Cleaning water manufacturing device and cleaning water manufacturing method

Abstract

To provide a cleaning water manufacturing device and a cleaning water manufacturing method capable of following fluctuations in amount of water used in a post-stage device without lowering a dissolved gas concentration of gas-dissolved water, and capable of reducing generation of excess water.SOLUTION: A cleaning water manufacturing device comprises: a deaeration membrane module configured to deaerate ultrapure water; a gas dissolving membrane module configured to dissolve gas in deaerated water from the deaeration membrane module; at least one of a dissolved gas concentration detection sensor configured to detect a dissolved gas concentration of the gas dissolving water and a gas pressure detection sensor configured to detect a pressure of gas supplied to the gas dissolving membrane module; a gas dissolving water supply line configured to supply the gas dissolving water from the gas dissolving membrane module to a use point; and a circulation line for refluxing the gas dissolving water from the gas dissolving water supply line to a downstream side of the gas dissolving membrane module and an upstream side of the dissolving membrane module.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for producing cleaning water for semiconductor wafers, etc., by dissolving gases such as pH adjusters and oxidation-reduction potential adjusters in ultrapure water, and in particular to an apparatus and method for producing cleaning water that are suitable for producing dilute cleaning water containing solutes such as pH adjusters and oxidation-reduction potential adjusters at very low concentrations. [Background technology]

[0002] In the cleaning and rinsing water process for semiconductor wafers, dilute water quality-adjusted water, in which an acid or alkaline pH adjuster or an oxidation-reduction potential adjuster such as an oxidizing agent or reducing agent is dissolved in ultrapure water at a very low concentration, the minimum necessary, is sometimes used as cleaning water (including rinsing water) for the purpose of suppressing wafer charging, metal corrosion and dissolution, and particle adhesion (see, for example, Patent Document 1). Fluctuations in the solute concentration of cleaning water can lead to deterioration of the cleaning ability of semiconductor materials and corrosion, so cleaning water of the desired concentration must be stably supplied to downstream equipment (such as a cleaning machine, CMP equipment, or wafer bonding equipment).

[0003] One method for producing dilute cleaning water is to dissolve reducing, oxidizing, acidic, or alkaline gases such as H2, O3, CO2, NH3, N2, or O2 in ultrapure water depending on the application.

[0004] When dissolving gases in ultrapure water, it is easy to achieve the desired solute concentration if the flow rate of ultrapure water is constant. However, in downstream equipment where cleaning water is actually used, the supply and stop of water poured onto the wafer is controlled by opening and closing multiple valves, causing the flow rate to fluctuate irregularly.

[0005] To counter these fluctuations, various methods of dissolution control are used to keep the solute concentration of the diluted cleaning water within a desired range, such as proportional control of the ultrapure water flow rate and PID control based on concentration monitor signals. However, particularly in single-wafer cleaning machines with multiple cleaning chambers, dissolution control that can adequately track irregular flow rate fluctuations has not been achieved, and as a result, the quality of the cleaning water and rinse water poured onto the wafers has remained controlled within a wide range that is far from ideal.

[0006] One simple method would be to prioritize stabilizing the liquid quality and continue to produce and supply diluted cleaning water under constant conditions, but in this case, excess water would simply be discharged.In recent multi-chamber single-wafer cleaning machines, there is a large difference between the maximum and minimum flow rates required at any given time, and if diluted functional water is continuously supplied at the maximum flow rate, a considerable amount of excess water will be discharged, which will cause problems in terms of burdening the water and drainage facilities and excessive use and discharge of chemicals.

[0007] To avoid discharging such excess water, one method is to provide a primary storage tank within the cleaning water production equipment or between the cleaning water production equipment and downstream equipment. However, if gas-dissolved water is stored in the storage tank, the concentration of dissolved gases will decrease over time, causing a decline in the cleaning performance of the cleaning water.

[0008] One known method for reducing excess water is to return unused wash water from downstream equipment (point-of-use) to the primary side of the wash water production equipment. In this case, the solutes contained in the excess water must be completely removed, requiring a treatment system for the excess recovered water, either within the wash water production equipment or separately from the equipment. This leads to an increase in the size of the equipment and excessive use of gases used for the solutes. Furthermore, because excess water is usually returned via a return pipe branched just before the downstream equipment, the dissolved gas concentration drops significantly as it returns from the downstream equipment to the wash water production equipment, making it difficult to reuse the excess water as is.

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-139766 Summary of the Invention [Problem to be solved by the invention]

[0010] When the amount of water used by downstream equipment fluctuates greatly, the produced gas-dissolved water may be temporarily stored in a tank, but the partial pressure of the gas in the gas-dissolved water gradually changes in proportion to the partial pressure of the gas filling the tank. Therefore, even if the target gas is dissolved in ultrapure water up to the saturated gas solubility, the dissolved gas concentration will gradually decrease when stored in a tank.

[0011] The present invention aims to provide a cleaning water producing apparatus and a cleaning water producing method that can follow fluctuations in the amount of water used in downstream equipment without reducing the dissolved gas concentration in the gas-dissolved water, and that can reduce the generation of excess water. [Means for solving the problem]

[0012] The gist of the present invention is as follows.

[0013] [1] A degassing membrane module that degasses ultrapure water; a gas dissolving membrane module that dissolves gas in the degassed treated water from the degassing membrane module; at least one of a dissolved gas concentration detection sensor for detecting the dissolved gas concentration of the gas-dissolved water and a gas pressure detection sensor for detecting the pressure of the gas supplied to the gas-dissolved membrane module; a gas-dissolved water supply line that supplies the gas-dissolved water from the gas-dissolved membrane module to a point of use; a circulation line for returning the gas-dissolved water from the gas-dissolved water supply line to the downstream side of the gas degassing membrane module and the upstream side of the dissolution membrane module; A cleaning water producing device comprising:

[0014] [2] The cleaning water producing apparatus according to [1], wherein the flow rate of the gas supplied to the gas-dissolving membrane module is increased when the detection value of the sensor falls below a predetermined value.

[0015] [3] The cleaning water producing device of [1], wherein when the detection value of the sensor falls below a predetermined value, the flow rate of the gas supplied to the gas-dissolved membrane module is increased so that the dissolved gas concentration in the gas-dissolved water becomes 1 to 20 ppm.

[0016] [4] The cleaning water producing apparatus according to [1], wherein the sensor is a dissolved gas concentration detection sensor provided in the gas-dissolved water supply line.

[0017] [5] The cleaning water producing device according to [1], wherein the pressure of the gas supplied to the gas-dissolved membrane module is increased when the detection value of the sensor falls below a predetermined value.

[0018] [6] The cleaning water producing apparatus according to [1], wherein the sensor is a gas pressure detection sensor provided in a gas supply line that supplies gas to the gas dissolution membrane module.

[0019] [7] The cleaning water producing apparatus according to any one of [1] to [6], wherein the gas contains at least one of nitrogen and hydrogen.

[0020] [8] Ultrapure water is degassed using a degassing membrane module. a step of dissolving gas in the degassed treated water from the degassing membrane module using a gas dissolution membrane module; supplying the gas-dissolved water from the gas-dissolved membrane module to a point of use through a gas-dissolved water supply line; a step of returning the gas-dissolved water from the gas-dissolved water supply line to the upstream side of the gas-dissolved membrane module and the downstream side of the degassing membrane module according to the amount of the gas-dissolved water used at the point of use; A cleaning water producing method comprising: [Effects of the Invention]

[0021] In the present invention, the produced gas-dissolved water is circulated within the cleaning water production apparatus while the dissolved gas concentration or the gas pressure supplied to the gas-dissolved membrane module is monitored. By dissolving additional gas to compensate for the decrease in the concentration of the gas-dissolved water during circulation, it is possible to suppress the decrease in the concentration of the gas-dissolved water and reduce the amount of excess water produced. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a configuration diagram of a cleaning water producing device according to an embodiment. [Figure 2] 1 is a configuration diagram of a cleaning water producing device according to an embodiment. [Figure 3] 1 is a configuration diagram of a cleaning water producing device according to an embodiment. [Figure 4] 1 is a configuration diagram of a cleaning water producing device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in further detail below.

[0024] In the present invention, cleaning water of a certain concentration is produced by dissolving a gas such as a pH adjusting gas, a redox potential adjusting gas, or an inert gas such as nitrogen gas in ultrapure water.

[0025] Examples of pH adjusting gases include, but are not limited to, acidic gases such as CO2, HF, HCl, HBr, HI, Cl2, H2S, SO2, and NO2, and alkaline gases such as NH3, dimethylamine, trimethylamine, and ethylamine. Examples of oxidation-reduction potential adjusting gases include oxidizing substances such as H2O2, O3, and O2, H2, CO, and hydrocarbon gases (CH4, C3H8, C4H 10 Examples of reducing substances include, but are not limited to, nitrogen, argon, and helium. Examples of inert gases include, but are not limited to, nitrogen, argon, and helium.

[0026] The upper limit of the concentration of the above gas components in the produced cleaning water is usually 50 ppm or less, preferably 45 ppm or less. The lower limit of the concentration of the above gas components is usually 1 ppm or more, preferably 1.2 ppm or more. When the concentration is within the above range, the properties of the cleaning water can be stabilized.

[0027] In one aspect of the present invention, the gas is nitrogen or hydrogen, and the upper limit of the nitrogen or hydrogen concentration at the outlet of the cleaning water producing apparatus is usually 20 ppm or less, preferably 18 ppm or less. The lower limit of the nitrogen or hydrogen concentration is usually 1 ppm or more, particularly preferably 1.2 ppm or more. When it is within the above range, the properties of the cleaning water can be stabilized.

[0028] Conventional gas dissolution mechanisms can be used to dissolve gases in ultrapure water to a desired solute concentration by gas-liquid contact using a gas-permeable membrane module or an ejector. It is preferable to degas the ultrapure water before dissolving the gas. A membrane degasser or the like can be used as the degasser.

[0029] The produced gas-dissolved water is sent to a downstream device as a point-of-use. While the gas-dissolved water is being used in the downstream device, the amount of gas-dissolved water produced is adjusted to match the amount of water used in the downstream device to prevent excess water from being generated. At this time, the dissolved gas concentration is controlled using various methods, such as proportional control of the ultrapure water flow rate and PID control based on the signal from the concentration monitor.

[0030] Furthermore, the amount of dissolved gas water used in the downstream equipment may sometimes reach zero. During this time, the produced dissolved gas water cannot be sent to the downstream equipment, so the surplus dissolved gas water is circulated within the cleaning equipment using a circulation line within the cleaning water production equipment. At this time, the longer the circulation time, the lower the dissolved gas concentration of the dissolved gas water, so it is desirable to monitor the dissolved gas concentration with a dissolved gas monitor and dissolve additional gas to make up for the decrease.

[0031] Depending on the type of gas, a diaphragm-type dissolved gas concentration meter, pressure meter, conductivity meter, etc. can be used as a dissolved gas monitor.

[0032] FIG. 1 shows an example of a cleaning water producing apparatus according to the present invention.

[0033] The ultrapure water flows through pipe 1, valve 2, degassing membrane module 3, pipe 4, gas dissolution membrane module 5, pipe 6, and valve 7 in that order, becoming gas-dissolved water, which is then sent to a downstream device. Pipe 6 and pipe 4 are connected by circulation pipe 8, which is equipped with a valve 9 and a circulation pump (not shown).

[0034] The degassing membrane module 3 is separated into a liquid phase chamber 3a and a gas phase chamber 3b by a degassing membrane 3m, and ultrapure water is passed through the liquid phase chamber 3a. By reducing the pressure in the gas phase chamber 3b with a vacuum pump 11, gas components in the ultrapure water flowing through the liquid phase chamber 3a permeate into the gas phase chamber 3b and are degassed.

[0035] The gas-dissolving membrane module 5 has a liquid-phase chamber 5a and a gas-phase chamber 5b separated by a gas-permeable membrane 5m, and ultrapure water is passed through the liquid-phase chamber 5a. A gas containing H2 or N2 or the like is supplied to the gas-phase chamber 5b via piping 12, and the gas permeates the gas-permeable membrane 5m and dissolves in the ultrapure water in the liquid-phase chamber 5a. The concentration of H2 or N2 in the gas supplied to the gas-dissolving membrane module 5 is preferably 99.99% or higher, and particularly 99.999% or higher. Examples of components in the gas other than H2 or N2 include N2, O2, CO, CO2, HO, hydrocarbons, etc.

[0036] The pipe 6 is provided with a dissolved gas monitor 13 as a sensor for measuring the gas concentration in the ultrapure water in which the gas is dissolved.

[0037] The pipe 8 branches off from the downstream side of the dissolved gas monitor 13 (on the side of the on-off valve 7).

[0038] When cleaning water is produced using the cleaning water production apparatus configured in this manner, valves 2 and 7 are opened and on-off valve 9 is closed when gas-dissolved water is to be sent to the downstream device. In this case, the H2 or N2 concentration in the gas supplied from pipe 12 to gas-dissolved membrane module 5 or the gas pressure supplied to gas-dissolved membrane module 5 is controlled so that the dissolved gas concentration detected by dissolved gas monitor 13 becomes a predetermined concentration.

[0039] In one embodiment of the present invention, when the gas concentration detected by the dissolved gas monitor 13 falls below a predetermined value, the flow rate of the gas supplied to the gas-dissolved membrane module 5 is increased. The upper limit of the dissolved gas concentration in the gas-dissolved water is usually 20 ppm or less, preferably 18 ppm or less. The lower limit of the dissolved gas concentration in the gas-dissolved water is usually 1 ppm or more, preferably 1.2 ppm or more. When the concentration is within the above range, the properties of the cleaning water can be stabilized.

[0040] In another embodiment of the present invention, when the gas concentration detected by the dissolved gas monitor 13 falls below a predetermined value, the pressure of the gas supplied to the gas-dissolved membrane module 5 is increased.

[0041] When gas-dissolved water is not to be sent to the downstream device, valves 2 and 7 are closed, on-off valve 9 is opened, and the circulation pump in pipe 8 is operated to circulate the gas-dissolved water through pipe 4, gas-dissolved membrane module 5, and pipes 6 and 8. In this case as well, the gas concentration or gas pressure supplied from pipe 12 to gas-dissolved membrane module 5 is controlled so that the dissolved gas concentration detected by dissolved gas monitor 13 becomes a predetermined concentration.

[0042] 2 shows another embodiment. In this embodiment, a flow meter 14 is installed in pipe 6 upstream of the branch point of pipe 8. Also, an opening adjustment valve is installed as valve 2.

[0043] In this cleaning water production apparatus, the gas-dissolved water is either fed to or circulated in the downstream equipment depending on the amount of gas-dissolved water used in the downstream equipment, in the same manner as in the cleaning water production apparatus of Fig. 1. When supplying the gas-dissolved water to the downstream equipment, valves 2 and 7 are opened and valve 9 is closed. When circulating the gas-dissolved water through pipe 4, gas-dissolved membrane module 5, and pipes 6 and 8, valves 2 and 7 are closed, valve 9 is opened, and the circulation pump in pipe 8 is operated.

[0044] In this embodiment, similarly to the case of FIG. 1, the concentration of H2 or N2 in the gas supplied to the gas dissolved membrane module 5 is controlled or the gas pressure is controlled according to the gas concentration detected by the dissolved gas monitor 13.

[0045] In the cleaning water production apparatus of Figure 2, when the amount of gas-dissolved water being circulated decreases, the opening of valve 2 can be adjusted to supply ultrapure water to the degassing membrane module 3 to compensate for the decrease, thereby producing new gas-dissolved water and replenishing the gas-dissolved water.

[0046] 1 and 2, a dissolved gas monitor 13 is installed in the pipe 6 as a sensor, but instead of or in addition to that, a pressure sensor for detecting gas pressure may be installed in the pipe 12. When the gas pressure falls below a predetermined value, the flow rate of gas supplied to the gas-dissolved membrane module 5 is increased to increase the pressure of the gas-dissolved water. For example, when the pressure of the gas-dissolved water becomes negative, the flow rate of gas supplied to the gas-dissolved membrane module 5 is increased to increase the pressure of the gas-dissolved water.

[0047] In the present invention, as shown in Figures 3 and 4, a buffer tank 20 may be provided midway along the pipe 6. It is more preferable to have a buffer tank 20. In Figures 3 and 4, a mass flow controller 21 is provided in the pipe 12, and a booster pump 22 is provided in the pipe 8. It is more preferable to have these. The other configurations in Figures 3 and 4 are the same as those in Figures 1 and 2, and the same reference numerals indicate the same parts. [Explanation of symbols]

[0048] 2, 7, 9 valves 3. Degassing membrane module 5. Gas dissolution membrane module 13 Dissolved Gas Monitor 14 Flow meter

Claims

1. a degassing membrane module that degasses ultrapure water; a gas dissolving membrane module that dissolves gas in the degassed treated water from the degassing membrane module; at least one of a dissolved gas concentration detection sensor for detecting the dissolved gas concentration of the gas-dissolved water and a gas pressure detection sensor for detecting the pressure of the gas supplied to the gas-dissolved membrane module; a gas-dissolved water supply line that supplies the gas-dissolved water from the gas-dissolved membrane module to a point of use; a circulation line for returning the gas-dissolved water from the gas-dissolved water supply line to the downstream side of the gas degassing membrane module and the upstream side of the dissolution membrane module; A cleaning water producing device comprising:

2. 2. The cleaning water producing apparatus according to claim 1, wherein the flow rate of the gas supplied to the gas-dissolved membrane module is increased when the detected value of the sensor falls below a predetermined value.

3. 2. The cleaning water producing apparatus of claim 1, wherein when the detected value of said sensor falls below a predetermined value, the flow rate of the gas supplied to said gas-dissolved membrane module is increased so that the dissolved gas concentration in the gas-dissolved water becomes 1 to 20 ppm.

4. 2. The cleaning water producing apparatus according to claim 1, wherein the sensor is a dissolved gas concentration detection sensor provided in the gas-dissolved water supply line.

5. 2. The cleaning water producing apparatus according to claim 1, wherein the pressure of the gas supplied to the gas-dissolved membrane module is increased when the detected value of the sensor falls below a predetermined value.

6. 2. The cleaning water producing apparatus according to claim 1, wherein the sensor is a gas pressure detection sensor provided in a gas supply line that supplies gas to the gas dissolution membrane module.

7. 7. The cleaning water producing apparatus according to claim 1, wherein the gas contains at least one of nitrogen and hydrogen.

8. Ultrapure water is degassed using a degassing membrane module, a step of dissolving gas in the degassed treated water from the degassing membrane module using a gas dissolution membrane module; supplying the gas-dissolved water from the gas-dissolved membrane module to a point of use through a gas-dissolved water supply line; a step of returning the gas-dissolved water from the gas-dissolved water supply line to the upstream side of the gas-dissolved membrane module and the downstream side of the degassing membrane module according to the amount of the gas-dissolved water used at the point of use; A cleaning water producing method comprising:

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