JPS58105042A - Detecting and measuring means for methyl alcohol in reutilization system for waste water obtained through cleansing wafer - Google Patents

Abstract

PURPOSE:To measure a very small quantity of methyl alcohol in regenerated ultrapure water continuously in a short time, by mixing the regenerated ultrapure water with an I2 solution of prescribed concentration, and by measuring the absorption strength thereof at the absorption peak in an ultraviolet region by a spectroscopic method. CONSTITUTION:A sample which is introduced into a sampling unit 2 from a regenerated ultrapure water tank, etc. by a pump 1 and led therefrom into a reaction tank 4 by a weighing pump 3 is mixed with a prescribed quantity of iodine solution which is led from an iodine solution tank 5 by a weighing pump 6. The sample thus mixed is introduced into a flow cell 8 made of quartz by a weighing pump 7 and the absorption strength thereof at the absorption peak of a complex substance is measured by a spectroscopic method. The result of measurement is transduced into an electric signal, and the signal is amplified and recorded. When the measurement is ended, solenoid valves 9, 10, 12 and 13 are opened, and the reaction tank 4 and the flow cell 8 are cleansed with cleansing water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the provision of a novel means for detecting and measuring methyl alcohol in a wafer cleaning wastewater reuse system.

Recently, in semiconductor manufacturing factories, there has been a trend toward sound treatment and reuse of wafer cleaning wastewater in order to reduce the amount of factory wastewater as a measure to conserve water or to regulate the total amount of factory wastewater.

Cleaning wastewater from semiconductor manufacturing factories has various properties depending on the cleaning process, but in particular, the system for reusing methyl alcohol cleaning wastewater discharged from the degreasing process is almost the current state of the art as a water supply technology. However, the establishment of water quality management technology remains a technical FIA issue.

In particular, it is desired to establish a detection and measurement technology for extremely violet methyl alcohol in reused water.In other words, the water quality required for ultrapure water used as reused water in semiconductor manufacturing processes is of a high grade. Water quality management indicators include specific resistance (MΩ), number of fine particles (α2μm or less/m+4), number of microorganisms (number/mt), and organic matter concentration.

In general, water often contains organic matter, which is a component of food, and it is difficult to know the concentration of each component.Ninth, as a water quality management index regarding organic matter concentration,
Organic? 'f'Oc as an indicator to be displayed comprehensively in l'
(total organic carbon) is used. First, this is sent into a tube filled with a high temperature oxidation catalyst together with a small amount of sample water t-oxygen (or friendly air excluding carbon dioxide), and organic carbon and inorganic carbon are removed. After converting carbon to carbon dioxide, its concentration is measured using a non-dispersive infrared gas analyzer to determine total carbon [(TC)
On the other hand, separately test the water tππ and send it to an oxidation catalyst-filled tube maintained at a flow rate that does not decompose the initial product, and collect the generated carbon dioxide i
Determine inorganic carbon (IC) k by measuring tk.

The TOC is obtained by subtracting the total IC from the TC.

A recycling system for methyl alcohol cleaning waste water in wafer cleaning is generally as shown in FIG.

Whether methyl alcohol has been removed or not is determined by sampling water from the latter part of the water supply system in the diagram and determining the TOC value using a 'roc measuring device in the laboratory, as an alternative indicator of methyl alcohol concentration.

However, this method has the disadvantage that it takes a long time to obtain the measurement results, and that the recycled ultrapure water from the treatment cannot be reused quickly in the water supply system.

From this point of view, when recycled ultrapure water is used in the manufacturing process, it is desirable to monitor water quality using a continuous and automated measuring device.

For TOC measurement, there are continuous automated measuring machines,
With this method, it is difficult to accurately measure 2 ppm or less as '1' OC, so it is not used in the above-mentioned recycled ultrapure water system.

In the above-mentioned reuse cycle, the substances contained in the wastewater can be considered to be methyl alcohol, so it is sufficient to be able to accurately measure methyl alcohol, so high-performance liquid chromatography as a method for measuring methanol,
Analytical chemical means such as gas chromatography can be considered, but these methods are time-consuming and lack continuity, making them difficult to use for process control.

Spectroscopic measurement is available as a method with excellent continuity and accuracy, and currently there is no device that spectroscopically measures the total concentration of methyl alcohol itself in water.

The present invention was developed in view of the actual situation of restriction, and since it is 7f%, the above-mentioned methyl alcohol cleaning waste water can be reused! In the first cycle, a very small amount of methyl alcohol (TO
We have developed a complete method that can continuously measure up to 2' Ppm or less (as a C equivalent value) in a short period of time.

The present invention will be explained in detail below.

That is, in the present invention, trace amounts of methyl alcohol in regenerated ultrapure water in the methanol cleaning wastewater recycling system in the semiconductor manufacturing process shown in FIG. 1 are spectroscopically measured.

The principle is: [)H1I HQHI ■ 2 ← 2 HOHI2+CL (80H2fl)H+CH,OHI,
As shown in the formula (2), iodine in water forms a complex, 7jf()HI, shown in formula 0. When a liquid containing (hereinafter referred to as ``■'' and ``<'') is mixed, a charge transfer complex of CH, 0f (I2 as shown in the formula ``■'' is formed because CH2O() has a greater electron-donating property than HOH.

Spectroscopically, this w-transfer complex shows total absorption in the ultraviolet region,
The absorption intensity is determined by the optical density of the CH30f-II2 complex shown in Fig. 2 and Cf (80f (which is obvious from the graph of the concentration relationship, C contained in the solution) 1.01 (depending on the concentration, As OH,01( increases, its absorption intensity increases.

Moreover, as shown in the same figure, it was found that CH, CI (has linearity up to 4 ppm at 1 ■ Kanji concentration, and is 21 as TOO) can be detected up to 9 m.
According to this method, it is possible to achieve Cf(, (E) of 2 ppm or less, which is difficult to achieve with conventional continuous automated TOC measuring instruments.

Therefore, CH301 ('t-) in recycled ultrapure water can be detected by mixing the recycled ultrapure water with a certain m degree of I solution, and using a spectroscopic method to detect the absorption at the absorption maximum wavelength in the di-ultraviolet region. All that is needed is to measure the strength.

An example of the configuration of a measuring device based on this principle is shown in FIG.

That is, in the figure, the sample is introduced from a regenerated ultrapure water tank or the like into a sample collector 2 by a pump 1, and then led to a reaction tank 4 by a weighing pump 3. Mixed with iodine solution.

The mixed sample is introduced into a diquartz flow cell 8 by a weighing pump 7, and the absorption intensity is measured at the complex absorption maximum wavelength by a spectroscopic method, and the original absorption intensity is converted into an electrical signal, amplified, and recorded.

When the measurement is completed, the solenoid valve 9. IO opens, the reaction tank 4 and flow cell 8 are washed with washing water, and the 11ta valve 9,
10, 12, and 1.3 are all closed, all operations are completed, and the next measurement is performed.

According to the present invention as on paper, the predetermined f'p1
Since it is possible to measure the methanol concentration at
It is suitable as a new water quality control means in a methanol cleaning wastewater reuse system in a semiconductor manufacturing factory.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a system for reusing methyl alcohol cleaning wastewater in wafer cleaning, Fig. 2 is a graph showing the relationship between the optical density of CH30HI2 complex and 0H80H concentration, and Fig. 3 shows an example of the configuration of the measuring device of the present invention. It is a diagram. 2... Sample collector 4... Reaction tank 5... Iodine solution tank 8... Inventor of quartz flow cell
Takehiko Tazawa Applicant Representative Takenaka Corporation Osamu Takenaka −

Claims (2)

[Claims] (1) A solution containing a very small amount of methyl alcohol and a solution containing iodine are mixed to produce CHIOHI2, a charge transfer complex that spectroscopically shows absorption in the ultraviolet region, and this is analyzed spectroscopically. By measuring the absorption intensity at the thickest absorption wavelength in the ultraviolet region, we have already determined that the methyl alcohol concentration can be determined from the relationship between the optical sound intensity of the OF(B OHI 2 complex) and the C0aOH isoformity. A method for measuring methyl alcohol in a wafer cleaning wastewater reuse system. (2) A reaction tank that receives a sample from a regenerated ultrapure water tank, etc. and receives iodine solution &ffi from an iodine solution tank, and a reaction tank that receives a mixed sample from the reaction tank and absorbs it in the ultraviolet region using a full spectroscopic method. It is characterized by consisting of a measurement device that measures the absorption intensity at the maximum wavelength, converts it into an all-electric signal, amplifies and records it, and a Kutani cleaning device that accommodates the mixed sample phase. A methyl alcohol measuring device in a wafer cleaning wastewater reuse system which is directly used in carrying out the invention according to claim 7.