JPH10202242A - Method for regulating specific resistance of ultrapure water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the regulating accuracy of specific resistant value by dividing the flow rate of a gaseous CO2 into the first flow rate content having a fixed flow rate corresponding to the fixed flow rate part of the flow rate of an ultrapure water and the second flow rate content having a varying flow rate corresponding to a residual flow rate part when the specific resistant value of the ultrapure water is regulated by dissolving the gaseous CO2 into the ultrapure water. SOLUTION: A part of the gaseous CO2 circulating in a cylindrical body 12 is penetrated and dissolved to the ultrapure water by penetrating a hydrophobic permeating membrane into a treating tank 11 in which the ultrapure water having the fixed flow rate is circulated. Then the specific resistant value of the ultrapure water is detected with a specific resistant value sensor 31 and solenoid valves 22a-22d are switched and controlled by a controller 32. In this case, one valve among each solenoid valve 22a-22d is always opened and remainders are controlled to be opened or closed, and the always opened solenoid valve is in charge of the first flow rate content of the gaseous CO2 and the remaining each solenoid valve is in charge of the second flow rate content of the gaseous CO2 , and the specific resistant value of the ultrapure water is regulated within a prescribed range by controlling in accordance with a flow rate variation of the ultrapure water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific resistance adjusting method for adjusting the specific resistance of ultrapure water by dissolving carbon dioxide gas in ultrapure water.

[0002]

2. Description of the Related Art Ultrapure water is used for cleaning a substrate in a semiconductor manufacturing process. If the specific resistance of the ultrapure water is high, static electricity is generated on the substrate and dielectric breakdown occurs on the substrate. And inconveniences such as adhesion of fine particles occur. For this reason,
It is preferable that the ultrapure water used as the cleaning water for the substrate is subjected to a specific resistance treatment before its use, so that the specific resistance value is adjusted to a predetermined range. As an example of a method for adjusting the specific resistance value of ultrapure water, there is a specific resistance adjustment method disclosed in Japanese Patent Publication No. 5-21841.

[0003] The method of adjusting the specific resistance is such that carbon dioxide gas is passed through a flow path formed of a hydrophobic permeable membrane provided with a hydrophobic carbon dioxide gas disposed in a processing chamber through which a constant flow of ultrapure water always flows. By allowing the carbon dioxide gas to flow through the hydrophobic permeable membrane constituting the flow passage, a part of the carbon dioxide gas is dissolved in the ultrapure water flowing in the processing chamber, and the specific resistance value of the ultrapure water is increased. How to adjust.

[0004]

In the specific resistance adjusting method, the purity of the ultrapure water is maintained by constantly flowing the ultrapure water in the processing chamber to prevent the stagnation in the processing chamber as much as possible. However, when using this method, the supply flow rate of ultrapure water fluctuates, so it is necessary to precisely control the flow rate of carbon dioxide gas to the flow passage in accordance with the fluctuation amount of ultrapure water. .

The control of the flow rate of the carbon dioxide gas requires high precision because the flow rate of the carbon dioxide gas supplied to the flow passage is very small, and means for proportionally controlling or opening and closing the control valve with high precision is employed. In this case, the flow rate control of the carbon dioxide gas is based on the total flow rate of the ultrapure water supplied into the processing chamber, and the control width is large and the control accuracy is not always good. For this reason, the adjustment accuracy of the specific resistance value of ultrapure water is
Not always good.

Accordingly, an object of the present invention is to improve the accuracy of adjusting the specific resistance value of ultrapure water in the specific resistance adjusting method.

[0007]

The present invention relates to a method for adjusting the resistivity of ultrapure water, and more particularly, to a method of adjusting the specific resistance of ultrapure water, which is disposed in a processing chamber through which a constant flow of ultrapure water flows constantly. The carbon dioxide gas flows through the flow path formed by the hydrophobic permeable membrane, and a part of the carbon dioxide gas passes through the hydrophobic permeable membrane forming the same flow path, so that the carbon dioxide gas flows into the ultrapure water flowing through the processing chamber. A specific resistance adjusting method for ultrapure water in which carbon dioxide gas is dissolved to adjust the specific resistance value of ultrapure water.

According to the present invention, in the above specific resistance adjusting method, the flow rate of the carbon dioxide gas flowing through the flow passage corresponds to a constant flow rate portion of the flow rate of the ultrapure water flowing through the processing chamber. It is divided into a first flow rate, which is a set constant flow rate, and a second flow rate, which is a variable flow rate set corresponding to the remaining flow rate part of the ultrapure water flow rate excluding the constant flow rate part. The second flow rate of the carbon dioxide gas is controlled in accordance with the remaining flow rate portion of the ultrapure water.

In the method for adjusting the resistivity of ultrapure water according to the present invention, the second flow rate of the carbon dioxide gas is reduced by 60 times the total flow rate.
% To 95%.

[0010]

In the method for adjusting the specific resistance of ultrapure water according to the present invention, the flow rate of carbon dioxide gas flowing through the flow passage in the processing chamber is set to a constant value of the flow rate of ultrapure water flowing through the processing chamber. A first flow rate (constant flow rate) set corresponding to the flow rate part and a second flow rate (variation) set corresponding to the remaining flow rate part of the ultrapure water flow rate excluding the constant flow rate part Flow rate)
And means for controlling the second flow rate of the carbon dioxide gas in accordance with the remaining flow rate portion of the ultrapure water.

Since the flow rate of the variable portion to be controlled by the ultrapure water is small, the control range of the flow rate of the carbon dioxide gas when the flow rate varies in the ultrapure water is small, and the specific resistance of the ultrapure water is reduced. The value adjustment accuracy can be improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(Specific Resistance Adjusting Apparatus) FIG. 1 shows an example of a specific resistance adjusting apparatus used for carrying out the method for adjusting the specific resistance of ultrapure water according to the present invention. The specific resistance adjusting device includes a processing tank 11 and a cylindrical body 12 formed of a hydrophobic permeable membrane provided in the processing tank 11. The treatment tank 11 constitutes the treatment chamber of the present invention, and the cylindrical body 12 constitutes the flow passage formed of the hydrophobic film of the present invention.
1 has an inlet connected to a supply pipe 13a of ultrapure water, an outlet connected to an outlet pipe 13b, and the cylinder 12 has a supply pipe for carbon dioxide gas at the inlet. The line 14a is connected, and the outlet line is connected to the outlet line 14b.

In the specific resistance adjusting apparatus, a gas flow rate adjusting mechanism 20 is interposed in a carbon dioxide supply pipe 14a, and an ultrapure water outflow pipe 13b is used for detecting a specific resistance value. A specific resistance value sensor 31 is provided. The gas flow control mechanism 20 includes four flow paths 21 parallel to each other.
a to 21d, and each of the flow paths 21a to 21d has an electromagnetic valve 22a to 22d and a gas filter 23a to
23d is interposed. Each electromagnetic valve 22a-22
d is an electromagnetic on-off valve, and each of the gas filters 23a to 23d has a different gas permeation amount. For example, when the permeation amount of the first gas filter 23a is 1, the second gas filter 23b Is 透過
The transmission amount of the third gas filter 23c is set to 1/4, and the transmission amount of the fourth gas filter 23d is set to 1/8.

In the gas flow adjusting mechanism 20, each electromagnetic valve 22 is controlled based on an operation signal from a controller 32.
The opening / closing operation of a to 22d is controlled to control the flow rate of the carbon dioxide gas into the cylinder 12, and the controller 32 controls each of the electromagnetic valves 22a to 22d based on a detection signal from the specific resistance sensor 31. An operation signal is output to the terminal.

(Specific Resistance Adjustment Method) In order to adjust the specific resistance value of ultrapure water using the specific resistance adjusting device, ultrapure water having a constant temperature, which is to be treated, is supplied through a supply pipe 13a. At a constant flow rate and into the treatment tank 11 and flow out through the outflow pipe 13b, and supply carbon dioxide into the cylinder 12 through the gas flow control mechanism 20 and through the gas outflow pipe 14b. Let out.

During this time, part of the carbon dioxide gas flowing through the cylindrical body 12 penetrates through the hydrophobic permeable membrane, enters the treatment tank 11 and dissolves in the ultrapure water, and sets the specific resistance of the ultrapure water to a predetermined value. To the value of During this time, the specific resistance value of the ultrapure water flowing out of the processing tank 11 is constantly detected by the specific resistance value sensor 31,
The controller 32 outputs an operation signal to each of the electromagnetic valves 22a to 22d based on the detection signal.
The supply amount of carbon dioxide into the cylinder 12 is appropriately controlled, and the specific resistance value of the ultrapure water is adjusted to a predetermined range.

According to the specific resistance adjusting method, each of the electromagnetic valves 22 constituting the gas flow rate adjusting mechanism 20 is used.
a to 22d are set to always open state,
Means for constantly supplying and circulating a predetermined amount of carbon dioxide into the cylinder 12 is adopted, and in consideration of the supply of such carbon dioxide, the gas flow rate adjusting mechanism 20 uses the carbon dioxide gas into the cylinder 11. A means for controlling the supply amount of the gas is employed.

That is, in the specific resistance adjusting method,
The flow rate of the carbon dioxide gas flowing through the cylinder 12 is equal to a first flow rate which is a constant flow rate set in accordance with a constant flow rate portion of the flow rate of the ultrapure water flowing through the processing chamber 11, and The second flow rate of the carbon dioxide gas is divided into a second flow rate which is a variable flow rate which is set corresponding to the remaining flow rate section excluding the constant flow rate section of the water flow rate. Means for controlling corresponding to the flow rate unit is adopted. The second flow rate of carbon dioxide is
It is in the range of 20% to 80% of the total flow rate of the carbon dioxide gas.

Therefore, in the gas flow rate adjusting mechanism 20, one of the electromagnetic valves 22a to 22d is always opened, and a means for controlling the opening and closing of the remaining electromagnetic valves is employed. The electromagnetic valves that are always open take charge of the first flow rate of carbon dioxide gas, the remaining solenoid valves take charge of the second flow rate of carbon dioxide gas, and these solenoid valves respond to fluctuations in the flow rate of ultrapure water. To control the flow rate of carbon dioxide gas.

As described above, according to the specific resistance adjusting method, the flow rate of the carbon dioxide gas flowing through the cylindrical body 12 in the processing chamber 11 is changed to the constant flow rate of the ultrapure water flowing through the processing chamber 11. The first flow rate (constant flow rate) that is set corresponding to the flow rate and the second flow rate (variable flow rate) that is set corresponding to the remaining flow rate part of the ultrapure water flow rate other than the constant flow rate part And means for controlling the second flow rate of the carbon dioxide gas in accordance with the remaining flow rate portion of the ultrapure water, so that the flow rate of the variable portion to be controlled by the ultrapure water is controlled. The control range of the flow rate of carbon dioxide gas when the flow rate fluctuation occurs in the ultrapure water is small, and the precision of the adjustment of the specific resistance value of the ultrapure water can be improved.

(Experiment) In this experiment, the specific resistance adjusting device shown in FIG. 1 was used, and the cylindrical body 12 formed of a hydrophobic permeable membrane made of polypropylene was used as the cylindrical body 12. An experiment was conducted to adjust the specific resistance of.

In this experiment, ultrapure water having a water temperature of 25.3 ° C. and a specific resistance of 17.5 MΩ · cm was used.
The inside of the processing chamber 11 is caused to flow at a flow rate of 2 l / min, and carbon dioxide gas is supplied at a pressure of 0.8 kg / cm ² during the gas supply line 1.
4a and supplied into the cylindrical body 12 to adjust the specific resistance of the ultrapure water to 0.1 MΩ · cm. During this time, the flow rate of the ultrapure water was reduced by reducing the flow rate of the ultrapure water from 12 l / min for 2 minutes to 2 l / min for 3 minutes and returning the flow rate to 12 l / min for 2 minutes.

The specific resistance value sensor 31 is connected to the outflow line 1.
It is installed 400 mm downstream from the connection on the processing tank 11 side in 3b.

In this experiment, the first control method for controlling the opening and closing of all the electromagnetic valves 22a to 22d constituting the gas flow rate adjusting mechanism 20, the first electromagnetic valve 22a is always opened, and the remaining electromagnetic valves are opened. Two control methods, a second control method for controlling the opening and closing of 22b to 22d, were adopted.
When the first electromagnetic valve 22a is always opened, the carbon dioxide gas pressure is 0.8 kg / cm ² and the flow rate is 60 cc / m 2.
in.

In the second control method, a flow rate of 2 l / min of the flow rate of the ultrapure water flowing through the processing chamber 11 is set as a constant flow rate section, and a flow rate of 90 cc / min, which is a flow rate of carbon dioxide gas corresponding thereto, is set. The flow rate is set so as to be supplied through the first electromagnetic valve 22a, and the remaining flow rate part of the ultrapure water flow rate, excluding the constant flow rate part, is set to a flow rate of 10 l / min, and the flow rate of the corresponding carbon dioxide gas is 350 cc / min. The flow rate of min is set to be supplied in a controlled manner through the second electromagnetic valve 22b to the second electromagnetic valve 22d.

In these two control methods, the fluctuation state of the specific resistance value when the flow rate of the ultrapure water changes is shown in FIG.
This is shown in the graphs of (a) and (b). In these graphs, the graph shown in FIG. 3A shows the case of the second control method, and the graph shown in FIG. 3B shows the case of the first control method. As described above, in the case of the second control method shown in FIG. This means that, when the second control method is adopted, the fluctuation range of the carbon dioxide gas supply amount can be made smaller than when the first control method is adopted, and the specific resistance value of the ultrapure water can be more accurately determined. It means that you can adjust well.

When the flow rate of the ultrapure water is 2 l / min, the fluctuation of the specific resistance is measured by supplying carbon dioxide gas, measuring the specific resistance value, further supplying carbon dioxide gas, measuring the specific resistance value, and further measuring the specific resistance value. This is a hunting of the operation of changing the gas supply amount. This is a phenomenon that occurs when the flow rate of ultrapure water is small. Generally, when the flow rate of ultrapure water fluctuates, the specific resistance value of the ultrapure water temporarily fluctuates, but immediately returns to the set specific resistance value and becomes constant.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a specific resistance adjusting device used for performing a specific resistance adjusting method of ultrapure water according to the present invention.

FIG. 2 is a graph showing the amount of change in the specific resistance value in the method of adjusting the specific resistance of ultrapure water. FIG. 2 (a) shows the control of carbon dioxide gas with the remaining flow rate other than a constant flow rate of ultrapure water being controlled. FIG. 3B shows the state of the variation of the specific resistance value when the carbon dioxide gas amount is controlled based on the total amount of the supplied ultrapure water.

[Explanation of symbols]

11: treatment tank, 12: cylindrical body, 13a: water supply pipe, 13
b ... water outflow line, 14a ... gas supply line, 14b ... gas outflow line, 20 ... gas flow rate adjustment mechanism, 21a-21d ...
Channels, 22a to 22d ... electromagnetic valves, 23a to 23d ...
Gas filter, 31: specific resistance value sensor, 32: controller.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI G05F 1/00 G05F 1/00 Z H01L 21/304 341 H01L 21/304 341S

Claims (2)

[Claims] A carbon dioxide gas is circulated through a flow passage formed by a hydrophobic permeable membrane, which is provided in a processing chamber and constantly passes a ultra-pure water at a constant flow rate and is permeable to carbon dioxide gas. Ultrapure water that adjusts the specific resistance value of ultrapure water by dissolving carbon dioxide in ultrapure water flowing through the processing chamber by allowing a part of the gas to permeate through the hydrophobic permeable membrane forming the flow passage In the specific resistance adjusting method, the flow rate of the carbon dioxide gas flowing through the flow passage is a constant flow rate set in accordance with a constant flow rate portion of the flow rate of the ultrapure water flowing through the processing chamber. The second flow rate of the carbon dioxide gas is divided into a flow rate part and a second flow rate part which is a variable flow rate set corresponding to the remaining flow part except the constant flow part of the ultrapure water flow rate. The ratio of ultrapure water, wherein the ratio is controlled according to the remaining flow rate of the ultrapure water Anti-adjustment method. 2. A method according to claim 1, wherein the second flow rate of said carbon dioxide gas is reduced to 6 times the total flow rate.
A method for adjusting the specific resistance of ultrapure water, wherein the specific resistance is 0% to 95%.