JP2002214221A - Impurities detector and impurities detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of detectors at the time of detection of impurities and to detect impurities for a short time. SOLUTION: An organic compound and a peroxide recovered by circle return piping 2 are decomposed by an ultraviolet oxidizing treatment device 11 and conductivity is measured by a resistivity meter 12 and dissolved oxygen is measured by a dissolved oxygen meter 13 to detect impurities of water recovered by the circle return piping 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impurity detecting apparatus and an impurity detecting method, and more particularly to an apparatus for detecting inorganic substances, dissolved oxygen, organic compounds, peroxides and the like contained in pure water or ultrapure water. It is suitable.

[0002]

2. Description of the Related Art Conventionally, pure water (ultra pure water) supplied to a semiconductor manufacturing process, a liquid crystal display element manufacturing process, or the like is called a point of use through a pipe, where the pure water or ultra pure water is actually used. Supplied to At this time, after the required amount of pure water (ultra pure water) is used while passing through the use point, the surplus returns to a tank called a primary pure water tank again. This is to make the (ultra) pure water always flow through the pipe for supplying the (ultra) pure water, thereby preventing the generation of bacteria and a decrease in purity. This is usually called circle piping.

[0003] In this case, depending on the state of use of pure water or ultrapure water at the use point, chemicals used at the use point may be mixed into the return pipe of the circle pipe. Therefore, in the return pipe of the ultrapure water circle pipe, the impurities contained in the returned (ultra) pure water are monitored, and the water containing the impurities is mixed into the pure water or ultrapure water supply system. It has been carried out to prevent this.

FIG. 4 is a block diagram showing a conventional method of monitoring ultrapure water contamination. In FIG. 4, pure water produced by the primary pure water system 3 is stored in a primary pure water tank 4. Then, the pure water stored in the primary pure water tank 4 is sent to the ultrapure water system 6 via the pump 5 to produce ultrapure water. Ultrapure water produced by the ultrapure water system 6 is supplied to the use point 7 via the circle pipe 1.
Then, of the ultrapure water supplied to use point 7,
Ultra pure water not used at the use point 7 is returned to the primary pure water tank 4 via the return pipe 2 of the circle pipe 1. At this time, a part of the ultrapure water returned to the primary pure water tank 4 via the return pipe 2 is
4 sampled.

The impurity detector 14 comprises a resistivity meter 12, a dissolved oxygen meter 13, a TOC meter 15, and an H ₂ O ₂ monitor 16.
By using these measuring instruments, impurities such as inorganic substances, dissolved oxygen, organic compounds, and peroxides contained in pure water or ultrapure water are detected. When impurities are detected by the impurity detection device 14, the valves 8 and 9 are opened and closed based on the detection result, whereby the water containing the impurities is returned to the pure water tank 4 as pure water or ultrapure water. To prevent that from happening.

[0006]

However, in the conventional method for monitoring ultrapure water contamination, in order to monitor impurities contained in pure water or ultrapure water, a resistivity meter 12, a dissolved oxygen meter 13, a TOC It is necessary to provide the total 15 and the H ₂ O ₂ monitor 16, and there is a problem that many detectors are required.

[0007] Furthermore, the TOC meter 15 takes several minutes to make a measurement, and when the TOC meter 15 shows an abnormal value, the primary pure water tank 4 may already be contaminated. In some cases, it could not be prevented.

Accordingly, an object of the present invention is to provide an impurity detecting apparatus and an impurity detecting method capable of reducing the number of detectors for detecting impurities and capable of detecting impurities in a short time. It is to provide.

[0009]

According to the present invention, there is provided, in accordance with the present invention, an ultraviolet irradiation means for irradiating water containing at least one of an organic substance and a peroxide with ultraviolet light; It is characterized by comprising electrical conductivity measuring means for measuring the conductivity or resistivity of the water, and dissolved oxygen measuring means for measuring the dissolved oxygen of the ultraviolet-irradiated water.

Accordingly, the organic compound contained in the water is
The ultraviolet rays decompose into organic acid ions or carbon dioxide gas, and the resistivity of water decreases. In addition, peroxides contained in water are decomposed into water and oxygen by ultraviolet irradiation, and dissolved oxygen increases.

For this reason, it is possible to detect inorganic substances, dissolved oxygen, organic compounds, peroxides, and the like mixed in pure water or ultrapure water only by using a conductivity meter (or resistivity meter) and a dissolved oxygen meter. This makes it possible to reduce the number of detectors when detecting impurities mixed in pure water or ultrapure water.

In addition, the configuration of a device such as a conductivity meter (or resistivity meter) and a dissolved oxygen meter that instantaneously detects and displays measured values after ultraviolet irradiation can greatly reduce the time required to detect impurities.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for detecting impurities according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an impurity detection system according to one embodiment of the present invention. In the following description, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, an impurity detecting device 10 includes an ultraviolet oxidation treatment device 11, a resistivity meter 12, and a dissolved oxygen meter 13. Use points 7 such as semiconductor factories
The pure water or ultrapure water supplied by the circle pipe 1 returns to the primary pure water tank 4 by the circle return pipe 2. Here, as impurities that may be mixed into the primary pure water tank 4 by the circle return pipe 2, for example, surfactants, alcohols such as methyl alcohol and isopropyl alcohol, hydrofluoric acid, ammonium fluoride, ammonium hydroxide, There are inorganic ions such as sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid and metal ions, and oxidizing agents and peroxides such as ozone and hydrogen peroxide.

In the present specification, “pure water” refers to 2
5 ° C conversion electric resistivity 10.0MΩ · cm or more, TOC
The number of fine particles having a concentration of 50 ppb or less and
Water having a high degree of cleanliness of less than particles / ml, and “ultra pure water” means that the electrical resistivity at 25 ° C. is 18.0 MΩ · cm or more,
Higher cleanliness water having a TOC concentration of 5 ppb or less and particles of 0.05 μm or more and 10 particles / ml or less.

A part of the water returned to the primary pure water tank 4 by the circle return pipe 2 is adjusted to a predetermined flow rate and supplied to the ultraviolet oxidation treatment device 11. The ultraviolet oxidation treatment device 11 generates OH radicals by irradiating water with ultraviolet light (wavelength λ = 185 nm), and a small amount of TO
The C component is oxidatively decomposed and changed into carbonate ions or organic acid ions.

In the case of peroxide (H ₂ O ₂ ), water is irradiated with ultraviolet rays (wavelength λ = 185 nm) to be decomposed into water and oxygen as shown by the following chemical formula.

H ₂ O ₂ → H ₂ O + ／ O ₂ = 2H ₂ O + O ₂ Here, the irradiation amount of ultraviolet rays is 0.2 kW or more, preferably 0.5 kW or more per 1 m ³ / h of water. However, if the power is 1.0 kW or more, it is too large considering the amount of impurities expected in the circle return pipe 2.
The optimum value is around kw. Further, the chamber capacity is determined by the residence time of the (ultra) pure water to be introduced, and is 1 second or more, preferably 2 seconds or more at the irradiation amount.

Thus, when there is impurity contamination in the pure water or ultrapure water returned to the primary pure water tank 4 by the circle return pipe 2, the impurity contamination in the pure water or ultrapure water occurs within about 5 seconds. Can be detected.

The resistivity (or conductivity) of the water irradiated with ultraviolet rays by the ultraviolet oxidation treatment device 11 is measured by the resistivity meter 12. By measuring the resistivity, it is possible to detect inorganic substances and organic compounds mixed in pure water or ultrapure water. Note that the resistivity meter 12 may be a conductivity meter.

In the water irradiated with ultraviolet rays by the ultraviolet oxidation apparatus 11, the dissolved oxygen is measured by a dissolved oxygen meter 13 to detect dissolved oxygen and peroxide mixed in pure water or ultrapure water. It is possible to do.

As a result, inorganic substances, dissolved oxygen, organic compounds, and peroxides contained in pure water or ultrapure water can be detected only by using the resistivity meter 12 and the dissolved oxygen meter 13. 4 TOC meter 15 and H ₂ O ₂
The monitor 16 can be omitted.

When impurities are detected by the impurity detecting device 10, the valve 8 provided on the return pipe 2 is closed and the valve 9 is opened to stop returning contaminated water to the primary pure water tank 4. Discharge this contaminated water to the outside. Thereby, even when impurities are mixed in the circle return pipe 2, it is possible to prevent the primary pure water tank 4 from being contaminated. The opening and closing of the valves 8 and 9 can be automatically performed based on a signal from the impurity detection device 10.

FIG. 2 is a diagram showing a method for decomposing an organic compound according to one embodiment of the present invention. In the embodiment shown in FIG. 2, isopropyl alcohol ((CH ₃ ) ₂ CHOH) will be described as an example of the organic compound to be decomposed.

In FIG. 2A, when water mixed with isopropyl alcohol ((CH ₃ ) ₂ CHOH) is irradiated with ultraviolet rays, OH radicals are generated, and these OH radicals act on OH groups of isopropyl alcohol. Thus, acetone (CH ₃ COCH ₃ ) shown in FIG. 2B is generated.

Next, in FIG. 2 (b), the OH radical generated by the irradiation of the ultraviolet rays acts on the CH ₃ group of acetone, so that the acetic acid (CH ₃ COO) shown in FIG.
H) is generated.

Next, in FIG. 2 (c), the OH radical generated by the irradiation of the ultraviolet rays is converted into acetic acid (CH ₃ COOH).
By acting on the carbon dioxide (CO 2) shown in FIG.
₂ ) and water (H ₂ O) are produced.

The acetic acid (C) produced in FIGS. 2 (c) and 2 (d)
H₃COOH) and carbon dioxide (CO ₂) Dissolve in water
This lowers the resistivity of water. Because of this, water
By measuring the resistivity of
Pill alcohol can be detected.

FIG. 3 is a block diagram showing a configuration example of an ultrapure water supply system according to an embodiment of the present invention. This ultrapure water supply system produces primary pure water by removing most of impurities such as ions, particles, and organic matter from raw water. Primary water system, further polishing the primary water to reduce impurities to the utmost. Secondary pure water system that manufactures purified ultrapure water and supplies it to each use point in the clean room,
And a recovery system that collects and reuses ultrapure water used for cleaning at each use point in the clean room.

In FIG. 3, raw water is introduced into a pretreatment device 21, and suspended substances and the like in the raw water are separated and removed. Next, the water to be treated that has been treated by the pretreatment device 21 is sent to the activated carbon adsorption device 22, where the organic matter contained in the water to be treated is decomposed. Next, the treated water from which the organic matter was decomposed is divided into two beds, three towers,
Sent to 3. The two-bed three-column 23 is provided with a cation exchange resin tower, a (vacuum) degassing tower and an anion-exchange resin tower, and the two-bed three tower 23 removes ionic components from the water to be treated. Next, the water to be treated from which the ionic components have been removed is introduced into the reverse osmosis device 24 to remove organic substances, fine particles, colloidal substances and the like.

Next, the water to be treated, from which organic substances, fine particles, colloidal substances and the like have been removed, is sent to a mixed-bed ion exchanger 25, where the ionic components in the water to be treated are removed, followed by vacuum degassing. The dissolved gas, mainly dissolved oxygen, is removed by the device 26 and stored in the primary pure water tank 27. The water to be treated stored in the primary pure water tank 27 is supplied to the heat exchanger 28.
The dissolved organic matter is introduced into the low-pressure ultraviolet oxidizer 29 through the process, and dissolved in the water to be treated. Next, the water to be treated in which the dissolved organic matter has been decomposed is sent to the non-regenerative polisher 30, where the ionic components in the water to be treated are removed. Next, the water to be treated from which the ionic components have been removed is introduced into the ultrafiltration membrane device 31 to remove trace amounts of fine particles and the like.

The ultrapure water thus produced is supplied to a use point (water sampling point) 32, and an excessive amount of ultrapure water is supplied to a primary pure water tank 27 through a return pipe 33.
Refluxed. Here, the impurity detection device 34 collects ultrapure water flowing through the return pipe 33 and measures impurities mixed in the ultrapure water. When the impurities mixed in the ultrapure water exceed the specified value, the valve 35 provided in the return pipe 33 is closed and the valve 36 is opened to discharge the contaminated water to the outside of the pure water production system. Water is prevented from being returned to the primary pure water tank 27. Further, the recovered water collected by the recovery device 37 is supplied to the activated carbon adsorption device 2.
2 and the recycled water is recycled.

[0033]

As described above, according to the present invention,
By decomposing organic compounds and peroxides with ultraviolet light, inorganic substances, dissolved oxygen, organic compounds and peroxides mixed in pure or ultrapure water can be obtained simply by using a conductivity meter (or resistivity meter) and a dissolved oxygen meter. Oxides and the like can be detected, and furthermore, these impurities can be detected in a short time of 5 seconds or less, and water pollution can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an impurity detection system according to an embodiment of the present invention.

FIG. 2 is a view showing a method for decomposing an organic compound according to one embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration example of an ultrapure water supply system according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional method for monitoring ultrapure water contamination.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circle piping 2, 33 Return piping 3 Primary pure water system 4 Primary pure water tank 5 Pump 6 Ultrapure water system 7, 32 Use point 8, 9, 35, 36 Valve 10, 34 Impurity detector 11, 29 Low pressure ultraviolet oxidation Treatment device 12 Resistivity meter 13 Dissolved oxygen meter 21 Pretreatment device 22 Activated carbon adsorption device 23 2 beds 3 towers 24 Reverse osmosis device 25 Mixed bed type ion exchange device 26 Vacuum deaerator 27 Primary pure water tank 28 Heat exchanger 30 Non Regenerative polisher 31 Ultrafiltration device 37 Recovery device

Continuing from the front page (72) Inventor Kim Seng-sung Sun 24, Nonseo-ri, Kifun-eup, Yongji-si, Gyeonggi-do, Republic of Korea (72) Inventor Hideo Takeuchi 2-9-8 Okada, Atsugi-shi, Kanagawa Nomura Micro-Science Incorporated (72) Inventor Mitsuhiro Jung 6-4 Songne-dong, Bundang-ku, Seongnam-si, Gyeonggi-do, Republic of Korea Nomura Korea Co., Ltd. F-term (reference) 2G060 AA06 AC04 AE16 AF07 AF08

Claims (2)

[Claims] An ultraviolet irradiation means for irradiating ultraviolet light to water containing at least one of an organic substance and a peroxide; an electric conduction measurement means for measuring conductivity or resistivity of the water irradiated with the ultraviolet light; An impurity detection device, comprising: dissolved oxygen measuring means for measuring dissolved oxygen in water irradiated with ultraviolet light. 2. a step of decomposing an organic substance and a peroxide contained in water based on ultraviolet irradiation, a step of measuring a conductivity or a resistivity of the water irradiated with the ultraviolet light, and the step of water irradiated with the ultraviolet light. Measuring the dissolved oxygen of the impurities.