JPH11192480A - Device for recovering and treating waste alkaline silica polishing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering and treating a waste alkaline silica polishing water by which the silica in the waste water is easily and efficiently removed by incorporating a membrane separator for separating the waste alkaline silica polishing water and an anion-exchange treating device for treating the permeated water obtained from the separator. SOLUTION: A membrane separator for separating a waste alkaline silica polishing water discharged from the chemical and mechanical polishing stage in a semiconductor producing process by using a separation membrane (preferably ultrafilter membrane) and an ion-exchange treating device for bringing the permeated water obtained from the membrane separator into contact with an ion-exchange resin including an anion-exchange resin (preferably a strongly basic anion-exchange resin) to obtain the treated water are provided to constitute this device for recovering and treating the waste alkaline silica polishing water. The device including a single-bed anion-exchange resin is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for collecting and recovering alkaline silica polishing wastewater, and more particularly to a method for recovering water from alkaline silica polishing wastewater discharged from a chemical mechanical polishing (CMP) step in a semiconductor device manufacturing process. The present invention also relates to an alkaline silica polishing wastewater recovery treatment apparatus which is preferably used when recovering a polishing liquid (polishing agent).

[0002]

2. Description of the Related Art A semiconductor device usually has a multilayer structure in which an insulating layer, a wiring layer, and the like are stacked on a wafer. In such a semiconductor device, it is often required to flatten the surface of the wafer or each layer formed on the wafer. For example, when forming a semiconductor integrated circuit having a multilayer wiring layer, it is necessary to flatten the surface of the interlayer insulating layer between the multilayer wirings. For example, if a silicon oxide film as an insulating layer is formed thereon after forming the first wiring layer, the surface of the silicon oxide film becomes uneven due to the presence of the first wiring layer, and photolithography and dry etching are performed as they are. Thus, when the second wiring layer is formed, there occur problems such as that the focus of exposure is not focused on the concave and convex portions in the resist patterning, and that dry etching remains on the step portions.

Therefore, in the process of manufacturing a semiconductor device, a polishing step for polishing a wafer, an interlayer insulating film for multilayer wiring, a metal film for buried wiring, and the like formed on the wafer is performed. Have been done.

With the recent increase in the degree of integration of semiconductor devices, more precise polishing is required in such a polishing step, and chemical mechanical polishing (CMP) is required.
A system referred to as a "square" is adopted. Specifically, chemical mechanical polishing refers to polishing of abrasive particles such as SiO ₂ (colloidal silica), CeO ₂ , Al ₂ O ₃ , and MnO _{2 with} a solution of an electrolyte such as an ammonium salt or a potassium salt.
Oxidizing agents such as hydrogen peroxide, acids such as nitric acid, hydrofluoric acid, and buffered hydrofluoric acid; inorganic alkali agents such as potassium hydroxide and ammonium hydroxide; organic dispersants such as organic amines such as alkanolamines and organic alkalis; Polishing is performed by using a dispersion obtained by dispersing in water containing a drug as a polishing liquid (slurry), and is usually polished on a polishing pad made of polyurethane or the like. Among them, the alkaline silica polishing liquid (slurry) is mainly used for flattening an interlayer insulating film (SiO ₂ film) in a semiconductor device manufacturing process. The alkaline silica polishing liquid contains colloidal silica and an alkaline agent as main components.

[0005] In such a polishing step, polishing liquid and polishing wastewater containing polishing debris generated by scraping from the material of each layer of the wafer and the semiconductor device and the polishing pad are discharged. Note that the abrasive particles themselves are also crushed to produce abrasive dust. The polishing debris reduces the polishing power of the abrasive particles. Further, during polishing, the abrasive particles may dry and gel, or may aggregate and coarsen. Among such polishing debris, large-diameter polishing debris and aggregates cause damage to the polished surface of each layer of the semiconductor device, and
Since the polishing power is reduced due to the accumulation of polishing debris, the polishing wastewater is drained without being reused.

[0006]

On the other hand, in the semiconductor device manufacturing process, the precision polishing process has been increasing with the recent increase in the degree of integration of semiconductor devices, and the amount of polishing liquid used has increased dramatically. Accordingly, the discharge amount of the polishing wastewater also increases, and the amount of sludge (sludge) generated by solid-liquid separation in the wastewater treatment process of the polishing wastewater also increases. Disposal methods of this polishing wastewater include (1) a method of collecting all the waste by an external contractor (industrial waste treatment), and (2) a sludge obtained by solid-liquid separation such as coagulation and sedimentation and filtration. Industrial waste treatment), neutralizing permeated water (treated water) and discharging it. (3) Ultrafiltration membrane treatment, concentrated water collected by external contractors (industrial waste treatment), and permeated water (Treated water) is neutralized and discharged. With the rapid increase in the amount of polishing wastewater discharged from the CMP process in recent years, the disposal method of polishing wastewater has also changed from (1) to (2) to (3). It is expected that the polishing wastewater volume will continue to increase in the future, and the need for wastewater recycling has arisen.

The polishing wastewater generated from the above-mentioned alkaline silica polishing liquid in the CMP step, that is, the alkaline silica polishing wastewater is mainly composed of an interlayer insulating film (SiO ₂ film)
Therefore, it is inevitable to use fine silica particles and alkali as main components. On the other hand, since the alkaline silica polishing wastewater is wastewater discharged from a semiconductor device manufacturing process, impurities other than these components are extremely small. Alkaline silica polishing wastewater is generally diluted to several tens to several hundred times by rinsing water and discharged as compared with the stock solution of the polishing liquid,
The amount of silica particles contained in this wastewater is still large,
Some processing is required.

[0008] Ultrafiltration membrane (optionally microfiltration membrane)
Although silica particles can be effectively separated and removed from the alkaline silica polishing wastewater, the permeated water is still highly alkaline and contains a large amount of dissolved silica, so that it has not been used as recovered water.

The treated water obtained by solid-liquid separation such as coagulation sedimentation treatment and filtration has not been used as recovered water because it contains a large amount of impurities such as a coagulant added. For this reason, an increase in the amount of alkaline silica polishing wastewater not only causes an increase in treatment cost, but also poses a problem from the viewpoint of effective utilization of water resources.

In view of the above situation, an object of the present invention is to provide an apparatus for recovering and processing alkaline silica polishing wastewater which can efficiently obtain treated water that can be reused as recovered water from the alkaline silica polishing wastewater. And

[0011]

SUMMARY OF THE INVENTION The present invention provides a membrane separation apparatus for subjecting an alkaline silica polishing wastewater discharged from a chemical mechanical polishing (CMP) step in a semiconductor device manufacturing process to a membrane separation treatment using a separation membrane. An alkaline silica polishing wastewater recovery treatment apparatus, comprising: an ion exchange treatment apparatus for obtaining treated water by bringing permeated water obtained from the membrane separation apparatus into contact with an ion exchange resin containing at least an anion exchange resin. Is what you do. In the apparatus of the present invention, as the separation membrane,
In some cases, a microfiltration membrane or the like can be used,
From the viewpoint of the removal rate of colloidal silica, etc.
A 00 nm ultrafiltration membrane is preferable, and as described later, it is particularly preferable that the ion exchange treatment device includes at least a single-bed anion exchange resin. Further, the separation membrane may be an organic membrane or an inorganic membrane such as a ceramic membrane.

As described above, the alkaline silica polishing liquid (slurry) contains colloidal silica, a chemical etching agent and a dispersant (in the graph showing the effect of pH in the colloidal silica-water system shown in FIG. (It is understood that the alkali functions as a dispersant because of the presence of a phase.) The main component is an alkali agent which plays both roles as a dispersant, and is mainly used for flattening an interlayer insulating film (SiO ₂ film) in a semiconductor device manufacturing process. Is used for the purpose of. This flattening mechanism is to polish the interlayer insulating film (SiO ₂ film) with fine silica particles while chemically etching it with alkali. Therefore, the silica fine particles generated as polishing dust are ultrafine, which is at the level of colloid particles. In addition, bare silicon (Si, bare silicon) such as wafers may be partially polished with an alkaline silica polishing agent. Therefore, Si may be contained in polishing wastewater. Since the polishing is accompanied by this, it is colloidal ultra-fine Si, reacts with water, generates hydrogen gas, and at least the surface portion of the Si fine particles is oxidized to silica or the like. As is clear from the above, the alkaline silica polishing wastewater is a dispersion in which high-concentration silica fine particles are dispersed in a high-pH aqueous solution.

Generally, potassium hydroxide (KOH), ammonia, organic amines, etc. are used as the alkaline agent.
The pH of the polishing liquid is adjusted to 9 to 12 (usually around pH 10). Further, the silica fine particles are ultrafine with a particle size distribution of several nm to several hundred nm (the average particle size is several hundred nm), and the concentration of the silica fine particles is several percent by weight.
Alkaline silica polishing liquid having a concentration of more than 10% is used.

For this reason, the dissolved silica concentration in the new polishing liquid is almost saturated, and when the pH is 10 or more, the dissolved silica concentration becomes 1000 ppm or more (see the graph showing the relationship between silica solubility and pH in FIG. 5). .

On the other hand, the polishing wastewater discharged after the CMP step is usually diluted with rinsing water or the like about several tens to several hundreds times the polishing liquid. Accordingly, although the concentration of dissolved silica in the polishing wastewater immediately after being discharged from the polishing apparatus is reduced, the polishing wastewater still has a high pH value (for example, even if a polishing liquid having a pH of 10 is diluted 100 times with water). The pH value is 8). Since the silica fine particles are dispersed in such high-pH water, the silica gradually dissolves from the surface of the silica fine particles toward the saturated dissolved silica concentration with the lapse of time. Therefore, the concentration of dissolved silica in the polishing wastewater increases (see the graph in FIG. 5). Therefore, the alkaline silica polishing wastewater as the water to be treated at the stage of sending to the alkaline silica polishing wastewater treatment apparatus usually contains dissolved silica having a high concentration of 100 ppm or more. However, the dissolved silica concentration is determined by the dilution ratio, p
H, elapse time, etc.

Silica exhibits various behaviors depending on pH.
(I) The solubility of silica dramatically increases at pH 8 or higher (FIG. 5)
(See graph showing relationship between silica solubility and pH.) (I
i) Dissolved silica has no charge when neutral, but takes a negative charge when alkaline (see the concentration distribution of dissolved silica in water in FIG. 6; however, in FIG. 6, z represents electric charge and −1 valence to −). -3). (iii) Colloidal silica is p
It has a negative surface charge above H2 (see graph of pH effect in colloidal silica-water system in FIG. 4).

The present inventors have discovered that when permeated water obtained by treatment with a membrane separation device is treated with an ion-exchange resin, a change in pH occurs in the resin, and the silica removal effect is different. However, it is the anion exchange resin that has a substantial silica removing effect. Next, an example in which the permeated water is treated with an ion exchange resin will be described. Here, for simplification, AER = single bed of a strongly basic anion exchange resin, CER =
Single bed of cation exchange resin, MB = mixed bed composed of mixed ion exchange resin of strongly basic anion exchange resin and cation exchange resin. Permeated water → AER → CER → Treated water Permeated water → AER → MB → Treated water Permeated water → CER → AER → Treated water Permeated water → MB → AER → Treated water Permeated water → MB → Treated water

The pH change in the AER layer when permeated water is treated in each of the above examples is as follows. In the case of AER layer, in the case of always alkaline in the AER layer, in the case of acidic at the entrance of the AER layer to neutral in the exit of the AER layer, in the case of neutral at the entrance of the AER layer, the case of neutral in the exit of the AER layer Alkaline at the entrance of the MB layer-neutral at the exit of the MB layer

The acidity at the entrance of the AER layer in the case of the above is because the alkali is removed from the permeated water by the treatment with CER, and the silica is a weak acid. On the other hand, in the case of
This is because the alkali is removed from the permeated water by the cation exchange resin and silica, which is a weak acid, is almost completely removed by the strongly basic anion exchange resin.

When the pH of the dissolved silica becomes high on the alkaline side, the solubility of the silica is drastically reduced when the pH is shifted from neutral to acidic, and the polymerization of the silica which cannot be completely dissolved at the point of exceeding the saturation starts, and colloidal silica is started. Changes to

[0021] Colloidal silica can also be removed by an anion exchange resin, but its adsorption capacity is smaller than that of dissolved silica. This is because colloids are large and
This is probably because the surface charge density is low.

When the pH is inclined from neutral to acidic, the proportion of electrically neutral dissolved silica increases. However, since silica is a weak acid, it must be absorbed and removed using a strongly basic anion exchange resin. Can be. Although the surface charge of colloidal silica becomes zero around pH 2 (see FIG. 4), the pH of the treated water does not become 2 or less even after the treatment with the anion exchange resin (silica is a weak acid, and other strong acid components are Therefore, the surface charge of the colloidal silica always has a negative charge. Further, the surface of the colloidal silica is covered with a silanol group. Since the silanol group is a weakly acidic functional group, the colloidal silica can be adsorbed and removed using a strongly basic anion exchange resin.

That is, as the anion exchange resin, a strongly basic anion exchange resin is preferable. If at least a single bed of the strongly basic anion exchange resin is used, silica in the permeated water can be effectively removed. .

On the other hand, when the ion-exchange resin is used as a mixed bed of an anion-exchange resin and a cation-exchange resin, a downstream end of an adsorption zone (a zone in which the adsorption reaction of the mixed-bed ion-exchange resin layer is occurring). Is always almost neutral, so the silica removal effect in the permeated water is considered to be weak for the following reasons. (A) The solubility of silica is lowest near neutrality, and the amount of colloidal silica produced relatively increases (see FIG. 5). (B) In the vicinity of neutrality, since the association of silica fine particles (colloidal silica) occurs rapidly (see FIG. 4), the particle system of colloidal silica becomes relatively large (that is, becomes heavy). (C) Since the inside of the mixed-bed ion exchange resin layer is in a neutralized state of solid acids and bases, the alkalinity is apparently low.

Since CMP is used in the manufacture of semiconductor devices, the permeated water obtained by subjecting the polishing wastewater discharged from the CMP process to membrane separation contains very few impurities other than dissolved silica and alkali, such as Ca and Mg. Since the hardness component is not originally contained, even if the permeated water is directly treated with an anion exchange resin, the hardness component does not precipitate and cause a problem.

Since silica is weakly acidic, it is preferable to use a strongly basic anion exchange resin as the anion exchange resin as described above. Further, even if a cation exchange resin is used as required, when the alkaline agent in the polishing solution is potassium hydroxide (KOH), since this is a strong base, a strongly acidic cation exchange resin or a weakly acidic cation exchange resin is used. There is no problem in using any of them, but when the alkaline agent is a weak base such as ammonia or organic amine, it is preferable to use a strongly acidic cation exchange resin.

By treating the alkaline silica polishing wastewater with a membrane separation device such as an ultrafiltration membrane treatment device, concentrated silica fine water and permeated water containing a high concentration of dissolved silica (colloidal silica is hardly contained) can be obtained. Is separated into

When the anion exchange resin is provided upstream, the ionic silica does not change to colloidal silica, but the alkali concentration of the permeated water obtained from a membrane separation device such as an ultrafiltration membrane treatment device is reduced. If the pH is high (high pH), the alkali acts as a regenerating agent for the anion exchange resin, so that a constant leak (steady leak) of silica occurs. In such a case, if a mixed bed of an anion exchange resin and a cation exchange resin is provided downstream, the alkali can be removed while capturing the dissolved silica that has leaked, which is effective.

The arrangement of the anion exchange resin after the cation exchange resin is advantageous in that alkali is removed from the permeated water in advance, but is disadvantageous in that colloidal silica is generated during passage through the cation exchange resin. It is.

It is advantageous to dispose an anion exchange resin after the mixed bed in that most of the silica and alkali can be removed in the mixed bed. However, the amount of colloidal silica produced is reduced by the treatment with the cation exchange resin. And more than
This is disadvantageous in that the size of colloidal silica tends to increase.

When the anion exchange resin and the cation exchange resin are used in combination as described above, the choice of the ion exchange system described above depends on the properties of the alkaline silica polishing wastewater, the treatment cost, and the specifications of the treated water. It may be determined according to the desired water quality standard or the like. However, the present invention is not limited to these systems, and other systems may be employed as long as they include at least an anion exchange resin. Further, each ion exchange resin layer may be packed in one column or column as a laminated structure to constitute an ion exchange treatment device, or may be filled in a plurality of separate columns or columns to constitute an ion exchange treatment device. It may be.

When the silica concentration in the permeated water obtained from the membrane separation device is low, or when the quality standard of the treated water is low, for example, water polishing after CMP (without using a polishing liquid,
When only water is used and polishing is performed with a polishing pad made of urethane or the like) or cleaning water is used, and silica may be slightly contained, or when used as miscellaneous water, etc. There is no problem with the exchange processing device. Further, if a reverse osmosis membrane device is further arranged at the subsequent stage and reverse osmosis membrane treatment is performed, a small amount of residual colloidal silica can be removed, so that high-quality treated water can be obtained even with an ion exchange treatment device having only a mixed bed. Can be done and there is usually no problem. However, when the silica concentration is high, there is a problem that the silica is concentrated on the reverse osmosis membrane and the reverse osmosis membrane is blocked (that is, it is difficult to treat the high-concentration silica-containing water with the reverse osmosis membrane). In such a case, it is preferable to employ an ion exchange system capable of reducing the silica concentration.

The treated water recovered through at least the membrane separation device and the ion exchange treatment device can be returned to raw water (that is, mixed with city water or industrial water) in any of the above-described systems. Further, since silica can be sufficiently removed by performing the treatment with an ion exchange treatment apparatus containing at least a single bed of anion exchange resin, in this case, primary pure water for polishing alkaline silica or other ultrapure water for production It can be recovered as primary pure water.

In the case where the recovered treated water is returned to the polishing apparatus to be used as water for polishing or cleaning water, the silica concentration does not matter so much. Local recycling may be performed.

As the anion exchange resin or cation exchange resin, fibrous or granular ion exchange resins such as styrene or acrylic are preferred from the viewpoint of processing efficiency. Needless to say, it is preferable to use a hydroxide ion form (OH form) as the anion exchange resin and a hydrogen ion form (H form) as the cation exchange resin.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

First, FIG. 1 shows a basic flow chart of an apparatus for collecting and processing alkaline silica polishing wastewater of the present invention. The polishing apparatus is an apparatus for performing a polishing step of an object to be polished such as a wafer or an intermediate product of a semiconductor device, and may be an apparatus for a single polishing step or an apparatus for a plurality of polishing steps. This polishing apparatus has a rotating base on which a polishing pad made of polyurethane or the like is adhered, and a substrate holding head for holding an object to be polished above the rotating base. Then, the polishing liquid is dropped on the polishing pad, and the polishing pad is impregnated with the polishing liquid, and the object to be polished, such as a wafer fixed to a substrate holding head or an intermediate product of a semiconductor device having an interlayer insulating film layer formed thereon. Press against the polishing pad while rotating. Thereby, precise polishing of the object to be polished, such as a wafer or an intermediate product of a semiconductor device, is achieved by utilizing both the mechanical polishing action of colloidal silica as the abrasive particles and the chemical etching action of alkali. . Before and after polishing and during polishing, cleaning using (ultra) pure water or the like is appropriately performed, and after polishing with a polishing liquid, (ultra)
Water polishing with pure water is also performed.

The polishing wastewater discharged from the polishing apparatus is temporarily stored in a polishing wastewater tank, and then is supplied from a polishing wastewater tank to a membrane separation apparatus provided with a separation membrane such as an ultrafiltration membrane by a pump (not shown). The polishing wastewater is fed, where it is separated into concentrated water containing colloidal silica and permeated water containing impurities such as dissolved silica and alkali. The permeated water is sent to an ion exchange treatment device filled with an ion exchange resin containing at least an anion exchange resin. Here, impurities such as dissolved silica are removed, and the resulting treated water is recovered. Although not shown, a pre-filter (a security filter having a pore diameter of 25 μm or less) for removing coarse solid impurities is preferably installed before the membrane separation device.

A preferred system (flow) of the ion exchange apparatus is as follows. (1) anion exchange resin → cation exchange resin (2) anion exchange resin → mixed bed (mixed ion exchange resin of anion exchange resin and cation exchange resin) (3) cation exchange resin → anion exchange Resin (4) Mixed Bed → Anion Exchange Resin As described above, each of these ion exchange resin layers may be packed in a plurality of separate columns or columns to constitute an ion exchange treatment apparatus. The ion-exchange resin and the cation-exchange resin may be stacked in a single column or column to form an ion-exchange treatment apparatus. In addition to these, for example, a mixed bed, an anion exchange resin, and a cation exchange resin may be further added and arranged at an arbitrary place in the system of (1) to (4) as needed. Depending on the purpose, the cation exchange resin alone may be sufficient, but in the present invention, at least an anion exchange resin is included in order to remove dissolved silica. In some cases, only a mixed bed of an anion exchange resin and a cation exchange resin may be used. However, in order to effectively remove dissolved silica and obtain high-purity treated water, the above (1) to (4) Like the system of
As described above, it is preferable to include a single-bed anion exchange resin.

On the other hand, the concentrated water obtained from the membrane separation device is
Dispose of by a supplier or collect as a polishing liquid. In the case of collecting as a polishing liquid, for example, Japanese Patent Application Laid-Open No.
As shown in the system disclosed in Japanese Patent Application Publication, the membrane separation device is composed of a first-stage microfiltration membrane treatment device and a second-stage ultrafiltration membrane treatment device. Filtration removes coarse impurities by concentrating to the concentrated water side (concentrated water is treated as wastewater), ultrafiltrate the permeated water with an ultrafiltration membrane treatment device, and concentrate the concentrated water to colloidal silica. The apparatus of the present invention may be configured to collect the polishing liquid containing the water and send the permeated water to the ion exchange treatment apparatus.
As in the device (system) proposed in No. 9, the membrane separation device is constituted by an ultrafiltration membrane treatment device, and the permeated water is sent to an ion exchange treatment device, while a predetermined water generated from the ultrafiltration membrane treatment device is generated. Install a microfiltration membrane processing device that performs microfiltration processing of concentrated water in which particles having a diameter greater than or equal to the diameter are concentrated, and treat the above concentrated water with this. It may be configured to remove (the concentrated water is treated as waste water) and recover the permeated water as a polishing liquid.

Next, a secondary pure water production subsystem for producing ultrapure water is incorporated in addition to the apparatus shown in FIG. 1, and the present invention is constructed so that the treated water recovered from the apparatus shown in FIG. 1 can be recycled. The apparatus for recovering the alkaline silica polishing wastewater will be described with reference to FIG.

As in the case of the apparatus shown in FIG. 1, the polishing wastewater discharged from the polishing apparatus is temporarily stored in a polishing wastewater tank,
It is separated into concentrated water and permeated water by a membrane separation device such as an ultrafiltration membrane treatment device, and the permeated water is passed through an ion exchange treatment device,
The obtained treated water is sent to a raw water tank via a line L1, where it is combined with industrial water or city water, or when the treated water purity is at the level of the primary purified water, the primary treated water is supplied via a line L2. Water is sent to the pure water tank. The water in the raw water tank is sent to the primary pure water production device, and the obtained primary pure water is temporarily stored in the primary pure water tank. From the primary pure water tank, the primary pure water is sent to a secondary pure water production subsystem, where it is purified to ultrapure water and used at various points of use at the point of use (POU). At least some of the ultrapure water is supplied through line L3
The water is sent to the polishing apparatus via the water, and is used as cleaning water or water for water polishing. The extra ultrapure water is returned to the primary pure water tank via line L4 and circulated.

Next, in addition to the apparatus shown in FIG. 1, a polishing secondary pure water producing subsystem for producing (ultra) pure water for polishing is incorporated, and the treated water recovered from the apparatus shown in FIG. 1 can be locally recycled and used. With reference to FIG. 3, a description will be given of an apparatus for collecting and processing alkaline silica polishing wastewater of the present invention configured as described above.

As in the case of the apparatus shown in FIG. 1, the polishing wastewater discharged from the polishing apparatus is temporarily stored in a polishing wastewater tank,
It is separated into concentrated water and permeated water by a membrane separation device such as an ultrafiltration membrane treatment device, and the permeated water is passed through an ion exchange treatment device,
The obtained treated water is sent to the treated water tank as the primary purified water for polishing, where the makeup water supplied from the primary purified water tank of the main ultrapure water producing apparatus on the right side of FIG. Join. The water in the treated water tank is sent to the secondary polishing pure water production subsystem, where it is purified to (ultra) pure water for polishing, sent to the polishing apparatus, and used as washing water and water for water polishing. The main ultrapure water production apparatus described above does not differ greatly from that described with reference to FIG.

As the secondary pure water production subsystem, various systems can be used according to the use of the ultrapure water to be obtained. One specific example is “heat exchanger → ultraviolet oxidizer → cartridge polisher”. → Ultrafiltration membrane treatment device ”.

[0046]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Alkaline silica wastewater discharged from a semiconductor device polishing step was sampled and processed by an ultrafiltration membrane processing apparatus equipped with an ultrafiltration membrane module “ACP-1050” manufactured by Asahi Kasei Corporation. Then, concentrated water and permeated water were obtained. The quality of the permeated water has a pH of 9.7 and an electric conductivity of 120 μS / c.
m, the ionic silica concentration was 162 ppm, and the total silica concentration was 162 ppm. The ionic silica concentration was measured by a molybdenum yellow absorption spectrophotometer (JIS K0101). The total silica concentration was determined by adding an alkali to a permeated water sample and heating to convert colloidal silica to ionic silica, and then similarly to the molybdenum yellow color. It was measured by the spectrophotometric method.

Next, the permeated water was passed through an ion exchange treatment apparatus at a space velocity SV = 10 to obtain treated water. The following five devices were configured as ion exchange treatment devices, and treated water was obtained for each of them. 1. 1. Anion exchange resin packed column → Cation exchange resin packed column 2. Anion exchange resin packed column → mixed bed packed column 3. Cation exchange resin packed column → anion exchange resin packed column 4. Mixed bed packed column → anion exchange resin packed column Mixed bed packed column

As the anion exchange resin, a strongly basic anion exchange resin Amberlite IRA-402BL (OH
Form, manufactured by Rohm and Haas Co.), and as the cation exchange resin, a strongly acidic cation exchange resin Amberlite IR-124 (H form, manufactured by Rohm and Haas Co.)
Was used. In the mixed bed, the above anion exchange resin and the above cation exchange resin were mixed at an anion exchange resin / cation exchange resin volume ratio of 2/1 and packed in a column for use. Table 1 shows the water quality data of each treated water.

[0050]

[Table 1] ─────────────────────────────────── Ion exchange treatment equipment Treated water 1 2 3 4 5 ─────────────────────────────────── Specific resistance (MΩcm)> 18> 18> 18> 18 > 18 Ionic silica (ppm) <2 <2 <2 <2 <2 Total silica (ppm) <2 <2 <2 <2 4.1 ──────────────── ───────────────────

From Table 1, it can be seen that all of the treated water has a low ionic silica concentration and a low total silica concentration, and that a single-bed anion-exchange resin-filled column is included in the ion-exchange treatment apparatus rather than a mixed-bed only. It can be seen that good results are obtained at all silica concentrations.

[0052]

According to the present invention, there is provided an apparatus for recovering alkaline silica polishing wastewater, which is provided with an ion-exchange treatment apparatus containing at least an anion-exchange resin at the subsequent stage of the membrane separation apparatus. Dissolved silica in water and colloidal silica formed therefrom can be easily and effectively removed by an anion exchange resin.

[Brief description of the drawings]

FIG. 1 is a basic flow chart of an apparatus for collecting and processing alkaline silica polishing wastewater of the present invention.

FIG. 2 is a diagram showing a configuration in which a secondary pure water production subsystem for producing ultrapure water is incorporated in addition to the apparatus shown in FIG. 1 so that the treated water recovered from the apparatus shown in FIG. 1 can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows an example of the collection | recovery processing apparatus of the alkaline silica polishing wastewater of this invention.

FIG. 3 incorporates a polishing secondary pure water production subsystem for polishing (ultra) pure water in addition to the apparatus of FIG. 1;
FIG. 2 is a flowchart showing another example of the apparatus for collecting and processing alkaline silica polishing wastewater of the present invention configured so that treated water recovered from the apparatus of FIG. 1 can be locally recycled.

FIG. 4 shows pH in colloidal silica-water system.
It is a graph which shows the effect of.

FIG. 5 is a graph showing the relationship between silica solubility and pH.

FIG. 6 is a graph showing a concentration distribution of dissolved silica in water and a chemical species (charge) distribution thereof.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01D 61/58 B01D 61/58 B01J 39/04 B01J 39/04 J 41/04 41/04 J 47/04 47/04 B C02F 1/44 C02F 1/44 E 1/60 1/60

Claims (8)

[Claims] 1. A membrane separation apparatus for subjecting an alkaline silica polishing wastewater discharged from a chemical mechanical polishing (CMP) step in a semiconductor device manufacturing process to a membrane separation treatment using a separation membrane, and a permeation obtained from the membrane separation apparatus. An alkaline silica polishing wastewater recovery treatment device, comprising an ion exchange treatment device for obtaining treated water by bringing water into contact with an ion exchange resin containing at least an anion exchange resin. 2. The apparatus according to claim 1, wherein the ion exchange processing apparatus includes at least a single-bed anion exchange resin. 3. The apparatus according to claim 1, wherein the anion exchange resin contains at least a strongly basic anion exchange resin. 4. The ion exchange treatment apparatus further comprises a cation exchange resin and / or a mixed ion exchange resin (mixed bed) obtained by mixing a cation exchange resin and an anion exchange resin on an upstream side, and a downstream side. 4. The apparatus for recovering and polishing alkaline silica polishing wastewater according to claim 1, wherein an anion exchange resin is disposed in the apparatus. 5. The mixed ion exchange apparatus according to claim 1, wherein the ion exchange treatment device has an anion exchange resin disposed upstream and a cation exchange resin and / or a mixture of the cation exchange resin and the anion exchange resin disposed downstream. 4. The apparatus according to claim 1, wherein a resin (mixed bed) is provided. 6. The separation membrane has a pore size of 1 nm to 100 n.
The apparatus for collecting and processing alkaline silica polishing wastewater according to any one of claims 1 to 5, wherein m is m. 7. The alkaline silica polishing wastewater according to claim 1, further comprising a reverse osmosis membrane treatment device for treating the treated water with a reverse osmosis membrane at a stage subsequent to the ion exchange treatment device. Collection processing equipment. 8. A primary pure water tank for temporarily storing recovered treated water, and a secondary pure water production subsystem for processing the primary pure water to produce ultrapure water or polishing (ultra) pure water. The apparatus for recovering alkaline silica polishing wastewater according to any one of claims 1 to 7, further comprising: