JPH0521038B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is useful for recovering ultrapure water used for final cleaning of semiconductor wafers, for example, when reusing it as pure water for initial cleaning. The present invention relates to a treatment system that processes used water into a reusable state.

<Conventional technology> Highly purified ultrapure water used for the final cleaning of semiconductor wafers has a high purity as pure water and can be reused.
The ultrapure water used for final cleaning is collected and treated.

Conventionally, a system for collecting and processing used ultrapure water includes a recovered water tank 2o that collects and stores the high purity ultrapure water used in the cleaning tank 1o, as shown in the block diagram of FIG. An adsorption tank 3o that mainly adsorbs and removes organic solvents from the recovered water pumped from the recovered water tank 2o, an ion exchange tank 4o that removes ions from the recovered water in the next stage of the adsorption tank 3o, and an ion exchange tank 4o that removes fine particles in the recovered water. It is comprised of a filter 5o for cleaning, a primary pure water tank 6o for storing the recovered water that has passed through the filter 5o as primary pure water for initial cleaning, and the like.

<Problems to be Solved by the Invention> In such a recovered water treatment system, ultrapure water comes into contact with air during cleaning, and bacteria are mixed into the ultrapure water.
Ultra-pure water does not contain any sterilizing substances, so any bacteria that enters it will grow.

By the way, conventional systems do not give any consideration to the contamination of such bacteria and do not have sterilization equipment, so if bacteria contaminate the system, the bacteria will cause damage to the system. The water supply line for the recovered water becomes contaminated, and it becomes necessary to frequently stop the operation of the entire system and perform sterilization cleaning.

In addition, in conventional systems, the adsorption tank 3o containing an adsorbent such as activated carbon becomes a breeding ground for contaminated bacteria, and the bacteria and a small amount of organic matter generate slime, which quickly spreads to the inlet area. The adsorbent in the adsorbent becomes clogged, increasing the pressure drop across the adsorption tank 3o, and even though most of the adsorbent still has sufficient adsorption capacity, the adsorbent must be replaced. It will stop happening. Therefore, it is necessary to frequently replace the adsorbent, which takes time and effort for maintenance, and moreover, the adsorbent is discarded without being used effectively, resulting in a lot of waste.

In view of the above-mentioned problems, the present invention aims to provide a recovered water treatment system that can prevent contamination and propagation of various bacteria in the system and eliminate contamination by slime.

<Means for Solving the Problems> The recovered water treatment system of the present invention includes a recovery tank in which recovered water to be treated is stored, and an adsorption tank that removes organic substances contained in the recovered water sent from the recovery tank. , an ion exchange tank that removes ions contained in the recovered water sent from the adsorption tank, and is connected to the recovery tank so that the recovered water can be circulated between the tank and the recovered water is recovered in a single tank. It is characterized by being equipped with a sterilizer that sterilizes the collected water by irradiating the water with ultraviolet rays and bringing it into contact with ozone.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a configuration diagram of a recovered water treatment system for ultrapure water according to an embodiment of the present invention, and the recovered water treatment system includes a recovered water tank 1
, an adsorption tank 3 to which the recovered water in the recovered water tank 1 is supplied by the feed pump 2, an ion exchange tank 4 provided at the next stage of the adsorption tank 3, and an ion exchange tank 4.
A filter 5 into which the recovered water that has passed is sent;
A primary pure water tank 6 stores recovered water that has passed through the filter 5, and ultrapure water used for final cleaning of semiconductor wafers is fed into the recovered water tank 1 from a cleaning tank 7 in the clean room. Furthermore, the treated water stored in the primary pure water tank 6 is sent to a secondary pure water system (not shown) by a delivery pump 8 as primary pure water used for initial cleaning. The cleaning tank 7 is supplied with high-purity water that has passed through the secondary pure water system and a tertiary pure water system (not shown) at a later stage.
The adsorption tank 3 is filled with an adsorbent such as activated carbon, and the ion exchange tank 4 contains an ion exchange resin.

A sterilizer 9 is arranged in parallel with the recovered water tank 1, and the recovered water is circulated between the recovered water tank 1 and the sterilizer 9 by a circulation pump 10.

FIG. 2 is a block diagram showing the configuration of the sterilizer 9. As shown in the figure, the sterilizer 9 irradiates the recovered water with ultraviolet rays in the same tank, and also contacts the recovered water with ozone. It is equipped with a single sterilization tank 11, an ultraviolet irradiation section 12 provided inside the sterilization tank 11, and an ozone generator 13 that supplies ozone into the sterilization tank 11. 14 is an inflow pipe for recovered water from the recovered water tank 1 to the sterilization tank 11; 15
is an outflow pipe for recovered water from the sterilization tank 11 to the recovered water tank 1. The ultraviolet irradiation section 12 includes an ultraviolet lamp 16 and a cover 17 that transmits ultraviolet rays, and the ultraviolet lamp 16 emits ultraviolet rays when powered by a power supply device 18 . Further, air is pressurized into the ozone generator 13 by an air pump 19, and the ozone generated by the ozone generator 13 is ejected into the recovered water through the supply pipe 20 near the outlet of the recovered water. Note that an inlet for ozone into the sterilization tank 11 may also be provided on the outflow pipe 15 side so that a large amount of ozone is mixed into the recovered water.

In the above configuration, when the feed pump 2 operates and the recovered water is sent into the adsorption tank 3, the circulation pump 10 operates and each part of the sterilizer 9 also operates. The recovered water tank 1 is driven by the circulation pump 10.
The recovered water inside circulates between the sterilization tank 11 and the sterilization tank 11. At this time, the entire interior of the sterilization tank 11 is irradiated with ultraviolet rays from the ultraviolet irradiation unit 12, and ozone is blown into the sterilization tank 11 from the ozone generator 13. Therefore, in the sterilization tank 11, the recovered water is irradiated with ultraviolet rays and comes into contact with ozone, and due to the synergistic effect of the ultraviolet rays and ozone,
The recovered water is sterilized with a high sterilization effect.

The ozone blown into the sterilization tank 11 remains in the recovered water and is transferred to the recovered water tank 1 along with the recovered water.
The recovered water flows into the water supply line below. In this way, ozone flows out from the sterilization tank 11 together with the recovered water, and not only sterilizes bacteria that have mixed into the recovered water during the flow process, but also decomposes algae and mold that have already adhered to the inner walls of the pipes. and remove it.

In the recovered water treatment system of the present invention, since the recovered water containing ozone flows into the adsorption tank 3, it comes into contact with an adsorbent such as activated carbon in the adsorption tank 3, and ozone is removed from the recovered water by its adsorption action. be done. Therefore, ozone does not flow into the water supply line below the adsorption tank 3, so that problems such as oxidation of the object to be cleaned due to residual ozone do not occur.

In the adsorption tank 3, in addition to removing the above-mentioned residual ozone, organic substances such as organic solvents contained in the recovered water are removed, and in the next stage ion exchange tank 4, ions are removed and initial cleaning is performed. Further, in the next filter 5, contaminant particles other than those mentioned above are removed, resulting in pure water of higher purity (primary pure water).

Since the sterilizing effect of the combination of ultraviolet rays and ozone is strong, the sterilizer 9 and the circulation pump 10
does not need to be running all the time; it only needs to be run intermittently.

In addition, as in the above embodiment, if the recovered water is irradiated with ultraviolet rays and brought into contact with ozone in the sterilization tank that circulates the recovered water between the recovered water tank and the recovered water tank, the conventional recovery method It can be implemented inexpensively using a water treatment system.

<Effects of the Invention> As described above, according to the present invention, the recovered water is repeatedly sterilized using ultraviolet rays and ozone by circulating the recovered water between the recovery tank and the sterilizer. Since recovered water is sterilized quickly and effectively, more than 10 times faster than chlorine sterilization, contamination of the entire treatment system with bacteria can be prevented, and the water supply line for recovered water can be sterilized and cleaned.
In addition to reducing maintenance efforts when the processing system is shut down for cleaning, it also enables continuous operation of the processing system over long periods of time, improving operational efficiency.

Furthermore, since ozone remains in the recovered water and exerts a sterilizing effect up to the adsorption tank, contamination of the recovered water line can be effectively prevented.

Furthermore, since the bactericidal effect of ozone extends to the adsorption tank, the adsorption tank does not become a breeding ground for bacteria, unlike in the past, and no slime is generated in the adsorption tank. Therefore, the adsorbent does not become unusable early due to slime, and the adsorbent can be used effectively until its adsorption capacity is exhausted, and the number of replacements of the adsorbent is significantly reduced.

In addition, residual ozone in the recovered water that flows out of the sterilization tank is adsorbed and removed by an adsorbent such as activated carbon in the adsorption tank, so it does not flow into the water supply line below the adsorption tank.
Therefore, problems such as oxidation of objects to be cleaned due to ozone do not occur in places where treated water is used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recovered water treatment system according to an embodiment of the present invention, FIG. 2 is a block diagram of its sterilizer, and FIG. 3 is a block diagram of a conventional recovered water treatment system. 1... Recovered water tank, 3... Adsorption tank, 4... Ion exchange tank, 5... Filter, 9... Sterilizer,
11... Sterilization tank, 12... Ultraviolet irradiation section, 13...
...ozone generator.

Claims (1)

[Claims] 1 Recovery tank 1 in which recovered water to be treated is stored
In a recovered water treatment system having an adsorption tank 3 for removing organic substances contained in the recovered water sent from the recovery tank 1, and an ion exchange tank 4 for removing ions contained in the recovered water sent from the adsorption tank 3. A sterilizer 9 is provided which is connected to the recovery tank 1 so that the recovered water can be circulated therebetween, and which sterilizes the recovered water by irradiating the recovered water with ultraviolet rays and bringing it into contact with ozone in a single tank. A recovered water treatment system characterized by: