JPH02119989A - Device for producing ultra pure water using ion-exchange resin - Google Patents

Abstract

PURPOSE:To prevent the elution of org. matter into pure water trom the ion- exchange resin, etc., by connecting an ion-exchange resin preparing system for cleaning the resin with liquefied carbon dioxide to an ion-exchange resin desalting device to form the title device for producing ultra pure water. CONSTITUTION:Raw water is filtered by a filter 1 in the pure water producing system, hence relatively large suspende solid matter is removed, and the medium- sized suspended matter and some ion are removed by a reverse-osmosis device 3. The water is especially deoxygenated by a deaerator 4, and the residual ions are removed by the desalting device 5 to obtain primary pure water. The primary pure water is sterilized by a sterilizer 7, a trace amt. of metal ion is removed by a polisher 8, and the residual suspended solid matter is removed by an MF or UF device 9. The TOC of the obtained ultra pure water is controlled to 30ppb, and the water quality can complete with VISI. The obtained ultra pure water is used in the cleaning of semiconductors, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrapure water production apparatus using an ion exchange resin.

[Background of the invention]

In the semiconductor industry, the market for LSIs (Large Scale Integrated Circuits) is rapidly expanding, and LSIs with increased integration density up to 64 bits are currently being mass-produced. In addition, 256
Prototyping of bits is progressing, and research on the IM bit class, which is the next generation of super LSIs, is progressing. In this way, as LSI technology progresses, the minimum pattern size decreases. The minimum pattern size for LSI is 2 to 3 μm, and for IM bit class VLSI it is 1.5 μm.
It becomes less than μm.

Pure water is used in each cleaning step of the LSI manufacturing process.

The purpose is to remove these chemicals and fine particles that remain on the wafer surface after the wafer has been subjected to acid or organic treatment. Therefore, the presence of ■ions, ■fine particles, ■microorganisms, ■organic substances, etc. in pure water will adversely affect the oxide films, polycrystalline films, wiring, etc. incorporated into wafers, causing defects in the electrical characteristics of LSIs. , it will damage its reliability. The above-mentioned influence increases as the degree of accumulation increases, and the requirements for the quality of the pure water also become stricter. Naturally, the pure water level obtained by the current pure water production system cannot support semiconductors of 1 to 4 Mbits.

Table 1 shows the analysis of the effects of Φ to ■.

That is, with the intervention of microorganisms, organic matter reacts with oxygen, causing microorganisms to proliferate. As a result, microorganisms are released in the semiconductor manufacturing field, reducing wafer purity. Incidentally, the maximum particle diameter that causes short circuits is preferably 115 or less of the minimum pattern. Since the size of microorganisms is about 1 μm, there is a problem even with 64-bit size. Furthermore, even if only a trace amount of organic matter is used, specific substances such as Cu, Fe, and P present in the organic matter are required to be less than i PPb.

In the fields of medicine and biology, the above phenomenon causes microorganisms to produce metabolites and increase pyrogens.

As a result, product purity decreases and heat generation problems occur.

In the field of nuclear power, organic substances are reduced to low molecular weight, and C00H
− is generated. This forms CO complexes, reduces ion exchange removal capacity and increases plant radioactivity.

The above analysis results show that removing organic matter from pure water can also reduce the effects of other factors. Currently, 6
4.Total Organic Carbo (Total Organic Carbo)
n) is less than 300 ppb, which increases to 50 ppb for IM bit class.

In such a state, elution of organic substances from the organic material becomes a problem. This is considered to be one of the reasons why the current pure water production technology is not compatible with VLSI.

In fact, in the 64-bit grade pure water manufacturing process, organic substances are also present in pure water produced through multiple stages of treatment using membrane separators and demineralizers, which are the main equipment. It has been pointed out that organic substances may be leached from organic materials such as membranes and ion exchange resins used.

On the other hand, in desalination treatment using ion exchange resins, which are essential for producing pure water, there is also the problem that resin fragments generated by collisions between the resins or the resins and the walls of the device flow out of the resin group as fine particles.

[Purpose of the invention]

An object of the present invention is to provide an ultrapure water production apparatus using a high-performance ion exchange resin.

[Summary of the invention]

The above objectives include a filtration device to remove relatively large suspended solids, a reverse osmosis device to remove medium suspended solids and ions, a deaerator to remove oxygen, and an ion device to remove residual ions. In a device equipped with an exchange resin desalination device, a sterilization device to remove germs, and an ultrafiltration device or membrane filtration device to remove residual suspended solids, the ion exchange resin is removed using liquefied carbon dioxide gas or supercritical carbon dioxide gas. This is achieved by an ultrapure water production apparatus characterized in that an ion exchange resin preparation system for washing water is connected to the ion exchange resin desalting apparatus.

Regarding the cleaning of ion exchange resins to elute organic matter from the ion exchange resins, the present inventors have discovered that by contacting the ion exchange resins with liquefied carbon dioxide gas or supercritical carbon dioxide gas, the protrusions or deposits on the surfaces of ion exchange resin particles (lower This was made based on the discovery that by removing the strength matrix, the elution of organic substances from the ion exchange resin was reduced to 1/10 or less compared to untreated resin.

It is also possible to desorb organic matter adsorbed onto the ion exchange resin from the outside. Furthermore, the ion exchange resin used in the present invention is
The surface projections (low-strength matrix) are removed and the strength of the resin surface is made uniform, so it may cause problems such as when filling a desalting device or polyrasher that is observed when untreated ion exchange resin is used. There is no resin fragmentation caused by collisions between the resins or the walls of the equipment, and the generation of fine particles (resin fragments) from the resin group can be prevented, and among the four problems mentioned above in ultrapure water production, problems related to fine particles are also avoided. It can be greatly improved.

Therefore, at the current level of LSI manufacturing.

It is possible to improve product reliability and yield, and furthermore, it enables mass production of first-generation VLSI.

In the above embodiment of the present invention, the ion exchange resin preparation device 6
Although the method of filling the desalination device 5 and the polylasha-8 with the resin treated with the
is a pressure-resistant structure, and here.

The resin and liquefied carbon dioxide gas may be brought into contact with each other. In this case, the above-mentioned effect (2) of the present invention can be further enhanced.

Further, supercritical carbon dioxide gas may be used instead of liquefied carbon dioxide gas, but in this case, it is necessary to provide a temperature control system. The critical temperature of carbon dioxide gas is about 31°C, and the critical pressure is about 73 atmospheres. Therefore, the maximum temperature of liquefied carbon dioxide gas is 31°C, which is lower than the temperature at which the performance of the ion exchange resin deteriorates, so temperature control is not necessary unless the operation is performed at 0°C or lower. Since supercritical carbon dioxide gas has a temperature higher than 31''C, it is necessary to control the temperature within a temperature range that does not deteriorate its performance.Furthermore, the pressure of supercritical carbon dioxide gas is high, about 73 atmospheres or higher.

Note that the term "supercritical gas" refers to a gas that is in a state of not less than a critical temperature and not less than a critical pressure in a pressure-temperature state diagram. Also, what is liquefied gas?

In a pressure-temperature state diagram, a substance that is in a pressure state above the vapor pressure line and is a gas at atmospheric pressure and room temperature.

[Embodiments of the invention]

The present invention will be specifically explained below using examples.

Figure 1 shows an ultrapure water production flow showing one embodiment of the present invention. The six flows are a pure water production system (indicated by a solid line in the figure) and a liquefied carbon dioxide gas preparation system (indicated by a broken line in the figure). The pure water production system consists of a filter 1. Pump 2゜2', reverse osmosis device 3. Deaerator i! 4. Desalination equipment 5゜sterilization equipment 7. Polilasha-8
, MF (membrane filtration) or UF (ultrafiltration) device 9, etc. The liquefied carbon dioxide gas preparation system uses liquefied carbon dioxide piping (
(indicated by a broken line in the figure), an ion exchange resin preparation device 6, etc. Usually, 50 to 70 to obtain liquefied carbon dioxide at room temperature.
Since atmospheric pressure is required, the liquefied carbon dioxide piping and the ion exchange resin preparation device 6 should be made of structures or materials that can withstand the above pressure. After preparing the ion exchange resin 1 by bringing the ion exchange resin 10 into contact with liquefied carbon dioxide gas in the container 6, it is filled into the desalting device 5 and the polyrasher 8. In some cases, fill after washing with water. The liquefied carbon dioxide that comes into contact with the ion exchange resin and dissolves unpolymerized organic matter in the resin is taken out from the liquefied carbon dioxide preparation system and gasified. Depending on the case, it may be used repeatedly.

After the ion exchange resin prepared with liquefied carbon dioxide is filled into the desalting device and polyurethane, the raw water is introduced into the pure water production system to produce ultrapure water.

In water purification systems, raw water is first filtered to remove relatively large suspended solids. It is then treated with reverse osmosis to remove moderate suspended solids and some ions. The deaerator 4 is particularly deoxidized to remove oxygen, which is a factor in the reaction between oxygen and organic matter caused by microorganisms. Next, residual ions are removed in a desalination device 5. in general,
Pure water that has been treated up to this point is called primary pure water.

-Next, the purified water is passed through a sterilizer, trace metal ions are removed with a Polylasha-8, and residual S is removed with a MF or UF device 9.
Turbid solids are removed. The quality of the ultrapure water thus obtained is 30 ppb in terms of TOC, and the ultrapure water obtained with a TOC of 0 or more is used for cleaning semiconductors and the like.

FIG. 2 shows the organic matter elution characteristics of ion exchange resin A used in Examples of the present invention. In addition, the characteristics of ordinary ion exchange resin B are shown by broken lines. Resin A was in contact with liquefied carbon dioxide gas for 4 hours, and a large number of four parts formed by falling protrusions were observed on its surface. On the contrary, many protrusions are observed on the surface of resin B.

Figure 2 shows the amount of organic matter (Total Organic Carbon) obtained when the same amount of resins A and B were washed with 10 times as much distilled water and then immersed in 100 mQ of distilled water.
(hereinafter abbreviated as TOC) shows the change in elution rate over time.

The TOC elution rate decreases with the immersion time, but after a certain time it becomes constant and reaches a steady state. In the figure, the results after the mark are the results of continuing the experiment by replacing the soaked resin with the same amount of fresh distilled water, but the TOC elution rate does not change, that is, the organic matter elutes from the resin at the elution rate in the steady state. continue. TO from resin A which is an example of the present invention
The elution rate of C is less than 1/10 of that of normal resin B.The organic matter concentration of pure water produced in the current pure water production system including a desalination device using normal ion exchange resin B is 6.
300p, which satisfies the water quality standards for bit-class LSIs.
pb has been achieved. Therefore, by using the ion exchange resin of the present invention, from the above results, 30ρρb
can be achieved, and this water quality is 1 to 4 MBiVLS I (7)
Water quality group'Q! (50 ppb).

FIG. 3 shows the ion exchange performance of Resin A used in one example of the present invention. The performance of resin B is shown by a broken line. The figure is
0.3% NaCl shows the change over time in the electrical conductivity of the same group when a resin of 1 mmΩ is placed in the solution.The properties of resins A and B are almost the same. In general, fallen protrusions may be attached to the resin surface after treatment with liquefied carbon dioxide.

It is desirable to wash the resin with a high-density fluid (for example, water). Therefore, when removing the protrusions, it is also possible to use mechanical operations such as ultrasonic irradiation in combination.

As the solvent, those that cause an exchange reaction with the ion exchange groups of the resin are unsuitable. When preparing an anion exchange resin using liquefied carbon dioxide gas, the carbon dioxide gas dissolves in the resin-containing water, becomes carbonate ions, and causes an ion exchange reaction with these ions using such a solvent.

Even if it is possible to remove the protrusions, this results in a decrease in the ion exchange performance of the resin. In such a case, after the treatment described above, degassing treatment such as pH control is performed, or ■ ion exchange is performed by contacting with liquefied carbon dioxide in the Na-type or CQ-type state. performance can be maintained.

Figure 4 is a graph showing the cleaning effect of the present invention, in which the treated cation exchange resin and the untreated cation exchange resin obtained in the above experiment were separately crushed in pure water, and dissolved over time. The concentration of organic matter (TOC) was measured, and after 100 hours had passed, the cation exchange resin was washed with pure water, and then immersed separately in pure water again to see how the concentration of organic matter in the pure water changed over time. That's what I saw. As a result, in the case of a cation exchange resin that is placed in pure water immediately after treatment, a large amount of TOC elutes at first, but the elution rate gradually decreases, and eventually the TOC elution rate of the untreated ion exchange resin increases. . Comparing the treated ion exchange resin washed with pure water and the untreated ion exchange resin washed with pure water, there is a significant difference in the TOC elution rate. It can be seen that the effect is significant. Note that liquefied carbon dioxide gas and supercritical carbon dioxide gas have the same ability to dissolve organic matter, and the only difference between the two is that the latter has the ability to dissolve water.

Furthermore, as is clear from FIGS. 5(a) and (b), resin protrusions are seen in FIG. 5(a) showing the untreated ion exchange resin surface, but the ion exchange resin surface after treatment is Looking at the surface of FIG. 5(b), traces of resin convexities falling off can be seen.

It can also be seen that xylem is present on the surface of the ion exchange resin.

Since liquefied carbon dioxide gas or supercritical carbon dioxide gas is under high pressure, it is brought into contact with the resin at high pressure, but after the contact, the pressure of the resin is reduced to atmospheric pressure. The ejection of gas accompanying this pressure reduction has the effect of removing the fallen matrix adhering to the resin surface.

Sudden pressure reduction causes cracks to occur in the resin, significantly reducing its crushing strength. As a result, the generation of fine particles from the resin group increases. It is necessary to depressurize at an appropriate speed. Specifically 5
It is best to reduce the pressure over about 10 minutes.

〔Effect of the invention〕

According to the present invention, (1) In practice, it is possible to prevent the elution of organic substances from resins and the like into pure water, and as mentioned above, it is possible to obtain ultrapure water that is free of organic substances, which is the source of problems in the production of ultrapure water.

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing the ultrapure water production apparatus of the present invention, and FIG.
3 and 3 are graphs showing the performance of an ion exchange resin according to an embodiment of the present invention, FIG. 4 is a graph showing the cleaning effect of an ion exchange resin according to an embodiment of the present invention, and FIGS. (b) is an electron micrograph showing the surface of an untreated ion exchange resin and an ion exchange resin after treatment according to an example of the present invention. 1... Filtration device, 2, 2'... Pump, 3... Reverse osmosis device, 4... Deaerator, 5... Desalination device, 6...
... Ion exchange resin preparation device, 7... Sterilization device, 8.
...Borisha 9...UF or MF device, 10.
...Ion exchange resin. Diagram ion exchange time m1n1 Diagram 5! ('C dondo taha' A kun plays, Umada Nai Y-ma,
ri;, 57G. (,6) 1 ridge each BF

Claims (1)

[Claims] 1. A filtration device to remove relatively large suspended solids, a reverse osmosis device to remove medium suspended solids and ions, a deaeration device to remove oxygen, and an ion exchange resin to remove residual ions. In a device equipped with a desalination device, a sterilization device to remove germs, and an ultrafiltration device or membrane filtration device to remove residual suspended solids, the ion exchange resin is washed with liquefied carbon dioxide gas or supercritical carbon dioxide gas. An apparatus for producing ultrapure water, characterized in that an ion exchange resin preparation system is connected to the ion exchange resin desalting apparatus.