JPS614587A - Demineralized water supply system and its method - Google Patents

Abstract

PURPOSE:To control the proliferation of microorganisms by providing a branch valve at each use point, and circulating demineralized water supplied from an extremely pure water apparatus whether the demineralized water is discharged from the use point or not. CONSTITUTION:A three-way valve 8 is provided to each use point 6, and one branch of each three-way valve 8 is connected to a reflux pipeline 7. The other end of the reflux pipeline 7 is connected to a water storage tank 1, and demineralized water is sent from the three-way valve 8 to the water storage tank 1 through the reflux pipeline 7 and recovered. When the demineralized water is used at the use point 6, the three-way valve 8 is turned to the use point 6 side, and the demineralized water is supplied to the use point 6 from an extremely pure water apparatus 4 through a circulating pipeline 5a and a branch pipe 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pure water supply system and method for supplying pure water used in semiconductor manufacturing processes and the like.

[Technical background of the invention]

In the semiconductor manufacturing process, so-called pure water with high resistivity and no impurities is often used, and pure water supply systems that supply pure water are widely used.

FIG. 2 is a configuration diagram of an example of a conventional pure water supply system. In addition, in the following description of the drawings, -C identical elements are indicated by the same reference numerals. Water, which is not necessarily of high purity, is supplied to the water storage tank 1 from a primary water supply pipe 2. Water is supplied from the water storage tank 1 to an ultrapure water device 4 via a pump 3, and the ultrapure water device 4 supplies purified water to a level suitable for semiconductor manufacturing processes through a circulation pipe 5a and a branch. It is supplied to each use point 6 via a pipe 5b. Circulation piping 5
A forms a circulation system so that pure water is fed back to the water storage tank 1 again, and pure water that is not used at the use point 6 is circulated to the water storage tank 1.

[Problems with background technology]

In such a conventional pure water supply system, when pure water is not constantly used at use point 6 (J,
Pure water may accumulate in the branch pipe 5b, and microorganisms slightly present in the pure water may proliferate. In particular, the point of use is likely to be at a temperature higher than the constriction temperature due to heat treatment and chemical treatment.
Microorganisms may proliferate.

Therefore, when using the pure water at use point 6 after stopping the use of pure water for a long time at use point 6, pure water containing microorganisms (bacteria) that have grown in the branch pipe 5b is supplied. Microorganisms may adhere to washed items.

Usually, such microorganisms possess phosphorus (P), which causes various adverse effects if it is subsequently subjected to heat treatment.

For example, in a semiconductor manufacturing process, if a P-type substrate is subjected to a heat treatment process with microorganisms containing phosphorus attached to it, the phosphorus will diffuse N-type impurities, resulting in electrical defects. Therefore, there is a drawback that the yield of semiconductor devices is significantly reduced.

Therefore, it is desirable to use the pure water supplied through the ultrapure water device 4 as quickly as possible, or to constantly drip a certain amount of it to prevent the growth of such microorganisms. However, the former method is difficult from the point of view of process control, and the latter method results in an increase in the amount of pure water used and thus in the cost of the product.

[Purpose of the invention]

The present invention has been made to overcome the above-mentioned drawbacks of the prior art.
The purpose of the present invention is to provide a pure water distribution system that prevents water from stagnation for a long time and suppresses the growth of microorganisms.

[Summary of the invention]

In order to achieve the above object, the present invention provides a pure water supply system that supplies purified pure water to use points 1 to 1.
The purpose of the present invention is to provide a pure water supply system and method in which pure water in a branch pipe leading to a use point is returned to a water storage tank when pure water cannot be taken out at a use point.

(Embodiment of the Invention) FIG. 1 is a block diagram of a pure water piping system according to an embodiment of the present invention. A three-way valve 8 is installed at each use point 6, and one branch of each three-way valve 8 is connected to a separately provided reflux pipe 7. This reflux pipe 7
The other end is connected to the water storage tank 1, and pure water is recovered from the three-way valve 8 to the water storage tank 1 via the reflux pipe 7. When using the 1st point 6'C-pure water, rotate the three-way valve 8 to the 2nd point 6 side to supply 1st point 6'C-pure water from the ultrapure water device 4 through the circulation piping 5a and the branch pipe 5b. --supplied to point 6.

When pure water is not used, by rotating the three-way valve 8 so that the circulation pipe 5 and the reflux pipe 7 are connected, the pure water from the ultrapure water device 4 is bypassed by the three-way valve 8. and flows to the reflux pipe 7.

Therefore, the pure water discharged from the ultrapure water device 4 always forms a circulation cycle regardless of whether it is used at the point of use 6, and does not accumulate in the pipe 5b leading to the point of use 6 for a long time. Therefore, the proliferation of microorganisms is suppressed.

Figure 3 is a characteristic diagram in which the number of bacteria contained in pure water is counted as 1 when pure water is taken out again after the use of pure water at use point 6 is stopped for a predetermined time. Figure (A) corresponds to the conventional supply system, and Figure 3 (B) corresponds to the supply system according to the present invention.As is clear from the figure, when the supply system according to the present invention is used, the use point Since there is no accumulation of pure water even if the water is stopped for a long time, microorganisms hardly breed in the branch pipe 5b.

In the above embodiment, a 3-way valve was provided on the use point 1 side of the branch pipe, and the pure water in the branch pipe was refluxed by the valve. Any type of material may be used as long as it can reflux pure water when there is no extraction of pure water.

(Effects of the Invention) As described above, according to the present invention, for example, a branch valve is installed at each use point, and the pure water supplied from the ultrapure water device is circulated regardless of whether or not pure water is taken out from the use point. This structure prevents pure water from accumulating in the branch pipes leading to the point of use, and prevents the growth of microorganisms, making it possible to supply pure water suitable for use in semiconductor manufacturing processes. A pure water supply system and method thereof can be realized.

[Brief explanation of drawings]

l No., □□E,,)-Real 0. Person in charge. . FIG. 2 is a block diagram of a conventional pure water supply system, and FIG. 3 is a characteristic diagram comparing the relationship between the use point stop time and the number of bacteria generated. 4... Ultrapure water device, 5a... Circulation piping, 5b...
- Branch pipe, 6... Point of use, 7...)? Diversion piping, 8... Three-way valve (branch valve). Applicant's agent Kiyoshi Inomata ← ・、− Oni (A) One use point stop 3 diagram (B)

Claims (1)

[Scope of Claims] 1. A circulation pipe that circulates purified pure water from a water storage device along a predetermined route, and a branch pipe whose one end is connected to the circulation pipe and the other end is connected to a point of use. a branch valve provided on the use point side of the branch pipe; and a reflux pipe whose one end is connected to at least one branch of the branch valve to return pure water from the branch pipe to the water storage device. A pure water supply system equipped with . 2. The pure water supply system according to claim 1, wherein the branch valve is a three-way valve. 3. In a pure water supply method in which purified pure water is circulated from a water storage device through a circulation pipe and the pure water is supplied to a point of use via a branch pipe whose one end is connected to the circulation pipe, at least the above-mentioned method is provided. A pure water supply method characterized in that when pure water is not taken out at a use point, the pure water is returned to the water storage device from the use point side of the branch pipe.