Filter cleaning method

Abstract

Provided is a filter cleaning method capable of effectively reducing particles generated from an unused filter. The filter cleaning method comprises: a first cleaning step in which a fluororesin filter is cleaned with ozone water as a first cleaning solution; and a second cleaning step for cleaning the filter after the first cleaning step with an acid-containing solution or an alkali-containing solution as a second cleaning solution.

Description

Technical Field

[0001] This invention relates to a filter cleaning method. Background Technology

[0002] Filters used in the silicon wafer cleaning process for cleaning silicon wafers are known (e.g., see Patent Document 1).

[0003] Existing technical documents Patent documents Patent document 1: Japanese Patent Application Publication No. 2015-139734. Summary of the Invention

[0004] The problem that the invention aims to solve When using unused filters for cleaning silicon wafers, it is preferable to reduce the amount of metal particles generated from the filters beforehand.

[0005] Therefore, the purpose of this invention is to provide a filter cleaning method that can effectively reduce particles generated by a filter that has never been used.

[0006] Methods used to solve problems One technical solution of the present invention is as follows.

[0007] [1] A filter cleaning method comprising: a first cleaning step of cleaning a fluororesin filter with ozone water as a first cleaning solution; and a second cleaning step of cleaning the filter after the first cleaning step with an acidic or alkaline solution as a second cleaning solution.

[0008] [2] In the filter cleaning method described in [1], the ozone concentration of the first cleaning liquid in the first cleaning step is 5 ppm or more and 40 ppm or less, and the flow rate of the first cleaning liquid in the first cleaning step is 2 L / min or more and 20 L / min or less.

[0009] [3] In the filter cleaning method described in [1] or [2], the first cleaning solution is passed through the filter for more than 1 hour in the first cleaning step.

[0010] [4] The filter cleaning method as described in any one of [1] to [3], wherein the second cleaning solution is hydrofluoric acid or an aqueous solution containing ammonia and hydrogen peroxide.

[0011] [5] The filter cleaning method as described in any one of [1] to [4], wherein the second cleaning step comprises a second cleaning liquid circulation step that allows the second cleaning liquid to pass through the filter and circulates the passed second cleaning liquid back to the filter.

[0012] [6] The filter cleaning method as described in [5] includes a second cleaning step comprising a pure water supply step of replacing the second cleaning solution with pure water and allowing the pure water to pass through the filter; a particle measurement step of measuring the number of particles in the pure water after the pure water supply step; and a calculation step of calculating the amount of decrease in the number of particles based on the measurement results in the particle measurement step. The second cleaning fluid circulation process, the pure water supply process, the particle measurement process, and the calculation process are repeated in sequence until the aforementioned attenuation amount reaches the specified benchmark.

[0013] [7] The filter cleaning method as described in any one of [1] to [6], wherein the filter is a PTFE membrane.

[0014] [8] A silicon wafer cleaning method comprising a filter cleaning step of cleaning the aforementioned filter by means of any one of [1] to [7]; and using the aforementioned filter after being cleaned by the aforementioned filter cleaning step to clean the silicon wafer.

[0015] [9] The silicon wafer cleaning method as described in [8] includes a third cleaning fluid circulation step in which the silicon wafer is cleaned using the aforementioned filter after being cleaned in the aforementioned filter cleaning step. This third cleaning fluid circulation step allows the third cleaning fluid to pass through the aforementioned filter and circulates the passed third cleaning fluid back to the aforementioned filter. In the aforementioned second cleaning step of the aforementioned filter cleaning process, the aforementioned second cleaning solution passing through the aforementioned filter is composed of the same components as the aforementioned third cleaning solution.

[0016]

[10] In the silicon wafer cleaning method described in [9], in the second cleaning step of the filter cleaning process, the concentration of the aforementioned component other than water in the second cleaning liquid that passes through the filter is greater than the concentration of the aforementioned component in the third cleaning liquid. In the case that there are multiple aforementioned components other than water in the second cleaning liquid, the concentration of each of the aforementioned components other than water in the second cleaning liquid is greater than the concentration of the aforementioned component in the third cleaning liquid.

[0017]

[11] In the silicon wafer cleaning method described in

[10] , in the second cleaning step of the filter cleaning process, the concentration of the aforementioned component other than water in the second cleaning liquid that passes through the filter is more than 1 to 5 times the concentration of the aforementioned component in the third cleaning liquid. In the case that there are multiple aforementioned components other than water in the second cleaning liquid, the concentration of each of the aforementioned components other than water in the second cleaning liquid is more than 1 to 5 times the concentration of the aforementioned component in the third cleaning liquid.

[0018] Invention Effects According to the present invention, a filter cleaning method is provided that can effectively reduce particles generated by a filter that has never been used. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a silicon wafer cleaning method according to an embodiment of the present invention. Detailed Implementation

[0020] The following is a reference to the appendix. Figure 1 The embodiments of the present invention are illustrated below.

[0021] like Figure 1 As shown, in one embodiment of the present invention, the filter cleaning method includes: a first cleaning step S11, in which an ozone water solution is used as a first cleaning liquid to clean a filter made of fluororesin; and a second cleaning step S12, in which an acidic or alkaline solution is used as a second cleaning liquid to clean the filter after the first cleaning step S11.

[0022] According to the above structure, the oxidation effect of ozone water as the first cleaning solution makes it easy for particles such as metals attached to the unused filter to be detached from the filter. This allows the particles to be easily removed using an acidic or alkaline solution as the second cleaning solution, thus effectively reducing the amount of particulate matter from the filter. Therefore, a filter cleaning method that effectively reduces particulate matter generated by an unused filter can be realized.

[0023] The ozone concentration of the first cleaning solution in the first cleaning step S11 is between 5 ppm and 40 ppm, and the flow rate of the first cleaning solution in the first cleaning step S11 is between 2 L / min and 20 L / min. Based on this structure, particles can be more easily removed from the filter using the first cleaning solution, thus effectively reducing particles generated by filters that have never been used. If the ozone concentration of the first cleaning solution is less than 5 ppm, it is difficult to achieve a particle reduction effect; if it exceeds 40 ppm, it can easily lead to a decrease in filter function due to filter damage.

[0024] In the first cleaning step S11, the filter cleaning method involves passing a first cleaning solution through the filter for at least one hour. Based on this structure, particles can be more easily removed from the filter using the first cleaning solution, thus easily and effectively reducing particles generated by filters that have never been used.

[0025] The second cleaning solution is hydrofluoric acid or an aqueous solution containing ammonia and hydrogen peroxide. Based on the above structure, the particles can be removed more easily with the aid of the second cleaning solution, thus easily and effectively reducing particles generated by filters that have never been used.

[0026] The second cleaning step S12 includes a second cleaning fluid circulation step S121 that allows the second cleaning fluid to pass through the filter and circulates the passed second cleaning fluid back into the filter. According to this structure, particles can be removed from the filter while the second cleaning fluid is circulated via the second cleaning fluid circulation step S121, thus reducing the amount of expensive second cleaning fluid used. Therefore, it is easy and economical to reduce particles generated by filters that are never used.

[0027] The second cleaning step S12 includes: a pure water supply step S122, in which the second cleaning solution is replaced with pure water and the pure water is passed through the filter; a particle measurement step S123, in which the number of particles in the pure water after the pure water supply step S122 is measured; and a calculation step S124, in which the amount of particle count reduction is calculated based on the measurement results in the particle measurement step S123; the second cleaning solution circulation step S121, the pure water supply step S122, the particle measurement step S123, and the calculation step S124 are repeated in this order until the amount of reduction reaches a predetermined benchmark. According to the above structure, by appropriately setting the predetermined benchmark, particles generated by an unused filter can be reduced to a desired level.

[0028] The filter is a PTFE membrane. PTFE membranes possess excellent chemical resistance, heat resistance, and weather resistance. PTFE membranes have a porous structure and are hydrophobic; therefore, to improve permeability, PTFE membranes that have undergone hydrophilic treatment are preferred. Hydrophilic treatment can be achieved through known methods such as passing water through a solvent like IPA into the PTFE membrane and then rinsing it with pure water.

[0029] In this embodiment, the silicon wafer cleaning method includes a filter cleaning step S1 in which a filter is cleaned using a filter cleaning method, and the silicon wafer is cleaned using the filter that has been cleaned in the filter cleaning step S1. According to the above structure, a silicon wafer cleaning method can be realized that can effectively reduce particles generated by unused filters before cleaning the silicon wafer.

[0030] The silicon wafer cleaning process S2, which uses a filter cleaned in the filter cleaning process S1 to clean silicon wafers, includes a third cleaning solution circulation process S21. This third cleaning solution circulation process S21 allows a third cleaning solution to pass through the filter and circulates the passed third cleaning solution back to the filter. The second cleaning solution that passes through the filter in the second cleaning process S12 of the filter cleaning process S1 consists of the same components as the third cleaning solution. According to this structure, silicon wafers can be cleaned while the third cleaning solution is circulated using the third cleaning solution circulation process S21, thus reducing the amount of expensive third cleaning solution used and enabling economical silicon wafer cleaning. Furthermore, by using a filter cleaned with the second cleaning solution, which consists of the same components as the third cleaning solution, silicon wafers can be cleaned effectively.

[0031] In the second cleaning step S12 of the filter cleaning process S1, the concentration of components other than water in the second cleaning liquid passing through the filter is greater than the concentration of those components in the third cleaning liquid. If there are multiple components other than water in the second cleaning liquid, the concentration of each of these components in the second cleaning liquid is greater than the concentration of those components in the third cleaning liquid. Based on this structure, the filter can be effectively cleaned using a second cleaning liquid with a higher concentration than the third cleaning liquid.

[0032] In the second cleaning step S12 of the filter cleaning step S1, the concentration of components other than water in the second cleaning liquid passing through the filter is more than 1 to 5 times the concentration of that component in the third cleaning liquid. If there are multiple components other than water in the second cleaning liquid, the concentration of each component in the second cleaning liquid is more than 1 to 5 times the concentration of that component in the third cleaning liquid. Based on this structure, the filter can be effectively and easily cleaned using a second cleaning liquid of an appropriate concentration.

[0033] The above describes the embodiments of the present invention, but the present invention is not limited to the foregoing embodiments. Various modifications can be made to the foregoing embodiments without departing from the spirit of the present invention.

[0034] [Example] For cases where ozone water was passed through a filter (10 ppm, 10 L / min, 6 hours) followed by the passage of acid-containing liquid, and for cases where pure water was passed through a filter at the same flow rate and time (10 L / min, 6 hours) without passing ozone water through a filter followed by the passage of acid-containing liquid, a liquid particle counter was used to measure the liquid particles larger than 20 nm in the acid treatment. The measurement results are shown in Table 1. It can be seen that ozone water treatment can promote a reduction in the amount of particles generated from the filter.

[0035] [Table 1]

[0036] Explanation of reference numerals in the attached figures S1 Filter Cleaning Process S11 First Cleaning Process S12 Second Cleaning Process S121 Second Cleaning Fluid Circulation Process S122 Pure Water Supply Process S123 Particle Measurement Process S124 Calculation process S2 Silicon Wafer Cleaning Process S21 Third cleaning fluid circulation process.

Claims

1. A filter cleaning method, comprising: a first cleaning step of cleaning a fluorine resin filter with ozone water as a first cleaning liquid; and a second cleaning step of cleaning the filter after the first cleaning step with an acid-containing liquid or an alkali-containing liquid as a second cleaning liquid.

2. The filter cleaning method according to claim 1, wherein the ozone concentration of the first cleaning liquid in the first cleaning step is 5 ppm or more and 40 ppm or less, and the flow rate of the first cleaning liquid in the first cleaning step is 2 L / min or more and 20 L / min or less.

3. The filter cleaning method according to claim 1, wherein the first cleaning liquid is passed through the filter for 1 hour or more in the first cleaning step.

4. The filter cleaning method according to claim 1, wherein the second cleaning liquid is hydrofluoric acid or an aqueous solution containing ammonia and hydrogen peroxide.

5. The filter cleaning method according to claim 1, wherein the second cleaning step includes a second cleaning liquid circulation step of passing the second cleaning liquid through the filter and circulating the second cleaning liquid after passing through the filter to the filter.

6. The filter cleaning method according to claim 5, wherein the second cleaning step includes a pure water supply step of replacing the second cleaning liquid with pure water and passing the pure water through the filter, a particle measurement step of measuring the number of particles in the pure water after the pure water supply step, and a calculation step of calculating the amount of decrease in the number of particles based on the measurement result in the particle measurement step, the second cleaning liquid circulation step, the pure water supply step, the particle measurement step, and the calculation step are sequentially repeated until the amount of decrease reaches a predetermined reference value.

7. The filter cleaning method according to claim 1, wherein the filter is a PTFE membrane.

8. A silicon wafer cleaning method, comprising: a filter cleaning step of cleaning a filter by the filter cleaning method according to any one of claims 1 to 7; and a silicon wafer cleaning step of cleaning a silicon wafer using the filter cleaned in the filter cleaning step.

9. The silicon wafer cleaning method according to claim 8, wherein the silicon wafer cleaning step of cleaning a silicon wafer using the filter cleaned in the filter cleaning step includes a third cleaning liquid circulation step of passing a third cleaning liquid through the filter and circulating the third cleaning liquid after passing through the filter to the filter, the second cleaning liquid passed through the filter in the second cleaning step of the filter cleaning step is composed of the same components as the third cleaning liquid.

10. The silicon wafer cleaning method according to claim 9, wherein ​ The concentration of the component other than water in the second cleaning solution is more than 1 times and 5 times or less than the concentration of the component in the third cleaning solution. In the case where there are a plurality of components other than water in the second cleaning solution, the concentration of each of the components other than water in the second cleaning solution is more than 1 times and 5 times or less than the concentration of the component in the third cleaning solution.

11. The silicon wafer cleaning method according to claim 10, wherein The concentration of the component other than water in the second cleaning solution is more than 1 times and 5 times or less than the concentration of the component in the third cleaning solution. In the case where there are a plurality of components other than water in the second cleaning solution, the concentration of each of the components other than water in the second cleaning solution is more than 1 times and 5 times or less than the concentration of the component in the third cleaning solution.

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