Etching liquid regeneration method

Abstract

Provided is an etching liquid regeneration method capable of, when regenerating an etching liquid (exhausted liquid) that has been used in an etching treatment of a semiconductor, regenerating not only conventional etching liquids but also a high-function etching liquid to which an agent for inhibiting deposition of silica is added.　This etching liquid regeneration method is for regenerating, through diffusion dialysis, an inorganic acid-based etching liquid that is to be used or that has been used in etching of a semiconductor, and comprises an extraction step for bringing an etching liquid containing a dialysis aid into contact with water through an anion exchange membrane to extract an inorganic acid contained in the etching liquid into the water.

Description

How to regenerate etching solution

[0001] The present invention relates to a method for regenerating an etching solution, in which an inorganic acid-based etching solution used or intended for etching a semiconductor is regenerated by a diffusion dialysis method.

[0002] As semiconductor circuits become more highly integrated and have higher capacities, there is a demand for more precise etching techniques. In particular, in the manufacture of semiconductors (e.g., 2D NAND, 3D NAND, CMOS, DRAM, 3DRAM, logic ICs, etc.) that have a silicon nitride film as a sacrificial layer in addition to a silicon oxide film, precise removal of only the silicon nitride film is required. Therefore, in order to achieve high etching selectivity, etching solutions are formulated with etching inhibitors that suppress etching of silicon oxide.

[0003] For example, the etching solution described in Patent Document 1 is used in the manufacturing process of three-dimensional semiconductors and is a composition containing a solution containing silica and alkali, phosphoric acid, and water. According to Patent Document 1, the use of such an etching solution suppresses etching of silicon oxide films and improves etching selectivity for silicon nitride films (see paragraph 0013 of the specification of Patent Document 1).

[0004] However, since disposal of etching solutions is costly, it is desirable to reuse them. However, since the etching solution (fatigue solution) used in the etching process of semiconductors contains a large amount of Si compounds derived from the semiconductor, it is necessary to remove the Si compounds from the etching solution in order to reuse the used etching solution.

[0005] As a method for removing Si compounds contained in an etching solution, for example, there is a removal method using a filter described in Patent Document 2. According to Patent Document 2, by using a filter medium having a high rate of removing Si compounds as a filter, it is possible to regenerate an etching solution suitable for industrial processes (see paragraph 0018 of the specification of Patent Document 2).

[0006] JP 2020-96160 A Patent No. 4944558 A

[0007] However, because the etching solution of Patent Document 1 originally contains silica (silicic acid) as an additive, the concentration of silicic acid in the solution increases when silicon nitride is etched, which makes it easier for silica to precipitate as fine crystals in the solution. Therefore, if a filter such as that of Patent Document 2 is used to regenerate the etching solution of Patent Document 1, there is a risk that the filter will become clogged in a short period of time.

[0008] In addition, in response to user demands for higher performance, some etching solutions used in recent years have been designed to prevent Si compounds dissolved in the etching solution from precipitating as silica on semiconductor substrates. To distinguish such etching solutions in which silica precipitation is suppressed from conventional etching solutions, they are referred to as "high-performance etching solutions" in this specification. High-performance etching solutions contain a precipitation inhibitor that suppresses silica precipitation, so the Si compounds are present in a dissolved state in the solution. Therefore, when regenerating high-performance etching solutions, the removal method using a filter, such as that described in Patent Document 2, is incapable of removing the Si compounds from the solution in the first place.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide a method for regenerating an etching solution that can regenerate not only conventional etching solutions but also high-performance etching solutions containing a silica precipitation inhibitor when regenerating an etching solution (fatigue solution) used in a semiconductor etching process.

[0010] A characteristic feature of the method for regenerating an etching solution according to the present invention for solving the above-mentioned problems is that it is a method for regenerating an inorganic acid-based etching solution that is to be used or has been used in etching a semiconductor by a diffusion dialysis method, and includes an extraction step of extracting the inorganic acid contained in the etching solution into water by contacting the etching solution containing a dialysis aid with water via an anion exchange membrane.

[0011] According to the etching solution regeneration method of this configuration, when regenerating an inorganic acid-based etching solution that is used or has been used in semiconductor etching, diffusion dialysis using an anion exchange membrane is employed instead of the conventional filtration method. Diffusion dialysis is a method in which the inorganic acid contained in the etching solution is extracted into water by contacting the etching solution with water through an anion exchange membrane. Since the etching solution contains a dialysis aid, the inorganic acid can be recovered without clogging during diffusion dialysis. Therefore, it is possible to regenerate not only conventional etching solutions but also high-performance etching solutions that contain a deposition inhibitor that suppresses silica deposition in the etching solution.

[0012] The method for regenerating an etching solution according to the present invention preferably includes, before the extraction step, an addition step of adding a dialysis aid to the etching solution to prepare an etching solution containing the dialysis aid.

[0013] According to the etching solution regeneration method of this configuration, when regenerating an etching solution by diffusion dialysis, a dialysis aid is added to the etching solution (used solution) before the extraction step (addition step). This ensures sufficient dialysis of the anion exchange membrane and allows the inorganic acid contained in the etching solution to be efficiently extracted into water. As a result, the used etching solution (fatigue solution) can be regenerated not only as an etching solution, but also in a state usable for various purposes other than as an etching solution.

[0014] The method for regenerating an etching solution according to the present invention preferably includes a preparation step of adding all or part of a dialysis aid to the etching solution to prepare an etching solution containing the dialysis aid before etching the semiconductor.

[0015] According to the etching solution regeneration method of this configuration, when regenerating an etching solution by diffusion dialysis, all or part of the dialysis aid is added to the etching solution (unused solution) before etching a semiconductor (preparation step). This sufficiently maintains the dialysis ability of the anion exchange membrane and efficiently extracts the inorganic acid contained in the etching solution into water. As a result, the used etching solution (fatigue solution) can be regenerated as an etching solution again, and can also be regenerated into a state that can be used for various purposes other than as an etching solution. Note that when part of the dialysis aid is added to the etching solution (unused solution), the remaining part of the dialysis aid can be added to the etching solution (used solution) before the extraction step.

[0016] In the method for regenerating an etching solution according to the present invention, the dialysis aid is preferably a heteroatom-containing compound.

[0017] According to the method for regenerating an etching solution of this configuration, the use of a heteroatom-containing compound as a dialysis aid improves dialysis efficiency, and as a result, inorganic acids contained in the etching solution can be efficiently extracted into water.

[0018] In the method for regenerating an etching solution according to the present invention, the heteroatom-containing compound is preferably a Si atom-containing compound, an N atom-containing compound, and / or a P atom-containing compound.

[0019] According to the method for regenerating an etching solution of this configuration, by using a Si atom-containing compound, an N atom-containing compound, and / or a P atom-containing compound as a dialysis aid, the dialysis efficiency is further improved, and as a result, the inorganic acid contained in the etching solution can be more efficiently extracted into water.

[0020] In the method for regenerating an etching solution according to the present invention, the Si atom-containing compound is preferably a silane compound having, in its molecular structure, three or less alkoxy groups, hydroxyl groups, and / or functional groups that serve as precursors of hydroxyl groups, and / or a silane compound having, in its molecular structure, four or more alkoxy groups, hydroxyl groups, and / or functional groups that serve as precursors of hydroxyl groups, and / or a silane compound containing a halogen atom.

[0021] According to the method for regenerating an etching solution of this configuration, by using the above-mentioned silane compound as a dialysis aid, particularly excellent dialysis efficiency can be achieved.

[0022] In the method for regenerating an etching solution according to the present invention, the N atom-containing compound is preferably a hydrazide and / or an ammonium compound.

[0023] According to the method for regenerating an etching solution of this configuration, by using hydrazides and / or ammonium compounds as the dialysis aid, particularly excellent dialysis efficiency can be achieved.

[0024] In the method for regenerating an etching solution according to the present invention, the P atom-containing compound is preferably a phosphonic acid compound.

[0025] According to the method for regenerating an etching solution of this configuration, by using a phosphonic acid compound as a dialysis aid, particularly excellent dialysis efficiency can be achieved.

[0026] In the method for regenerating an etching solution according to the present invention, the inorganic acid is preferably phosphoric acid.

[0027] The method for regenerating an etching solution of this configuration is suitable for regenerating a semiconductor etching solution that uses phosphoric acid as an inorganic acid.

[0028] In the method for regenerating an etching solution according to the present invention, the etching solution preferably contains Si derived from the semiconductor at a concentration equal to or higher than a predetermined concentration.

[0029] The method for regenerating an etching solution according to the present invention is useful because it can regenerate any etching solution that contains semiconductor-derived Si at a concentration equal to or higher than a predetermined concentration.

[0030] In the method for regenerating an etching liquid according to the present invention, the etching liquid is preferably a fatigue liquid used in etching the semiconductor.

[0031] According to the method for regenerating an etching solution of this configuration, the benefits of regeneration are great, especially when it is performed on fatigued solutions used in etching semiconductors.

[0032] In the method for regenerating an etching solution according to the present invention, the extraction step is preferably carried out by countercurrent contact of the etching solution with the water via an anion exchange membrane.

[0033] According to the method for regenerating an etching solution of this configuration, the inorganic acid contained in the etching solution can be efficiently extracted into water by performing countercurrent contact.

[0034] In the method for regenerating an etching solution according to the present invention, the semiconductor is preferably a semiconductor having a silicon nitride film as a sacrificial layer.

[0035] The etching solution regeneration method of this configuration is suitable for regenerating an etching solution (fatigue solution) with a high concentration of silicon derived from silicon nitride.

[0036] FIG. 1 is a schematic diagram of a regeneration device for regenerating an etching solution. FIG. 2 is a flowchart showing the method for regenerating an etching solution according to the present invention. FIG. 3 is a graph showing the recovery rates of phosphoric acid recovered from the etching solutions of Examples 1 to 6 and Comparative Example 1. FIG. 4 is a graph showing the results of etching tests (without dialysis aid) of Example 7 and Comparative Example 2. FIG. 5 is a graph showing the results of etching tests (with dialysis aid) of Example 8 and Comparative Example 3. FIG. 6 is a graph showing the results of etching tests (without dialysis aid) of Example 9. FIG. 7 is a graph showing the results of etching tests (without dialysis aid) of Example 10. FIG. 8 is a graph showing the results of etching tests (without dialysis aid) of Example 11. FIG. 9 is a graph showing the results of etching tests (without dialysis aid) of Example 12. FIG. 10 is a graph showing the results of etching tests (without dialysis aid) of Example 13. FIG. 11 is a graph showing the results of etching tests (with dialysis aid) of Example 14 and Comparative Example 4. Fig. 12 is a graph showing the results of the etching test according to Example 15 (with dialysis aid) and the etching test according to Comparative Example 5. Fig. 13 is a graph showing the results of the etching test according to Example 16 (with dialysis aid) and the etching test according to Comparative Example 6. Fig. 14 is a graph showing the results of the etching test according to Example 17 (with dialysis aid) and the etching test according to Comparative Example 7. Fig. 15 is a graph showing the results of the etching test according to Example 18 (with dialysis aid) and the etching test according to Comparative Example 8.

[0037] An embodiment of the method for regenerating an etching solution according to the present invention will be described below, although it is not intended that the present invention be limited to the following embodiment.

[0038] [Etching Solution] In the etching solution regeneration method according to the present invention, the etching solution to be regenerated is an etching solution that is used or has been used for etching a semiconductor. Here, an etching solution that is used for etching a semiconductor includes an etching solution that is not unused but is still in a usable state. An etching solution that has been used for etching a semiconductor includes an etching solution that has been fully used up (a so-called fatigued solution). The etching solution regeneration method according to the present invention is applicable to the regeneration of not only conventional etching solutions but also highly functional etching solutions that suppress silica precipitation (high-performance etching solutions).

[0039] The etching solution (treatment solution) used in the etching solution regeneration method according to the present invention is based on an inorganic acid and contains a dialysis aid. The dialysis aid functions to improve dialysis efficiency or suppress an increase in dialysis resistance when the etching solution is subjected to diffusion dialysis using an anion exchange membrane. The inorganic acid and dialysis aid contained in the etching solution are described below.

[0040] <Inorganic Acid> Examples of inorganic acids include phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, and mixed acids of these inorganic acids. Of these inorganic acids, phosphoric acid is preferred. When phosphoric acid is used after dilution, it is in the form of an aqueous solution, and its concentration is preferably 50 to 100 wt %, more preferably 70 to 95 wt %, and even more preferably 85 to 95 wt %. The phosphoric acid may be adjusted to the above concentration when the etching solution is used. For example, a stock solution containing a low-concentration aqueous phosphoric acid solution may be concentrated at or before use, a stock solution containing phosphoric acid (strong phosphoric acid) with a concentration exceeding 100 wt % may be diluted with water at or before use, or anhydrous phosphoric acid (P ２ O ５ ) can be dissolved in water at the time of use or before use to adjust to the above appropriate concentration.

[0041] <Dialysis Aid> Examples of the dialysis aid include heteroatom-containing compounds. Examples of heteroatom-containing compounds include Si atom-containing compounds, N atom-containing compounds, and / or P atom-containing compounds. The Si atom-containing compounds can also function as etching inhibitors that inhibit etching of silicon oxide, and the N atom-containing compounds and P atom-containing compounds can also function as precipitation inhibitors that inhibit silica from being precipitated on the surface of silicon oxide.

[0042] [Si Atom-Containing Compound] Examples of Si atom-containing compounds include silane compounds having three or less alkoxy groups, hydroxyl groups, and / or functional groups that serve as hydroxyl group precursors in their molecular structure (hereinafter referred to as "first silane compounds"), and / or silane compounds having four or more alkoxy groups, hydroxyl groups, and / or functional groups that serve as hydroxyl group precursors in their molecular structure (hereinafter referred to as "second silane compounds"). Regarding the first and second silane compounds having hydroxyl groups, any silane compound can be used as long as it can be converted to eventually have hydroxyl groups in the solution. The content of the Si atom-containing compound in the etching solution is preferably 0.5 to 20 wt % for the first silane compound, more preferably 1 to 20 wt %, and even more preferably 1 to 6 wt %. Regarding the second silane compound, it is preferably 0.01 to 5 wt %, more preferably 0.01 to 1 wt %, and even more preferably 0.09 to 0.6 wt %. Examples of Si atom-containing compounds are described below.

[0043] Examples of the first silane compound include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, 1,6-bis(trimethoxysilyl)hexane, vinyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and N-2-(aminoethyl)-4-aminobutyltrimethoxysilane. , N-2-(aminoethyl)-5-aminopentyltrimethoxysilane, N-2-(aminoethyl)-6-aminohexyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, and hydrochlorides of the above aminosilanes, tris-(trimethoxysilylpropyl)isocyanurate, 3-mercaptopropylmethyldimethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride, as well as hydrolysates of the above alkoxysilanes. Among these first silane compounds, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, as well as hydrolysates of these alkoxysilanes, are preferred. The above first silane compounds may be used alone or in a mixture of two or more.

[0044] The second silane compound generally has the chemical structure shown in formula (I) below.

[0045] Here, R in formula (I) １ ~R ６ are substituents, at least four of which are at least one specific substituent selected from the group consisting of an alkoxy group, a hydroxyl group, and chlorine, and the substituents other than the specific substituents are at least one substituent selected from the group consisting of an alkyl group, an aryl group, a carbonyl group, a carboxyl group, an amino group, an ethylenediamine group, and derivatives or composite groups of these substituents. X in formula (I) is "O" (oxygen atom) or "-" (single bond). n in formula (I) is an integer from 0 to 3. Thus, the second silane compound may be a compound having an alkoxy group (a siloxane compound or a disilane compound, the same applies hereinafter) and a compound having a hydroxyl group, or a compound having a chlorine group. Note that compounds having an alkoxy group and compounds having a chlorine group are ultimately converted to compounds having a hydroxyl group by hydrolysis.

[0046] Specific examples of the second silane compound include compounds represented by the following chemical structural formula (1):

[0047] 1,3-dimethyltetramethoxydisiloxane shown in the following chemical structural formula (2):

[0048] a siloxane compound represented by the following chemical structural formula (3):

[0049] a siloxane compound represented by the following chemical structural formula (4):

[0050] Hexamethoxydisiloxane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, hexamethoxydisilane, hexaethoxydisilane, hexabutoxydisilane, hexamethoxydisiloxane, hexaethoxydisiloxane, hexabutoxydisiloxane, 1,3-dimethyltetraethoxydisiloxane, 1,3-dimethyltetrabutoxydisiloxane, 1,3-diethyltetramethoxydisiloxane, 1,3-diethyltetraethoxydisiloxane, 1,3 Examples of the second silane compound include 1,3-dimethyltetrachlorodisiloxane, 1,3-diethyltetrabutoxydisiloxane, 1,3-divinyltetramethoxydisiloxane, 1,3-divinyltetraethoxydisiloxane, 1,3-divinyltetrabutoxydisiloxane, 1,3-bis(3-aminopropyl)tetramethoxydisiloxane, silicon tetrachloride, hexachlorodisilane, hexachlorodisiloxane, 1,3-dimethyltetrachlorodisiloxane, 1,3-diethyltetrachlorodisiloxane, and 1,3-dibutyltetrachlorodisiloxane. Commercially available siloxane compounds include silane coupling agents "X-12-1098," "X-12-1135," "KBP-64," and "KBP-90" manufactured by Shin-Etsu Chemical Co., Ltd. The second silane compounds may be used alone or in a mixture of two or more.

[0051] The Si atom-containing compound may include, in addition to the first and second silane compounds, a silane compound containing a halogen atom, such as hexafluorosilicic acid or a salt thereof.

[0052] [N-Atom-Containing Compounds] Examples of N-atom-containing compounds include hydrazine compounds, pyrazoles, triazoles, hydrazides, ammonium compounds, compounds having an imidazole skeleton, compounds having a pyrrolidine skeleton, compounds having a piperidine skeleton, compounds having a morpholine skeleton, compounds having a pyridine skeleton, compounds having a quaternary ammonium skeleton, compounds having a pyrimidine skeleton, compounds having a purine skeleton, and compounds having a urea skeleton, with hydrazides and ammonium compounds being preferred. The above compounds and compounds may be used alone or in a mixture of two or more. Using two or more different N-atom-containing compounds can be very useful not only in terms of performance in the etching process but also in terms of extending the life of the solution and reducing costs. The content of the N-atom-containing compound in the etching solution is preferably 0.1 to 1 wt %, more preferably 0.3 to 0.4 wt %. Examples of N-atom-containing compounds are described below.

[0053] [Hydrazine Compound] Examples of the hydrazine compound include hydrazine, butylhydrazine, isopropylhydrazine, benzylhydrazine, N,N-dimethylhydrazine, 1,2-diacetylhydrazine, phenylhydrazine, N,N-dicarbamoylhydrazine, hydrazine sulfate, hydrazine monohydrochloride, hydrazine dihydrochloride, butylhydrazine hydrochloride, hydrazine carbonate, and hydrazine monohydrobromide. The above hydrazine compounds may be used alone or in a mixture of two or more.

[0054] [Pyrazoles] Examples of pyrazoles include 3,5-dimethylpyrazole, 3-methyl-5-pyrazone, etc. The above pyrazoles may be used alone or in a mixture of two or more kinds.

[0055] [Triazoles] Examples of triazoles include 4-amino-1,2,4-triazole, 1,2,4-triazole, 1,2,3-triazole, 1-hydroxybenzotriazole, and 3-mercapto-1,2,4-triazole. The above triazoles may be used alone or in a mixture of two or more.

[0056] [Hydrazides] Examples of hydrazides include propionic acid hydrazide, lauric acid hydrazide, salicylic acid hydrazide, formhydrazide, acetohydrazide, acetohydrazide chloride, p-hydroxybenzoic acid hydrazide, naphthoic acid hydrazide, 3-hydroxy-2-naphthoic acid hydrazide, benzhydrazide, carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, succinic acid 2,2 dimethylhydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, hydrazide, fumaric acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, diglycolic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, 2,6-naphthoic acid dihydrazide, citric acid trihydrazide, pyromellitic acid trihydrazide, 1,2,4-benzenetricarboxylic acid trihydrazide, nitrilotriacetic acid trihydrazide, 1,3,5-cyclohexanetricarboxylic acid trihydrazide, ethylenediaminetetraacetic acid tetrahydrazide, and 1,4,5,8-naphthoic acid tetrahydrazide, etc. Of these hydrazides, adipic acid dihydrazide, succinic acid dihydrazide, acetohydrazide chloride, succinic acid 2,2-dimethylhydrazide, and azelaic acid dihydrazide are preferred. The above hydrazides may be used alone or in a mixture of two or more kinds.

[0057] [Ammonium Compound] Examples of the ammonium compound include ammonium phosphate, ammonium sulfate, ammonium nitrate, and ammonium chloride, and ammonium phosphate is preferred. The above ammonium compounds may be used alone or in combination of two or more.

[0058] [Compound Having an Imidazole Skeleton] Examples of compounds having an imidazole skeleton include compounds such as imidazole, imidazole carboxylic acid, imido urea, diazolidinyl urea, 3-(2-oxoimidazolidin-1-yl)benzoic acid, and imidazole hydrochloride, as well as imidazolium salts such as 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1,3-dimethylimidazolium methyl sulfate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-octylimidazolium tetrafluoroborate, 1,3-dimethylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-ethyl-3-methylimidazolium phosphate. The above compounds having an imidazole skeleton may be used alone or in a mixture of two or more.

[0059] [Compound Having a Pyrrolidine Skeleton] Examples of compounds having a pyrrolidine skeleton include compounds such as pyrrolidine, 2-pyrrolidone, N-methylpyrrolidone, N-vinyl-2-pyrrolidone, pyroglutamic acid, and piracetam, as well as pyrrolidinium salts such as 1-ethyl-1-methylpyrrolidinium chloride, 1-butyl-1-methylpyrrolidinium chloride, 1-ethyl-1-methylpyrrolidinium acetate, 1-ethyl-1-methylpyrrolidinium tetrafluoroborate, 1-butyl-1-methylpyrrolidinium tetrafluoroborate, 1-ethyl-1-methylpyrrolidinium hexafluorophosphate, and 1-butyl-1-methylpyrrolidinium hexafluorophosphate. The above-mentioned compounds having a pyrrolidine skeleton may be used alone or in a mixture of two or more.

[0060] [Compound Having a Piperidine Skeleton] Examples of compounds having a piperidine skeleton include compounds such as piperidine, ethyl piperidine-4-carboxylate, piperidin-2-ylacetic acid, and piperidine-4-carboxylic acid methylamide, as well as piperidinium salts such as (piperidinium-1-ylmethyl)trifluoroborate, 1-butyl-1-methylpiperidinium bromide, and 1-butyl-1-methylpiperidinium bisimide. The above compounds having a piperidine skeleton may be used alone or in a mixture of two or more.

[0061] [Compound Having a Morpholine Skeleton] Examples of compounds having a morpholine skeleton include compounds such as morpholine, morpholin-2-ylmethanol, morpholin-3-one, morpholine-4-carbothioic acid amide, morpholin-4-ylacetic acid, and morpholin-4-ylethyl acetate, as well as morpholinium salts such as 4-ethyl-4-methylmorpholinium bromide and 4-(2-ethoxyethyl)-4-methylmorpholinium bisimide. The above compounds having a morpholine skeleton may be used alone or in a mixture of two or more.

[0062] [Compound Having a Pyridine Skeleton] Examples of compounds having a pyridine skeleton include compounds such as pyridine, N,N-dimethyl-4-aminopyridine, bipyridine, 2,6-lutidine, and pyridinium p-toluenesulfonate, as well as pyridinium salts such as 1-butyl-3-methylpyridinium chloride, 1-butylpyridinium tetrafluoroborate, and 1-butylpyridinium hexafluorophosphate. The above compounds having a pyridine skeleton may be used alone or in a mixture of two or more.

[0063] [Compound having a quaternary ammonium skeleton] Examples of compounds having a quaternary ammonium skeleton include tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetramethylammonium hydroxide, tetramethylammonium iodide, tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate, tetramethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, and choline acetate. The above-mentioned compounds having a quaternary ammonium skeleton may be used alone or in a mixture of two or more.

[0064] [Compounds Having a Pyrimidine Skeleton] Examples of compounds having a pyrimidine skeleton include thymine, cytosine, uracil, and nucleosides, ribonucleosides, and deoxyribonucleosides of the above-mentioned compounds. The above-mentioned compounds having a pyrimidine skeleton may be used alone or in a mixture of two or more.

[0065] [Compounds Having a Purine Skeleton] Examples of compounds having a purine skeleton include purine, adenine, guanine, uric acid, caffeine, hypoxanthine, xanthine, theophylline, theobromine, isoguanine, and nucleosides, ribonucleosides, and deoxyribonucleosides of the above-mentioned compounds. The above-mentioned compounds having a purine skeleton may be used alone or in a mixture of two or more.

[0066] [Compound Having a Urea Skeleton] Examples of the compound having a urea skeleton include urea, hydroxyurea, N,N-diethylthiourea, N,N-dibutylthiourea, biurea, biuret, N-amidinothiourea, etc. The above-mentioned compounds having a urea skeleton may be used alone or in a mixture of two or more.

[0067] [P atom-containing compound] Examples of the P atom-containing compound include phosphonic acid compounds. Examples of the phosphonic acid compound include compounds such as phosphonic acid, diphenyl phosphonate, butyl phosphonate, dipentyl phosphonate, phosphorous acid, hypophosphorous acid, and ammonium phosphate, as well as phosphonium salts such as tetrabutyl phosphonium hexafluorophosphate, tetrabutyl phosphonium bisimide, and tetrabutyl phosphonium bromide. Note that the ammonium phosphate compound is a P atom-containing compound, but is also an N atom-containing compound. The above phosphonic acid compounds may be used alone or in a mixture of two or more.

[0068] [Preparation of Etching Solution Before Regeneration Treatment] The etching solution to be subjected to the regeneration treatment is prepared by adding a dialysis aid. The dialysis aid can be added directly to the etching solution, or the dialysis aid may be added to the etching solution in a state where it is dissolved or suspended in a solvent. The dialysis aid is generally added to the etching solution used for etching a semiconductor, but it can also be added in advance to a new etching solution before use for etching a semiconductor. The dialysis aid may be added to the etching solution at room temperature or while the solution is being heated.

[0069] <Solvent> Examples of solvents for dissolving or suspending the dialysis aid include water, alcohols such as methanol, ethanol, 2-propanol, butanol, octanol, benzyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and 2,2,2-trifluoroethanol, ethers such as diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether (CPME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane, and dimethoxyethane, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and 4-fluoroethylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, butyl acetate, Examples of suitable esters include methyl propionate, ethyl propionate, methyl butyrate, and γ-lactone; nitriles such as acetonitrile, propionitrile, valeronitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, and benzonitrile; amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); ureas such as dimethyl sulfoxide (DMSO), hexamethylphosphoric triamide (HMPA), N,N,N',N'-tetramethylurea (TMU), and N,N'-dimethylpropyleneurea (DMPU); and ionic liquids such as imidazolium salts, pyrrolidinium salts, piperidinium salts, pyridinium salts, morphonium salts, phosphonium salts, quaternary ammonium salts, and sulfonium salts. As for the ionic liquid, examples of the cation include an imidazolium skeleton, a pyrrolidinium skeleton, a piperidinium skeleton, a morphonium skeleton, a pyridinium skeleton, a quaternary phosphonium skeleton, a quaternary ammonium skeleton, and a sulfonium skeleton, and examples of the anion include Br － , B.F. ４ － , P.F. ６ － , (CN) ２ N － , Cl － , I － , (CF ３ SO２ ) N － , (F ２ SO ２ ) N － , C.H. ３ COO － , HSO ４ － , (CH ３ ) ２ P.O. ４ － , C.F. ３ COO － , C.H. ３ SO ３ － , C.F. ３ SO ３ － , and SCN － The above solvents may be used alone or in a mixture of two or more.

[0070] <Surfactant> When dissolving or suspending a dialysis aid in a solvent, a surfactant can be used in combination. As the surfactant, any of cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants can be used, and these surfactants can also be used in combination.

[0071] [Regeneration of Etching Solution] When an etching solution is used for etching a semiconductor, Si components derived from silicon nitride gradually accumulate in the solution, and when the Si concentration exceeds a certain concentration, the solution becomes unusable. On the other hand, high-performance etching solutions also contain Si components derived from silane coupling agents, etc. However, high-performance etching solutions can be used even when the concentration of Si derived from silicon nitride in the solution reaches a significantly higher concentration than that of conventional etching solutions. This is because silane coupling agents, etc., maintain a stable structure in the etching solution even at any high temperature, and do not contribute to the deterioration of the performance of the etching solution due to the precipitation of Si components derived from silane coupling agents, etc. as silica.

[0072] However, even in a high-performance etching solution, if the concentration of silicon nitride-derived silicon in the solution becomes too high, the Si component will aggregate to form silica microcrystals, which are likely to precipitate in the solution. Therefore, in the present invention, a used etching solution (fatigue solution) is subjected to a regeneration treatment, so that it can be reused as an etching solution (including a high-performance etching solution) or for various other products.

[0073] Hereinafter, an embodiment of the method for regenerating an etching solution of the present invention will be described. In the following embodiment, phosphoric acid (H ３ P.O. ４ The unit (%) of the concentration of phosphoric acid used in the etching solution is weight %. The unit (ppm) of the concentration of Si derived from silicon nitride in the etching solution is a weight-based unit (mg / kg).

[0074] <Regeneration Apparatus> First, a regeneration apparatus used to carry out the etching solution regeneration method of the present invention will be described. FIG. 1 is a schematic diagram of a regeneration apparatus 100 for regenerating an etching solution. FIG. 1(a) is an overall diagram of the regeneration apparatus 100, and FIG. 1(b) is an enlarged view of a portion of the regeneration apparatus 100 surrounded by a dashed ellipse A in FIG. 1(a). The regeneration apparatus 100 regenerates an etching solution that is used or has been used in semiconductor etching. The regeneration apparatus 100 mainly comprises a raw solution storage tank 10 for storing a used etching solution, a water storage tank 20 for storing water, a dialysis aid storage tank 30 for storing a dialysis aid, a diffusion dialysis apparatus 40 for regenerating the etching solution, a treated solution storage tank 50 for storing a treated solution (hereinafter also referred to as "recovered acid") generated from the diffusion dialysis apparatus 40, and an effluent storage tank 60 for storing an effluent (hereinafter also referred to as "deacidification solution") discharged from the diffusion dialysis apparatus 40. The entire dialysis aid may be added in advance to a new etching solution before use in etching a semiconductor, in which case the aid reservoir 30 can be omitted. Alternatively, a portion of the dialysis aid may be added in advance to a new etching solution before use in etching a semiconductor, in which case the remaining portion of the dialysis aid is stored in the aid reservoir 30.

[0075] The stock solution reservoir 10 stores a phosphoric acid-based etching solution (fatigue solution) that has been used to etch semiconductors (e.g., 2D NAND, 3D NAND, CMOS, DRAM, 3DRAM, logic ICs, etc.) that have a silicon nitride film as a sacrificial layer. Because this etching solution has been used, it contains silicon nitride-derived Si at a concentration equal to or higher than a predetermined concentration. The concentration of silicon nitride-derived Si (predetermined concentration) is typically 10 ppm or higher, but is expected to be in the range of 50 to 2000 ppm, for example, and may even be as high as 3000 ppm.

[0076] Water used for regenerating the etching solution is stored in the water storage tank 20. The water is preferably pure water, as it serves as a medium for extracting phosphoric acid from the etching solution.

[0077] The auxiliary agent reservoir 30 stores an aqueous solution in which a dialysis aid is dissolved in water. The various heteroatom-containing compounds described above can be used as the dialysis aid. The dialysis aid is added to the raw solution reservoir 10 by an auxiliary agent addition pump 31. If the etching solution already contains a sufficient amount of the heteroatom-containing compound, it is considered that the dialysis aid has already been added, and the amount of dialysis aid added to the raw solution reservoir 10 can be reduced or the addition of the dialysis aid to the raw solution reservoir 10 can be omitted.

[0078] The diffusion dialysis device 40 primarily comprises a plurality of anion exchange membranes 42. The anion exchange membranes 42 are sandwiched between frames 41 at both ends. The number of anion exchange membranes 42 can be set as desired. The anion exchange membranes 42 are arranged in parallel at regular intervals via spacers (not shown). This forms parallel spaces 43 between adjacent anion exchange membranes 42. The etching solution transported from the stock solution storage tank 10 by the stock solution pump 11 and the water transported from the water storage tank 20 by the water pump 21 flow alternately in opposite directions through the spaces 43. This allows the etching solution and the water to come into countercurrent contact via the anion exchange membranes 42. The etching solution may be passed through a filtration device 12, if necessary, before being introduced into the diffusion dialysis device 40. This removes insoluble components from the etching solution, thereby reliably preventing clogging of the anion exchange membranes 42 during diffusion dialysis.

[0079] The treated liquid storage tank 50 stores the recovered acid (aqueous phosphoric acid solution) treated in the diffusion dialysis device 40. The aqueous phosphoric acid solution is pumped out by a treated liquid pump 51, and is passed through a concentrator 52 as necessary before being reused.

[0080] The wastewater storage tank 60 stores the wastewater (deoxidized solution remaining after phosphoric acid has been extracted from the etching solution) generated in the diffusion dialysis device 40. The wastewater is pumped out by a wastewater pump 61, and then subjected to neutralization treatment, desiliconization treatment, etc. in a wastewater treatment facility (not shown) as necessary.

[0081] <Regeneration Method> FIG. 2 is a flowchart showing a method for regenerating an etching solution according to the present invention. The etching solution regeneration method includes, as an essential step, an extraction step in which an inorganic acid contained in an etching solution containing a dialysis aid is extracted into water. A preferred step also includes an addition step in which a dialysis aid is added to the etching solution before the extraction step. Additional steps that are performed as needed include a filtration step before the extraction step and a concentration step after the extraction step. Note that, in addition to the steps shown in FIG. 2 , a preparation step in which a dialysis aid is added to the etching solution before etching a semiconductor may also be performed. In the following embodiment, a case in which an addition step and an extraction step are performed will be described as an example of a method for regenerating an etching solution.

[0082] For example, if the phosphoric acid concentration is H ３ P.O. ４ In order to regenerate 80 to 100% of the used etching solution (fatigue solution), a dialysis aid is added to the etching solution (S1; adding step). The dialysis aid is preferably added in the form of an aqueous solution dissolved in water, but a solid (powdered) dialysis aid can also be added directly to the etching solution. When adding a powdered dialysis aid to the etching solution, a screw feeder, for example, can be used instead of the aid storage tank 30 and the aid addition pump 31 shown in FIG. 1(a).

[0083] The etching solution containing the added dialysis aid is contacted with water through an anion exchange membrane, thereby extracting the phosphoric acid contained in the etching solution into water (S3; extraction step). Here, the extraction step will be described in more detail. A used etching solution typically contains silicon nitride-derived silicon at a concentration equal to or greater than a predetermined concentration. Generally, when Si compounds accumulate in the etching solution (when the Si concentration increases), as described above, the Si compounds are more likely to precipitate as fine silica crystals. However, in the present invention, the addition of a dialysis aid to the etching solution keeps the Si compounds stable in the solution, suppressing silica precipitation. However, in such an etching solution with suppressed silica precipitation, conventional filtration cannot remove the Si component from the solution. Therefore, the present invention employs a diffusion dialysis method using an anion exchange membrane. The diffusion dialysis method transfers phosphoric acid contained in the etching solution to water by contacting the etching solution with water through an anion exchange membrane. In the present invention, when phosphoric acid is extracted by diffusion dialysis, the etching solution and water are brought into countercurrent contact through an anion exchange membrane. In the example shown in FIG. 1( a), among the multiple spaces 43 formed in parallel between adjacent anion exchange membranes 42, an etching solution is passed through the spaces 43 in the even-numbered rows from the left of the drawing from below the anion exchange membranes 42, and pure water is passed through the spaces 43 in the odd-numbered rows from above the anion exchange membranes 42. As shown in FIG. 1( b), the etching solution contains phosphate ions (PO ４ ３－ ) and silicon-containing cations (Si ＋ ) is included. Silicon is an element that is difficult to ionize by itself, and therefore is thought to actually exist in the form of complex ions, etc. However, for the sake of convenience, silicon ions (Si ＋) When the etching solution and water are brought into countercurrent contact via an anion exchange membrane, phosphate ions in the etching solution can pass through the anion exchange membrane 42 and move to the water, but silicon ions cannot pass through the anion exchange membrane 42 and remain in the etching solution. Because a dialysis aid is added to the etching solution, the dialysis ability of the anion exchange membrane 42 is maintained during diffusion dialysis. Therefore, according to the present invention, phosphoric acid contained in the etching solution can be efficiently extracted (recovered) into water.

[0084] In the method for regenerating an etching solution of the present invention, although it is not an essential step, the etching solution can be filtered before the extraction step (S3) (S2; filtration step). By performing the filtration step (S2), insoluble matters present in the etching solution can be removed, thereby reliably preventing clogging of the anion exchange membrane 42 when performing the extraction step (S3). Furthermore, if necessary, after the extraction step (S3), the treatment solution containing phosphoric acid obtained in the extraction step (S3) can be concentrated (S4; concentration step).

[0085] As described above, the method for regenerating an etching solution of the present invention involves contacting the etching solution with water via an anion exchange membrane, thereby regenerating the etching solution by diffusion dialysis, which extracts phosphoric acid contained in the etching solution into water. According to the present invention, the treated solution (recovered acid) can not only be regenerated as an etching solution, but also can be regenerated into a state usable for various purposes other than as an etching solution.

[0086] Furthermore, because the etching solution contains a dialysis aid, silica precipitation does not occur even when the silicon nitride-derived Si concentration in the etching solution increases from about 10 ppm to about 50-2000 ppm, or even to a very high concentration of about 3000 ppm, and the dialysis properties of the anion exchange membrane are sufficiently maintained. As a result, the phosphoric acid contained in the etching solution can be efficiently extracted into water.

[0087] As described above, the method for regenerating an etching solution of the present invention makes it possible to regenerate not only conventional etching solutions but also high-performance etching solutions containing a precipitation inhibitor that inhibits silica precipitation in the etching solution.

[0088] Examples of the method for regenerating an etching solution according to the present invention will be described below. Note that the percentages used to represent the amount of each component added (content in the etching solution) in each example are by weight unless otherwise specified.

[0089] Preparation of Etching Solution (Fatigue Solution) Example 1 A silicon nitride membrane was dissolved in 85% phosphoric acid (manufactured by Rasa Kogyo Co., Ltd.) to adjust the Si concentration to 200 ppm. This solution was heated at 80 to 100°C to evaporate the water and adjust the phosphoric acid concentration to 87%, and 3-aminopropyltrimethoxysilane (2%) and adipic acid dihydrazide (0.2%) were added as dialysis aids to obtain the etching solution (simulation solution) of Example 1. When the etching solution of Example 1 was used, this corresponds to an addition step of adding the dialysis aid to the etching solution prior to the extraction step.

[0090] Example 2 The etching solution of Example 2 was obtained in the same manner as in Example 1, except that only 3-aminopropyltriethoxysilane (3%) was added as the dialysis aid.

[0091] Example 3 The etching solution of Example 3 was obtained by the same procedure as in Example 1, except that 3-aminopropyltriethoxysilane (3%) and hexafluorosilicic acid (0.001%) were added as dialysis aids.

[0092] Example 4 The etching solution of Example 4 was obtained by the same procedure as in Example 1, except that 3-aminopropyltriethoxysilane hydrolysate (1.2%) and ammonium phosphate (0.1%) were added as dialysis aids.

[0093] Example 5 The etching solution of Example 5 was obtained by the same procedure as in Example 1, except that 3-aminopropyltriethoxysilane hydrolysate (1.2%) and phosphorous acid (0.1%) were added as dialysis aids.

[0094] Example 6 To 85% phosphoric acid (manufactured by Rasa Kogyo Co., Ltd.), 3-aminopropyltrimethoxysilane hydrolyzate (10.2%), the siloxane compound (0.34%) shown in the chemical formula (2), and adipic acid dihydrazide (0.3%) were added as dialysis aids. A silicon nitride film was then dissolved to adjust the Si concentration to 2000 ppm. This solution was heated at 80 to 100°C to evaporate the water and adjust the phosphoric acid concentration to 87%, yielding the etching solution of Example 6. Using the etching solution of Example 6 corresponds to a preparatory step of adding a dialysis aid to the etching solution before etching a semiconductor.

[0095] Comparative Example 1 The etching solution of Comparative Example 1 was obtained by carrying out the same procedure as in Example 1, except that no dialysis aid was added (i.e., no dialysis aid was included).

[0096] <Regeneration Test> The etching solutions of Examples 1 to 6 and Comparative Example 1 were subjected to diffusion dialysis using a regeneration device 100 shown in FIG.

[0097] FIG. 3 is a graph showing the recovery rates of phosphoric acid recovered from the etching solutions of Examples 1 to 6 and Comparative Example 1. The etching solution of Example 1 maintained a phosphoric acid recovery rate of approximately 90% for 30 days, and the anion exchange membrane did not clog. The etching solutions of Examples 2 to 5 also maintained a phosphoric acid recovery rate of approximately 90% or higher for at least 7 days. Note that regeneration tests were not conducted for Examples 2 to 5 after the 8th day because, based on the trends observed in Example 1, it was expected that the phosphoric acid recovery rate would be maintained for at least 30 days for Examples 2 to 5 as well. For the etching solution of Example 6, the phosphoric acid recovery rate from the first day (Day 1) to the 7th day was approximately 73 to 74%, but the anion exchange membrane still did not clog. In contrast, the phosphoric acid recovery rate of the etching solution of Comparative Example 1, which did not contain a dialysis aid, remained at approximately 60% from the first day (Day 1), and the anion exchange membrane subsequently clogged, making it impossible to continue the regeneration test.

[0098] <Performance Confirmation Test 1 of Regenerated Etching Solution> A performance confirmation test was conducted on the etching solution regenerated by the etching solution regeneration method of the present invention to confirm whether the etching performance was reduced compared to a new etching solution. The performance confirmation test was first conducted on the regenerated etching solution regenerated by supplying the etching solution of Example 1 to the regeneration device 100 and the new etching solution, in a "system without added dialysis aid" (Example 7, Comparative Example 2) and a "system with added dialysis aid" (Example 8, Comparative Example 3).

[0099] [Systems without added dialysis aid: Example 7, Comparative Example 2] Using a regenerated etching solution in which the phosphoric acid concentration (87%) and the Si concentration in the solution (0 to 100 ppm) were adjusted, an etching test for a silicon oxide film (Example 7-1) and an etching test for a silicon nitride film (Example 7-2) were carried out. Similarly, an etching test for a silicon oxide film (Comparative Example 2-1) and an etching test for a silicon nitride film (Comparative Example 2-2) were also carried out using a new etching solution.

[0100] FIG. 4 is a graph showing the results of etching tests (without dialysis aid) conducted in Example 7 and Comparative Example 2. FIG. 4(a) shows the results of etching tests on silicon oxide conducted in Example 7-1 and Comparative Example 2-1. FIG. 4(b) shows the results of etching tests on silicon nitride conducted in Example 7-2 and Comparative Example 2-2. In the manufacture of semiconductors having a silicon nitride film as a sacrificial layer in addition to a silicon oxide film, it is desirable to maintain a low etching rate for silicon oxide and a high etching rate for silicon nitride. Regarding the etching characteristics for silicon oxide, the regenerated etching solution was confirmed to have an etching inhibitory effect on silicon oxide equivalent to or greater than that of a fresh etching solution in a Si concentration range of 0 to 100 ppm. Regarding the etching characteristics for silicon nitride, the regenerated etching solution was confirmed to have an etching inhibitory effect on silicon nitride equivalent to or greater than that of a fresh etching solution in a Si concentration range of 0 to 100 ppm. In particular, in the low Si concentration range, the regenerated etching solution exhibited a superior etching inhibitory effect on silicon oxide compared to a fresh etching solution. The reason for this is thought to be that the regenerated etching solution contains a small amount of Si compounds that are not derived from silicon nitride (for example, Si compounds derived from etching inhibitors or dialysis aids), and these Si compounds act to inhibit etching of silicon oxide.

[0101] [Systems with Added Dialysis Aid: Example 8, Comparative Example 3] A regenerated etching solution in which the phosphoric acid concentration (87%) and the Si concentration in the solution (0 to 200 ppm) were adjusted was used to which 3-aminopropyltrimethoxysilane (2%) and adipic acid dihydrazide (0.2%) were added as dialysis aids, and an etching test for a silicon oxide film (Example 8-1) and an etching test for a silicon nitride film (Example 8-2) were carried out. Similarly, a new etching solution to which 3-aminopropyltrimethoxysilane (2%) and adipic acid dihydrazide (0.2%) were added as dialysis aids was also used to carry out an etching test for a silicon oxide film (Comparative Example 3-1) and an etching test for a silicon nitride film (Comparative Example 3-2).

[0102] FIG. 5 is a graph showing the results of etching tests (with dialysis aid) for Example 8 and Comparative Example 3. The results of the etching tests for silicon oxide for Example 8-1 and Comparative Example 3-1 are shown in FIG. 5(a). The results of the etching tests for silicon nitride for Example 8-2 and Comparative Example 3-2 are shown in FIG. 5(b). Regarding the etching characteristics for silicon oxide, the regenerated etching solution was confirmed to have the same etching inhibitory effect on silicon oxide as a new etching solution when the Si concentration was in the range of 0 to 200 ppm. Regarding the etching characteristics for silicon nitride, the regenerated etching solution was confirmed to have the same etching inhibitory effect on silicon nitride as a new etching solution when the Si concentration was in the range of 0 to 200 ppm. Since the regenerated etching solution contains a small amount of Si compounds that are not derived from silicon nitride, in Example 7 and Comparative Example 2, the regenerated etching solution exhibited better performance than the new etching solution (higher etching rate for silicon nitride and lower etching rate for silicon oxide). However, in Example 8 and Comparative Example 3, by adding 3-aminopropyltrimethoxysilane (2%) and adipic acid dihydrazide (0.2%) as dialysis aids, the new etching solution also contained Si compounds that were not derived from silicon nitride, and as a result, it is thought that the difference in performance between the regenerated etching solution and the new etching solution was narrowed.

[0103] [Selectivity] For Examples 7 and 8 and Comparative Examples 2 and 3, the etching rate (R １ ), and the etching rate for silicon oxide (R ２ ) to obtain the selectivity (R １ / R ２ ) are shown in Table 1 below. １ / R ２ The larger the absolute value of R , the more etching ability is obtained for silicon nitride while suppressing etching of silicon oxide, and therefore the etching solution can be evaluated as having excellent etching selectivity. The recycled etching solutions of Examples 7 and 8 have selectivity ratios (R ) equal to or greater than those of the new etching solutions of Comparative Examples 2 and 3. １ / R ２) was achieved and was fully usable.

[0104]

[0105] <Performance Confirmation Test 2 of Regenerated Etching Solution> Furthermore, performance confirmation tests were conducted on the regenerated etching solutions obtained by feeding each of the etching solutions of Examples 2 to 6 to the regeneration device 100, for "a system without added dialysis aid" (Examples 9 to 13) and "a system with added dialysis aid" (Examples 14 to 18). For comparison, similar performance confirmation tests were also conducted on each of the etching solutions of Examples 2 to 6 themselves (Comparative Examples 4 to 8), which were new etching solutions to which a dialysis aid had been added.

[0106] [Examples 9 to 13: Systems without the addition of a dialysis aid] Using a regenerated etching solution in which the phosphoric acid concentration (87%) and the Si concentration in the solution (0 to 100 ppm) were adjusted, etching tests for silicon oxide membranes (Examples 9-1 to 13-1) and etching tests for silicon nitride membranes (Examples 9-2 to 13-2) were carried out. Figures 6 to 10 are graphs showing the results of the etching tests (without a dialysis aid) in Examples 9 to 13.

[0107] [Examples 14 to 18: Systems with Added Dialysis Aid] The same dialysis aid as used in Examples 2 to 6 was added to the regenerated etching solution, in which the phosphoric acid concentration (87%) and the Si concentration in the solution (0 to 2000 ppm) were adjusted, and etching tests for silicon oxide membranes (Examples 14-1 to 18-1) and etching tests for silicon nitride membranes (Examples 14-2 to 18-2) were carried out using the same dialysis aid added to the regenerated etching solution. Figures 11 to 15 are graphs showing the results of the etching tests (with dialysis aid) for Examples 14 to 18.

[0108] [Comparative Examples 4 to 8] Using the etching solutions of Examples 2 to 6, which were prepared by adding a dialysis aid to a new etching solution, etching tests for silicon oxide membranes (Comparative Examples 4-1 to 8-1) and etching tests for silicon nitride membranes (Comparative Examples 4-2 to 8-2) were carried out. The results of the etching tests for Comparative Examples 4 to 8 are also shown in Figures 11 to 15.

[0109] [Selectivity] For Examples 9 to 13, the etching rate (R １ ), and the etching rate for silicon oxide (R ２ ) to obtain the selectivity (R １ / R ２ ) are shown in Table 2 below. The regenerated etching solutions of Examples 9 to 13 had selectivity (R １ / R ２ ) was sufficiently large and was therefore fully usable.

[0110]

[0111] For Examples 14 to 18, the etching rate (R １ ), and the etching rate for silicon oxide (R ２ ) to obtain the selectivity (R １ / R ２ ) are shown in Table 3 below. Furthermore, for Comparative Examples 4 to 8, the etching rates (R １ ), and the etching rate for silicon oxide (R ２ ) to obtain the selectivity (R １ / R ２ ) are shown in Table 4 below.

[0112]

[0113]

[0114] The regenerated etching solutions of Examples 14 to 18 had selectivity (R １ / R ２ ) was achieved and was fully usable.

[0115] The method for regenerating an etching solution of the present invention regenerates an etching solution used in the manufacture of a semiconductor having a silicon nitride film as a sacrificial layer in addition to a silicon oxide film, and can be used, for example, to regenerate an etching solution used in the manufacture of 2D NAND, 3D NAND, CMOS, DRAM, 3DRAM, logic ICs, etc.

Claims

1. A method for regenerating an inorganic acid-based etching solution that is to be used or has been used in etching a semiconductor by diffusion dialysis, comprising an extraction step of extracting the inorganic acid contained in the etching solution into water by contacting the etching solution containing a dialysis aid with water through an anion exchange membrane.

2. A method for regenerating an etching solution according to claim 1, further comprising the step of adding a dialysis aid to the etching solution prior to the extraction step to obtain an etching solution containing the dialysis aid.

3. A method for regenerating an etching solution according to claim 1, further comprising a preparation step of adding all or a part of a dialysis aid to the etching solution before etching the semiconductor to obtain an etching solution containing the dialysis aid.

4. The method for regenerating an etching solution according to claim 2 or 3, wherein the dialysis aid is a compound containing a heteroatom.

5. The method for regenerating an etching solution according to claim 4, wherein the heteroatom-containing compound is a Si atom-containing compound, a N atom-containing compound, and / or a P atom-containing compound.

6. The method for regenerating an etching solution according to claim 5, wherein the Si-atom-containing compound is a silane compound having, in its molecular structure, three or less alkoxy groups, hydroxyl groups, and / or functional groups which are precursors of hydroxyl groups, and / or a silane compound having, in its molecular structure, four or more alkoxy groups, hydroxyl groups, and / or functional groups which are precursors of hydroxyl groups, and / or a silane compound which contains a halogen atom.

7. The method for regenerating an etching solution according to claim 5, wherein the N-atom-containing compound is a hydrazide and / or an ammonium compound.

8. The method for regenerating an etching solution according to claim 5, wherein the P-atom-containing compound is a phosphonic acid compound.

9. A method for regenerating an etching solution according to any one of claims 1 to 3, wherein the inorganic acid is phosphoric acid.

10. A method for regenerating an etching solution according to any one of claims 1 to 3, wherein the etching solution contains Si originating from the semiconductor at a concentration equal to or higher than a predetermined concentration.

11. A method for regenerating an etching solution according to any one of claims 1 to 3, wherein the etching solution is a fatigued solution used in etching the semiconductor.

12. A method for regenerating an etching solution according to any one of claims 1 to 3, wherein the extraction step is carried out by countercurrent contact of the etching solution with the water via an anion exchange membrane.

13. A method for regenerating an etching solution according to any one of claims 1 to 3, wherein the semiconductor is a semiconductor having a silicon nitride film as a sacrificial layer.

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