JPH1157417A - Manufacturing of ultrapure water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To positively sterilize a microbe by implanting an ozone into a water to be filtered prior to filtration and thereafter, performing the ozonolysis of a residual ozone in the water to be filtered, when the final filtration step of a step to manufacture a ultrapure water is carried out using a microfiltration membrane. SOLUTION: An untreated water 1 is caused to pass through a filtration process using a primary pure water 2 (steps S1-S3). This primary pure water 2 is filtered with the addition of a specified amount of ozone to a water to be filtered before filtration for a specified time, in a step (step S7) to implant the ozone using an ozone-resistant membrane fitted in a microfiltration membrane module or an ultrafiltration membrane module as a final stage filter of step 8 when each of the treatment steps (steps S5-S8) is put into practice. Thereafter, the ozonolysis of the residual ozone in the water to be filtered is conducted in a step (step S10) to remove oxygen and the ozone provided downstream near a use point 3. Thus it is possible to sterilize a microbe interrupted by the ozone-resistant membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrapure water production method for producing ultrapure water used for semiconductor production and the like, and more particularly to an ultrapure water production method capable of maintaining water quality and improving maintainability. It is about.

[0002]

2. Description of the Related Art In a process for producing ultrapure water used for cleaning the surface of a semiconductor wafer, microorganisms blocked by a filtration membrane inhabit on the filtration membrane, and metabolites of the microorganisms are removed from the filtration membrane. If the metabolites enter the ultrapure water after passing through the ultrapure water, the metabolites may adversely affect the properties of the semiconductor wafer, and the microorganisms that live in the piping to the point of use will proliferate in the long term. Need to kill microorganisms.

[0003] As a conventional example of disinfecting microorganisms in ultrapure water or on a filtration membrane, an ultrapure water production apparatus is temporarily stopped.
The hot water of 80 to 90 ° C. is circulated or stagnated from the filtration membrane path of the ultrapure water production apparatus to the point of use to sterilize and remove microorganisms stuck on the surface of the filtration membrane or microorganisms in the piping, or In some cases, hydrogen peroxide (H ₂ O ₂ ) is circulated or stagnated in the filtration membrane path of the ultrapure water producing apparatus to sterilize and remove microorganisms stuck to the surface of the filtration membrane.

[0004]

However, in each of the above-mentioned prior arts, since the ultrapure water production apparatus is temporarily stopped to perform the sterilization treatment of the microorganism, the production of the ultrapure water is stopped. When the semiconductor wafer manufacturing process is performed continuously in the manufacturing process, there is a problem that the production of the semiconductor wafer must be stopped.

[0005] In addition, since the facility manager must periodically sample the ultrapure water or the filtered water to check the habitat of microorganisms, there is a problem that the management cost is high.

In particular, hydrogen peroxide (H_TwoO_Two)
In this case, the hydrogen peroxide (H_TwoO _Two) Is a strong oxidizer
Therefore, hydrogen peroxide (H
_TwoO_Two) Waste liquid is temporarily stored in the pit and used for catalase etc.
Hydrogen peroxide (H_TwoO_Two) Disassembly and disposal
Wastewater treatment is costly.
there were.

[0007] The present invention is to solve the above-mentioned problems,
The purpose is to inject ozone into the water to be filtered to surely sterilize the microorganisms blocked by the filtration membrane,
In addition, the sterilization of the downstream ultrapure water line is performed, and the sterilization treatment of microorganisms can be performed without temporarily stopping the ultrapure water production apparatus. It is an object of the present invention to provide an ultrapure water production method capable of reducing the management cost by omitting the investigation of the inhabiting state of the microorganisms in the medium or the filtered water and reducing the waste liquid treatment after the microorganisms are sterilized.

[0008]

A typical configuration according to the present invention for achieving the above object is that the final filtration step of the ultrapure water production step is performed using a microfiltration membrane or an ultrafiltration membrane. A method for producing ultrapure water, comprising adding ozone to water to be filtered before filtration, filtering the water, and decomposing or removing ozone or oxygen remaining in the filtered water after the filtration.

According to the above configuration, the microorganisms in the water to be filtered supplied to the filtration membrane can be sterilized in a short time easily and reliably by applying ozone to the microorganisms, and the sterilized microorganisms lose their ecological functions. It is turned into organic matter (dust) by the filtration membrane and removed from the ultrapure water production path in the same manner as the fine particles.

[0010] Accordingly, since living microorganisms do not inhabit on the filtration membrane, metabolites of the microorganisms do not enter the ultrapure water, and the quality of the produced ultrapure water is maintained at a high level. Can be done.

When an ozone-resistant membrane is used as the microfiltration membrane or the ultrafiltration membrane, ozone does not reduce the amount of water filtered by the microfiltration membrane module or the ultrafiltration membrane module. The life of the outer filtration membrane module can be improved.

In addition, ozone or oxygen added to the water to be filtered before filtration is decomposed or removed after filtration, so that the produced ultrapure water is not adversely affected by ozone, and Since the waste liquid treatment after microbial sterilization is not required unlike the conventional example, the cost can be reduced.

[0013] Further, by adding ozone to the water to be filtered before the filtration, the microorganisms hindered by the filtration membrane are sterilized without stopping the ultrapure water production apparatus, and the ultrapure water is produced continuously. In such a case, for example, the following effects can be obtained. In other words, the microorganisms can be sterilized while the ultrapure water production process is continuously performed without being temporarily stopped. Therefore, there is no need to stop the semiconductor production line, and the semiconductor production efficiency is improved, and the supervision by the facility manager is improved. The management cost can be reduced by omitting the investigation of the habitation state of the microorganisms in the pure water or the filtered water.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the ultrapure water production method according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a view showing the processing steps of the first embodiment of the ultrapure water production method according to the present invention, and FIG. 2 is a view showing the processing steps of the second embodiment of the ultrapure water production method according to the present invention.

First, the processing steps of the first embodiment of the ultrapure water production method according to the present invention will be described with reference to FIG. In FIG. 1, raw water 1 such as river water, lake water, groundwater, or the like is subjected to a coagulation sedimentation device, a pressurized flotation device, a cross-flow type microfiltration device, or an ultrafiltration in a turbidity step shown in step S1 of FIG. It is purified and turbid by the device.

In step S2 of FIG. 1, a reverse osmosis membrane (R
In the reverse osmosis filtration step by O), small substances, specifically ions and organic substances, which are not eliminated by the coagulation sedimentation method or the microfiltration membrane or the ultrafiltration membrane in Step S1, are eliminated.
Then, ions in the water are removed by the ion exchange resin in step S3, and in step S4, primary pure water 2 is generated.

In step S5, the generated primary pure water 2 is irradiated with ultraviolet rays (UV) having a wavelength of 185 nm to react with water in the primary pure water 2 to generate OH radicals (hydroxy radicals). The OH radicals (hydroxy radicals) oxidize and decompose organic substances present in the primary purified water. Further, residual ozone (O ₃ ) injected and circulated, which will be described later, is also decomposed. Further, in step S6, ions in the water are removed by the ion exchange resin, and a polisher process is performed.

Ion exchange resin used in step S6
Means that ozone (O_Three) Is included,
(O_Three)), The function is deteriorated by the strong oxidizing action of
In step S5, ozone (O_Three) Disassembly process
To carry out ozone (O _Three) Is disassembled and step S
6. The maintenance of the ion exchange resin used in 6 is ensured.

Step S7 is an ozone (O ₃ ) injection step. In step S6, ions are removed by a polisher, and ozone (O ₃ ) is injected into water having a resistivity of 18.3 MΩ · cm. Ozone (O ₃ ) is usually ionized by purified oxygen gas or air by a silent discharge method to generate ozone (O ₃ ) gas, and the generated ozone (O ₃ ) gas is used using a porous diffuser or the like. And pour into water. The microorganism is sterilized by the ozone injection.

In step S7, the bactericidal action of the microorganism is proportional to the product of the injection concentration C of the injected ozone (O ₃ ) and the time T. Therefore, as described later, it is preferable to always continuously inject ozone (O ₃ ). In this case, the injection concentration C of ozone (O ₃ ) may be low. ₃ ) The injection concentration C is preferably 1 ppm or less. In the case where ozone (O ₃ ) is injected intermittently at a predetermined timing, ozone (O ₃ )
Is preferably 3 ppm or less.

Step S8 is a filtration step using a final-stage filter in an ultrapure water production process in which a microfiltration membrane module or an ultrafiltration membrane module having an ozone-resistant membrane having ozone resistance is installed.
Microorganisms that have been sterilized by injecting ozone into the filtered water before filtration are captured by the ozone-resistant membrane. Since the sterilized microorganism loses its ecological function and turns into organic matter (garbage), it can be removed from the ultrapure water production route to the outside similarly to the fine particles.

The ozone-resistant film is a hollow fiber film made of an organic ozone-resistant material such as a fluororesin. The ozone resistant film is made of polyvinylidene fluoride (PVDF)
Is preferable because it has excellent ozone (O ₃ ) resistance, excellent hole diameter controllability of the hollow fiber membrane, and excellent reliability (sharpness) of the hole diameter distribution. Also, the adhesive or the like for the hollow fiber membrane is preferably an ozone-resistant material such as a silicone resin.

Although the ceramic membrane or the like has ozone resistance, it is not preferable because it is expensive and fragile, and further, metal ions from the ceramic membrane flow out into the filtered water.

Usually, the ozone (O ₃ ) injected in step S7 is self-decomposed and reduced to oxygen (O ₂ ) in about 15 minutes. In this embodiment, the generated ultrapure water 4 is used for the purpose. If the dissolved oxygen concentration is particularly regulated downstream of the use point 3 (step S9) to be distributed and used accordingly, the deoxidation and deozone steps shown in step S10 are provided. An ozone / oxygen decomposition / removal step of decomposing or removing ozone (O ₃ ) or oxygen (O ₂ ) remaining in the filtered water is performed.

Thus, in step S10, the decomposition of ozone / oxygen is performed by injecting hydrogen gas using a platinum or palladium-based catalyst according to the intended use of the ultrapure water 4 taken out through the use point 3 in step S9. / O2 (O ₃ ) or oxygen (O ₂ ) remaining in the filtered water is decomposed or removed by performing a deoxygenation and deozone process as a removal process or the like. When cleaning the surface of a semiconductor wafer, the strong oxidizing action of ozone (O ₃ ) does not adversely affect the semiconductor wafer.

Step S4 → Step S5 → Step S6 → Step S7 → Step S8 → Step S9 of FIG.
→ Step S4 is a circulation processing step, and the primary purified water 2 obtained by filtering the raw water 1 in steps S1 to S3 performs the processing steps of steps S5 to S8 described above and uses step S9. .., 20,..., Etc., and the unused ultrapure water is mixed with the primary pure water 2 in step S4 to continuously perform the circulation process. Circulate.

According to the above structure, the ozone-resistant membrane provided in the microfiltration membrane module or the ultrafiltration membrane module, which is the last-stage filter in step S8, is used to perform the ozone injection step in step S7 to perform filtration before filtration. By injecting a predetermined amount of ozone (O ₃ ) into water at a predetermined time, the microorganisms blocked by the ozone-resistant membrane can be sterilized without stopping the ultrapure water production apparatus, and the ultrapure water can be continuously removed. 4 to 20 can be manufactured. Also, the ultrapure water at the use point 3 which is the ultrapure water circulation line is sterilized with ozone (O ₃ ) and returns to the primary pure water 2 in step S4.

A specific example in the case of producing ultrapure water in the above configuration will be described in detail.

Example 1 A 3 inch diameter, 1 m long module using a hollow fiber membrane made of polyvinylidene fluoride (PVDF) having an average pore diameter of 0.05 μm as the ozone resistant membrane module used in step S8. , The operation is performed for one year by continuously injecting ozone (O ₃ ) having an ozone concentration of 0.3 ppm in step S7 at a filtered water amount of 3 m ³ / hr, and then operating for one year. When microorganisms living in pure water 20 were measured, 0 living organisms / 1000 ml, that is, no living microorganisms were detected.

According to this result, there is no need to temporarily stop the ultrapure water production apparatus and carry out the sterilization treatment of microorganisms as in the conventional example. Can be implemented.

Further, it is not necessary for the facility manager to periodically sample the ultrapure water or the filtered water to check the habitation state of the microorganisms, and the management cost can be reduced.

[Comparative Example 1] As a comparative example, polyacrylonitrile (PAN) was used, and the molecular weight cut off (CMW; cut of
3 modules of 3 inches in diameter and 1 m in length using a hollow fiber membrane with a f molecular weight of 13,000, and a filter water volume of 3 m ³ / hr, every 4 months (3 per year)
), The ultrapure water producing apparatus is temporarily stopped, and the microorganisms are sterilized with a hydrogen peroxide solution (H ₂ O ₂ ). After operating for one year, the ultrapure water of use point 3 in step S9 is similarly operated. Microorganisms inhabiting before hydrogen peroxide water sterilization were measured at 20. Microorganisms inhabiting were 10 / 100m.
Detected in the range of 1 to 40 cells / 100 ml.

[Comparative Example 2] As a comparative example, a polysulfone (PS) product having a cut-off molecular weight (CMW; cut of fmolecule) was used.
ar weight) is 3 m ³ / h using a module having a diameter of 3 inches and a length of 1 m using a hollow fiber membrane of 10,000.
every 4 months (three times a year), suspend the ultrapure water production equipment and perform heat sterilization at 80-90 ° C.
After the operation for one year, the microorganisms that inhabit before heat sterilization were similarly measured in the ultrapure water 5 at the use point 3 in step S9, and the inhabiting microorganisms were detected in the range of 5 / 100ml to 20 / 100ml. Was done.

Example 2 The molecular weight cutoff (CMW; cut) was used as the ozone resistant membrane module used in step S8.
off molecular weight) is used three modules length of 1m 3 inch diameter using 100,000 polyvinylidene fluoride (PVDF) manufactured by the hollow fiber membrane, 3m ³ /
hr of filtered water, ozone concentration of 3 ppm in step S7
Ozone (O ₃ ) was injected once a day for 10 minutes, and the microorganisms living at use point 3 in step S9 were measured every three months.
ml, that is, no inhabiting microorganisms were detected.

According to the result of the second embodiment, similarly to the first embodiment, it is not necessary to suspend the ultrapure water production apparatus and perform the sterilization treatment of microorganisms as in the conventional example.
Ultrapure water can be produced efficiently.

Further, it is not necessary for the facility manager to periodically sample the ultrapure water or the filtered water to check the habitation state of the microorganisms, thereby reducing the management cost.

Next, a second embodiment of the method for producing ultrapure water according to the present invention will be described with reference to FIG. In the present embodiment, the step S10 shown in FIG. 1 is located on the upstream side near the use point 3 in the step S9 of the first embodiment shown in FIG.
(Step S9 in FIG. 2). In step S9 in FIG. 2, ozone (O ₃ ) or oxygen (O ₂ ) remaining in the filtered water after the filtration is decomposed or removed. The ozone / oxygen decomposition / removal process is collectively performed. Therefore, use point 3 in FIG.
The deoxygenation and deozone steps are not provided downstream of the individual use ports in (Step S10).

With the above configuration, all of the filtered water filtered by the ozone-resistant membrane module in step S8 of FIG. 2 is converted to ozone / oxygen such as injecting hydrogen gas using a platinum or palladium catalyst in step S9. After the deoxygenation and deozonization steps, which are the decomposition / removal steps, are performed to decompose or remove the ozone (O ₃ ) or oxygen (O ₂ ) remaining in the filtered water, the pure water is passed through use point 3 in step S10. Water 4 to 20 is removed. Thus, similarly to the first embodiment, the strong oxidizing action of ozone (O ₃ ) adversely affects the semiconductor wafer when cleaning the surface of the semiconductor wafer using the generated ultrapure water 4, for example. Not to be.

Step S4 → Step S5 → Step S6 → Step S7 → Step S8 → Step S9 of FIG.
→ Step S10 → Step S4 is also a circulation processing step as in the first embodiment, and the primary pure water 2 obtained by filtering the raw water 1 in steps S1 to S3 is the same as that in steps S5 to S9 described above. Each processing step is performed, and from the use point 3 in step S10, the ultrapure water 4,
Unused ultrapure water is taken out as 5,..., 20 and mixed with the primary pure water 2 in step S4 to continuously circulate through the circulating process.

According to the above configuration, similarly to the first embodiment, the ozone-resistant membrane provided in the microfiltration membrane module or the ultrafiltration membrane module which is the final filter in step S8 is used. Ozone (O ₃ ) in water by a predetermined amount at a predetermined time by an ozone injection process
By injecting water, it is possible to sterilize microorganisms and to remove them with an ozone-resistant film without stopping the apparatus for producing ultrapure water. The ultrapure water not used at the use point 3 returns to the primary pure water 2 in step S4, and circulates in the ultrapure water circulation line.

The other configuration is the same as that of the first embodiment, and the same effects as described above can be obtained.

[0042]

Since the present invention has the above-described structure and operation, it is possible to easily and reliably sterilize microorganisms in a short time by applying ozone to microorganisms contained in primary purified water. The quality of the ultrapure water produced can be maintained at a high level.

In the final filtration step, ozone or oxygen added to the water to be filtered before filtration is decomposed / removed after the filtration, so that when the produced ultrapure water is used, it is adversely affected by ozone. This eliminates the need for waste liquid treatment after microbial sterilization as in the conventional example, so that the cost can be reduced.

Further, according to the present invention, it is not necessary to suspend the ultrapure water production apparatus and carry out the sterilization treatment of microorganisms as in the conventional example. Water production efficiency can be improved. Further, for example, when the semiconductor wafer manufacturing process is performed continuously with the ultrapure water manufacturing process, the semiconductor wafer production efficiency does not decrease.

Further, it is not necessary for the facility manager to periodically sample the ultrapure water or the filtered water to check the habitation state of the microorganisms, thereby reducing the management cost.

[Brief description of the drawings]

FIG. 1 is a view showing processing steps of a first embodiment of a method for producing ultrapure water according to the present invention.

FIG. 2 is a view showing processing steps of a second embodiment of the ultrapure water production method according to the present invention.

[Explanation of symbols]

 1… raw water 2… primary pure water 3… use point 4,5,20… ultra pure water

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/50 531 C02F 1/50 531R 540 540B 550 550C 560 560E 560C 1/78 1/78

Claims (2)

[Claims] When the final filtration step in the ultrapure water production step is performed using a microfiltration membrane or an ultrafiltration membrane, ozone is added to the water to be filtered before filtration, and the filtrate is filtered. A method for producing ultrapure water, comprising decomposing or removing remaining ozone or oxygen. 2. The method according to claim 1, wherein the primary pure water is irradiated with ultraviolet rays, and then supplied to a final filtration step using a microfiltration membrane or an ultrafiltration membrane as water to be filtered before filtration. Ultrapure water production method.