JPH0796273A - Ultrapure water making apparatus - Google Patents

Abstract

PURPOSE:To prevent the occurrence of air bubbles at the time of heating by connecting the supply parts of the respective circulating passages of a primary pure water tank and an ultrapure water tank to the lower parts under the surfaces of water of the respective pure water tanks to prevent the involution of nitrogen gas at the time of circulation. CONSTITUTION:The primary pure water from a degassing device is supplied into a primary pure water tank 2 and the interior of the primary pure water tank 2 is purged with the nitrogen gas from a nitrogen gas purging device 3. The primary pure water in the primary pure water tank is circulated through a discharge part 5, a circulating passage 8, a UV device 4 and a supply part 14. The supply part 14 of the circulating passage 8 is connected to the lateral wall of the lower part under the surface of pure water of the primary pure tank 2 to prevent the involution of the nitrogen gas. An ultrapure water tank 5 is purged with the nitrogen gas from a nitrogen gas purging device 6 in the same way and ultrapure water is circulated through a discharge part 20, circulating passages 9, 10, a UV device 7 and supply parts 18, 19. These supply parts 18, 19 are connected to the lower part under the surface of ultrapure water of the ultrapure water tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing ultrapure water, and more particularly to an apparatus for producing ultrapure water which is installed in, for example, a semiconductor factory and which requires nitrogen gas purging. Regarding the device.

[0002]

2. Description of the Related Art Generally, a semiconductor factory is equipped with an apparatus for producing ultrapure water, and a water tank provided in the apparatus is purged with nitrogen gas in order to prevent contamination from the outside. .

That is, as shown in FIG. 2, a conventional apparatus for producing ultrapure water of this kind stores primary pure water obtained by various deaerators 1a such as vacuum deaeration and membrane deaeration. 1 to do
A secondary pure water tank 2a, a nitrogen gas purging device 3a for injecting nitrogen gas into the primary pure water tank 2a, a UV device 4a for sterilization,
Ultrapure water tank for storing pure water supplied from primary pure water
5a, a nitrogen gas purging device 6a for injecting nitrogen gas into the ultrapure water tank 5a, and a secondary pure water device 7a for purifying pure water in the ultrapure water tank 5a when recycling is there.

In such an ultrapure water producing apparatus, the pure water in the primary pure water tank 2a is circulated and recycled by the circulation passage 8a to purify it, and the circulation passage 9a and the circulation passage 10a. The ultrapure water in the ultrapure water tank 5a is circulated and recycled for purification.

[0005]

However, in the conventional apparatus for producing ultrapure water as described above, the circulation channels 8a, 9a, 10a
In order to make the pure water circulated and recycled by the above flow into the primary pure water tank 2a and the ultrapure water tank 5a while spraying water from the top,
The water surface is disturbed by the water spray, and the purged nitrogen gas is dissolved in the ultrapure water, and the nitrogen gas becomes bubbles, and impurities adhere to the bubble particles, which may adversely affect the wafer cleaning. There was a point.

[0006] In particular, when ultrapure water is heated, the generation of bubbles becomes remarkable as the temperature rises, so that the above-mentioned problems become more remarkable.

The present invention has been made in order to solve such a problem, and an object thereof is to prevent the generation of bubbles in the ultrapure water as described above, particularly the bubbles during heating. To do.

[0008]

The present invention is intended to solve such a problem, and means for solving the problem is to store primary pure water obtained by various degassing means. Primary pure water tank 2 and an ultrapure water tank 5 for storing pure water supplied from the primary pure water tank 2 as ultrapure water.
And nitrogen gas purging devices 3 and 6 for injecting nitrogen gas into the primary pure water tank 2 and the ultrapure water tank 5, respectively.
In order to circulate the pure water and the ultrapure water in the secondary pure water tank 2 and the ultrapure water tank 5, respectively, a circulation flow path connected to the primary pure water tank 2 and the ultrapure water tank 5 via a supply unit and a discharge unit is provided. In the provided apparatus for producing ultrapure water, the supply parts of the respective circulation channels of the primary pure water tank 2 and the ultrapure water tank 5 are connected below the liquid surface of the primary pure water tank 2 and the ultrapure water tank 5. It is to be done.

[0009]

That is, as described above, the supply parts of the respective circulation channels of the primary pure water tank 2 and the ultrapure water tank 5 are connected below the liquid surface of the primary pure water tank 2 and the ultrapure water tank 5. Therefore, the nitrogen gas is not entrained in the ultrapure water during circulation, and the nitrogen gas being purged is not dissolved in the ultrapure water.

[0010]

EXAMPLES Examples of the present invention will be described below. In FIG. 1, 1 is a degassing device for performing various degassing processes such as vacuum degassing and membrane degassing, and 2 is a primary pure water tank 2 for storing the primary pure water obtained by the degassing device 1. A level gauge unit 11 and a pure water sampling unit 12 are connected to the primary pure water tank 2, and a valve 13 is arranged between the level gauge unit 11 and the pure water sampling unit 12.

Reference numeral 3 denotes a nitrogen gas purging device for purging the primary pure water tank 2 with nitrogen gas, which is provided above the primary pure water tank 2.

Numeral 8 circulates the pure water in the primary pure water tank 2.
A circulation channel connected to the primary pure water tank 2 via a supply unit 14 and a discharge unit 15 for recycling, and the supply unit 14 is laterally connected to a portion below the liquid surface of the primary pure water tank 2. It is arranged as described above.

Reference numeral 4 denotes an ultraviolet device for sterilization, which is provided in the middle of the circulation passage 8.

Numeral 5 is an ultrapure water tank for storing the pure water supplied from the primary pure water tank 2 as ultrapure water, which is connected to a midway portion of the circulation flow path 8 via a flow path 16. There is.

Reference numeral 6 denotes a nitrogen gas purging device for purging the ultrapure water tank 5 with nitrogen gas, which is provided above the ultrapure water tank 2.

Circulation flow paths 9 and 10 are connected to the primary pure water tank 2 through the supply units 18 and 19 and the discharge unit 20 in order to circulate and recycle the ultrapure water in the ultrapure water tank 5. In the discharge section
20 is shared by both channels 9 and 10.

Reference numeral 7 is a secondary pure water device for purifying pure water in the ultrapure water tank 5 when circulating and recycling the pure water, which is provided in the middle of the flow path 10. The secondary pure water device 7 is composed of, for example, an ultraviolet irradiation device, an ion exchange device, an ultrafiltration membrane and the like.

Reference numeral 21 is an ultrapure water sampling unit, which is a valve 22.
It is connected to the flow path 10 via.

The case of producing ultrapure water with the ultrapure water producing apparatus having the above structure will be described below.
First, the various degassing devices 1 such as vacuum degassing and membrane degassing 1
Secondary pure water is produced, and the primary pure water is supplied to the primary pure water tank 2 and stored in the primary pure water tank 2.

Next, nitrogen gas is sent into the primary pure water tank 2 by the nitrogen gas purging device 3 to perform nitrogen gas purging.

The primary pure water in the primary pure water tank 2 is discharged from the discharge part.
It is discharged from 15 and circulates in the circulation flow path 8 to 1 from the supply unit 14.
It is then supplied into the pure water tank 2.

In this case, the supply section 14 of the circulation channel 8
Is disposed so as to be laterally connected to a portion below the pure water surface of the primary pure water tank 2, so that nitrogen gas is not entrained in the pure water during circulation, and the circulation flow path 8 The nitrogen gas injected from the nitrogen gas purging device 3 into the primary pure water tank 2 does not dissolve in the pure water circulating in the above.

Further, since the ultraviolet device 4 for sterilization is provided in the middle of the circulation passage 8, the primary pure water circulated by the ultraviolet device 4 is sterilized.

As described above, the primary pure water in the primary pure water tank 2 side, which is prevented from being contaminated from the outside by the nitrogen gas purging and sterilized by ultraviolet irradiation, is circulated and recycled in the circulation passage 8 and purified. Flowed as ultrapure water 16
It is supplied to the ultrapure water tank 5 via the tank and stored in the ultrapure water tank 5.

Next, nitrogen gas is fed into the ultrapure water tank 5 to which ultrapure water is supplied and stored by the nitrogen gas purging device 6, and the nitrogen gas purge is performed in the same manner as the primary pure water tank 2 side.

Then, the ultrapure water in the ultrapure water tank 5 is discharged from the discharge portion.
It is discharged from 20 and circulates through the two circulation channels 9 and 10 and is supplied into the ultrapure water tank 5 from the supply portions 18 and 19 of the respective circulation channels 9 and 10.

Also in this ultrapure water tank 5, the circulation flow paths 9, 1
Since the supply units 18, 19 of 0 are arranged so as to be connected to the pure water storage portion of the ultrapure water tank 5 from the side, the circulation flow paths 9, 19 are the same as the primary pure water tank 2 side. In pure water circulating 10
The nitrogen gas from the nitrogen gas purging device 6 will not dissolve.

Further, in the middle of the circulation flow passage 10 of the two circulation flow passages 9 and 10, secondary pure water composed of the above-mentioned ultraviolet irradiation device, ion exchange device, ultrafiltration membrane, etc. Since the device 7 is provided, the ultrapure water is further purified by the secondary pure water device 7.

As described above, while the nitrogen gas purge prevents contamination from the outside and the secondary deionizing device 7 promotes purification, the side of the ultrapure water tank 5 which is circulated and recycled in the circulation channels 9 and 10 is provided. The ultrapure water is supplied to a semiconductor factory or the like after being subjected to treatments such as heating.

As described above, in this embodiment, in any of the pure water tanks of the primary pure water tank 2 and the ultrapure water tank 5,
The supply parts 14, 18, 19 of the pure water circulation paths 8, 9, 10 are arranged so as to be laterally connected below the liquid surfaces of the primary pure water tank 2 and the ultrapure water tank 5, respectively. Therefore, both deionized water tanks 2,
In both cases, mixture of nitrogen gas is prevented, and as a result, generation of bubbles during heat treatment is prevented.

Pure water is sampled from the primary pure water tank 2 and the ultrapure water tank 5 as described above, and the water is heated using a heating device as shown in FIG. Then, the amount of dissolved gas was obtained. In addition, the generated gas was recovered and chemical analysis was performed.

This will be described in more detail. Pure water sampling unit on the side of the primary pure water tank 2 in the ultrapure water production system.
When pure water sampled by 12 and the sampling unit 21 on the side of the ultrapure water tank 5 is heated by the heater 23 of FIG. 3, bubbles are generated in the collection bottle 24, and the bubbles generate gas analysis sample. The bag 25 collects the dissolved gas, the dissolved gas amount is determined by the collected gas, and the chemical analysis is performed.

The measurement temperatures were 40 ° C., 55 ° C., 70 ° C. and 80 ° C., respectively.

Further, the amounts of heat-generated gas of pure water and ultrapure water sampled by a conventional ultrapure water production apparatus were compared.

A graph of the result is shown in FIG.

In FIG. 4, (a) relates to the amount of gas generated by heating the pure water sampled from the pure water tank, and (b) shows the gas generated by heating the ultrapure water sampled from the ultrapure water tank. It is about quantity.

In the graph of FIG. 4 (A), A indicates the measurement result of this embodiment, and B to F indicate the results of measurement at a plurality of factories equipped with conventional devices.

Further, in the graph of FIG. 4B, a shows the measurement result of this embodiment, and b to h show the measurement results at a plurality of factories equipped with the conventional apparatus.

As is clear from the results shown in FIG. 4, the sample produced by the conventional manufacturing apparatus shows almost no bubbles at a water temperature of about 40 ° C., but the amount of gas produced increases as the temperature rises. Increased, and considerable gas evolution was observed at a temperature of 80 ° C.

On the other hand, in the present example, almost no gas generation was observed not only when the temperature was low but also when heated to 80 ° C.

In the above embodiment, the ultraviolet device 4 is provided in the middle of the circulation flow path 8 on the side of the primary pure water tank 2 and the secondary pure water device is provided in the middle of the circulation flow path 10 on the side of the ultrapure water tank 5. Because 7 is provided,
The desirable effect of increasing the purity of pure water and ultrapure water which are circulated and recycled in the primary pure water tank 2 and the ultrapure water tank 5, respectively, was obtained. The provision is not an essential condition for the present invention.

Further, the design of each of the other constituent parts can be freely changed within the scope intended by the present invention.

Further, in the above embodiment, the circulation flow path 8,
The supply parts 14, 18, 19 of 9, 10 are laterally connected to the storage parts of the primary pure water tank 2 and the ultrapure water tank 5, but not limited to this, for example, the primary pure water tank 2 and the ultrapure water tank. It is also possible to connect to the bottom of the water tank 5.

In short, a nitrogen gas purging device 3 for injecting nitrogen gas into the primary pure water tank 2 and the ultrapure water tank 5, respectively.
6, the primary pure water tank 2 and the ultrapure water tank 5 are provided with circulation flow paths 8, 9 and 10 connected to the primary pure water tank 2 and the ultrapure water tank 5 through the supply units 14, 18 and 19 and the discharge units 15 and 20, and the circulation flow thereof. Supply section 14,1 of paths 8, 9 and 10
It suffices that 8, 19 are connected below the liquid surfaces of the primary pure water tank 2 and the ultrapure water tank 5.

[0045]

As described above, according to the present invention, the supply portions of the respective circulation channels of the primary pure water tank and the ultrapure water tank are located above the water surfaces of the primary pure water tank and the ultrapure water tank as in the conventional case. The nitrogen gas to be purged should not dissolve in the primary pure water tank and the ultrapure water tank below the liquid level, so the nitrogen gas to be purged should be dissolved in the ultrapure water to be sprayed as in the past. Nonetheless, the nitrogen gas is prevented from being inadvertently dissolved in the ultrapure water.

As a result, there is no possibility that air bubbles will be generated in the ultrapure water due to the heat treatment, and therefore, adhesion of air bubble particles to impurities as in the conventional case can be prevented, which may adversely affect wafer cleaning and the like. It also becomes possible to solve problems.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an ultrapure water production system according to an embodiment.

FIG. 2 is a schematic block diagram of a conventional ultrapure water production system.

FIG. 3 is a schematic block diagram of a heating device of a test example.

FIG. 4 is a graph showing test results, where (a) is a gas amount generated by heating pure water and (b) is a graph of gas amount generated by heating ultrapure water.

[Explanation of symbols]

2 ... Primary pure water tank 3 ... Nitrogen gas purging device 5 ... Ultra pure water tank 6 ... Nitrogen gas purging device

Claims (1)

[Claims] 1. A primary pure water tank (2) for storing primary pure water obtained by various degassing means, and the primary pure water tank.
An ultrapure water tank (5) for storing the pure water supplied from (2) as ultrapure water, and a tank for injecting nitrogen gas into the primary pure water tank (2) and the ultrapure water tank (5), respectively. Nitrogen gas purging device
In order to circulate the pure water and ultrapure water in (3) and (6) and the primary pure water tank (2) and the ultrapure water tank (5), respectively.
(2) and an ultrapure water production apparatus comprising a circulation channel connected to the ultrapure water tank (5) through a supply unit and a discharge unit,
The supply parts of the circulation channels of the primary pure water tank (2) and the ultrapure water tank (5) are connected below the liquid surface of the primary pure water tank (2) and the ultrapure water tank (5). An apparatus for producing ultrapure water, which is characterized in that