JPH03275190A - Producing equipment for ultrapure water - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrapure water production device that produces ultrapure water used in semiconductor manufacturing processes and supplies it to points of use. In particular, the present invention relates to an ultrapure water production device that can maintain a low concentration of organic matter.

[Conventional technology]

As the degree of integration of semiconductors increases, the quality of ultrapure water used for cleaning during the manufacturing process is also improving year by year. especially,
Since organic substances dissolved in ultrapure water deteriorate the yield of semiconductors, there is a strong demand for their removal. For example, in 4 Mbit semiconductors that have been mass-produced in recent years, the TOC (total organic carbon concentration), which is an index of organic matter concentration, is 1 ppb.
It is said that it is necessary to use the following ultrapure water.

For this reason, in conventional ultrapure water production equipment, primary pure water that has been treated with a reverse osmosis membrane to remove high molecular weight organic matter is further processed in the order of ultraviolet oxidation, ion exchange, and ultrafiltration.
Most of the organic matter originating from raw water is removed.

However, in ultrapure water production equipment that includes piping to the point of use, in order to prevent deterioration of water quality due to the proliferation of microorganisms within the piping, ultrapure water is connected between the equipment and the point of use. It's constantly circulating. Therefore, organic substances eluted from piping and various equipment of the ultrapure water production equipment gradually accumulate in the ultrapure water. The eluted organic matter is
Conventionally, it has been thought to be a low-molecular substance that is difficult to decompose, and is removed by installing a reverse osmosis membrane in front of the ultraviolet oxidation device in ultrapure water production equipment.

[Problem to be solved by the invention]

However, when a reverse osmosis membrane is used, not only a high-pressure pump is required in addition to the membrane, but also it is not possible to filter the whole amount, and it is necessary to blow about 10% of ultrapure water. Therefore, the cost of producing ultrapure water increases by 20-30%.

Therefore, an object of the present invention is to provide an apparatus for producing ultrapure water that can economically maintain a low TOC concentration by eliminating the drawbacks of the prior art described above.

[Means to solve the problem]

The present invention discovered that most of the organic substances eluted from piping and various equipment of ultrapure water production equipment are substances with a molecular weight of 100,000 or less. The above objective was achieved by installing an ultrafiltration membrane that can be operated at low pressure and can completely filter the amount at the end of the ultrapure water circulation pipe provided between the points. In addition, as a means to prevent organic matter adhering to the ultrafiltration membrane from being decomposed and re-eluted during hot water sterilization, bypass piping has been installed to bypass the ultrafiltration membrane, making it possible to maintain a low TOC at all times. It is.

That is, in the ultrapure water production apparatus according to the present invention, the ultrapure water production apparatus has a pipe for supplying and circulating ultrapure water to a place of use.
It is characterized in that an ultrafiltration membrane of 0,000 or less is installed and a bypass piping that bypasses the ultrafiltration membrane is provided.

In the present invention, the ultrapure water production equipment generally includes an ultraviolet oxidation equipment, an ion exchange equipment, and an ultrafiltration membrane, but is not limited to these, and equipment with other configurations may also be used. However, it is equipped with piping to supply and circulate ultrapure water to the place where it is used, such as semiconductor cleaning equipment.

Further, most of the organic substances eluted from the piping and each device in this type of device have a molecular weight of 100,000 or more and 300,000 or less. Therefore, in the present invention, an ultrafiltration membrane with a molecular weight cut off of 100,000 or less is installed at the end of the circulation pipe.

Here, there is no particular restriction on the ultrafiltration membrane used as long as it can fractionate substances with a molecular weight of 100,000 or less.
Various membranes can be used, including membrane modules made of polysulfone.

〔Example〕

Next, the present invention will be explained in more detail based on Examples, but the present invention is not limited thereto.

FIG. 1 is a system diagram of an ultrapure water production apparatus showing an embodiment of the present invention. Primary pure water A from which impurities have been roughly removed using a reverse osmosis membrane or the like is stored in a storage tank 1. After pressurizing this pure water with a pump 2, it is sent to an ultraviolet oxidation device 3, where organic matter is decomposed, then ions are removed with an ion exchange device 4, and particles etc. are removed with an ultrafiltration membrane device 5. do. The ultrapure water produced in this way is supplied to use points such as the Ueno cleaning device 6, and then
It is circulated to storage tank 1.

In the ultrapure water production apparatus of the present invention, an ultrafiltration membrane 10 and a pressurizing low-pressure pump 8 are installed at the end of the circulation pipe 7, that is, immediately before the storage tank 1, and the bypass pipe 9 is further installed.
has been established. Since organic substances eluted from piping and equipment are blocked or adsorbed by the ultrafiltration membrane 10, they do not accumulate in the ultrapure water, and the TOC concentration of the ultrapure water can always be maintained at a low level. In addition, during hot water sterilization, valves 11 and 12 are closed, valves 13 and 14 are opened, and the liquid is passed through bypass piping 9 to prevent organic matter adhering to ultrafiltration membrane 10 from being decomposed and re-eluted by hot water. It can be prevented.

FIG. 2 shows an ultrafiltration membrane 10 of the ultrapure water production apparatus shown in FIG. 1 with a molecular weight cutoff of 6,000, a polysulfone hollow fiber type membrane module with a total filtration vortex type, and a molecular weight cutoff of 100. 2 is a graph showing changes over time in the TOC concentration of ultrapure water when operating using a hollow fiber type membrane module made of polysulfone with a molecular weight cut off of 300,000 and a plate type membrane module made of polysulfone with a molecular weight cut off of 300,000. As is clear from Figure 2, the molecular weight cut-off is 6.
000 membrane, it is possible to maintain the TOC of ultrapure water below 1 ppb for about one month,
When using a membrane with a molecular weight cutoff of 100,000, 3 p
Although it was possible to maintain it below pb, the molecular weight cutoff was 300.
When using a plate-type membrane module made of polysulfone of 1,000 ml, the TOC becomes approximately 30 ppb after 10 days and approximately 6 opppb after one month, and it is inevitable that low molecular weight substances will remain in ultrapure water. Ta.

From this result, the eluate had a molecular weight of too and oo.

It is thought that most of the numbers are above 300,000 or below. Therefore, it is appropriate to use a membrane with a molecular weight cut-off of 100,000 or less.

FIG. 3 is a graph showing changes over time in ultrapure water a'roc when bypass piping 9 is used and when it is not used during hot water sterilization. When hot water is passed through the ultrafiltration membrane 10 without using the bypass pipe 9 during hot water sterilization, the organic matter adhering to the membrane is decomposed and gradually eluted. Therefore, the TOC does not decrease until these are decomposed by the ultraviolet oxidizer 3. On the other hand, by using the bypass piping 9 during hot water sterilization, the organic substances attached to the membrane will not be eluted, and the TOC will be reduced to 1 pp within a short time after sterilization.
Becomes less than b. Therefore, there is no need to blow ultrapure water until the TOC decreases, which is economical.

[Effects of the Invention] As described above, the ultrapure water production apparatus according to the present invention uses an ultrafiltration membrane that can be operated at low pressure and can filter the entire amount, so the power cost of the pump is low and the ultrapure water production device of the present invention There is no need to blow pure water. Furthermore, since only the ultrapure water (approximately 10 to 20% of the total amount) that is recirculated to the storage tank is filtered, the area of the ultrafiltration membrane required is also small. Therefore, by providing an ultrafiltration membrane and bypass piping, the increase in production cost due to maintaining a low TOC concentration is only 2 to 3%. This is compared to the method using a reverse osmosis membrane. , it is very small and the ultrapure water production apparatus of the present invention is extremely economical.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an ultrapure water production apparatus showing an embodiment of the present invention, and Fig. 2 shows the molecular weight cut off of the ultrafiltration membrane and the TO of ultrapure water.
Relationship diagram with C concentration, Figure 3 shows ultrapure water with and without bypass piping during hot water sterilization]゛○C
FIG. 3 is a diagram of concentration changes over time. Explanation of symbols 1...Storage tank, 3...Ultraviolet oxidation device, 6...Wafer cleaning device, 9...Bypass piping, 10...Ultrafiltration membrane

Claims (1)

[Claims] (1) In an ultrapure water production device that has piping that supplies and circulates ultrapure water to the place of use, an ultrafiltration membrane with a molecular weight cutoff of 100,000 or less is installed at the end of the ultrapure water circulation piping, An apparatus for producing ultrapure water, comprising a bypass pipe that bypasses the ultrafiltration membrane.