a case where an object to be removed to be captured by the filtered fluid is mixed.
[0126]
When a part of the second filter membrane is broken or the filter membrane is torn, a large amount of an object to be removed is mixed in the filtration fluid.
[0127]
When a part of the second filter membrane collapses and becomes higher than a predetermined concentration (second predetermined value), the first valve 58 causes the filtered fluid to circulate through the pipe 59 so as to perform a filtration operation. To stop. Then, circulation is started to repair the second filter membrane, and when the object to be removed in the filtered fluid reaches a predetermined mixing rate (first predetermined value), the first valve 58 is switched to filter the filtered fluid. Is transferred to the pipe 60. The bubbles are generated at least when the first predetermined value is reached and filtration is started.
[0128]
Further, when the first filter membrane is torn, it is necessary to replace the first filter membrane or the filtration device 53 itself. However, since the filtration device 35 is integrated with the adhesives AD1 and AD2, it is virtually impossible to replace only the first filter membrane. Therefore, it replaces with the new filtration apparatus 53 in which the 2nd filter membrane was formed here. In this case, it is confirmed that the second filter membrane can capture a predetermined object to be removed, and if it cannot be captured, it is circulated to improve the filtration capacity. If it is confirmed that the trapping is possible, the first valve 58 is used to switch the filtered fluid to the pipe 60.
[0129]
The fourth case is a case where the drainage level of the raw water tank 50 is lowered and the filter membrane is in contact with the atmosphere.
[0130]
Before the filter membrane comes into contact with the atmosphere, filtration is stopped by a level sensor (reference numeral FS in FIG. 15) provided in the drainage. At this time, the generation of bubbles is also stopped. This is because drainage is supplied from the pipe 51, and turbulent flow is generated by bubbles, and the second filter membrane may collapse. Then, when a predetermined drainage level capable of being filtered is reached, circulation is started. Then, the object to be removed is detected while circulating, and when the object to be removed in the filtered fluid reaches a predetermined mixing ratio (first predetermined value), the first valve 58 is switched to connect the filtered fluid to the pipe. To 60.
[0131]
Note that the first predetermined value and the second predetermined value indicating the concentration of the object to be removed in the filtered fluid may be the same, and the second predetermined value has a certain width from the first predetermined value. It may be set larger.
[0132]
In addition, the sensor 67 constantly senses solid objects and objects to be removed. As the sensor, an optical sensor with a light receiving / light emitting element is preferable because it can always measure. The light emitting element may be a light emitting diode or a laser. The sensor 67 may be attached in the middle of the pipe 56 or in the middle of the pipe 59.
[0133]
Next, how the waste water mixed with the material to be removed flowing from the CMP apparatus is filtered will be described.
[0134]
14a and 14b show the particle size distribution of abrasive grains contained in the CMP slurry. The 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. These large particles are agglomerated particles made up of a plurality of particles therein. Further, the average particle diameter is about 0.1448 μm, and the distribution has a peak in the vicinity of 0.13 to 0.15 μm. As a slurry adjusting agent, KOH or NH3 is generally used. PH is between about 10-11.
[0135]
FIG. 14C is data showing that the 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 are prepared assuming that the drainage is about 50 to 5000 times because the wafer is cleaned with pure water in the CMP process. Was put into the raw water tank 50 of FIG. 13 and filtered using a filtering device 53.
[0136]
When the light transmittance of the test solution before filtration 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 It is 98.3%. Since the drainage contains abrasive grains, it can be seen that the light is scattered and the transmittance decreases as the concentration increases.
[0137]
On the other hand, the transmittance after filtration was 99.8% for all three types. That is, since the light transmittance after filtration is larger than the light transmittance before filtration, it can be seen that the abrasive grains are captured. The transmittance data of the 50-fold diluted test solution is omitted in the drawing because the value is small.
[0138]
From the above results, it was found that when the object to be removed discharged by CMP is filtered with a filter having the second filter film formed of the solid materials 16A and 16B, the transmittance can be reduced to about 99.8%. .
[0139]
The solid material forming the second filter film may be mechanically produced by polishing, grinding, pulverization, or the like, or may be collected from the natural world. The particle size distribution preferably has a particle size distribution as shown in FIG. In particular, the particle size distribution has a first peak at 1 μm or less and a second peak at 20 to 50 μm, and a larger solid in the vicinity of the second peak than a ratio of a small solid in the vicinity of the first peak. It is preferable that the ratio is larger.
[0140]
On the other hand, the object to be removed may be taken into the waste water with a particle size distribution as generated by processing, and filtered. Further, fine particles may be separately mixed in the waste water, and the total particle size distribution including the object to be removed and the fine particles may be adjusted so as to be the distribution shown in FIG. For example, as shown in FIG. 14, the object to be removed in the CMP wastewater has a peak in the vicinity of about 0.1 .mu.m and is distributed in a narrow range of 1 .mu.m or less around the peak. Therefore, from about 1 .mu.m in FIG. Fine particles having a distribution of (for example, dicing waste) may be mixed into the CMP waste water. Thus, the film formed on the second filter made of a solid material has the same gap as the second filter, and has the merit of maintaining the capture property of the object to be removed and the fluid permeability.
[0141]
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, yttria-based. There is. 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.
[0142]
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.
[0143]
These abrasive grains have the same particle size as those shown in FIGS. 14a and 14b. Of course, it is possible to filter the waste water contained in the objects to be removed and capture the abrasive grains.
[0144]
Next, the treatment of the concentrated water containing the object to be removed obtained by filtration will be described. In FIG. 13, the material to be removed is concentrated in the raw water tank over time. And when it becomes a desired density | concentration, a filtration operation | work is stopped, it is made to coagulate and precipitate and it is left to stand. The raw water in the tank is divided into layers. That is, it is distributed from a slightly transparent fluid to a completely non-transparent fluid from the upper layer to the lower layer. These are collected using the valves 61 to 64 separately.
[0145]
For example, raw water that is slightly transparent and has few objects to be removed is collected via the filtration device 66 by opening the second valve 61. Subsequently, the valves 62 and 63 are sequentially opened to collect the fluid. Finally, the concentrated slurry stored at the bottom of the raw water tank is recovered by opening the valve 64.
[0146]
If the valve 64 is opened first, the concentrated slurry flows at the same time due to the weight of the raw water, and the upper fluid also comes out and is difficult to control. For this reason, the valves are collected in the order of 61, 62, 63, 64 in this case.
[0147]
Moreover, the raw water level inspection means 80 of the raw water tank is shown in the lower center of FIG. 13 (the figure surrounded by the dotted line). In this, an L-shaped pipe 81 is attached to the side surface of the raw water tank 50, and at least one pipe 82 is attached depending on the level of the raw water. The pipe 82 has an outer diameter that matches the inner diameter of the pipe 81 and is fitted.
[0148]
For example, when the level of raw water reaches a position slightly higher than the height at which the valve 63 is mounted, this pipe 82 is attached, and a transparent observation window is attached to the pipe 82 that extends upward to check the level of the raw water. be able to. Therefore, raw water other than the concentrated slurry can be removed to the last while confirming the raw water level through this observation window.
[0149]
If the pipe itself is made of a transparent material such as glass, the level of the raw water can be confirmed without attaching a separate observation window. The inspection means may be attached in advance.
[0150]
On the other hand, the lower left of FIG. 13 shows a means for collecting the upper water above the concentrated slurry to the limit. That is, an L-shaped pipe 81 is attached to the inside of the raw water tank 50 as shown in the figure. If the amount of the object to be removed is specified in a fixed period or the amount of the concentrated slurry is specified, the height of the head of the pipe 81 is determined in advance. Therefore, if the heads of the pipes 81 and 82 are arranged at a position slightly higher than the upper layer of the concentrated slurry, the raw water can automatically flow out to the filtration device 66 to this height. Even if the valve 63 is accidentally opened, the outflow of raw water can be stopped at the level of the heads of the pipes 81 and 82. Further, when the level of the concentrated slurry increases or decreases, the level of the raw water can be adjusted by removing the pipe 82. Of course, any number of pipes 82 may be prepared, and many stages may be attached depending on the level.
[0151]
In addition, although the method of collect | recovering concentrated water by the coagulation sedimentation method was demonstrated, it does not restrict to this. For example, when the raw water 52 has a certain concentration, it may be transferred to another filtration device 66 (FD). For example, CMP uses a slurry containing chemicals and abrasive grains of 0.1 μm or less. And water is poured at the time of polishing, and the thing whose concentration is lower than the slurry is discharged as drainage. However, as the discharged stock solution is filtered, the concentration increases and the viscosity also appears. If the distance between the filtering device and the filtering device is narrow, the bubbles are difficult to enter between the filtering devices, and the bubbles do not apply an external force to the solid matter or the object to be removed. Moreover, if the object to be removed is very fine as shown in FIG. Therefore, it is preferable to transfer the stock solution to another filtration device FD when a predetermined concentration is reached. For example, as shown in the lower right of FIG. 13, a filtration device that pours raw water into the upper layer of the filter FT and sucks the raw water with a pump P may be employed. Further, the filtration device FD may be recovered by being attached to a concentration recovery pipe.
[0152]
Here, the solution is filtered through the filter FT and sucked until the high-concentration stock solution becomes a certain amount of mass. On the other hand, the raw water level in the raw water tank 50 is lowered by transferring the raw solution to the filtration device FD, but the raw water having a low concentration is supplied from the pipe 51. And when the concentration of the raw water becomes thin and the raw water completely immerses the filter, if the setting is made so that the filtration starts again, the viscosity of the raw water also decreases, bubbles enter between the filtration devices and give external force to the solid matter It becomes like this.
[0153]
Moreover, you may use filtration apparatus FD and 66 as a collection | recovery apparatus of a to-be-removed thing. For example, when the raw water tank 50 containing the object to be removed reaches a predetermined concentration, it may be separated by the filtration device 66 (FD) without performing aggregation precipitation. For example, when filtering silicon debris, the separated silicon debris does not react with the chemicals used in the coagulation sedimentation, so it is relatively pure and melts again into a Si ingot for the wafer. May be. In addition, it can be reused in various fields, such as tile materials, cement, and concrete materials.
[0154]
As described above, the system shown in FIG. 13 includes the raw water tank 50, the filtration device (immersion / suction) 53, and the small pump 57, and suction is performed at a low pressure so that the first filter is not clogged. Therefore, the pump 57 has an advantage of being small. Conventionally, since the stock solution passes through the pump, the inside of the pump is worn and its life is very short. However, this configuration has a much longer life because the filtered fluid passes through the pump 57. Accordingly, the scale of the system can be reduced, the electricity cost for operating the pump 57 can be saved, the cost for replacing the pump can be greatly reduced, and the initial cost and running cost can be reduced.
[0155]
The filter membrane is a polyolefin-based membrane that does not crack even when dropped, has high mechanical strength, and has high resistance to chemicals such as acid and alkali. Therefore, the raw water concentration can cope with a high concentration, and coagulation sedimentation is possible with the filter membrane attached.
[0156]
In addition, it does not coagulate and settle in a separate tank, but coagulates and precipitates using the raw water tank, eliminating the need for extra pipes and pumps, and enabling a resource-saving filtration system.
[0157]
In addition, since the filtration device performs filtration at a low flow rate and low pressure by suction filtration, and further, by forming the second filter membrane, the solid matter or the object to be removed enters the pores of the first filter membrane described above. Can be prevented, and the filtration performance can be improved. Moreover, continuous filtration was possible by means of external force generation such as air bubbling. Moreover, the filtration speed and the filtration pressure are set within a range in which the second filter membrane is not destroyed when the first filter membrane is broken or deformed. The Day and filtration pressure can be substantially up to 0.01 kg / cm 2 to 1.03 Kgf / cm 2 (1 atm).
[0158]
On the other hand, it is possible to prevent the solid matter or the object to be removed from adhering to the inside of the filtration membrane, and the reverse cleaning that has been conventionally required is almost unnecessary.
[0159]
As described above, silicon scrap generated from a Si wafer as a solid material, abrasive grains generated from CMP as a material to be removed, and material to be polished (ground material) have been described, but the present invention can be used in various fields. .
[0160]
In other words, the particle size distribution as shown in FIG. For example, the second filter membrane may be formed by making this distribution with an inorganic material such as alumina, zeolite, diatomaceous earth, ceramic, metal material or the like. Further, although there are two peaks in FIG. 2a, basically, filtration is possible if solids having a large particle size and a small particle size are distributed in a range of ˜several 500 μm. Furthermore, there is no problem with solid materials even if different materials are mixed. In addition, as long as the material to be removed is essentially a solid material, all materials can be filtered.
[0161]
Drainage caused some harm to the global environment, but as explained at the beginning of the examples, the present invention can be used in various fields, and the damage is greatly reduced by adopting the present invention. It can be made to.
[0162]
In particular, there are waste incinerators that generate dioxin-containing substances, uranium refineries that purify radioactive substances, and factories that generate powders containing harmful substances. Waste with toxic substances can be removed from large to small items.
[0163]
Moreover, if a to-be-removed object is an inorganic solid substance which contains at least 1 among the elements of 2a group-7a group, 2b group-7b group in a periodic table, these things are by employ | adopting this invention. Almost can be removed.
[0164]
Next, the recovery of the object to be removed will be described with reference to FIG.
[0165]
First, an object to be removed (for example, CMP waste water) is poured through the pipe 51, and filtration is started. Here again, the mixing rate of the object to be removed of the filtration fluid can be confirmed. If the mixing rate is higher than the desired mixing rate, it can be circulated, and filtration can be started after confirming that the mixing rate is lower than the desired mixing rate. When the filtration is started, the pipe 59 is switched to the pipe 60 by the first valve 58. The bubble generating device 54 is started at least from this time. Reference numeral 70 is a pressure gauge for detecting the pressure of the filtered fluid passing through the pipe 56, and reference numeral 71 is a flowmeter.
[0166]
And when filtration is continued continuously and the density | concentration of the waste_water | drain of the raw | natural water tank 50 exceeds predetermined density | concentration, either of the valves 61-64 will be opened and the raw | natural water 52 will be poured into the filtration apparatus FD. The filtering device 53 is arranged in parallel with dozens of sheets in the raw water tank 52. However, when the viscosity increases, it becomes difficult for bubbles to enter between the filtering devices 53, and the passage of bubbles to the second filter membrane surface is suppressed. Therefore, when the wastewater exceeds a predetermined concentration, in order to reduce the concentration of the wastewater, at least a part of the wastewater is transferred to the filtering device FD, and the concentration is reduced by the wastewater flowing from the pipe 51.
[0167]
This filtration device FD is divided into a first tank 72 and a second tank 73, and between these two tanks 72, 73 there is a filter FT having a coarser hole than the first filter membrane. Has been placed. Then, the stock solution is forcibly transferred to the second tank 73 by sucking the pipe 74 with a pump or the like.
[0168]
By performing filtration with the filtering device FD, a recovered material 75 that is a mass of the object to be removed is generated on the filter FT, and this recovered material is collected in a container 76. In addition, since the recovered material is scattered when dried, the container should be sealed.
[0169]
And while continuing this collection, the level of the raw water tank 50 is lowered, but the filtered fluid of the filtration device FD is returned to the raw water tank 50 again, or the waste water is supplied from the pipe 51, so that the raw water concentration in the raw water tank 50 is reduced. And the filtration can be started. The timing at which the pump is stopped or started depending on the level of drainage is detected by a level sensor FS.
[0170]
Further, a method of reusing the filtered fluid from which abrasive grains and polishing objects (ground objects) in the CMP waste water are removed will be described with reference to FIG.
[0171]
The CMP apparatus denoted by reference numeral 80 is generally arranged as a system as shown in FIG. 20, but for the convenience of drawing, the CMP apparatus of FIG. 19 is shown. The rest of the configuration excluding this CMP apparatus is the same as in FIGS.
[0172]
Reference numeral 252 denotes a semiconductor wafer provided on the rotating surface plate 250, and reference numeral 253 denotes slurry. Although not shown, a shower for showering the wafer 252 and the rotating surface plate 250 is also provided.
[0173]
Below the CMP apparatus, in the wafer cleaning mechanism section, there is a container BL for receiving drainage, and a pipe 51 connected to the raw water tank 50 is attached to a part of the container BL. Since details are described in FIGS. 19 and 20, they are omitted here.
[0174]
In addition to the slurry stock solution (which mainly contains a diluent, a pH adjuster, and abrasive grains), the wastewater is mixed with granular objects to be polished or objects to be polished, ions made up of semiconductor wafer constituents, and water. The filtration device 53 captures substantially all of the abrasive grains and the object to be polished (or object to be ground) mixed in the slurry. Accordingly, the fluid passing through the pipe 60 contains a slurry stock solution (for example, KOH or NH3 as a modifier and a diluent) excluding abrasive grains, water, and ions. The filtration fluid can be reused if a purification device is installed to remove the ions. If the abrasive grains are mixed again and stirred in the purified slurry stock solution, it can be reused as a slurry for a CMP apparatus.
[0175]
Moreover, the said filtration fluid may be transferred to another tank via the pipe 72, and this may be passed to a refinement | purification maker and may be refined. By using such a system, it is possible to reuse the CMP wastewater that is discarded in large quantities.
[0176]
Next, the relationship with the actual pure water production system will be described with reference to FIG.
[0177]
First, industrial water is stored in the industrial water tank 101. This industrial water is transported to the filtrate water tank 104 via the filters 102 and 103 by the pump P1.
The filter 102 is a carbon filter from which dust and organic substances are removed. The filter 103 removes carbon generated from the filter 102.
[0178]
Subsequently, the filtered fluid is transported to the pure water tank 106 via the reverse osmosis filter 105 by the pump P2. The filtration device 105 uses a reverse osmosis membrane, and scraps (dust) of 0.1 μm or less are removed here. The pure water in the pure water tank 106 is transported to the pure water tank 111 through the UV sterilizer 107, the adsorption devices 108 and 109, and the device 110 for reducing the resistance value of pure water.
[0179]
The UV sterilizer 107 sterilizes pure water with ultraviolet rays as shown in the figure, and reference numerals 108 and 109 denote apparatuses that exchange ions and remove ions. Reference numeral 110 denotes a mixture of carbon dioxide gas in pure water. This is because, if the resistance value of pure water is high, problems such as the occurrence of charge-up in the blade and the like occur, so the resistance value is intentionally lowered.
[0180]
Then, pure water is supplied for cleaning the CMP apparatus using the pump P3. The code | symbol 112 removes again the waste (dust) of about 0.22 micrometer or more.
[0181]
Subsequently, the waste water generated in the CMP apparatus is stored in the raw water tank 113 using the pump P4, and is filtered by the filtration apparatus 114 described above. This is the same as described in FIGS. The filtered fluid filtered by the filtering device 114 is purified by the purifying device 121 connected to the pipe 120, and the separated water is returned to the filtered water tank 104. The fluid refined by the refiner may be mixed with abrasive grains and reused again as a CMP slurry.
[0182]
Here, in the filtering device 114, when the object to be removed is mixed into the filtering fluid, it goes without saying that the filtering device 114 returns to the raw water tank 113 and circulates it.
[0183]
【The invention's effect】
In general, in order to remove 0.1 μm class particles such as abrasive grains mixed in a CMP slurry, it is common to employ a filter film having pores smaller than the particles. However, in the present invention, a solid material having the same size and larger size as the object to be removed is laminated as the second filter film, and a large number of gaps formed in the second filter film are utilized as fluid passages. Therefore, it was possible to remove the 0.1 μm class fluid simply by immersing the filtration device in which the second filter membrane was formed in the waste water. Therefore, it is possible to realize a high-accuracy filtration apparatus in which the system is assembled with the filtration apparatus, the pump, and the tank on which the second filter membrane is formed, the equipment cost is low, and the running cost is reduced.
[0184]
In addition, since the second filter membrane itself is an aggregate of solid matter, the object to be removed and the solid matter that cause clogging can be separated from the second filter membrane, and the filtration capacity of the filtration device can be increased for a long time. It was also possible to maintain for a long time. Furthermore, the object to be removed and / or the solid matter in the waste water is grown as a second filter membrane by circulating it, and is formed as a second filter membrane having a filtration performance capable of capturing up to a predetermined particle size. In addition, the second filter film can be self-repaired. Therefore, the filtration apparatus which can reduce maintenance significantly compared with the conventional filtration apparatus was implement | achieved.
[0185]
More specifically, by forming a laminate on the first filter, it is possible to secure more passages for fluid and drainage than the first filter to prevent clogging, and to have an uneven shape. Therefore, even if an external force is applied, only the solid matter located on the extreme surface of the laminate is released, or only the debris trapped in the laminate is released, and the laminate attached directly to the first filter. Objects are attached without being separated. This allows refreshing by applying an external force to the surface of the filter including the laminate, and enables long-time filtration. Therefore, the density | concentration of the waste of waste water can be raised and the efficiency is improved significantly when collecting waste. CMP wastewater is applied to each layer, and the wastewater is enormous. However, waste can be highly concentrated, so that the amount of waste treatment can be greatly reduced.
[0186]
Further, since the suction force is very small, the solids of the laminate can be separated.
[0187]
Further, the viscosity of the CMP wastewater increases. This makes it difficult for the bubbles to come into contact with the surface of the laminate. Also, the filter refresh function is degraded. Therefore, when a predetermined viscosity is reached, a part of the waste water is transferred from the raw water tank and diluted with waste water supplied from the manufacturing site. Therefore, the viscosity can be lowered and the refresh function can be improved.
[0188]
Furthermore, the laminate may be formed in a tank different from the raw water tank. By forming in a separate tank, a filter with a laminate can be prepared in advance, and transfer to a distance away is facilitated.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a filter film according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining the particle size distribution and shape of silicon waste in waste water generated during dicing.
FIG. 3 is a diagram illustrating a filter film according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating a filter film according to an embodiment of the present invention.
FIG. 5 is a diagram for explaining a method of forming a filter composed of a solid substance or a solid substance and an object to be removed.
FIG. 6 is a diagram for explaining a method of forming a second filter film on the first filter film of the filtration device.
FIG. 7 is a diagram illustrating a method for preparing a filter film.
FIG. 8 is a diagram illustrating a method of preparing a filtration device having a filter membrane.
FIG. 9 is a diagram for explaining a filtration device employed in the present invention.
FIG. 10 is a diagram illustrating a filtration device employed in the present invention.
11 is a diagram for explaining the filtering operation of FIGS. 9 and 10. FIG.
12 is a diagram illustrating the filtering operation of FIGS. 9 and 10. FIG.
FIG. 13 is a system diagram illustrating the filtration method of the present invention.
FIG. 14 is a diagram for explaining the particle size distribution of CMP abrasive grains and the light transmittance before and after filtration.
FIG. 15 is a system diagram illustrating the filtration method of the present invention.
FIG. 16 is a system diagram illustrating the filtration method of the present invention.
FIG. 17 is a diagram for explaining a system in which the filtration method of the present invention is applied to a CMP apparatus.
FIG. 18 is a diagram illustrating a conventional filtration system.
FIG. 19 is a diagram illustrating a CMP apparatus.
FIG. 20 is a diagram illustrating a system of a CMP apparatus.
[Explanation of symbols]
10 First filter
11 Filter hole
12 Metal scrap
13 Second filter
20 Raw water tank
21 Filter membrane
23 filtered water
24 pump
25 Switching valve
30 frames
31, 32 First filter
34 pipe
50 Raw water tank
52 Raw water
53 Filtration equipment
54 Bubble generator
67 sensors

Claims (2)

An apparatus for slicing a crystal ingot into a wafer, an apparatus for back grinding a semiconductor wafer, an apparatus for dicing a semiconductor wafer, or an apparatus for polishing by CMP;
Transports wastewater containing solids that are processing waste generated from an apparatus for slicing the crystal ingot into a wafer, an apparatus for back grinding the semiconductor wafer, an apparatus for dicing the semiconductor wafer, or an apparatus for polishing by CMP. Pipe to
A raw water tank for storing the waste water discharged from the pipe;
In a semiconductor material processing waste treatment system having at least a filtration device in which a filter membrane is immersed in the wastewater stored in the raw water tank,
By pressing or sucking the waste water through the filter membrane, the solid matter is laminated on the filter membrane, and the water flow of the waste water is separated so that the solid matter on the surface layer of the laminate composed of the solid matter is separated. Or applying an external force consisting of bubbles generated from a bubbling device located below the filter membrane to refresh the surface of the laminate,
A semiconductor material processing waste treatment system , wherein water is passed through between the solids constituting the laminate and the waste water is filtered.   The semiconductor material processing waste processing system according to claim 1, wherein the solid material is made of Si, and the Si is reused.

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