JPH0716580A - Preparation of ultrapure water - Google Patents

Abstract

PURPOSE:To provide the preparation process for ultrapure water which can remove dissolved oxygen as a representative oxidizing substance in ultrapure water to the extent of a specified value or under. CONSTITUTION:Treated liquid flowing out of a primary pure water device 1 is applied to an ultraviolet oxidation device 4, and then passed through a laminate ion exchange resin device 5 in which reducing resin is laminated on the upper section of a strong basic ion exchange resin layer, a mixed bed ion exchange resin device 6 and an ultrafiltration device 7 successively, in the preparation process of ultrapure water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultrapure water which contains almost no oxidizing substances such as dissolved oxygen and which is suitable for cleaning semiconductors.

[0002]

2. Description of the Related Art Ultra pure water used as water for cleaning semiconductors is usually produced by using primary pure water as raw water. That is, a trace amount of organic substances, fine particles, contained in the primary pure water,
The role of the ultrapure water production system is to remove ions and the like to even lower concentrations. Recently, it has been found that in addition to such impurities, oxidizing substances in water, such as dissolved oxygen, adversely affect semiconductor manufacturing. When oxidizing substances such as dissolved oxygen exist in water, a natural oxide film is rapidly formed on the surface of a silicon wafer, which is a semiconductor manufacturing material.For example, the contact resistance between metal and silicon is increased, and the selectivity during etching operation is increased. Will cause problems such as deterioration.

Therefore, development of an apparatus for removing oxidizing substances in water has been advanced. As this typical device,
Dissolve oxygen by blowing an inert gas such as nitrogen gas into the water and discharging the dissolved oxygen together with the nitrogen gas to the outside of the system, or by inserting nitrogen gas into the vacuum degasser and bringing the spray water and nitrogen gas into contact with each other. A method for removing oxygen has been put into practical use. However, in order to completely remove dissolved oxygen by a method using such an inert gas, an extremely large amount of inert gas is required. For this reason, the operation is actually carried out in consideration of economical efficiency, and is several ppb to several tens pp.
The fact is that the dissolved oxygen of b remains in the water. Therefore, there is a demand for the development of an inexpensive and easy method that can almost completely remove oxidizing substances such as dissolved oxygen.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing ultrapure water capable of removing dissolved oxygen, which is a typical oxidizing substance in ultrapure water, to 1 ppb or less.

[0005]

A method for producing ultrapure water according to the present invention is a method for producing ultrapure water by supplying a treatment liquid flowing out from a primary pure water apparatus to an ultrapure water production system.
It is characterized in that the treatment liquid is brought into contact with a reducing resin to remove an oxidizing substance in the treatment liquid.

The reducing resin used in the present invention is a resin having a reducing group such as a sulfite group and a nitrite group. For example, based on a strongly basic anion exchange resin,
For example, a resin in which a reducing group such as a sulfite group or a nitrite group is introduced into a methyl group of its molecular structure.

To bring the treating liquid into contact with the reducing resin, the treating liquid is passed through a reducing resin device filled with the reducing resin, or the treating liquid is applied to an ion exchange resin device in which the reducing resin is laminated or mixed. There is a method of passing water. Since the anionic impurities are eluted from the reducing resin itself when the treatment liquid is contacted with the reducing resin, in order to remove the anionic impurities, in the former method, a strong basic ion is added in the subsequent stage of the reducing resin device. It is preferable to connect an exchange resin device and, in the latter method, a strong basic ion exchange resin device in which a reducing resin is laminated or mixed on the upper part.

In the method of the present invention, specifically, after the treatment liquid flowing out from the primary deionized water device is passed through the ultraviolet oxidation device,
Water is passed through a strong basic ion exchange resin device in which a reducing resin is laminated or mixed on the top or a reducing resin device and a strong basic ion exchange resin device, a mixed bed type ion exchange resin device, and an ultrafiltration device in order. Can be implemented by Furthermore, by applying the method of the present invention to the treatment liquid flowing out from the primary deionized water device incorporating various degassing devices such as a vacuum degassing device, an inert gas aeration device, and a membrane degassing device having a membrane filter, The oxidizing substances can be removed more effectively.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described more specifically based on embodiments with reference to the drawings. FIG. 1 is a systematic diagram of an apparatus for carrying out a method for producing ultrapure water which is an embodiment of the present invention. The apparatus shown in FIG. 1 is mainly a primary pure water apparatus 1 including an oxidizing substance removing apparatus by blowing an inert gas, a storage tank 2 for storing primary pure water, a circulation pump 3, an ultraviolet oxidation apparatus 4, a reducing resin. Laminating ion exchange resin device 5 in which is superposed on a strong basic anion exchange resin, mixed bed type ion exchange resin device 6 in which a strong basic anion exchange resin and a strongly acidic cation exchange resin are mixed, and an ultrafiltration device Ultrapure water consisting of 7 and flowing out from the ultrafiltration device 7 is supplied to the use point 8.

Dissolved oxygen is present at a level of several ppb to several tens of ppb in primary pure water produced through an inert gas aeration system. In the conventional system, an organic substance in the primary pure water flowing out from the primary pure water device 1 is converted into an ionic organic substance such as carbon dioxide gas or acetic acid by the ultraviolet oxidation device 4, and this ionic organic substance is arranged in the subsequent stage. By removing with the device 6, the organic substances in the water are reduced, and at the same time, the trace amount of inorganic ions remaining in the primary pure water and the inorganic ions eluted from the ultrapure water system are removed, and finally, The ultrafiltration device 7 removes fine particles to obtain ultrapure water. The unused ultrapure water is returned to the storage tank 2. The ultrapure water system always maintains high-purity water quality by continuously repeating this water passing-removal. The effect of removing dissolved oxygen in such a conventional system is as shown by the broken line in FIG. 2, for example. That is, the dissolved oxygen in the treatment liquid flowing out from the primary deionized water device flows out from the ultrapure water system at a concentration of about 10 ppb with almost no change.

On the other hand, in the method of the present invention in which the laminated ion exchange resin device 5 in which the reducing resin is laminated on the strong basic anion exchange resin is added after the ultraviolet oxidation device 4, the solid line is shown in FIG. As shown in, the dissolved oxygen in the treatment liquid flowing out from the primary deionized water device 1 could be further removed to a concentration of 1 ppb or less. This result shows that the oxidizing substance removing device installed in the primary pure water device 1 and the laminated ion exchange resin device in which the reducing resin installed in the ultrapure water device is stacked on the strong basic anion exchange resin. It is shown that the action of 5 can completely remove dissolved oxygen which is an oxidizing substance.

The curve shown by the broken line in FIG. 3 is the curve of the outlet of the resin layer when ultra pure water (specific resistance 18.2 MΩ · cm) containing no ionic component is passed through the resin layer of the reducing resin. The specific resistance value is traced from the beginning of inflow. The specific resistance value of the liquid that has passed through the reducing resin layer is the lowest immediately before the start of inflow, and approaches the specific resistance value of the ultrapure water that is passing through with the passage of time. This decrease in the specific resistance value indicates that impurities are eluted from the reducing resin, which causes deterioration of the water quality of the ultrapure water.

On the other hand, when an ion exchange resin device in which a reducing resin is laminated on a strong basic anion exchange resin is installed, as shown by the solid line in FIG. It can be seen that the resistance value hardly decreases, and the elution amount of impurities decreases. This phenomenon indicates that the eluate from the reducing resin was removed by the underlying strongly basic anion exchange resin. The eluate from the reducing resin has not been completely clarified yet, but the monomer reactive group (sulfite group or nitrite group) of the reducing resin itself is present.
I'm guessing that.

In any case, in the present invention, it is necessary to remove impurities eluted from the reducing resin, and it is important to install a strong basic anion exchange resin layer below or after the reducing resin layer. . In the above examples, the reducing resin is a product name A- manufactured by Purolite Co., Ltd. in the United States.
310 is a strongly basic anion exchange resin, trade name 550A Monosphere manufactured by Dow Chemical Co., and strong acid cation exchange resin is a trade name 6 manufactured by Dow Chemical Co.
50C was used.

[0015]

EFFECTS OF THE INVENTION According to the method of the present invention, an oxidizing substance such as dissolved oxygen in primary pure water can be completely removed at low cost and efficiently (1 ppb or less). It is possible to provide ultrapure water that is suitable for applications where it is desired to eliminate the presence of oxidizing substances, such as pure water.

[Brief description of drawings]

FIG. 1 is a systematic diagram of an apparatus for carrying out a method for producing ultrapure water which is an embodiment of the present invention.

FIG. 2 is a graph showing the dissolved oxygen concentration of ultrapure water produced by the conventional method and the method of the present invention.

FIG. 3 is a graph showing the specific resistance of ultrapure water produced by the conventional method and the method of the present invention.

[Explanation of symbols]

 1 Primary Pure Water Device 2 Storage Tank 4 Ultraviolet Oxidation Device 5 Laminated Ion Exchange Resin Device 6 Mixed Bed Ion Exchange Resin Device 7 Ultrafiltration Device

Claims (3)

[Claims] 1. A method for producing ultrapure water by supplying a treatment liquid flowing out of a primary pure water apparatus to an ultrapure water production system, wherein the treatment liquid is brought into contact with a reducing resin, and an oxidizing substance in the treatment liquid is provided. A method for producing ultrapure water, which comprises: 2. The method for producing ultrapure water according to claim 1, wherein the treatment liquid is brought into contact with a reducing resin and a strongly basic ion exchange resin. 3. A strong basic ion exchange resin device or a reducing resin device in which a reducing resin is laminated or mixed on the upper side after the treatment liquid flowing out of the primary deionized water device is passed through an ultraviolet oxidation device. The method for producing ultrapure water according to claim 1, wherein water is sequentially passed through a basic ion exchange resin device, a mixed bed type ion exchange resin device, and an ultrafiltration device.