JP2001038153A - Regenerating system of waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging of fine holes due to reaction of a solid material by installing a pH adjusting means in a regenerating system of waste water for separating into the solid material and the water by passing the waste water in which the solid material is incorporated through the fine holes. SOLUTION: In the system, the pH adjusting means 12 for measuring the pH of waste water and controlling to the desired pH is attached. The waste water measured in the pH is controlled to the desired pH by adding a chemical showing alkalinity or acidity corresponding to the pH value of the waste water. Particularly in scrap of silicon, the waste water is adjusted to a neutral side or acidic side to prevent generation of a gel-like or colloidal material to prevent the clogging of the filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater regenerating system, and more particularly to a filter for filtering wastewater mixed with grinding or polishing debris generated during grinding or polishing. , A system for reusing water.

[0002]

2. Description of the Related Art At present, reducing industrial waste is an important theme from an ecological point of view, and is a corporate issue for the 21st century. This industrial waste includes wastewater, and the wastewater is reused as clean water by an expensive filtration device or the like, and the waste that cannot be removed is treated as industrial waste. In particular, it is an important future task to clean water and return it to the natural world such as rivers and seas, or to reuse it.

[0003] However, it is very difficult to employ these devices due to problems such as equipment costs such as filtration and running costs, and environmental problems occur in various places, and further, from the viewpoint of recycling. This is an important issue.

As an example, wastewater treatment in the semiconductor field will be described below. Generally, when grinding or polishing a plate such as metal, semiconductor, ceramic, etc., it is necessary to consider the prevention of temperature rise of equipment, improvement of lubricity, adhesion of grinding chips or cutting chips to the plate, etc. Is supplied.

FIGS. 17 to 23 illustrate a process for processing a Si semiconductor wafer. FIG. 17 shows a single crystal of Si pulled up into an ingot. For example, 8
There are 2 meters in inches. Unnecessary portions, upper and lower end portions 2 and 3 of the ingot 1 are cut and removed, and cut and separated into several cylindrical blocks 4. At this time, water is supplied by cutting with a blade (not shown). (The first
Polishing / Grinding Step) Subsequently, as shown in FIG. 18, the outer periphery is ground with a grinding blade 5 in order to make the cylindrical block 4 have a predetermined wafer diameter. Here, the water supply means 6 also serves to protect the grinding blade 5 and the block 4.
Shower through. (The Second Polishing and Grinding Step) Subsequently, as shown in FIG. 19, a notch called an orientation flat 7 is formed in the block 4 to indicate the in-plane crystal orientation of the wafer. (The Third Polishing / Grinding Step) Subsequently, as shown in FIGS. 20 and 21, the block 4 is attached to the support base SUB with an adhesive, and cut into one wafer. In FIG. 20, slicing is performed with a blade saw 8 to which diamond particles are attached. In FIG. 21,
The piano wire 9 is stretched, and diamond abrasive grains of slurry are flown along the piano wire to slice the block 4.

After the cutting, the adhesive is dissolved with a chemical solution, the wafer is peeled off from the support table, and separated as a wafer. (Fourth Polishing / Grinding Step) Further, in order to prevent the corners of the wafer from being chipped, chamfering is performed and wafer lapping is performed. For example, the front surface and / or the back surface of the wafer are mechanically and chemically polished using the lapping apparatus shown in FIG. (Fifth polishing / grinding process) Then, impurities are introduced and surface defects are processed to complete the crystal, and the wafer is shipped.

This wafer is manufactured as a desired IC by a semiconductor maker. This IC is formed in a matrix on a wafer, and at least the surface of the IC is covered with a protective film such as a resin or a Si nitride film.

Since the wafer is thick as it is and difficult to dice, and in order to reduce the electric resistance on the back surface, the wafer is back-wrapped and thinned to about 300 μm. This back wrap device is shown in FIG. Turntable 200
A wafer 201 is mounted on the wafer, and the back surface of the wafer is shaved by a grindstone 202. Reference numeral 204 denotes a nozzle (shower) 204 for supplying water. (Sixth polishing / grinding step) Finally, the semiconductor wafer is diced as shown in FIG. W is a semiconductor wafer, and DB is a dicing blade. SW1 and SW2 are showers for spraying water on the blade, and SW3 is a shower for spraying water on the wafer W. (The seventh polishing / grinding process) As described above, in the semiconductor manufacturing process, there are many polishing / grinding processes. In the polishing / grinding process, water such as well water, tap water or industrial water, or A method of flowing pure water such as distilled water or ion-exchanged water has been adopted. For example, in a dicing apparatus, 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 formed on the semiconductor wafer or pure water is applied to the blade. A nozzle for water discharge is installed. Also, when reducing the wafer thickness by back grinding, pure water is flown for the same reason.

[0009] On the other hand, under the theme of "environmentally friendly", the wastewater mixed with grinding dust or polishing dust of the semiconductor wafer is filtered and returned to the natural world as clean water, or is reused and concentrated. Wastewater is collected.

There are two types of wastewater treatment in which waste mainly composed of Si is mixed, including a coagulation sedimentation method and a method combining a filter filtration and a centrifugal separator, and each semiconductor maker adopts it.

In the former coagulation precipitation method, PA is used as a coagulant.
C (polyaluminum chloride) or Al2 (SO4) 3
(Sulfuric acid band) or the like was mixed in the wastewater to generate a reaction product with Si, and the reaction product was removed to filter the wastewater.

[0012] In the latter method combining filter filtration and centrifugal separation, the wastewater is filtered, the concentrated wastewater is centrifuged, collected as sludge, and the clean water formed by filtering the wastewater is returned to nature. Release,
Or was reused.

For example, as shown in FIG. 24, wastewater generated during dicing is collected in a raw water tank 301 and sent to a filtration device 303 by a pump 302. Filtration device 30
Since the filter 3 is equipped with a ceramic filter F, the filtered water is sent to a recovered water tank 305 via a pipe 304 and is reused. Or released to nature.

On the other hand, the filtering device 303 is periodically cleaned because the filter F is clogged. For example, the valve B1 on the raw water tank 301 side is closed and the valve B
3 and a valve B2 for sending the generated washing water to the raw water tank are opened, and the filter F is backwashed with the water in the recovered water tank 305. The wastewater mixed with the high-concentration Si waste generated thereby is returned to the raw water tank 301. The concentrated water in the concentrated water tank 306 is transported to the centrifugal separator 309 via the pump 308, and is separated into sludge (sludge) and a separated liquid by the centrifugal separator 309. The sludge composed of Si waste is collected in a sludge collection tank 310, and the separated liquid is collected in a separated liquid tank 311. Further, the drainage of the separated liquid tank 311 in which the separated liquid is collected is transported to the raw water tank 301 via the pump 312.

These methods include, for example, Cu, Fe, A
l, solid or plate-like material mainly composed of a metal material, grinding of solid or plate-like material such as ceramics,
A similar method has been employed for collecting the debris generated during polishing.

However, in the former coagulation-sedimentation method, since a chemical is used as a coagulant, the chemical is put into filtered water. However, it is very difficult to specify the amount of a chemical that completely reacts with the silicon waste, and a large amount of the chemical is inevitably introduced, leaving unreacted chemical. Conversely, if the amount of the chemical is small, all the Si debris are not coagulated and settled, and the silicon debris remains without being separated. In particular, when the amount of the drug is large, the drug remains in the supernatant. When this is reused, since chemicals remain in the filtered water, there is a problem that it cannot be reused for those who dislike the chemical reaction. For example, if filtered water containing chemicals is allowed to flow over a wafer, an undesirable reaction occurs, and there is a problem that water cannot be reused as dicing water.

Floc, which is a reaction product between a chemical and silicon waste, is generated as a floating substance such as an algae. The conditions for forming this floc are severe pH conditions, and about pH 6
It is necessary to maintain the pH at ~ 8, and a stirrer, a pH measuring device, a coagulant injection device, and a control device for controlling these are required. In addition, a large sedimentation tank is required to stably settle flocs. For example, with a wastewater treatment capacity of 3 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.
A large-scale system that requires a site of about a meter will be required.

Furthermore, some flocs are suspended in the sedimentation tank without being settled, and there is a risk that these flocks may flow out of the tank, and it is difficult to collect all of them. That is, there are problems such as the size of the equipment, the high initial cost of this system, the difficulty in reusing water, and the high running cost resulting from the use of chemicals.

On the other hand, as shown in FIG. 24, in a method in which a filter filtration of 5 m3 / 1 hour and a centrifugal separator are combined, a filter F (called a UF module, which is composed of a polysulfone-based fiber, Since a ceramic filter is used, water can be reused. However, four filters F are attached to the filtering device 303, and it is necessary to replace a high-priced filter of about 500,000 yen / filter at least once a year from the life of the filter F. Moreover, the pump 302 before the filtering device 303 has a large motor load because the filter F is a pressurized filtering method, and the pump 302 has a high capacity.
About ／ of the wastewater passing through the filter F was returned to the raw water tank 301. Further, since the wastewater containing the silicon waste is transported by the pump 302, the inner wall of the pump 302 is shaved and the life of the pump 302 is very short.

Summarizing these points, there is a problem that the running cost is very large because the electricity cost of the motor is very high and the replacement cost of the pump P and the filter F is expensive.

For this reason, the present applicant has developed a filtering device as shown in FIG. This is disclosed in Japanese Patent Application No. 11-148351.
No., Japanese Patent Application No. 11-148352, Japanese Patent Application No. 11-1483
The invention has already been filed in Japanese Patent No. 53.

This is because the filtration device 5 in the raw water tank 50
3 employs a suction type filter, and the filtered water is reused through the pipe 56, the first valve 58, and the pipe 60, or is discharged to the natural world. Grinding or polishing debris mixed into the raw water tank 50 is trapped by this filter, and the grinding or polishing debris becomes a self-forming film and functions as a second filter. The details will be described later with reference to FIGS.

Since the second filter is an aggregate of grinding dust or polishing dust, when bubbles are flowed from below the filter through the bubble generator 54, the bubbles are raised by an external force such as a bubble rising force or a bubble burst. , The surface of the second filter is refreshed, and long-term filtration is possible.

[0024]

FIG. 26 shows a general filter used in a filtering device. This filter is always used for filtering the above-mentioned waste water.

However, in the above-mentioned filter filtration method, most of the debris from which semiconductor materials and metals are filtered are dissolved in response to acids or alkalis. The dissolved ions are precipitated as hydroxide depending on the pH, or are present in water as a gel or colloidal substance, and may cause clogging of the filter.

For this reason, when an acid or alkali is mixed in the drainage process, a reaction product is formed, and the pores 71 of the filter are easily clogged by continuous filtration, so that the filter needs to be washed frequently, or Replacement was sometimes required. Further, there is a problem that filtration becomes difficult.

Generally, polishing after processing as an IC.
In the grinding process, distilled water, ion-exchanged water, or pure water is used as the water for flowing the grinding dust or the polishing waste. Therefore, the reactant of the grinding waste or the polishing waste is not generated, and even if it is generated, it is extremely small. . Therefore, the grinding debris or the polishing debris trapped in the filter is only a solid substance, and a gap is always generated, and the filtration time is relatively long. However, in the process of FIGS. When well water, tap water, and industrial water are used, the following problem occurs. In other words, the water itself mentioned above,
Before they were poured into grinding or abrasive debris, they could be lean to alkaline or acidic.

Even if the above-mentioned water is neutral and is poured into grinding dust or polishing dust, a treatment for dissolving the adhesive with a chemical solution after cutting is performed, so that some chemical solution may enter the wastewater. . For this reason, chemicals may be mixed into the receiving tray BL together with the drainage for flowing grinding dust or polishing waste.

Grinding or polishing debris reacts with these chemicals to produce hydroxide, gel or colloidal reactant, which causes clogging of the filter.

[0030]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and firstly, a wastewater regenerating system for passing wastewater mixed with solids through fine holes and separating the wastewater into solids and water. In the above, the problem is solved by providing a prevention means for preventing clogging of the fine holes due to the reaction of the solid matter.

In general, if the wastewater is inclined to be alkaline or acidic, grinding or polishing debris composed of solids reacts, and the reactants block fine pores, so that solids and water cannot be separated. For this reason, a chemical solution or the like is put into the waste water and this reaction is prevented, whereby the solid matter and the water can be separated.

[0032] Second, the prevention means is provided for controlling the pH of the wastewater.
The problem is solved by having the adjusting means.

As a method of separating the solid and water, there is filtration. For example, assuming that a large amount of wastewater containing silicon waste is filtered as filtration, as described below, if the pH of the wastewater is slightly alkaline, the Si in the wastewater is eluted, and the gel or colloidal form is formed. Material is produced. And this gel or colloidal substance blocks the pores of the filter,
It reduces the capacity of the filtration and eventually reaches a state where it is not filtered at all. However, it was found that elution of Si can be prevented by controlling the drainage to be neutral or weakly acidic. The present invention pays attention to this point, and installs a pH adjusting means to reduce the drainage water.
H is controlled to prevent solids from being eluted and to prevent clogging.

Third, the above-mentioned pH adjusting means can be solved by being provided in a drainage passage or a drainage storage tank.

By providing the pH adjusting means in the drain passage and the waste water storage tank, clogging of the filter can be prevented with a relatively simple system.

Fourthly, the above problem can be solved by providing the means for adjusting the pH in a water supply passage constituting drainage.

Tap water, well water, or industrial water may be used as the water through which grinding dust or polishing waste flows. These waters tend to be acidic or alkaline and the pH of this water
By controlling to a desired value, the elution of solids can be prevented from the polishing / grinding process.

Fifth, the above-mentioned pH adjusting means can be solved by providing a liquid, gas, powder or solid injection device which dissolves in water and shows an acidic or alkaline property.

Sixth, the above-mentioned pH adjusting means can be solved by having a pH measuring device.

When a pH sensor is used, it can be handled as an electric signal and automatic control of drainage becomes possible.

Seventh, the solid material is ground using a grinding device or /
The problem is solved by being generated by the polishing apparatus.

Eighth, the problem is solved by providing the minute holes in the drainage passage provided in the filtration device.

Ninth, the fine holes provided in the filtering device may be made of ceramic filter holes, foam metal filters, polymer filter holes, glass fiber filters or movable solids. The problem is solved by using a filter hole composed of an aggregate.

Tenth, the problem is solved by that the movable solid material is sand-like solid material, grinding dust of an object to be ground, or polishing dust of an object to be polished.

Eleventh, the grinding waste of the object to be ground or the polishing waste of the object to be polished is formed in different sizes, and the filter hole is larger than the minimum grinding waste or the grinding waste, and the maximum grinding waste or the grinding waste. This can be solved by reducing the size of the grinding dust.

In some cases, grinding or polishing debris is formed on the surface of the filter to form a second filter made of grinding or polishing debris and filtered using two filters. In this filtration, long-term filtration is possible because the second filter is made of a solid material and each solid material is in a movable state. Therefore, by controlling the pH of the wastewater, it is possible to prevent the generation of a reactant that stops the movement of the solid.

Twelfth, the minimum grinding or polishing debris is less than 0.25 μm, and the largest grinding or polishing debris is
The problem is solved when the thickness is 10 μm or more.

For example, using a 0.25 μm filter,
When a second filter made of grinding waste or polishing waste is formed and filtered, the second filter becomes 10 μm or more, 0.2 μm or more.
Grinding or polishing debris smaller than 5 microns can be trapped.

Thirteenth, the above problem can be solved by forming a filter made of the above-mentioned grinding dust or polishing dust by trapping the above-mentioned grinding waste or polishing dust on the surface of the filter.

Fourteenth, the problem is solved by adding air bubbles that refresh the film on the surface of the filter made of grinding dust or polishing dust to the filter made of grinding dust or polishing dust.

The substance consisting of grinding or polishing debris is a solid that can move, and when air bubbles are applied to the surface of the membrane, the solid can be moved. Therefore, the surface of the second filter can be removed, and the filter can be refreshed.

Fifteenth, the problem can be solved by using a filter made of a polymer made of a polyolefin polymer, a cellulose polymer, a fluorine polymer or a tetrafluoroethylene polymer.

The polyolefin-based polymer has resistance to acidity and alkalinity. Therefore, it is possible to prevent deterioration by the chemical solution injected from the pH adjusting means.

Sixteenth, the problem is solved by sucking or pressurizing the drainage so that the drainage passes through the fine holes of the filter.

Seventeenth, the problem can be solved by providing a drainage agitating means in the drainage passage or the drainage storage tank.

By employing the stirring means, the pH of the waste water can be quickly and uniformly made, and the elution of solids can be reduced.

Eighteenthly, in a wastewater regeneration system for passing grinding wastewater or polishing wastewater of a workpiece through a filtration device and separating the same into water, the grinding wastewater or the polishing wastewater is filtered. A pH measuring device for monitoring the pH of the waste water and a
The problem is solved by providing an injection means for injecting a substance which is soluble in water and showing an acidic or alkaline property in response to an output signal from the H measuring device, and a stirring means for stirring the substance and waste water.

Nineteenthly, the problem can be solved by the fact that the substance is a liquid, gas, powder or solid which shows an acidic or alkaline property when dissolved in water.

Twentiethly, the filtering device has a filter made of ceramic, a filter made of foamed metal, a filter made of polymer, a filter made of glass fiber, or a filter made of an aggregate of movable solids. Is the solution.

Twenty-first, the movable solid is sand,
The problem is solved by using grinding waste of the object to be ground or polishing waste of the object to be polished.

Twenty-second, the problem is solved by that the solid is grinding dust or polishing dust made of silicon.

Twenty-third, the filter made of the polymer is a polyolefin polymer, a cellulose polymer,
The problem is solved by using a fluorine-based polymer or a tetrafluoroethylene-based polymer.

Twenty-fourth is to solve the problem by allowing the drainage to pass through the filter hole by sucking or pressurizing the drainage.

Twenty-fifth, by injecting the substance, it is possible to prevent the generation of a reactant consisting of the grinding waste or the polishing waste, and the filter substantially removes the grinding waste or the polishing waste remaining in a solid state. This can be solved by trapping.

Twenty-sixth, the above-mentioned grinding dust or polishing dust is solved by being generated in a step of forming a semiconductor wafer from a semiconductor ingot, a step of dicing the semiconductor wafer, or a step of back grinding the semiconductor wafer. Things.

Twenty-seventh, a first transport for transporting wastewater having grinding or polishing debris obtained from a step of forming a semiconductor wafer from a semiconductor ingot, a step of dicing the semiconductor wafer, or a step of back-grinding the semiconductor wafer Means, a raw water tank containing waste water passing through the first transport means, and suction for trapping the grinding waste or polishing waste and sucking the fluid constituting the waste water by sucking the waste water from the raw water tank. Type of filtration device, a second transportation means for transporting the fluid purified by the filtration device, a pump for sucking the fluid of the second transportation means, and a transportation route for the fluid discharged from the pump. A valve; a third means of transport attached to the valve for transporting for reuse or natural discharge; And a fourth transport means attached to the raw water tank and returned to the raw water tank, wherein the first filter constituting the filtering device comprises the grinding dust or the polishing dust formed by trapping the grinding dust or the polishing dust. Second
A filter, and a bubble generator that applies an external force to the second filter and maintains a filtering function of the second filter.
The first transport means, a pH measuring device for measuring the pH of the wastewater from the raw water tank, and a chemical injection device for making the wastewater slightly alkaline, neutral or weakly acidic based on the measurement result of the pH measuring device. Is to be solved.

Twenty-eighth, a first transport for transporting wastewater having grinding or polishing debris obtained from a step of forming a semiconductor wafer from a semiconductor ingot, a step of dicing the semiconductor wafer, or a step of back-grinding the semiconductor wafer Means, a raw water tank containing waste water passing through the first transport means, and suction for trapping the grinding waste or polishing waste and sucking the fluid constituting the waste water by sucking the waste water from the raw water tank. Type of filtration device, a second transportation means for transporting the fluid purified by the filtration device, a pump for sucking the fluid of the second transportation means, and a transportation route for the fluid discharged from the pump. A valve; a third means of transport attached to the valve for transporting for reuse or natural discharge; A fourth transport means attached to the raw water tank and returned to the raw water tank, a second filter made of a solid material which is formed on a first filter constituting the filtration device, and which is easily separated individually; A bubble generator that applies an external force to the filter and maintains the filtering function of the second filter, the first transporter, a pH measuring device that measures the pH of the wastewater from the raw water tank, and a pH measuring device. This problem can be solved by providing a chemical injection device for making the wastewater slightly alkaline, neutral or weakly acidic based on the measurement results.

[0068]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment First, an outline of the present invention will be described with reference to FIGS.

For example, in the polishing / grinding step of silicon, a chemical for dissolving the adhesive of the bonded block, or a chemical of an anionic surfactant or another alkali component may be used. In this case, in the polishing / grinding process, the chemical is mixed into the drainage tray BL (see FIGS. 17 to 21), and the pH of the silicon wastewater may be weakly alkaline.

At this time, the grinding dust or polishing dust mixed in the waste water is a fine powder of the order of μm, and the surface area of this silicon powder is very large and active. Therefore, the silicon powder dissolves and turns into silicate ions as shown in Formula 1. The higher the alkalinity, the greater the amount of silicate ions. Then, as shown in Formula 2, a part of the silicate ions becomes gel or colloid with time, and the filter may be clogged by covering the surface of the filter, which may make filtering difficult. is there.

[0071]

(Equation 1)

[0072]

(Equation 2)

Further, even if the waste water flowing from the waste water receiving tray BL is neutral or acidic and the silicon powder does not dissolve, an alkaline substance is contained in the silicon waste water in the route to the raw water tank. Is also assumed. In this case, the pH of the wastewater from the raw water tank increases, the amount of hydroxyl groups increases, silicon dissolves, and silicate ions are generated. Further, the silicate ions become gel-like or colloidal silica. The gel or colloidal silica causes clogging of the filtration filter.

In the present invention, attention was paid to the fact that this wastewater was alkaline, and acid was added to the wastewater to reduce the amount of hydroxyl groups, thereby suppressing the dissolution of silicon and preventing clogging. A description is given below.

As shown in FIG. 1, waste water (raw water) generated during dicing is collected in a raw water tank 10. For example, the pH of the wastewater can be adjusted by providing the pH adjusting means 12 in the drainage path from the wastewater receiving tray BL attached to the polishing / grinding apparatus shown in FIGS. .

More specifically, the raw water tank 1
A pH adjusting means 12 is provided in a drain pipe or a raw water tank 10 for drainage up to zero.

The pH adjusting means 12 includes a pH sensor 13 and
Injection device 1 for adding acid and / or alkali
4 Acid can be hydrochloric acid, sulfuric acid, nitric acid, etc.
As the alkali, sodium hydroxide, potassium hydroxide or the like can be used.

Further, the pH sensor 13 is electrically linked with the acid-alkali injection device 14, and is supplied with an acid or alkali chemical corresponding to the measured value of pH to form a system capable of controlling waste water to a desired pH. I have. The wastewater into which the chemical has been injected is stirred by the stirring means. For example, when an acid or alkali chemical is injected into a pipe, it is necessary to provide a means for stirring the chemical in the pipe. In addition, when chemicals are injected into the raw water tank, a stirrer such as a screw is required. In addition, when the drainage of the raw water tank is constantly stirred by generating bubbles from below, it is not necessary to attach a stirrer.

The chemicals injected into the wastewater from the pH adjusting means 12 are alkaline or acidic liquids, solids or powders which dissolve in the wastewater and show alkalinity or acidity, and chemicals which dissolve in the wastewater and show alkalinity or acidity. The gases shown correspond.

Next, FIG. 2 is for adjusting the pH of the water to be poured into the polishing / grinding device 15. The water poured into the polishing / grinding device 15 does not necessarily need to be pure water or distilled water. For example, the shower water employed in FIGS. 17 to 21 is mirror-polished after being turned into a wafer.
Well water, industrial water or tap water which slightly contaminates the wafer surface may be used. However, these waters are not neutral but tend to be acidic or alkaline, and may react with grinding or polishing debris. Therefore, the shower 16
The water may be adjusted to a desired pH at the stage where the water is poured.

As described above, the drainage in the raw water tank 10 is adjusted more quickly by the mechanism shown in FIGS.
Then, the wastewater whose pH has been adjusted is sent to the filtration device 11 by being pulled or pushed out by a pump.
Although the filter 11 is equipped with a filter, no gel or colloidal reactant is generated,
The filtered water without clogging is sent to a recovered water tank or the like via a pipe and reused. In addition, since there is no reaction of the solid, the solid can be reused.

In the case of silicon waste water, if the waste water becomes alkaline, the elution of silicon becomes a problem. Therefore, clogging of the filter can be prevented by controlling to neutral or weakly acidic.

Next, the leaching of silicate ions by an alkaline aqueous solution mixed with silicon powder was investigated, and will be described below. As shown in FIG. 3, a certain amount of silicon powder was mixed with an aqueous solution having a certain pH, and the way of generating silicate ions was investigated.

Experiment 1 Reaction of Silicon Powder with Alkaline Aqueous Solution (Reaction Time) 5 ml of 0.01 N (0.01 N) aqueous NaOH solution was placed in a sealed polycontainer (100 ml), and pure water was added to make 100 ml. 100mg of silicon (99.99%) powder (about 10μm particle size)
Prepare 5 with the addition. After 4, 8, 23, 47 and 71 hours, 5 ml of 0.01N HCl aqueous solution was added and neutralized (not neutralized after 71 hours), and the mixture was filtered through a filter having a pore size of 0.5 μm. The amount was measured. In the measurement, the amount of silicon was specified by ICP (Inductively Coupled Plasma) emission analysis, and the column of the numerical value of the silicate ion is the amount of silicon to which no oxygen component was added. Therefore, the amount of silicate ions is a correct value obtained by adding oxygen to the amount of silicon.

The silicon powder added to the aqueous alkali solution reacts with the alkali to generate silicate ions, but the reaction stops when neutralized with an acid. In addition, the reaction with alkali attenuated with time, and with silicon (99.99%) powder (about 10 μm particle size) that reacts with 0.01N NaOH 5 ml / 100 ml alkali, the reaction was almost completed in 71 hours. . In 47 hours, 80 to 90% have reacted.

5 ml of 0.01N NaOH used here and 95 m of pure water
The theoretical pH of the solution is 10.7.

The pH is represented by -log [H +] for a strong acid and 14 + log [OH-] for a strong alkali. Therefore, 14 + log [0.01 × 5/100]
= 10.7.

Therefore, if the actual pH of the wastewater is up to about 10, the amount of silicate ions of several mg-Si / L is eluted within several hours from the polishing step to the filtration step.

The concentration of the silicate ion is the concentration level contained in ordinary tap water, and the filtration filter is not a concentration that causes clogging but has no serious problem. Therefore, if the pH can be adjusted within a few hours, the elution of silicate ions is extremely small, and it is understood that there is no influence on the filtration step. Experiment 2 Reaction of silicon powder with alkaline aqueous solution (optimum pH) Take a few ml of 0.01N NaOH aqueous solution and 0.01N HCl aqueous solution, mix them, and adjust them using a pH meter.
Make 100 ml of aqueous solution of 6, 7, 7.5, 8, 9 and 10. To this is added 100 mg of silicon (99.99%) powder (about 10 μm particle size). After 48 hours, the mixture was filtered with a filtration filter having a pore size of 0.5 μm, and the amount of silicate ions in the filtrate was measured. In addition, the ICP
(Inductively coupled plasma) Since the amount of silicon was specified by emission spectrometry, the column of silicate ion shows the amount of silicon.

As can be seen from FIGS. 5 and 6, silicate ions are not generated at an acidic pH, but silicate ions are eluted at a pH higher than pH 8.

Further, depending on the kind of the base showing alkalinity,
I checked whether the dissolution of silicon was different. As shown in FIGS. 7 to 9, NaOH as a strong base and N as a weak acid strong base
Three kinds of a2CO3 and NaHCO3 were prepared. First, dilute 1, 3, 5 ml with pure water to make 100 ml, pH
Was measured. Then, 100 mg of Si was added to each, and the silicate ion concentration was measured after 44 hours. As described in Experiment 1, the measurement method was as follows. After filtering through a 0.5 μm filter, the amount of silicon in the filtered water was measured by ICP emission spectroscopy.

As shown in FIG. 7, these three types of bases
NaOH is the most alkaline, then NaCO
3, weakening in the order of NaHCO3. In addition, when FIG. 8 is also taken into consideration, the aqueous solution showing strong alkalinity eluted more silicon.

However, as shown in FIG. 9, when the pH and the silicate ion concentration (the amount of silicon eluted) are shown in a graph,
It can be seen that a constant curve almost coincident with the curve in FIG. 6 is drawn, and it is considered that the concentration of the silicate ion is affected by the pH of the wastewater.

Therefore, from these facts, it is possible to suppress the elution of silicate ions by adjusting the wastewater to a pH of 8 or less, which is weakly alkaline.

In practice, it is desirable to control the pH to be neutral to minimize the amount of the reagent used for pH adjustment and to suppress the reactivity.

Here, 1 liter of pure water is mixed with NaOH, and p
Assuming that H10 was discharged, NaOH is contained in pure water at 0.
There are 0001 moles. 0.0001 mole of NaOH is 4 mg. When this is neutralized with HCl, 3.6 mg of HCl is required. In ordinary tap water, sodium (Na +) ions and chloride ions (Cl-) are dissolved at a concentration of several mg / L in tap water, and even if an acid or alkali necessary for neutralization is added, , The same level as the concentration level contained in tap water. In the polishing process, not only pure water but also tap water and groundwater are used.Even if alkali is mixed in the process and the pH becomes high, the water after filtration is almost equal to the original tap water by the neutralization treatment. It has the same water quality, is sufficiently recyclable, and can be released into nature.

As can be seen from the above results, within several hours p
If H can be adjusted, the amount of silicate ions generated is about the same as the amount of impurities generally contained in tap water, and p
By adjusting H to a neutral or acidic side, the precipitated amount of this silicate ion can be suppressed to 0.1 mg / L or less.

Therefore, in consideration of these points, a pH adjusting means and an acid or / alkali injector are provided, and the pH of the waste water is adjusted to a desired pH. Alternatively, the formation of colloidal silica can be prevented.

Also, in the filtration of metal grinding or polishing debris, by adjusting the pH of the waste water, the reaction of the metal can be prevented, and the filter can be prevented from being clogged by the reaction product.

Next, a specific embodiment will be described with reference to FIGS.

Second Embodiment FIG. 10 shows that waste water generated in the polishing / grinding process is stored in a raw water tank 50, and a filtration device 53 is immersed in the raw water tank 50. The filter 53 is provided with a ceramic filter, a filter made of foamed metal, a filter made of glass fiber, or a polymer filter, and may be pressurized or suctioned. As the polymer filter material, there are various materials having chemical resistance such as polyolefin, fluorine or polytetrafluoroethylene. Also, a polymer having relatively low chemical resistance, for example, a cellulosic polymer can be used. In the figure, the one that is suctioned and filtered by the pump 57 is shown. In the filtered water, grinding dust or polishing debris is constantly sensed by the sensor 67, and when the numerical value is lower than a desired concentration, the filtered water is reused through the pipe 60 or the natural water is removed. Will be released. When the concentration is higher than the desired concentration, the concentration is switched by the first valve 58, and the filtered water is returned to the raw water tank 50 via the pipe 59.

The raw water 52 in the raw water tank 50 is constantly controlled by pH adjusting means to prevent the formation of a gel or colloidal reactant.

Reference numeral 13 denotes a pH sensor constituting the pH adjusting means 12, and reference numeral 14 denotes an acid / alkali injection device. AT is a stirring means composed of a screw or the like. The pH sensor 13 measures the pH of the raw water, and the result is fed back to the injection device 14. For example, if the grinding debris or polishing debris is silicon and the raw water is inclined to alkaline, an acidic substance is injected by the injection device, and the raw water 52 becomes weakly alkaline to acidic, particularly weakly alkaline, neutral or weakly acidic. Is controlled as follows. When the raw water is tilted to a strong acidity, a very small amount or no silicon reactant is produced. However, in consideration of the mounting bracket of the filtration device, dissolution of the filter itself, and the like, it is better to control the raw water 52 to be neutral or weakly acidic by injecting an alkali chemical.

The filter attached to the filtering device 53 has many fine holes of several μm or 1 μm or less. Conventionally, a reactant of silicon has been generated to block the pores of the filter. However, in the present invention, since the pH of the raw water 52 is controlled, a reaction product of grinding dust or polishing waste mixed with the raw water is not generated, and clogging of the filter can be prevented.

In the experiment, silicon was employed as grinding dust or polishing dust, and only a negligible amount of silicon was eluted on the acidic side as shown in FIG. However, when using other semiconductor materials and metal materials,
Be careful. For example, if these reactants are generated on the acidic side but not alkaline, the reverse control is required.

Here, as the pH adjusting means 12,
An injection device into which an alkaline or acidic chemical solution is injected was employed. However, the chemical to be injected into the raw water 52 may be a solid or powder that dissolves in water and shows acid or alkali, or a gas that dissolves in water and shows acid or alkali.

According to this system, the raw water is further concentrated than before, and it is possible to recover this through the valve 64. Of course, recovery can also be performed by centrifugation or coagulation sedimentation described in the conventional example.

In particular, in FIG. 17 to FIG. 21, silicon grinding chips or polishing chips are single crystal chips into which impurities have not been introduced, and therefore are materials that can be collected and reused. In particular, unlike the polishing process, a large amount of debris is generated, so that recycling can greatly reduce the manufacturing cost.

Further, if the grinding dust or polishing dust without impurities and the polishing dust of the wafer into which impurities are introduced as shown in FIGS. 17 to 21 are mixed in one tank, the purity of the collected dust drops. Therefore, if the grinding waste or polishing waste to which impurities are not introduced and the polishing waste of the wafer to which impurities are introduced are collected in separate tanks, more efficient collection can be achieved. Third Embodiment This embodiment is shown in FIG. This embodiment is different from the second embodiment in that the raw water tank 50 in which the filtering device 53 is inserted and the stirring tank 50A in which the pH adjusting means 12 is attached are separated, and the other points are substantially the same. .

In FIG. 10, since the waste water is always supplied from the pipe 51, the raw water 52 is controlled to have a constant pH.
extremely difficult.

However, in the present embodiment, the stirring tank 50
The raw water is adjusted to the desired pH in
, So that pH controllability is further improved. Note that the size of the stirring tank 50A is
If smaller, the controllability will be further improved. Also, the raw water tank 50 may be provided with a stirring means AT2. Fourth Embodiment This embodiment is shown in FIG. FIG. 12A illustrates the mounting position of the pH adjusting means 12, and FIG.
Explains the stirring means AT.

Since the other parts are substantially the same as those in FIG. 10, only the different parts will be described here.

As described above, in the polishing / grinding process, when tap water, well water, or industrial water is used in order to prevent grinding dust or polishing dust from flowing or to prevent the temperature of the polishing / grinding jig from rising. There is. In this case, the raw water 52 may be adjusted as shown in FIGS. 10 and 11, but in this case, a pipe 51 for transporting waste water from the polishing / grinding process to the raw water tank 50 is used.
, A pH adjusting means 12 is attached. Specifically, the sensor part of the pH sensor 13 and the injection device 1 are placed in the pipe 51.
4 may be attached so that the injection part of FIG.
Adjustment chamber R larger than pipe 51 as in 2a
M may be attached, and the pH adjusting means 12 may be attached thereto.

Since the adjustment chamber RM has a small chamber size, the accuracy of pH adjustment of drainage can be extremely increased. The chemicals injected from the injection device 14 are shown in FIG.
As shown in FIG. 2b, a stirring means A for turbulently flowing the drainage flow
T is provided. For example, the pH of the waste water is measured using the pH sensor 13A at the entrance of the control room. Then, based on the measurement result, the wastewater into which the chemical is injected by the injection device 14 collides with the plate-shaped stirring means AT. When the wastewater collides, the flow path of the wastewater is separated into a plurality of parts, and the wastewater is stirred in the space to the right of the stirring means. And the stirred wastewater is p
By checking again with the H sensor 13B, highly accurate pH control becomes possible. Fifth Embodiment This embodiment is shown in FIG. This filtering means is the means shown in Japanese Patent Application No. 11-148351.

This corresponds to the filtering device 3 shown in FIGS.
5, and a suction type polymer filter is employed as the filter. The material described in the second embodiment can be used as the material. Here, a polyolefin resin is used, and the pore diameter is 0.25 μm.

First, a specific structure will be described. Reference numeral 30a in FIG. 14 has a shape like a cardboard as seen. 0.2mm thin resin sheet SHT1, SHT
2 overlap each other, a plurality of sections SC are provided in the vertical direction therebetween, and a space 33 is provided surrounded by the resin sheets SHT1, SHT2, and the 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 straw 33 has such a shape that a number of straws having the rectangular cross section are arranged and integrated. Symbol 30a
Keeps the filter films FT on both sides at fixed intervals, and is hereinafter referred to as a spacer.

The thin resin sheet SH of the spacer 30a
Many holes HL having a diameter of 1 mm are formed on the surfaces of T1 and SHT2, and a filter film FT is attached to the surface. Therefore, the filtered water filtered by the filter membrane FT passes through the hole HL and the space 33, and finally passes through the pipe 34.
Get out of.

The filter film FT is bonded to both surfaces SHT1 and SHT2 of the spacer 30a. On both surfaces SHT1 and SHT2 of the spacer 30a, there is a portion where the hole HL is not formed.
Is affixed, the filter membrane FT1 corresponding to the portion where the hole HL is not formed has no filtering function and does not allow drainage to pass therethrough, so that a portion where an object to be removed is not captured is generated. To prevent this phenomenon, a plurality of filter films FT are bonded. Filter film FT1 on the front side
Is a filter film for capturing an object to be removed, and a plurality of filter films having holes larger than the holes of the filter film FT1 are provided from the filter film FT1 toward the surface SHT1 of the spacer 30a. Here, the filter film FT
2 are bonded together. Hole HL of spacer 30a
Filter film F having a large hole even in a portion where
Since the filter film FT1 is bonded after the provision of T2, the entire surface of the filter film FT1 has a filtering function, the object to be removed is captured on the entire surface of the filter film FT1, and the filter film made of grinding dust or polishing dust. Are formed on the entire front and back surfaces. Although the filter films FT1 and FT2 are shown as rectangular sheets for convenience of the drawing, they are actually formed in a bag shape.

Next, the bag-like filter membranes FT1, FT2,
How the spacer 30a and the holding means RG are attached will be described with reference to FIGS. 14A, 14C, and 14D.

FIG. 14A is a perspective view showing a filtration device 35 as a completed product, and FIG. 14C is a diagram showing the direction in which the pipe 34 extends from the head of the pipe 34 (vertical direction) as indicated by the line AA in FIG. 14d is a cross-sectional view when the filtration device 35 is cut in the horizontal direction as indicated by line BB.

As can be seen from FIGS. 14C and 14D,
The spacer 30a is inserted into the bag-shaped filter FT, and four sides including the filter film FT are sandwiched by the holding means RG. Then, the three sides and the remaining one side bound in a bag shape are fixed by the adhesive AD1 applied to the holding means RG. In addition, the remaining one side (opening portion of the bag) and the holding means R
A space SP is formed between G and G, and the filtered water generated in the space 33 is sucked into the pipe 34 through the space SP. In addition, the adhesive AD is attached to the opening OP of the holding bracket RG.
2 is provided over the entire circumference, is completely sealed, and has a structure in which fluid cannot enter except from the filter.

Therefore, the space 33 and the pipe 34 are in communication with each other. When the pipe 34 is sucked, the fluid passes through the hole of the filter membrane FT and the hole HL of the spacer 30a toward the space 33, and the fluid flows from the space 33 to the pipe 34. The structure is such that filtered water can be transported to the outside via the. The spacer 30
a of the sheet SHT constituting the filter FT, except for the area where the hole HL is formed, is flat.
, The filter FT can always maintain a flat surface, and has a structure to prevent the destruction of the second filter film. FIG. 15 conceptually shows the operation of the filtering device 35. Here, if the pipe 34 side is sucked by a pump or the like, water flows and is filtered as indicated by an arrow without hatching.

The second filter film 36 is formed by the first filter films 31 and 32 and the layer of grinding dust or polishing dust captured by the films 31 and 32.

The point of this suction type filtration device is that grinding dust or polishing dust is captured on the surfaces of the first filter films 31 and 32, and the remaining layer is used as the second filter film 36.

Objects to be removed generated by machining such as grinding, polishing, or pulverization are distributed within a certain range of size (particle size), and the shapes of the respective objects to be removed are different. Also, grinding waste or polishing waste is randomly located in the waste water in which the first filter films 31 and 32 are soaked. Then, from large grinding dust or polishing waste to small grinding waste or polishing waste moves irregularly to the first filter hole. At this time, grinding dust or polishing dust 16B smaller than the filter hole passes, but grinding dust or polishing dust 16A larger than the filter hole is captured. Then, the captured large grinding debris or polishing debris 16A becomes the first layer of the second filter film 36, and this layer forms a filter hole smaller than the filter hole. Small grinding chips or polishing chips 16B are captured from the chips 16A. At this time, since the shapes of the grinding dust or the polishing dust are different from each other, gaps of various shapes are formed between the grinding dust and the polishing dust, and the water moves as a passage through the gap, and is finally filtered. You. This is very similar to a well-drained beach.

This second filter film 36 is formed by removing large grinding dust or polishing dust 16A from small grinding dust or polishing dust 1A.
6B gradually grows while randomly capturing, and small grinding dust or polishing dust 1 while securing a water (fluid) passage.
6B will be trapped. In addition, since the second filter film 36 can easily move grinding dust or polishing dust only by remaining in a layer, the second filter film 36 allows air bubbles to pass near the layer, gives a water flow, or gives a sound wave or an ultrasonic wave. By applying mechanical vibration or rubbing with a squeegee or the like, the surface layer of the second filter membrane 36 can be easily moved to the drainage side. That is, even if the filter performance of the second filter film 36 is reduced, there is an advantage that the capability can be easily restored by applying an external force to the second filter film 36. In other words, the cause of the decrease in the filter capacity is mainly clogging, and the object to be removed on the surface layer of the second filter membrane 36 causing the clogging is moved into the fluid again. And clogging can be eliminated.

[0127] As the grinding waste or polishing waste used in the present embodiment, cutting waste generated during dicing of a Si wafer was used. The particle size distribution of this debris, as shown in FIG.
It is distributed in the range of approximately 0.1 μm to 200 μm.

In addition, Since the particle size distribution measuring device could not detect particles smaller than 0.1 μm, the distribution of cutting chips smaller than 0.1 μm is not shown. But FIG.
Observe that in fact, something smaller than this is included. According to the experiment, when the wastewater mixed with the cuttings is filtered with the above-mentioned filter made of a polyolefin membrane having a pore size of 0.25 μm, the cuttings are uniformly formed into a layer on the filter membrane made of polyolefin,
It was found that even cutting chips of 0.1 μm or less were captured.

Referring to FIG. 16, there are two peaks, but the number of peaks may be one. It is important that they are present in a wide range of 1 μm or less to several hundred μm and that the shape of the debris is different in securing a water passage.

FIGS. 13 to 15 show examples in which the rising of bubbles is used as a method of removing the second filter film and a method of refreshing. Bubbles rise in the direction indicated by the hatched arrow in FIG. 15, and the rising force of the bubbles and the burst of the bubbles directly apply external force to the grinding dust or polishing dust, and the water flow generated by the rising force of the bubbles and the burst of the bubbles is reduced. Apply external force to grinding or polishing debris. Then, the filtering force of the second filter membrane 36 is constantly refreshed by this external force, and maintains a substantially constant value.

The point of the present filtration apparatus is to maintain the filtration ability. In other words, even if clogging occurs in the second filter membrane 36 and its filtration ability is reduced, by applying an external force to move grinding dust or polishing dust constituting the second filter membrane 36 like the air bubbles. , Grinding dust or polishing dust constituting the second filter membrane 36 can be moved to the drain side,
The filtration ability can be maintained for a long time.

There are two types depending on how the external force is applied.
One is a method of completely breaking (removing) the second filter film 36. In this case, grinding or polishing debris
Because they are not stacked on the first filter membrane, small grinding or polishing debris will pass through the filter membrane. Therefore, the filtered water is circulated to a water tank (tank) containing drainage (raw water) until it is confirmed that small grinding dust or polishing dust is trapped. Although not efficient, the filtered water mixed with the small object may be transferred to another tank until the small object is captured.

The second method is to move a film (an object to be clogged) formed on the very surface of the second filter films 31 and 32. In other words, since grinding dust or polishing dust that causes clogging is trapped on the outer surface of the filter membrane, the trapping is released by external force generated by air bubbles, and a constant filtration ability is always maintained. this is,
It is considered that the thickness of the second filter is made substantially constant by applying an external force. It is as if each of the grinding or polishing debris is plugged at the inlet of the filtered water. It's like going. This has the merit that the filtration ability can be always maintained by adjusting the size of the bubble, the amount thereof, and the time during which the bubble is applied.

As long as the filtration ability can be maintained, an external force may be constantly applied or may be applied intermittently.

In this embodiment, 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 or collapses. Also, if there is any place that is in contact with air, the filter membrane sucks air,
This is because the filtration ability decreases.

As described above, considering the principle of the present invention, the second filter film 36 is the first filter film 31, 3
2, the first filter films 31, 32
May be a sheet-like polymer film or a ceramic, and may be a suction type or a pressure type. But when it comes to adoption,
Each of the first filter films 31 and 32 is a polymer film, and is preferably a suction type. The reason is described below.

First, when a sheet-shaped ceramic filter is produced, the cost is considerably increased, and when a crack is generated, a leak is generated, and the filter cannot be filtered. In the case of a pressurized type, it is necessary to pressurize the wastewater.
For example, taking the tank 50 of FIG. 13 as an example, the upper part of the tank must be closed rather than open in order to apply pressure. However, if it is a closed type, it is difficult to generate air bubbles. On the other hand, as the polymer film, sheets and bag-shaped filters of various sizes are available at low cost. In addition, cracks do not occur because of flexibility, and it is easy to form irregularities on the sheet. By forming the unevenness, the second filter film bites into the sheet, and separation in drainage can be suppressed. Moreover, in the case of the suction type, the tank may be left open.

In the case of the pressure type, it is difficult to form the second filter film. In FIG. 15, assuming that the pressure in the space 33 is 1, it is necessary to apply one or more pressures to the drainage.
Therefore, it is considered that a load is applied to the filter membrane, and the trapped object is fixed at a high pressure, so that the object is difficult to move.

Next, a suction type system employing a polymer film as a filter film will be described with reference to FIG.

Reference numeral 50 in FIG. 13 denotes a raw water tank. Above the tank 50, a pipe 51 is provided as raw water supply means. The pipe 51 is a place through which a fluid mixed with grinding dust or polishing dust passes. For example, in the semiconductor field, in the polishing / grinding process described with reference to FIGS. 17 to 23, the wastewater (raw water) mixed with grinding dust or polishing dust passes. This wastewater will be described as wastewater mixed with silicon waste flowing from the dicing apparatus.

In the raw water 52 stored in the raw water tank 50, a plurality of filtration devices 53 are provided. Below the filtering device 53, an air bubble generating device 54 is provided, for example, such as a small hole made in a pipe, or a bubbling device when used for a fish tank, which is just passed through the surface of the filter membrane. The position has been adjusted. 55 is an air blow.

The pipe 56 fixed to the filtration device 53 is
A pipe 59 through which the filtered water filtered by the filtration device 53 passes and passes through the first valve 58 toward the raw water tank 50 side
And the pipe 60 going to the reuse (or drained) side
To be transported selectively. A second valve 61, a third valve 62, a fourth valve 63, and a fifth valve 64 are attached to a side wall and a bottom surface of the raw water tank 50. What is attached to the end of the pipe 65 is
It is a filtering device 66 provided separately.

The raw water 52 supplied from the pipe 51 is stored in a raw water tank 50 and is filtered by a filtration device 53. The surface of the filter membrane attached to this filtration device is maintained so that air bubbles pass therethrough, and the rising power or rupture of the air bubbles causes grinding or polishing debris trapped in the filter membrane to move, so that its filtering ability does not always decrease. ing.

The filter membrane may be newly installed, or may be stopped for a long time on holidays,
When silicon dust is mixed in the raw water, the filter water is designed to be circulated to the raw water tank 50 through the pipe 59 using the valve 58. Otherwise, the valve 58
Is switched to a pipe 60, and the filtered water is reused or discharged to the natural world.

When a new filter film is attached, the circulation time varies depending on the size of the filter film, the amount of silicon dust, and the suction speed, but the second filter film is formed on the surface of the filter film in about 4 to 5 hours. As a result, a film capable of capturing silicon dust of 0.1 μm or less is obtained. However, it has been found that 30 minutes may be used if the size of the filter film is small. Therefore, if the circulation time is known, a timer may be set, and the first valve 58 may be automatically switched after a predetermined time has elapsed.

The sensor 67 constantly senses grinding dust or polishing dust. 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.

On the other hand, the raw water tank is concentrated with time. When the concentration reaches a desired concentration, the filtration operation is stopped, and the mixture is coagulated and precipitated using PAC, Al2 (SO4) 3, or the like, and left. Then the raw water in the tank,
It is roughly divided into layers. In other words, from the upper layer to the lower layer,
It is distributed from slightly transparent water to a completely non-transparent liquid in the material to be removed. These are collected by properly using the valves 61 to 64.

For example, raw water that is slightly transparent and contains little silicon waste is recovered through the filtration device 66 by opening the second valve 61. Subsequently, the valves 62 and 63 are sequentially opened to collect the raw water. Finally, the concentrated slurry stored at the bottom of the raw water tank is recovered by opening the valve 64.

For example, if the valve 64 is opened first, the concentrated slurry flows at once due to the own weight of the raw water, and the water above it also comes out, making it difficult to control. Therefore, here, 61,
The valves are opened and collected in the order of 62, 63 and 64.

In the coagulation and sedimentation, the pH of the waste water is reduced once after making the water alkaline, and then the coagulant is added. Since the present regeneration system is provided with a pH adjusting means, it has a feature that it can be used also as a means for injecting a chemical when performing the coagulation and precipitation.

The method of recovering the concentrated water by the coagulation sedimentation method has been described above, but the present invention is not limited to this. For example, raw water 52
When the concentration reaches a certain value, it may be transferred to another filtration device 66 (FD).

The filtering device 66 may be used as a device for collecting grinding dust or polishing dust. For example, when the raw water tank 50 containing the silicon waste of the semiconductor wafer has a predetermined concentration, the raw water tank 50 may be separated by the filtration device 66 (FD) without performing the coagulation sedimentation. The separated silicon chips may be melted again to form Si ingots for wafers. Also the material of the tile,
It can be reused in various fields such as cement and concrete materials.

A feature of the present invention is that the pH adjusting means 12 is provided as described with reference to FIGS.

The present filtration apparatus utilizes a film made of grinding dust or polishing dust as a filter, and has a point in that it is made of a hard substance such as Si, which can separate and move grinding dust or polishing dust individually. Therefore, by applying an external force such as a bubble, grinding dust or polishing dust, which is a component of the filter, can move. The movement of the grinding dust or polishing dust refreshes the filter. However, if the pH of the drainage flowing into the pipe is inclined to, for example, alkalinity, solids such as grinding chips or polishing chips are removed from the raw water tank 5.
0 to form a gel-like or colloid-like sticky substance.

The gel or colloidal substance is
Blocks the holes in the filter made of grinding or polishing debris and at the same time hinders the movement of the grinding or polishing debris. As described above, since the grinding dust or polishing dust is present in a state that can be separated individually, the filter can be refreshed by applying an external force to the surface of the filter, but the gel-like or colloid-like sticky substance is removed. If it adheres to grinding dust or polishing dust, it becomes impossible to move and the refresh function is lost.

However, in the present invention, by attaching the pH adjusting means to the pipe 51 or the raw water tank 50, the raw water 52 in the raw water tank 50 can be adjusted to a desired pH, and the gel or colloidal reaction can be performed. The generation of a product can be prevented.

Accordingly, the function of a filter made of grinding dust or polishing dust can be maintained, and filtration can be performed for a long time.

In the present embodiment, the first filters 31, 3
The second filter 36 is formed on the surface of No. 2 by grinding or polishing debris in the drainage, and the film separates the grinding or polishing debris in the drainage from water. However, a filtering device 35 provided with a second filter 36 may be separately prepared, and may be charged into the drainage and filtered.

For example, a filtering device in which a second filter is formed with dicing waste of Si may be put into the wastewater generated in the steps of FIGS. 17 to 21 and filtered. Furthermore, using this filtration device, wastewater containing Si carbide grinding waste or polishing waste, wastewater containing diamond powder used as a polishing blade, wastewater containing expensive materials such as zirconia, etc. are used. It may be filtered. As described above, silicon scrap generated from a Si wafer is described as grinding waste or polishing waste. However, as described at the beginning of the embodiment, the present invention can be applied to various solid grinding waste or polishing waste. is there. Grinding or polishing debris, especially in the periodic table,
As long as it is an inorganic solid containing at least one of the elements of Groups 2a to 7a and 2b to 7b, these can be almost removed by employing the present invention.

[0160]

According to the present invention, the formation of a gel-like or colloidal reactant can be prevented by preventing the reaction of water and solid matter mixed in the waste water. Separation of solids becomes possible.

If a pH adjusting means is employed as this preventing means, the pH of the waste water can be set to a desired value, and the reaction between the solid matter and water can be further prevented.

In the wastewater stored in the storage tank, grinding dust or polishing waste becomes more and more concentrated and stays for a long time. Therefore, by controlling the wastewater supplied to the storage tank and the wastewater in the storage tank, it is possible to prevent the reaction between the more highly concentrated grinding waste or polishing waste and water.

Further, a sensor for monitoring pH and a means for injecting an acid or an alkali are provided in the path of the wastewater introduced into the filtration device, and the pH of the wastewater is controlled before filtration by filtering. Dissolution and settling of grinding dust or polishing waste made of a solid material can be prevented, and clogging of the filter can be prevented.

Finally, in a filter device which employs grinding or polishing debris made of a solid material as a filter and which has a refreshing function in the filter, if the pH adjusting means is employed, a gel or a colloid is obtained. Reactants are not generated. Therefore, since the movement of the solid material constituting the filter is maintained, the refresh function of the filter can be maintained, and long-term filtration, which is a feature of the filtering device, can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a wastewater regeneration system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a wastewater regeneration system according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating how silicate ions are generated over time when silicon powder is introduced into an alkaline aqueous solution.

FIG. 4 is a diagram showing FIG. 3 as a graph.

FIG. 5 is a diagram illustrating how silicate ions are generated depending on the pH value.

FIG. 6 is a graph of FIG. 5;

FIG. 7 is a diagram showing the concentration and pH of three types of bases prepared in the experiment.

FIG. 8 is a diagram for explaining how silicate ions are generated at the concentration of FIG. 7;

FIG. 9 is a diagram illustrating the pH of each base and the amount of silicate ions shown in FIG. 7;

FIG. 10 is a diagram illustrating a wastewater regeneration system.

FIG. 11 is a diagram illustrating a wastewater regeneration system.

FIG. 12 is a diagram illustrating a wastewater regeneration system.

FIG. 13 is a diagram illustrating a wastewater regeneration system.

FIG. 14 is a diagram illustrating a filtration device employed in FIG.

FIG. 15 is a diagram illustrating the filtration principle of FIG.

FIG. 16 is a diagram illustrating the particle size distribution of silicon waste in waste water generated during dicing and the shape and size thereof.

FIG. 17 is a diagram illustrating a silicon ingot.

FIG. 18 is a diagram illustrating a step of grinding a silicon block into a cylindrical shape.

FIG. 19 is a diagram illustrating a process of forming an orientation flat in a block.

FIG. 20 is a diagram illustrating a process of processing a silicon block into a wafer.

FIG. 21 is a diagram illustrating a process of processing a silicon block into a wafer.

FIG. 22 is a view illustrating a wafer polishing step.

FIG. 23 is a diagram illustrating a dicing step.

FIG. 24 is a diagram illustrating a conventional filtration system.

FIG. 25 is a diagram illustrating a suction-type filtration system.

FIG. 26 is a diagram illustrating clogging of a filter.

[Explanation of symbols]

 Reference Signs List 10 Raw water tank 11 Filtration device 12 pH adjusting means 13 pH sensor 14 Injection device 15 Polishing / grinding device 16 Shower 50 Raw water tank 51 Pipe 53 Filtration device AT stirring means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) E03F 5/14 E03F 5/14

Claims (28)

[Claims] 1. A wastewater regeneration system for passing wastewater mixed with solid matter through fine holes and separating the solid matter and water, wherein the solid matter reacts to clogging of the fine holes. A wastewater regeneration system, characterized in that a prevention means for preventing wastewater is provided. 2. The wastewater regeneration system according to claim 1, wherein said prevention means has a pH adjusting means for said wastewater. 3. The pH adjusting means is provided in a drain passage or a waste water storage tank.
2. A wastewater regeneration system according to claim 1. 4. The wastewater regeneration system according to claim 2, wherein the pH adjusting means is provided in a supply passage of water constituting the wastewater. 5. The apparatus according to claim 2, wherein the pH adjusting means has a liquid, gas, powder, or solid injection device which is soluble or soluble in water and exhibits acidic or alkaline properties. Drainage regeneration system. 6. The wastewater regeneration system according to claim 2, wherein said pH adjusting means has a pH measuring device. 7. The solid material according to claim 1, wherein the solid material is generated by a grinding device and / or a polishing device.
The wastewater regeneration system according to claim 6. 8. The method according to claim 1, wherein the fine holes are provided in a drainage passage provided in the filtration device.
The wastewater regeneration system according to claim 7. 9. The fine hole provided in the filtration device,
9. Drainage according to claim 8, characterized in that it is a filter hole made of ceramic, a filter made of foamed metal, a filter hole made of polymer or a filter made of glass fiber or a filter hole made of an aggregate of movable solids. Playback system. 10. The drainage regeneration system according to claim 9, wherein the movable solid is sand-like solid, grinding waste of an object to be ground, or polishing waste of an object to be polished. 11. Grinding chips of the object to be ground or polishing chips of the object to be polished are formed in different sizes, and the filter hole is
11. The system according to claim 10, wherein the waste is larger than the smallest grinding or polishing debris and smaller than the largest grinding or polishing debris. 12. The minimum grinding or polishing debris is:
Less than 0.25 μm, maximum grinding or polishing debris is 10
The drainage regeneration system according to claim 11, wherein the diameter is not less than μm. 13. The filter according to claim 11, wherein the grinding dust or the polishing waste is trapped on the surface of the filter to constitute a filter made of the grinding waste or the polishing waste.
Or the drainage regeneration system according to claim 12. 14. The drainage filter according to claim 13, wherein air bubbles for refreshing a film on a surface of the filter made of the grinding dust or the polishing debris are added to the filter made of the grinding waste or the polishing debris. Reproduction system. 15. The filter according to claim 9, wherein the polymer filter is made of a polyolefin polymer, a cellulose polymer, a fluorine polymer or a polytetrafluoroethylene polymer. Wastewater regeneration system as described. 16. The wastewater regeneration system according to claim 9, wherein the wastewater is passed through fine holes of the filter by suctioning or pressurizing the wastewater. 17. The drainage regeneration system according to claim 3, wherein a drainage stirring unit is provided in the drainage passage or the drainage storage tank. 18. A wastewater regeneration system for passing grinding wastewater or polishing wastewater of a workpiece through a filtration device to separate grinding waste or polishing waste from water, wherein the grinding wastewater or the polishing wastewater passes through the filtration device. A pH measuring device for monitoring the pH of the wastewater in a path before the introduction, and an injection means for injecting a substance which is soluble in water and indicates an acid or an alkali in response to an output signal from the pH measuring device, A wastewater regeneration system comprising a stirring means for stirring a substance and wastewater. 19. The system according to claim 18, wherein the substance is a liquid, a gas, a powder, or a solid that dissolves in water and shows an acidic or alkaline property. 20. The filter device according to claim 1, wherein the filter comprises a filter made of ceramic, a filter made of foamed metal, a filter made of polymer, a filter made of glass fiber, or a filter made of an aggregate of movable solids. The drainage regeneration system according to claim 18, wherein: 21. The drainage regeneration system according to claim 20, wherein the movable solid is sand, grinding waste of an object to be ground, or polishing waste of an object to be polished. 22. The wastewater regeneration system according to claim 21, wherein the solid matter is grinding waste or polishing waste made of silicon. 23. The drainage filter according to claim 20, wherein the polymer filter is made of a polyolefin polymer, a cellulose polymer, a fluorine polymer or a polytetrafluoroethylene polymer. Reproduction system. 24. The wastewater regeneration system according to claim 20, wherein the wastewater is passed through the filter hole by sucking or pressurizing the wastewater. 25. Injection of the substance prevents generation of a reactant generated by the reaction of the grinding waste or the polishing waste, and the filter removes the grinding waste or the polishing waste remaining in a solid state. The wastewater regeneration system according to any one of claims 19 to 24, wherein trapping is substantially trapped. 26. The grinding chips or polishing chips are generated in a step of forming a semiconductor wafer from a semiconductor ingot, a step of dicing the semiconductor wafer, or a step of back grinding the semiconductor wafer.
The wastewater regeneration system according to any one of claims 8 to 25. 27. A method for transporting wastewater having grinding or polishing debris obtained from a step of forming a semiconductor wafer from a semiconductor ingot, a step of dicing the semiconductor wafer, or a step of back grinding the semiconductor wafer.
A raw water tank containing wastewater passing through the first transport means; and sucking the wastewater from the raw water tank to trap the grinding dust or polishing waste and pass the fluid constituting the wastewater. A suction type filtration device, a second transportation means for transporting the fluid purified by the filtration device, a pump for sucking the fluid of the second transportation means, and a transportation route for the fluid discharged from the pump And a third transport means attached to the valve and transporting for reuse or natural discharge; and a fourth transport means attached to the valve and returning to the raw water tank. A second filter made of the grinding dust or the polishing dust formed by trapping the grinding dust or the polishing dust in a first filter constituting the filtering device; A bubble generator that applies an external force to the second filter and maintains the filtering function of the second filter; a first transporting means; a pH measuring device that measures the pH of drainage from the raw water tank; and the pH measuring device. And a device for injecting a chemical that renders the waste water weakly alkaline, neutral or weakly acidic based on the measurement results. 28. A method for transporting wastewater having grinding or polishing debris obtained from a step of forming a semiconductor wafer from a semiconductor ingot, a step of dicing the semiconductor wafer, or a step of back grinding the semiconductor wafer.
A raw water tank containing wastewater passing through the first transport means; and sucking the wastewater from the raw water tank to trap the grinding dust or polishing waste and pass the fluid constituting the wastewater. A suction type filtration device, a second transportation means for transporting the fluid purified by the filtration device, a pump for sucking the fluid of the second transportation means, and a transportation route for the fluid discharged from the pump And a third transport means attached to the valve and transporting for reuse or natural discharge; and a fourth transport means attached to the valve and returning to the raw water tank. A second filter made of a solid material which is formed on a first filter constituting the filtration device and is easily separated from each other; and an external force is applied to the second filter to form the second filter. A bubble generator that maintains the filtration function of the first transporting means, a pH measuring device that measures the pH of the wastewater of the raw water tank, and a weakly alkaline medium based on the measurement result of the pH measuring device. And a device for injecting a chemical to make it acidic or weakly acidic.