JP2014151269A - Method for regenerating an etchant and etchant regenerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for regenerating an etchant and an etchant regenerating apparatus each capable of removing, at a low cost, hydrosilicofluoric acid within the etchant.SOLUTION: The provided method for regenerating an etchant comprises: a deposition step of inducing the deposition of ammonium silicofluoride by cooling an etchant including ammonium fluoride and having treated a silicon-containing compound; a recovery step of subsequently recovering at least a portion of the deposited ammonium silicofluoride from the etchant; and an adjustment step of subsequently adjusting the ammonium fluoride concentration of the etchant from which the deposited ammonium silicofluoride has been at least partially recovered.

Description

  The present invention relates to an etching solution regeneration method and an etching solution regeneration apparatus.

Conventionally, an etching solution containing hydrogen fluoride (HF), ammonium fluoride (NH ₄ F), or the like is used in an etching process for glass or quartz. Etching solution after use contains hydrofluoric acid (H ₂ SiF ₆ ) and ammonium silicofluoride ((NH ₄ ) ₂ SiF ₆ ) produced by reaction with silicon contained in glass or quartz. Even if a large amount of hydrogen fluoride or ammonium fluoride that did not remain is left, there has been a problem that the etching rate is remarkably lowered by the silicofluoric acid or silicofluoride ions of ammonium silicofluoride.
Therefore, in Patent Document 1, sodium hydroxide (NaOH) is added to the used etching solution as an alkali metal hydroxide, and the silicofluoric acid of hydrofluoric acid and the sodium ion of sodium hydroxide are allowed to react with each other. A method is disclosed in which, after sodium fluoride (Na ₂ SiF ₆ ) is precipitated and removed, hydrogen fluoride remaining without reacting in the etching solution is concentrated by a concentrator and reused.

JP 2012-55841 A

  However, since sodium hydroxide is added to remove silicofluoric acid silicofluoride ions in the used etching solution, there is a problem in that the cost of regenerating the etching solution increases.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  [Application Example 1] An etching solution regeneration method according to this application example includes a preparation step of preparing an etching solution containing ammonium fluoride and treating a silicon compound, and cooling the etching solution to deposit ammonium silicofluoride. A precipitation step, a recovery step of recovering at least a portion of the precipitated ammonium silicofluoride from the etching solution, and an ammonium fluoride of the etching solution in which at least a portion of the ammonium silicofluoride is recovered after the recovery step And an adjusting step for adjusting the density.

  According to this application example, by cooling the etching solution containing ammonium fluoride and treating the silicon compound, ammonium silicofluoride dissolved in the etching solution becomes supersaturated and precipitates, so it is separated from the etching solution. can do. Thereafter, the concentration of ammonium fluoride in the etching solution from which ammonium silicofluoride has been collected is measured and adjusted by adding ammonium fluoride, whereby the etching solution having a desired etching rate can be regenerated. Therefore, since the silicofluoride ions contained in the etchant can be separated as ammonium silicofluoride simply by cooling the etchant without using an alkali metal hydroxide, the etching solution can be regenerated at low cost. There is.

  Application Example 2 In the etching solution regeneration method according to the application example, in the preparation step, the temperature of the etching solution is within a range of 30 ° C. or more and 85 ° C. or less, and the temperature for cooling the etching solution is 0 ° C. or more. It is within the range of 30 ° C. or less.

  According to this application example, by setting the temperature of the etching solution within the range of 30 ° C. or more and 85 ° C. or less, there is an effect that the silicon compound can be etched at a desired etching rate, and the temperature at which the etching solution is cooled. By setting the temperature within the range of 0 ° C. or higher and 30 ° C. or lower, there is an effect that only ammonium silicofluoride in the etching solution can be deposited, separated and recovered.

  Application Example 3 In the method for regenerating an etching solution according to the application example, the etching solution in the preparation step is an aqueous solution in which the ammonium fluoride is in the range of 15 wt% to 20 wt%. Features.

  According to this application example, the etching solution is cooled and the temperature is in the range of 0 ° C. or higher and 30 ° C. or lower by setting the ammonium fluoride concentration of the etching solution in the range of 15 wt% to 20 wt%. However, since it is saturated, ammonium fluoride is not deposited. Accordingly, there is an effect that the etching solution can be regenerated without lowering the ammonium fluoride concentration in the etching solution by cooling.

  Application Example 4 In the etching solution regeneration method according to the application example described above, ammonium fluoride is added in the adjustment step.

  According to this application example, by depositing and removing silicofluoride ions in the etching solution as ammonium silicofluoride, ammonium ions in the etchant are insufficient, and the ammonium fluoride concentration is lowered. Therefore, there is an effect that an ammonium fluoride concentration etching solution having a desired etching rate can be regenerated by newly adding ammonium fluoride.

  Application Example 5 In the etching solution regeneration method according to the application example described above, in the recovery step, the precipitated ammonium silicofluoride is recovered with a filter.

  According to this application example, by using the filter, the precipitated ammonium silicofluoride and the etching solution can be separated, and only the ammonium silicofluoride can be recovered, so that the amount of the etching solution can be efficiently reduced. There is an effect that the etching solution can be regenerated.

  [Application Example 6] An etching solution regenerating apparatus according to this application example includes a tank that cools an etching solution to precipitate at least a part of a solute to generate a precipitate, and the precipitate to collect the precipitate. And a flow path connecting the tank and the preparation tank, and a preparation tank for adjusting the concentration of the etching solution after the at least part of the solute is deposited. And

  According to the etching solution regenerating apparatus of this application example, a tank that cools the etching solution to precipitate a part of solute to generate a precipitate, a valve that passes the precipitate to collect the precipitate, By preparing a device that includes a preparation tank that adjusts the concentration of the etching solution after depositing a part of the solute, and a flow path that connects the tank and the preparation vessel, a part of the etching solution in the etching solution Solutes can be deposited and separated into precipitates for recovery. Therefore, it is possible to adjust the concentration of the etching solution from which a part of the solute has been separated, and there is no need for equipment such as a concentrating device. Therefore, there is an effect that the etching solution can be regenerated easily and at low cost.

  Application Example 7 In the etching solution regenerating apparatus according to the application example described above, a filter is provided in the tank for separating the precipitate from the etching solution.

  According to the etching solution regenerating apparatus of this application example, by installing a filter in the tank, the precipitated ammonium silicofluoride and the etching solution can be separated and only the ammonium silicofluoride can be recovered. There is an effect that the etching solution can be regenerated at a low cost without reducing the amount of the solution and without requiring an expensive separation and recovery facility.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the etching liquid reproduction | regeneration method and etching liquid reproduction | regeneration apparatus which concern on the 1st Embodiment of this invention. Schematic which shows the reproduction | regeneration method and etching liquid reproduction | regeneration apparatus of the etching liquid which concern on the 2nd Embodiment of this invention. Schematic which shows the reproduction | regeneration method and etching liquid reproduction | regeneration apparatus of the etching liquid which concern on the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 is a schematic view showing an etching solution regeneration method and an etching solution regeneration apparatus according to the first embodiment of the present invention.
Hereinafter, along with the description of the etching solution regeneration apparatus 1, a regeneration method using the etching solution regeneration apparatus 1 will be described.

An etching solution regenerating apparatus 1 shown in FIG. 1 includes a constant temperature tank 10 that keeps the etching solution at a constant temperature, a regeneration tank 20 that deposits ammonium silicofluoride 80 ((NH ₄ ) ₂ SiF ₆ ), and a deposited silica film. A flow connecting the three-way valve 30 for recovering the ammonium fluoride 80, the mixing tank 40 for adding ammonium fluoride 90 (NH ₄ F) to adjust the ammonium fluoride concentration of the etching solution, and the regeneration tank 20 and the mixing tank 40 And a path (a portion indicated by an arrow connecting the regeneration tank 20 and the three-way valve 30 and an arrow connecting the three-way valve 30 and the mixing tank 40).

  In the constant temperature tank 10, the etching solution is supplied to the processing tank 50 for etching a silicon compound, for example, glass or crystal while maintaining the etching solution at a constant temperature, for example, 60 ° C. ± 3 ° C. Etching solution is collected. Note that the temperature of the etching solution is maintained at an optimum temperature in order to obtain a desired etching residue shape and processing time in a range of 30 ° C. to 85 ° C.

  In the regeneration tank 20, the silicon compound is etched and the predetermined etching rate is not satisfied, and the etching solution having an ammonium fluoride concentration of 15 wt% to 20 wt% is naturally cooled or forcibly cooled by the chiller 22. By setting the temperature of the etching solution within the range of 0 ° C. or more and 30 ° C. or less, silicofluoride ions that are contained in the etching solution and cause a decrease in the etching rate are precipitated as ammonium silicofluoride 80. The removal of silicofluoride ions in the etching solution is effective not only in preventing the etching rate from decreasing but also in preventing the surface of the silicon compound substrate from being roughened. The ammonium fluoride concentration in the etching solution is 15% by weight or more and 20% by weight or less because the desired etching rate can be obtained, and even when the temperature is cooled to 0 ° C. or more and 30 ° C. or less. This is because ammonium fluoride does not precipitate because it is saturated.

  In the three-way valve 30, the ammonium silicofluoride 80 deposited on the bottom of the regeneration tank 20 and the flow path connecting the regeneration tank 20 and the three-way valve 30 is opened to the recovery tank 60 by opening a valve that leads to the recovery tank 60. . Moreover, the valve | bulb which connects the etching liquid which separated and collect | recovered the precipitated ammonium silicofluoride 80 to the preparation tank 40 is open | released, and it moves to the preparation tank.

  In the preparation tank 40, the concentration of ammonium fluoride in the etching solution obtained by removing the hydrosilicofluoric acid contained in the etching solution as ammonium silicofluoride 80 is measured by the densitometer 42, and the etching rate is adjusted so that the etching rate is within a predetermined range. The etching solution is regenerated by adding ammonium fluoride 90.

  In the flow path connecting the regeneration tank 20 and the mixing tank 40, the three-way valve 30 is provided in the middle, so that the ammonium silicofluoride 80 deposited in the flow path between the regeneration tank 20 and the three-way valve 30 is precipitated and separated and recovered. be able to. Further, the etching solution can be regenerated by separating and recovering the precipitated ammonium silicofluoride 80 and transferring the remaining etching solution to the preparation tank 40.

Here, the etching of the silicon compound according to the embodiment of the present invention will be described in detail using a crystal as an example.
In general, an etching liquid containing hydrogen fluoride (HF) and ammonium fluoride (NH ₄ F) is used for etching quartz (SiO ₂ ) which is one of silicon compounds. The reaction formula in which the quartz crystal is etched by the etching solution to generate ammonium silicofluoride ((NH ₄ ) ₂ SiF ₆ ) is expressed by the following formula (1).
SiO ₂ + 4HF + 2NH ₄ F → (NH ₄ ) ₂ SiF ₆ + 2H ₂ O (1)
Further, the reaction in which the crystal is etched will be described in detail. First, an etching solution, which is a mixed solution of hydrogen fluoride and ammonium fluoride, contains hydrogen ions (H ⁺ ) as shown in the formula (2). , Ammonium ion (NH ₄ ⁺ ) and fluorine ion (F ⁻ ).
4HF + 2NH ₄ F → 4H ⁺ + 2NH ₄ ⁺ + 6F ⁻ (2)

When crystal is present in this etching solution, as shown in the equation (3), fluorine ions in the solution react with silicon in the crystal, and silicofluoride ions (SiF ₆ ²⁻ ), oxygen ions (O ²⁻ ) and Produce.
SiO ₂ + 4H ⁺ + 2NH ₄ ⁺ + 6F ⁻
→ SiF ₆ ^2- + 2O ^2- + 4H ⁺ + 2NH ₄ ⁺ (3)
Thereafter, when a large amount of crystal is etched, silicic fluoride ions and ammonium ions become supersaturated, and the silicic fluoride ions and ammonium ions are combined to be precipitated as ammonium silicofluoride as shown in formula (4).
SiF ₆ ^2- + 2O ^2- + 4H ⁺ + 2NH ₄ ⁺
→ (NH ₄ ) ₂ SiF ₆ + 4H ⁺ + 2O ²⁻ (4)

  It should be noted that if the amount of silicofluoride ions generated by etching the crystal increases, the etching rate of the etchant decreases and the surface of the quartz substrate is roughened. It is very effective in maintaining.

Next, a method for regenerating an etching solution according to the first embodiment of the present invention will be described.
In the method for regenerating an etchant according to the first embodiment of the present invention, first, as a preparation step, the silicon compound is etched and the temperature at which the predetermined etching rate is no longer satisfied is in the range of 30 ° C. or higher and 85 ° C. or lower. A certain etching solution is prepared in the constant temperature tank 10. Next, as a deposition step, the prepared etching solution is transferred from the constant temperature tank 10 to the regeneration tank 20, and the temperature of the etching solution is within the range of 0 ° C. or more and 30 ° C. or less within the regeneration tank 20, or naturally cooled, or The cooling is forced by the chiller 22. The ammonium silicofluoride 80 deposited by cooling is deposited at the bottom of the regeneration tank 20 and inside the pipe connecting the regeneration tank 20 and the three-way valve 30.

  Thereafter, as a recovery step, the valve connected to the recovery tank 60 of the three-way valve 30 is opened, and the ammonium silicofluoride 80 precipitated in the bottom of the regeneration tank 20 or in the pipe connecting the regeneration tank 20 and the three-way valve 30 is recovered. By moving to 60, the ammonium fluorosilicate 80 can be separated and recovered in the recovery tank 60. At that time, by flowing pure water 70 from the middle of the pipe connecting the regeneration tank 20 and the three-way valve 30, the precipitated ammonium silicofluoride 80 can be easily transferred to the recovery tank 60. In addition, if the pure water 70 is warmed, the precipitated ammonium silicofluoride 80 is more dissolved, so that the transfer to the recovery tank 60 is easier and preferable.

Next, as an adjustment step, the valve for connecting the ammonium silicofluoride 80 and leaving the etching solution remaining in the regeneration tank 20 to the preparation tank 40 of the three-way valve 30 is opened and transferred to the preparation tank 40. Thereafter, the concentration of ammonium fluoride in the etching solution is measured by the densitometer 42, and the ammonium fluoride 90 is added and adjusted so as to obtain an ammonium fluoride concentration having a desired etching rate, thereby regenerating the etching solution. Is completed.
The regenerated etching solution is transferred to the constant temperature tank 10 and heated to a predetermined temperature, and then supplied to the treatment tank 50 and reused for etching of glass or quartz that is a silicon compound.

  As described above, the etching solution regeneration method and the etching solution regeneration apparatus 1 according to the first embodiment of the present invention cool the etching solution without using the alkali metal hydroxide disclosed in Patent Document 1. Only the silicofluoride ions contained in the etching solution can be separated as ammonium silicofluoride 80. Further, by measuring the ammonium fluoride concentration of the etching solution from which the ammonium silicofluoride 80 has been separated and adding ammonium fluoride 90, an etching solution having a desired etching rate can be easily regenerated. Therefore, no new chemicals or expensive concentrators are required, and the etching solution can be regenerated at a low cost.

<Second Embodiment>
FIG. 2 is a schematic view showing an etching solution regeneration method and an etchant regeneration device according to the second embodiment of the present invention.
Hereinafter, along with the description of the etching solution regeneration apparatus 1a, a regeneration method using the etching solution regeneration apparatus 1a will be described.
In addition, the second embodiment will be described with a focus on differences from the first embodiment described above, and description of similar matters will be omitted.

  As shown in FIG. 2, the etchant regenerator 1a according to the second embodiment has a filter inside the regeneration tank 20 of the etchant regenerator 1a as compared with the etchant regenerator 1 according to the first embodiment. The difference is that 24 is arranged. Another difference is that an injection position of pure water 70 for allowing the precipitated ammonium silicofluoride 80 to flow out is disposed in the upper part of the regeneration tank 20.

  In the etching solution regeneration method according to the second embodiment of the present invention, after the preparation step, as the precipitation step, the etching solution is cooled in the regeneration tank 20 to deposit ammonium silicofluoride 80, and then as the recovery step, The valve connected to the blending tank 40 of the three-way valve 30 is opened, and the etching solution is transferred to the blending tank 40. Since the precipitated ammonium silicofluoride 80 has a large crystal size, it does not pass through the filter 24 disposed at the bottom of the regeneration tank 20 and can therefore be separated from the etching solution. Thereafter, as an adjustment step, the concentration of ammonium fluoride in the etching solution transferred to the preparation tank 40 is measured, and an appropriate amount of ammonium fluoride 90 is added and adjusted to obtain an etching solution having a desired etching rate. The etching solution can be regenerated.

  In the recovery step, the ammonium silicofluoride 80 separated on the filter 24 is dissolved by pouring pure water 70 (more preferably heated to 60 ° C. or higher) heated to 30 ° C. or higher from the top of the regeneration tank 20. After that, the valve that leads to the recovery tank 60 of the three-way valve 30 is opened, so that it can flow into the recovery tank 60 and be recovered. The ammonium silicofluoride 80 on the filter 24 may be recovered by removing the filter 24 from the regeneration tank 20.

  With the etching solution regeneration method and the etching solution regeneration apparatus 1a according to the second embodiment, the deposited ammonium silicofluoride 80 and the etching solution are filtered by the filter 24 disposed in the regeneration tank 20 of the etching solution regeneration apparatus 1a. Since only the ammonium silicofluoride 80 can be recovered, the etching solution can be regenerated at a low cost without reducing the amount of the etching solution.

<Third Embodiment>
FIG. 3 is a schematic view showing an etching solution regeneration method and an etchant regeneration device according to the third embodiment of the present invention.
Hereinafter, along with the description of the etching solution regeneration apparatus 1b, a regeneration method using the etching solution regeneration apparatus 1b will be described.
In addition, the third embodiment will be described with a focus on differences from the first embodiment described above, and description of similar matters will be omitted.

  As shown in FIG. 3, the etchant regenerator 1 b according to the third embodiment has a flow path that connects the regenerator tank 20 and the preparation tank 40 as compared with the etchant regenerator 1 according to the first embodiment. Is different in that the three-way valve 30 is not arranged in the middle of Another difference is that an injection position of pure water 70 for allowing the precipitated ammonium silicofluoride 80 to flow out is disposed in the upper part of the regeneration tank 20.

  In the etching solution regeneration method according to the third embodiment of the present invention, after the preparation step and the precipitation step, as a recovery step, the etching solution is cooled in the regeneration tank 20 to deposit ammonium silicofluoride 80, and then etched. Only the supernatant liquid in which ammonium silicofluoride 80 in the liquid is precipitated is transferred to the preparation tank 40. Thereafter, as an adjustment step, the concentration of ammonium fluoride in the etching solution transferred to the preparation tank 40 is measured, and etching is performed by adding an appropriate amount of ammonium fluoride 90 to obtain an etching solution having a desired etching rate. Regenerate the liquid. Further, as a recovery process of the precipitated ammonium silicofluoride 80, a valve (not shown) provided between the regeneration tank 20 and the recovery tank 60 is an ammonium silicofluoride 80 precipitated at the bottom of the regeneration tank 20 and a small amount of etching solution. After being opened, pure water 70 (preferably heated to 30 ° C. or higher) is poured from the upper part of the regeneration tank 20, so that it can be recovered in the recovery tank 60.

  With the etching solution regeneration method and the etchant regeneration apparatus 1b according to the third embodiment, the three-way valve 30 is disposed in the middle of the flow path connecting the regeneration tank 20 and the preparation tank 40 of the etchant regeneration apparatus 1b. Accordingly, the precipitated ammonium silicofluoride 80 and the etching solution can be separated and the ammonium silicofluoride 80 can be recovered, so that the etching solution can be regenerated at a low cost.

  DESCRIPTION OF SYMBOLS 1 ... Etching liquid reproduction | regeneration apparatus, 10 ... Constant temperature tank, 20 ... Regeneration tank, 22 ... Chiller, 24 ... Filter, 30 ... Three-way valve, 40 ... Preparation tank, 42 ... Densitometer, 50 ... Treatment tank, 60 ... Collection tank, 70 ... pure water, 80 ... ammonium silicofluoride, 90 ... ammonium fluoride.

Claims (7)

A preparation step of preparing an etching solution containing ammonium fluoride and treating a silicon compound;
A deposition step of cooling the etching solution to deposit ammonium silicofluoride;
A recovery step of recovering at least a part of the precipitated ammonium silicofluoride from the etching solution;
An adjusting step of adjusting an ammonium fluoride concentration of the etching solution in which at least a part of the ammonium silicofluoride is recovered after the recovery step;
A method for regenerating an etching solution, comprising:   The temperature of the etching solution is in a range of 30 ° C. or more and 85 ° C. or less in the preparation step, and a temperature for cooling the etching solution is in a range of 0 ° C. or more and 30 ° C. or less. Of regenerating an etching solution.   The method for regenerating an etching solution according to claim 1 or 2, wherein the etching solution in the preparation step is an aqueous solution in which the ammonium fluoride is in the range of 15 wt% to 20 wt%.   The method for regenerating an etching solution according to any one of claims 1 to 3, wherein ammonium fluoride is added in the adjustment step.   5. The method for regenerating an etching solution according to claim 1, wherein in the collecting step, the precipitated ammonium silicofluoride is collected by a filter. A tank that cools the etchant and deposits at least a portion of the solute to produce precipitates;
A valve for passing the precipitate to collect the precipitate;
A blending tank for adjusting the concentration of the etching solution after the at least part of the solute is deposited;
A flow path connecting the tank and the mixing tank;
An etching solution regenerating apparatus comprising:   The etching solution regenerating apparatus according to claim 6, further comprising a filter in the tank for separating the precipitate from the etching solution.

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