JP4661009B2 - Ultrapure water production system - Google Patents

Description

【００４６】
表１より明らかなように、従来の超純水製造システムでは、殺菌処理後の運転再開後にＦｅ，Ｃｒ，Ｎｉが検出され、特にＦｅは一週間後においても０．１ｎｇ／Ｌ検出され、殺菌処理による純度低下の問題がある。これに対して、本発明の超純水製造システムによれば、殺菌処理後の運転再開直後から金属は検出されず、超純水の水質を高純度に安定化させることができることがわかる。
【００４７】
なお、図１に示す如く、殺菌剤貯槽と殺菌剤ポンプを用いて殺菌剤の循環系を形成し、殺菌剤を循環させる代りに、ＵＦ膜分離装置６の入口から殺菌剤を導入し、返送配管１７から殺菌剤を排出することにより、殺菌剤を一過式に通水し、その後浸漬殺菌及び押し出し洗浄したこと以外は実施例１と同様にして殺菌処理を行ったところ、実施例１と同様に、運転再開後、得られた超純水中には金属は検出されなかった。
【００４８】
【発明の効果】
以上詳述した通り、本発明の超純水製造システムによれば、系内の殺菌処理後、超純水製造システムの運転を再開した際の超純水中の金属濃度が著しく低く、運転再開直後から高純度で安定した水質の超純水を得ることができる。
【００４９】
このため、本発明によれば、今後益々高められる傾向にある半導体洗浄用超純水の水質要求に十分に対応することが可能となる。
【図面の簡単な説明】
【図１】 本発明の超純水製造システムの実施の形態を示す系統図である。
【図２】 従来の超純水製造システムを示す系統図である。
【符号の説明】
１ 原水槽
２ ポンプ
３ 熱交換器
４ ＵＶ酸化装置
５ イオン交換樹脂塔
６ ＵＦ膜分離装置
７ ユースポイント
２０ 殺菌剤貯槽
２１ ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrapure water production system for sending ultrapure water produced by an ultrapure water production apparatus to a use point.
[0002]
[Prior art]
In a cleaning process in the field of semiconductor manufacturing or the like, ultrapure water is used as cleaning water. This ultrapure water is required not to contain fine particles, organic matter, or inorganic substances that cause cleaning trouble. For example, resistivity: 18.2 MΩ · cm or more, fine particles: 1 piece / mL or less, viable bacteria: 1 piece / L or less, TOC (Total Organic Carbon): 1 μg / L or less, Silica: 1 μg / L or less, Metals: 1 ng / L or less, Ions: 10 ng / L or less are required water quality.
[0003]
The use location (use point) of ultrapure water is connected to the ultrapure water production equipment by piping (flow path), and the remaining ultra pure water not used at this use point passes through the other flow path. By returning to the pure water production apparatus, a circulation system is formed, and an ultrapure water production system is configured as a whole.
[0004]
FIG. 2 is a system diagram showing a conventional ultrapure water production system. In this ultrapure water production system, an ultrapure water produced by an ultrapure water production apparatus including an ultraviolet (UV) oxidation device 4, an ion exchange resin tower 5 and an ultrafiltration (UF) membrane separation device 6 is connected to a pipe 16. To the use point 7 and a part of the use point 7 is used, and unused ultrapure water is returned to the raw water tank 1 through the pipe 17 and processed again by the ultrapure water production apparatus. It has a circulatory system.
[0005]
That is, primary pure water introduced from the pipe 11 and unused ultrapure water returned from the use point 7 via the pipe 17 are accommodated in the raw water tank 1. Here, the primary pure water, for example, after pre-treatment such as coagulation sedimentation of raw water such as industrial water, well water, city water, reverse osmosis membrane separation treatment, treatment with anionic and cationic ion exchange resin in order, Further, it can be obtained by a reverse osmosis membrane treatment. The water in the raw water tank 1 is adjusted in temperature by the heat exchanger 3 through the pipe 12 by the pump 2, and then introduced into the UV oxidation apparatus 4 through the pipe 13 to remove organic substances. The treated water of the UV oxidizer 4 is introduced into the ion exchange resin tower 5 through the pipe 14 and desalted, and then introduced into the UF membrane separator 6 through the pipe 15 to remove the fine particles. The ultrapure water obtained in this way is supplied to the use point 7 through the pipe 16, and surplus ultrapure water is returned to the raw water tank 1 through the pipe 17.
[0006]
The use point 7 indicates a place where ultrapure water is used, and may include pipes, nozzles, and the like as appropriate in addition to a cleaning device for cleaning an object (for example, a semiconductor). Note that the ultrapure water used at the use point 7 is appropriately collected as drainage.
[0007]
In the ultrapure water production system, the ultrapure water is constantly circulated in this way by removing the eluted components from the materials constituting the pump, heat exchanger, piping, etc. of the ultrapure water production system. The purpose is to keep the interior highly pure. In general, a SUS material is applied as a constituent material of a pump, a heat exchanger, piping, or the like of an ultrapure water production system.
[0008]
In the ultrapure water production system, in order to make the number of viable bacteria in the ultrapure water supplied to the use point 7 the above required water quality level, the system is periodically sterilized. Conventionally, hydrogen peroxide is used as a sterilizing agent for an ultrapure water production system, and sterilization is generally performed in the following procedure.
(1) After the operation of the ultrapure water production system is stopped, a bactericidal agent (hydrogen peroxide solution) is added to the raw water tank 1 through the pipe 18 and is circulated by the pump 2 throughout the ultrapure water production system. That is, raw water tank 1, pipe 12 and pump 2, heat exchanger 3, pipe 13, UV oxidizer 4, pipe 14, bypass pipe 14A of ion exchange resin tower 5, pipe 15, UF membrane separator 6, pipe 16, Circulate in order of use point 7, pipe 17, and raw water tank 1 (circulation sterilization washing). In addition, as a method for adding the bactericide, there are a method of adding from a manhole of the raw water tank 1 and a method of adding using an ejector or a chemical pump.
(2) The pump 2 is stopped and the disinfectant is retained in the system for a predetermined time (immersion sterilization cleaning).
(3) The water in the system is discharged from the pipe 19, the raw water tank 1 is washed with water, and the pump 2 is activated to wash the inside of the ultrapure water production system with ultrapure water until no disinfectant is detected ( Extrusion cleaning).
[0009]
After the operations (1) to (3) above, the operation of the ultrapure water production system is resumed.
[0010]
[Problems to be solved by the invention]
Currently, the degree of integration of semiconductors has been increasing, and ultrapure water used for cleaning is also required to be increasingly pure. Therefore, in ultrapure water production systems, operation after sterilization is required. At the time of resumption, it is desired that high purity and stable water quality can be maintained immediately after resumption of operation.
[0011]
However, as a result of the investigation of the quality of ultrapure water after sterilization by the present inventors, the metal concentration in ultrapure water increases after sterilization, and the state of high metal concentration continues for a long time after restarting operation. It has been found. That is, when the operation of the ultrapure water production system is resumed after the sterilization treatment, metals such as Fe, Cr, Ni, etc. are detected in the produced ultrapure water, about 0.1 to 1 ng / L. Fe was detected in ultrapure water even after one week had elapsed since the resumption of operation.
[0012]
The present invention solves the above-mentioned conventional problems, the metal concentration in ultrapure water when the operation of the ultrapure water production system is resumed after sterilization in the system is remarkably low, and it is stable with high purity immediately after resuming operation. It is an object of the present invention to provide an ultrapure water production system capable of obtaining ultrapure water having a water quality.
[0013]
[Means for Solving the Problems]
An ultrapure water production system of the present invention includes a raw water tank for storing primary pure water, and an ultrapure water production apparatus having at least a membrane separation means for producing ultrapure water by introducing water in the raw water tank. Ultrapure water having water supply means for supplying ultrapure water produced by the ultrapure water production apparatus to a use point and return means for returning unused ultrapure water that has passed through the use point to the raw water tank in the production system, the membrane separation means is a UF membrane separation device supplies the disinfectant on the primary side of the membrane separation unit, thereby discharging the water containing the disinfectant from said returning means, membrane separation means And means for sterilizing the water supply means.
[0014]
In the conventional ultrapure water production system, the present inventors investigated the cause of the continued increase in metal concentration in ultrapure water when the operation was resumed after sterilization, and this cause is as follows. , Metals that elute from components such as ultrapure water production system pumps, heat exchangers, piping, etc. during circulating sterilization washing, or metal that has accumulated in the standby pumps, etc., are stopped by a disinfectant such as hydrogen peroxide. After being oxidized and turned into fine particles, this is captured by the separation membrane means installed at the last stage of the ultrapure water production apparatus and contaminates the separation membrane, and after hydrogen peroxide in the system is discharged by extrusion cleaning, It was found that it was due to re-dissolution in ultrapure water.
[0015]
By the way, the purpose of the sterilization treatment in the ultrapure water production system is mainly to prevent the growth of bacteria in the flow path from the membrane separation means of the ultrapure water production apparatus to the use point. That is, in the ultrapure water production system of the ultrapure water production system, the membrane separation means such as the UF membrane separation apparatus usually provided at the last stage can reliably remove the bacterial cells in the water, Considering that the cells contained in the primary pure water always flow into the ultrapure water production device, sterilization of the path from the raw water tank to the membrane separation means of the ultrapure water production device is not so important. However, it is only necessary to sterilize the flow path to the use point after the membrane separation means.
[0016]
In the ultrapure water production system of the present invention, the bactericide is supplied to the primary side of the membrane separation means of the ultrapure water production apparatus, and the bactericides are returned from the return means for returning unused ultrapure water from the use point to the raw water tank. And a means for sterilizing the water separation means for discharging ultrapure water from the membrane separation means to the point of use from the membrane separation means. Sterilize only the upstream side of the water supply means and the return pipe after the membrane separation means, and to the piping, heat exchanger, pump, etc. before the membrane separation means as in the conventional ultrapure water production system Do not circulate germicide.
[0017]
For this reason, the elution of the metal during the sterilization process in the previous stage of the membrane separation means is prevented, and the eluted metal contaminates the membrane separation means and then re-dissolves when the operation of the ultrapure water production system is restarted. The problem of increased metal concentration in water is solved.
[0018]
In the present invention, as means for supplying the sterilizing agent to the membrane separation means, a sterilizing agent storage tank for storing the sterilizing agent, and a sterilizing agent introducing means for guiding the sterilizing agent in the sterilizing agent storage tank to the primary side of the membrane separation means; Preferably, it has a sterilizing agent returning means for returning the water containing the sterilizing agent discharged from the returning means to the sterilizing agent storage tank, whereby the sterilizing agent is introduced from the sterilizing agent storage tank to the inlet side of the membrane separation means. It can be circulated in the ultrapure water production equipment after the membrane separation means, the ultrapure water supply means to the use point, the return pipe of unused ultrapure water and the sterilizer storage tank for efficient sterilization treatment. it can.
[0019]
Further, in this case, the sterilizing agent introduction means includes a pump for feeding the sterilizing agent in the sterilizing agent storage tank, and the wetted part of the pump is preferably made of a non-metallic material. Further, it is possible to prevent the metal from being eluted from the pump during the sterilization treatment, and to further suppress the metal concentration of the ultrapure water when the operation is resumed.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the ultrapure water production system of the present invention will be described below in detail with reference to the drawings.
[0021]
FIG. 1 is a system diagram showing an embodiment of the ultrapure water production system of the present invention. In FIG. 1, members having the same functions as those shown in FIG.
[0022]
In this ultrapure water production system, at the time of sterilization, the sterilant-containing water in the sterilant storage tank 20 is introduced to the inlet side of the UF membrane separation device 6 by the pump 21 and water containing the sterilant is piped from the return pipe 17. 23 is configured to be introduced into the bactericide storage tank 20.
[0023]
In this embodiment, the discharge-side tip of the pipe 22 is connected to a bactericide inlet provided near the inlet of the UF membrane separation device 6 of the pipe 15. In addition, the inflow side tip of the pipe 23 is connected to the pipe 17.
[0024]
An opening / closing valve V ₁ is provided on the downstream side of the connection portion of the piping 23 in the piping 17, and an opening / closing valve V ₂ is provided on the piping 23. When ultrapure water production operation, the valve V ₁ opened and valves V ₂ is closed, also at the time of sterilization, the valve V ₁ is closed, and the valve V ₂ opens. Note that the disinfectant tank 20 side of the valve V ₂ of the pipe 23 is branched piping 24 for discharging the extruding detergent drain-off valve V ₃ is provided in the pipe 24. The valve V ₃ is opened only when the drainage of the extruded detergent drain.
[0025]
Other configurations of the ultrapure water production system in FIG. 1 are the same as those in FIG. The ultrapure water production operation of this ultrapure water production system is performed in the same manner as the conventional ultrapure water production system shown in FIG.
[0026]
In the sterilization process, the valve V ₁ is closed and the valve V ₂ is opened as described above, and the inflow of primary pure water into the raw water tank 1 is stopped and the pump 2 is stopped. Then, the pump 21 is activated to return the sterilizing agent-containing water in the sterilizing agent storage tank 20 to the sterilizing agent storage tank 20 via the piping 22, the UF membrane separator 6, the piping 16, the use point 7, the piping 17, and the piping 23. Wash. After the circulation sterilization cleaning is performed for a predetermined time, immersion sterilization cleaning is performed in which the pump 21 is stopped and held for a predetermined time.
[0027]
Thereafter, the pump 21 is stopped, while the valve V ₃ is opened, performs extrusion washed Start pump 2. The extruded cleaning waste water is discharged from the pipe 24. The extrusion cleaning is performed until no bactericidal agent is detected in the extrusion cleaning wastewater discharged from the pipe 24.
[0028]
After the extrusion cleaning, the valve V ₁ is opened, the valves V ₂ and V ₃ are returned to the closed state, and normal ultrapure water production operation is resumed.
[0029]
In the ultrapure water production system of FIG. 1, at the time of sterilization treatment, the UF membrane separation device 6 includes a bactericide storage tank 20, a pump 21, a pipe 22, a UF membrane separation device 6, a pipe 16, a use point 7 and a pipe 17. Circulating disinfectant-containing water is passed, and this disinfectant does not pass through the pump 2, the heat exchanger 3 or the upstream pipe of the ultrapure water production apparatus, so the metal elution from these pipes and equipment Membrane contamination of the UF membrane separation device 6 due to this is prevented. For this reason, it is possible to stably produce high-purity ultrapure water immediately after restarting the ultrapure water production operation after the sterilization treatment.
[0030]
From the viewpoint of preventing metal contamination of the UF membrane separation device 6 during the sterilization treatment, the sterilizing agent inlet (connecting portion of the pipe 22) provided on the inlet side of the UF membrane separation device 6 is a UF membrane on the pipe 15. The vicinity of the inlet of the separation device 6 is preferable. In addition, some ultrapure water production apparatuses are provided with a booster pump in front of the membrane separation means in order to secure the raw water introduction pressure to the membrane separation means. In this case, the booster pump discharge port Preferably, a bactericidal agent inlet is provided between the inlet of the membrane separation means.
[0031]
Similarly, from the viewpoint of preventing metal contamination of the UF membrane separation device 6, it is preferable that the liquid contact surface of the circulation path of the bactericide is composed of a non-metallic material. The surface is preferably made of a non-metallic material such as tetrafluoride resin, high-density polyethylene, polybutene, vinyl chloride, PVDF (polyvinylidene fluoride), or polypropylene. Also, the disinfectant introduction pipe 22 and the return pipe 23 may be made of a non-metallic material having a liquid contact surface.
[0032]
In the present invention, a hydrogen peroxide solution can generally be used as the sterilizing agent, and at the time of circulating sterilization cleaning, the hydrogen peroxide solution having a concentration of about 0.1 to 1% by weight is circulated through the sterilizing agent circulation system. Is preferred.
[0033]
The ultrapure water production system of FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one as long as it does not exceed the gist thereof.
[0034]
For example, means for circulating the sterilizing agent such as the sterilizing agent storage tank 20, the sterilizing agent pump 21, and the pipes 22 and 23 are not necessarily required, and sterilization introduced from the sterilizing agent inlet on the inlet side of the UF membrane separation device 6. After passing the agent through the UF membrane separation device 6, the pipe 16, the use point 7 and the pipe 17, it may be discharged from a discharge port provided in the middle of the pipe 17, and may be sterilized and washed temporarily. Even if there is, it is possible to prevent the metal contamination of the separation membrane of the UF membrane separation device 6 during the sterilization treatment, and to stably produce the high purity ultrapure water immediately after the operation of the ultrapure water production system after the sterilization treatment is resumed. it can.
[0035]
In addition, the configuration of the ultrapure water production apparatus is not limited to the one shown in the figure, and the membrane separation means includes a UF membrane separation apparatus, a microfiltration membrane separation apparatus, a reverse osmosis membrane separation apparatus, or these. You may use it in combination. In either case, a bactericidal agent introduction port is provided on the inlet side of the membrane separation means. Generally, a bactericidal agent is introduced on the inlet side of the membrane separation means for removing fine particles provided at the last stage of the ultrapure water production apparatus. It is preferable to provide a mouth.
[0036]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0037]
Example 1
In the ultrapure water production system of the present invention shown in FIG. 1, an experiment was conducted to examine the metal concentration in ultrapure water after sterilization treatment.
[0038]
Note that hydrogen peroxide was used as the sterilizing agent, and the concentration of hydrogen peroxide in the circulating system was 1% by weight.
[0039]
After stopping the operation of introducing the primary pure water and a pump 2 into the raw water tank 1, valve V ₁ is closed, the valve V ₂ is opened, UF membrane via a pipe 22 by the pump 21 the disinfectant-containing water disinfectant tank 20 After being introduced into the inlet side of the separator 6 and circulating through the circulation system of the UF membrane separator 6, pipe 16, use point 7, pipe 17, pipe 23 and bactericide storage tank 20 at 8 L / min, the pump 21 was stopped and immersed for 120 minutes. In addition, as the pump 21, what used the liquid contact part with the polypropylene was used.
[0040]
Thereafter, the pump 21 is stopped, the valve V ₃ is opened, and the pump P ₂ is actuated with resuming the introduction of a primary pure water, by passing water at 20L / min, washed extrusion sterilant in the system Then, after 70 minutes of extrusion cleaning, the operation of the ultrapure water production system was resumed when hydrogen peroxide was no longer detected in the cleaning waste water. After restarting the operation, the time-dependent change in the metal concentration in the obtained ultrapure water was examined, and the results are shown in Table 1.
[0041]
Comparative Example 1
In the conventional ultrapure water production system shown in FIG. 2, an experiment was conducted to examine the metal concentration in the ultrapure water after sterilization.
[0042]
Note that hydrogen peroxide was used as the sterilizing agent, and the concentration of hydrogen peroxide in the circulating system was 1% by weight.
[0043]
After the introduction of primary pure water into the raw water tank 1 and the operation of the pump 2 are stopped, the sterilizing agent is added to the raw water tank 1, and the pump 2 is operated again, so that the entire inside of the ultrapure water production system is sterilized. Was circulated at 8 L / min for 30 minutes, and then the pump 2 was stopped and immersed for 120 minutes.
[0044]
Thereafter, the introduction of primary pure water was resumed, and water was passed at 20 L / min to extrude and clean the disinfectant in the system. After 120 minutes of extrusion cleaning, hydrogen peroxide was no longer detected in the cleaning waste water. At that time, the operation of the ultrapure water production system was resumed. After restarting the operation, the time-dependent change in the metal concentration in the obtained ultrapure water was examined, and the results are shown in Table 1.
[0045]
[Table 1]

[0046]
As is clear from Table 1, in the conventional ultrapure water production system, Fe, Cr, Ni is detected after restarting the operation after the sterilization treatment, and in particular, Fe is detected at a rate of 0.1 ng / L even after one week. There is a problem of purity reduction due to processing. On the other hand, according to the ultrapure water production system of the present invention, it can be seen that the metal is not detected immediately after the resumption of operation after the sterilization treatment, and the quality of the ultrapure water can be stabilized with high purity.
[0047]
As shown in FIG. 1, a sterilizing agent circulation tank is formed using a sterilizing agent storage tank and a sterilizing agent pump. Instead of circulating the sterilizing agent, the sterilizing agent is introduced from the inlet of the UF membrane separation device 6 and returned. By discharging the bactericide from the pipe 17 and passing the bactericide in a transient manner, and then performing sterilization treatment in the same manner as in Example 1 except that immersion sterilization and extrusion cleaning were performed. Similarly, no metal was detected in the obtained ultrapure water after restarting operation.
[0048]
【The invention's effect】
As described above in detail, according to the ultrapure water production system of the present invention, after the sterilization treatment in the system, the metal concentration in the ultrapure water when the operation of the ultrapure water production system is resumed is remarkably low, and the operation is resumed. Immediately after that, high purity and stable ultrapure water can be obtained.
[0049]
For this reason, according to the present invention, it is possible to sufficiently meet the water quality requirements for ultra-pure water for semiconductor cleaning, which tends to be increased in the future.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of an ultrapure water production system of the present invention.
FIG. 2 is a system diagram showing a conventional ultrapure water production system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw water tank 2 Pump 3 Heat exchanger 4 UV oxidation apparatus 5 Ion exchange resin tower 6 UF membrane separator 7 Use point 20 Bactericidal agent storage tank 21 Pump

Claims (3)

A raw water tank for storing primary pure water;
An ultrapure water production apparatus having at least a membrane separation means for producing ultrapure water by introducing water in the raw water tank;
Water supply means for supplying ultrapure water produced by the ultrapure water production apparatus to a use point;
In the ultrapure water production system having return means for returning unused ultrapure water that has passed through the use point to the raw water tank,
The membrane separation means is a UF membrane separation device supplies the disinfectant on the primary side of the membrane separation unit, thereby discharging the water containing the disinfectant from said returning means, membrane separation means and said water supply means An ultrapure water production system comprising means for sterilizing water. In claim 1, as means for supplying a bactericide to the membrane separation means,
A bactericide storage tank for storing bactericides;
A bactericidal agent introduction means for guiding the bactericidal agent in the bactericidal agent storage tank to the primary side of the membrane separation means;
An ultrapure water production system comprising: a bactericide return means for returning water containing the bactericide discharged from the return means to the bactericide storage tank. In Claim 2, the disinfectant introducing means is
A pump for feeding the bactericidal agent in the bactericide storage tank;
An ultrapure water production system, wherein a liquid contact portion of the pump is made of a non-metallic material.

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