Treatment of organics-containing wastewater using improved Fenton reagents

Abstract

A method for removing one or more azoles from wastewater of a semiconductor production facility includes obtaining copper from the wastewater and introducing an oxidizing agent into the wastewater to produce hydroxyl radicals from the oxidizing agent to react with the one or more azoles, where the copper catalyzes the production of hydroxyl radicals from the oxidizing agent.

Description

Technical Field

[0001] Aspects and embodiments disclosed herein relate to systems and methods for treating wastewater, such as copper chemical-mechanical polishing (CMP) wastewater, containing organic contaminants such as azoles. The methods disclosed herein provide for destroying organic contaminants in wastewater using a modified Fenton reagent. Overview

[0002] According to one aspect, a method for removing one or more azoles from wastewater of a semiconductor production facility is provided. The method includes obtaining copper from the wastewater and introducing an oxidant into the wastewater to generate hydroxyl radicals from the oxidant to react with the one or more azoles, wherein the copper catalyzes the generation of the hydroxyl radicals from the oxidant.

[0003] In some embodiments, the method further comprises maintaining the pH of the wastewater at a level at which copper catalyzes the production of hydroxyl radicals from the oxidant.

[0004] In some embodiments, the method further comprises obtaining wastewater from a copper chemical mechanical polishing (CMP) operation at a semiconductor fabrication facility.

[0005] In some embodiments, removing one or more azoles from the wastewater includes removing one or more of 1,2,4-triazole, pyrazole, benzotriazole, 5-methyl-1H-benzotriazole (Tolutriazole), or 3-amino-1,2,4-triazole from the wastewater.

[0006] In some embodiments, introducing the oxidizing agent into the wastewater comprises introducing hydrogen peroxide into the wastewater.

[0007] In some embodiments, the method further comprises obtaining the hydrogen peroxide from a waste stream from a semiconductor manufacturing facility.

[0008] In some embodiments, the copper is present in the wastewater in the form of copper sulfate.

[0009] According to another aspect, a system for removing one or more azoles from copper-containing wastewater from a semiconductor manufacturing facility is provided. The system includes a container fluidly connectable to a wastewater source; an oxidant source configured to introduce the oxidant into the wastewater in the container, wherein copper catalyzes the generation of hydroxyl radicals from the oxidant to react with the one or more azoles; and a pH adjustment chemical source configured to introduce the pH adjustment chemical into the wastewater in the container.

[0010] In some embodiments, the system further comprises a pH monitor disposed within the container and a controller configured to control the source of pH adjusting chemical to introduce the pH adjusting chemical into the wastewater in the container in an amount and at a rate sufficient to maintain the pH of the wastewater at a level at which copper catalyzes the production of hydroxyl radicals from the oxidant.

[0011] In some embodiments, the wastewater comprises one or more of 1,2,4-triazole, pyrazole, benzotriazole, 5-methyl-1H-benzotriazole (toluenetriazole), or 3-amino-1,2,4-triazole, and the system is configured to decompose the one or more of 1,2,4-triazole, pyrazole, benzotriazole, toluenetriazole, or 3-amino-1,2,4-triazole using hydroxyl radicals.

[0012] In some embodiments, the wastewater is copper chemical mechanical polishing (CMP) wastewater at a semiconductor fabrication facility.

[0013] In some embodiments, the copper is in the form of copper sulfate.

[0014] In some embodiments, the oxidant source is a source of hydrogen peroxide.

[0015] In some embodiments, the source of hydrogen peroxide comprises a waste stream from a semiconductor manufacturing facility. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component illustrated is represented by a like reference numeral. For clarity, not every component may be labeled. In the drawings: Figure 1 The figure shows an example of a system as disclosed herein. Details

[0017] Chemical mechanical polishing (CMP) planarization process involves a polishing slurry containing an oxidizing agent and an abrasive, a complexing agent, and other additives to remove and / or etch semiconductor wafers during the manufacturing process. Polishing is performed using a polishing pad to remove excess copper from the semiconductor wafer. Silicon, copper, and various trace metals are removed from the silicon structure via the polishing slurry. The polishing slurry is introduced into the silicon wafer on the planarization workbench together with the polishing pad. Oxidizing agents and etching solutions are introduced to control the removal of materials. Deionized water rinsing is typically used to remove debris from the silicon wafer. UPW, demineralized water, and polishing water from reverse osmosis (RO) can also be used in semiconductor manufacturing facility tools to rinse silicon wafers.

[0018] Hydrogen peroxide (H2O2) oxidizing agent is often used to help dissolve copper from microchips. Therefore, hydrogen peroxide (H2O2) can also be present in the by-product polishing slurry wastewater at levels of about 300 ppm and higher.

[0019] In the manufacturing process of semiconductor devices, when copper wiring is installed, a large amount of wastewater containing anticorrosives for copper is discharged from the CMP step for polishing the copper surface. Therefore, it is necessary to treat the wastewater to prevent the discharge of undesirable pollutants into the environment.

[0020] Among copper corrosion inhibitors, azole-type copper corrosion inhibitors are particularly effective in preventing corrosion. However, azole-type copper corrosion inhibitors generally have a chemically stable structure and are not easily biodegraded. Therefore, when treating wastewater containing azole-type copper corrosion inhibitors discharged from the process, oxidants with high oxidizing power, such as ozone, ultraviolet rays, or hydrogen peroxide, or advanced oxidation processes combining these oxidants, are typically used to decompose the azole-type copper corrosion inhibitors, and the treated water is then discharged or collected.

[0021] However, as mentioned above, since azole-type copper corrosion inhibitors are chemically stable, even when using a highly oxidizing agent such as ozone, a large amount of the oxidizing agent must be added to oxidatively decompose the azole-type copper corrosion inhibitor, resulting in significant cost issues. In particular, with the increasing integration of semiconductor devices in recent years, the number of fine polishing steps has increased, and with this, the amount of polishing wastewater discharged has also increased. Consequently, the cost increase caused by the increased capacity of wastewater treatment equipment has become a problem.

[0022] Fenton's reagent is frequently used to treat organic compounds. For every 0.3 parts of organic compound, Fenton's reagent can be produced by adding 10 parts of peroxide to 1 part of ferrous iron (ferrous sulfate). Fenton's reagent is effective in treating some azoles, such as pyrazole. However, laboratory tests have shown that other forms of azoles, such as 1,2,4-triazole, do not decompose when exposed to Fenton's reagent.

[0023] As discussed above, azoles are often used as anti-corrosion additives in facilities that manufacture computer chips. These facilities also typically have high-strength copper-containing wastewater from the CMP process, which needs to be treated and disposed of after failure, which adds costs to the facility. In one embodiment, a waste copper stream is used to treat and degrade azole compounds in the wastewater instead of iron in the Fenton reagent. Tests have shown that 1,2,4-triazole, 1H-benzotriazole and methylbenzotriazole: 4,5-tolyltriazole (4,5 Tolytriazole) can all be treated using a copper-substituted Fenton reagent. In one test, it was found that waste hydrogen peroxide (which contains the azoles to be treated) and waste copper sulfate (which can be used to replace iron sulfate in the Fenton reaction) produced an oxidant-containing solution that successfully degraded the azoles.

[0024] In some embodiments, copper replaces iron in a modified Fenton reaction (referred to herein as a Fenton-like reaction). Scrap copper streams from semiconductor production facilities can be used as a source of copper. Scrap copper can be present in the effluent of a copper CMP process.

[0025] As mentioned above, wastewater from semiconductor production facilities or other industrial sources can comprise high levels of azoles, for example, from about 20 mg / l until about 200 mg / l or more total azoles, which are used as anti-corrosive agents for copper during wafer planarization and polishing processes. Wastewater from these processes can also comprise heavy metals, other organic compounds, for example alcohols, and / or surfactants, for example ammonium salts, and inorganic abrasives, for example colloidal silica, all of which should be removed before the discharge of wastewater. These other pollutants can exist with levels from about 0.01 wt% until about 1 wt%. Wastewater can also have a high background total organic carbon (TOC) concentration, in which total azoles constitute a part for TOC. For example, oxidants such as hydrogen peroxide (H2O2) are typically used to help dissolve copper from microchips, and can be present in CMP wastewater at a concentration exceeding 1,000 mg / L or 0.1wt%.

[0026] U.S. regulatory agencies do not currently regulate maximum contaminant levels (MCLs) for azoles, but they are believed to have negative environmental impacts when discharged into open waterways. Recent evidence has indicated bioaccumulation of azoles in fish and toxic incidences of naturally occurring algal blooms, necessitating their removal from process waters prior to discharge.

[0027] As described in U.S. Patent No. 8,801,937, azole compounds are widely used as corrosion inhibitors for copper during silicon wafer processing in the semiconductor industry, the disclosure of which is incorporated herein by reference in its entirety for all purposes. Examples of such azole compounds include, but are not limited to, imidazole, pyrazole, oxazole, isoxazole, thiazole, isothiazole, selenazole, 1,2,3-triazole, 1,2,4-triazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,3,4-thiadiazole, tetrazole, 1,2,3,4-thiatriazole, any derivatives thereof, amine salts thereof, and metal salts thereof. Examples of azole derivatives include compounds having a condensed ring of an azole ring and a benzene ring or the like, such as indazole, benzimidazole, benzotriazole, and benzothiazole, and also include derivatives thereof, such as alkylbenzotriazoles (e.g., benzotriazole, o-tolyltriazole, m-tolyltriazole, p-tolyltriazole, 5-ethylbenzotriazole, 5-n-propylbenzotriazole, 5-isobutylbenzotriazole, and 4-methylbenzotriazole), alkoxybenzotriazoles (e.g., 5-methoxybenzotriazole), alkylaminobenzotriazoles, and the like. azoles, alkylaminosulfonylbenzotriazoles, mercaptobenzotriazoles, hydroxybenzotriazoles, nitrobenzotriazoles (e.g., 4-nitrobenzotriazole), halogenated benzotriazoles (e.g., 5-chlorobenzotriazole), hydroxyalkylbenzotriazoles, hydrogenbenzotriazoles, aminobenzotriazoles, (substituted aminomethyl)-tolyltriazole, carboxybenzotriazole, N-alkylbenzotriazoles, bisbenzotriazoles, naphthotriazoles, mercaptobenzothiazoles, aminobenzothiazole, amine salts thereof, and metal salts thereof.

[0028] Figure 1 One embodiment of a system for treating azole-containing wastewater from a semiconductor production facility is schematically shown in FIG. A semiconductor production facility 110 typically includes hundreds of unit operations, three of which are located in Figure 1 is marked in. Figure 1 The unit operations identified in FIG. 1 are a copper CMP unit operation 120; a unit operation 130 that generates wastewater with a high concentration of dissolved copper, such as a copper plating operation; and a unit operation 140 that generates wastewater with a high concentration of hydrogen peroxide, such as one of the wafer cleaning unit operations within semiconductor fabrication facility 110. The disclosed system is used to decompose organic contaminants, such as azoles, present in the wastewater from the copper CMP unit operation 120 using a Fenton-like reaction in which copper catalyzes the production of hydroxyl radicals from hydrogen peroxide. The hydroxyl radicals oxidize the organic contaminants into less hazardous byproducts, such as nitrogen oxides (NO2 / NO3), carbon dioxide, and water.

[0029] Wastewater from CMP unit operation 120 is directed into vessel 150, for example, by pump P1. An oxidant, such as hydrogen peroxide, from oxidant source 160 is added to the wastewater in vessel 150, for example, using another pump P4, in an amount and at a rate sufficient to maintain the hydrogen peroxide concentration in the vessel at a desired level (e.g., 300 mg / L or higher) to promote reactions that result in the decomposition of organic compounds in the wastewater. In some embodiments, the addition of oxidant from oxidant source 160 can be supplemented by, for example, adding wastewater containing hydrogen peroxide from unit operation 140 using pump P3. If the wastewater containing hydrogen peroxide from unit operation 140 contains sufficient hydrogen peroxide, hydrogen peroxide can be used as the sole source of hydrogen peroxide added to the wastewater in vessel 150.

[0030] In other embodiments, persulfates such as ammonium persulfate, potassium persulfate, and / or sodium persulfate may be used as the oxidant. The aspects and embodiments disclosed herein are not limited by the type of oxidant added to the treatment system. Upon reaction with the dissolved copper in vessel 150, peroxides generate hydroxyl radicals and peroxyhydroxyl radicals, while persulfates generate persulfate radicals.

[0031] A pH adjusting chemical source 170, such as a sulfuric acid source and / or a sodium hydroxide source, may add a pH adjusting agent to the wastewater in the vessel 150 in an amount and at a rate sufficient to maintain the pH of the wastewater in the vessel at a desired level (e.g., between 2 and 4 or approximately 3) to promote reactions that result in the decomposition of organic compounds in the wastewater.

[0032] The wastewater from the CMP unit operation 120 may contain sufficient copper, such as copper sulfate, to catalyze the production of hydroxyl radicals from hydrogen peroxide in a Fenton-like reaction in the vessel 150, which will decompose one or more organic substances in the wastewater in the vessel 150. Byproducts of the decomposition of organic pollutants, such as nitrogen oxides (NO2 / NO3) and carbon dioxide, may exit the vessel 150 through the exhaust port V. The one or more organic substances may include one or more azoles, such as one or more of 1,2,4-triazole, 1H-benzotriazole, or tolyltriazole:4,5-toluenetriazole, that may be present in the wastewater from the CMP unit operation 120. A Fenton-like reagent for decomposing the azoles may be prepared by adding about 500 mg / l to about 3000 mg / l of an oxidizing agent, such as hydrogen peroxide or a persulfate, to about 50 mg / l to about 300 mg / l of a soluble copper compound, such as copper (Cu) 2+ ) sulfate).

[0033] Fenton-like reactions can occur according to chemical equations (1)-(3): Cu 2++ H2O2→ Cu 3+ + HO• + OH - (1) Cu 3+ + H2O2→ Cu 2+ + HOO• + H + (2) Cu 2+ + S2O8 2- → Cu 3+ + SO4• - + SO4 2- (3).

[0034] Persulfate and Cu 2+ Oxidation or Cu 3+ The hydroxyl radicals, peroxyhydroxyl radicals, and persulfate radicals formed by the reduction of azoles can react with azoles in the CMP wastewater and decompose the azoles into primarily nitrogen oxides (NO2 / NO3), carbon dioxide, and water. Without wishing to be bound by any particular theory, the decomposition of nitrogen-containing organic molecules such as azoles can occur via the reaction shown in Equation 4: C x N y H z + OH• → CO2+ NO3+ H2O (4).

[0035] One or more sensors or monitors, such as a temperature sensor, a pH sensor, an ORP sensor, a chemical concentration sensor, etc., collectively represented by "S", can be present in the container 150 and in contact with the wastewater in the container. The one or more sensors S can communicate with the controller 190. The controller 190 can be a conventional computer including a conventional processor, such as a Core i7 processor from Intel Corporation. ® processor and runs a conventional operating system, such as Windows from Microsoft ® 1 and 12. The controller 190 may optionally be or include a specially programmed controller, such as an application specific integrated circuit (ASIC) programmed to perform the functions disclosed herein. The controller 190 is programmed or otherwise configured to control the pH adjustment chemical source 170 to introduce the pH adjustment chemical into the wastewater in the vessel 150 in an amount and at a rate sufficient to maintain the pH of the wastewater at a level at which the copper catalyzes the production of hydroxyl radicals by the oxidant. The controller 190 may also control the operation of any of the pumps P1-P6 to control, for example, the introduction of wastewater from the CMP unit operation 120, the introduction of oxidant from the oxidant source 160, the introduction of wastewater containing hydrogen peroxide from the unit operation 140, and the removal of treated wastewater from the vessel 150.

[0036] In some embodiments, the wastewater from CMP unit operation 120 may not contain sufficient copper to catalyze the production of sufficient hydroxyl radicals to decompose the organic contaminants in the wastewater from CMP unit operation 120 to the lowest possible level as desired. Therefore, additional copper may be added to the wastewater in vessel 150 from, for example, unit operation 130, which generates wastewater having a high concentration of dissolved copper, via pump P2 operated by controller 190.

[0037] Wastewater in vessel 150, from which organic compounds have been removed by Fenton-like decomposition as disclosed herein, can exit the vessel and be directed, for example, by pump P6, to a post-treatment system 180. Post-treatment system 180 can be used to remove residual copper and other undesirable components from the partially treated wastewater exiting vessel 150 using methods known in the art, and can produce treated water that can be discharged to the environment, recycled, or sent for further treatment or disposal.

[0038] Aspects and embodiments disclosed herein also relate to a method for removing one or more azoles from wastewater from a semiconductor production facility, such as wastewater from a chemical mechanical polishing (CMP) unit operation utilizing a Fenton-like reagent. Removing the one or more azoles from the wastewater may include removing one or more of 1,2,4-triazole, 1H-benzotriazole, or tolyltriazole:4,5-toluenetriazole from the wastewater. The method may include obtaining copper from the wastewater. The wastewater from the CMP unit operation may already contain sufficient copper in the form of copper sulfate or other copper compounds, and thus supplementing the CMP unit operation wastewater with additional copper may not be necessary. The method may also include introducing an oxidizing agent into the wastewater to generate hydroxyl radicals from the oxidizing agent to react with the one or more azoles, wherein copper catalyzes the generation of hydroxyl radicals from the oxidizing agent. The pH of the wastewater may be maintained at a level at which copper catalyzes the generation of hydroxyl radicals from the oxidizing agent. Introducing the oxidizing agent into the wastewater may include introducing hydrogen peroxide into the wastewater. In some embodiments, the hydrogen peroxide may be obtained from a waste stream from the semiconductor manufacturing facility.

[0039] Example CMP slurry wastewater (slurry copper waste - SCW) and wastewater with high Cu concentration (concentrated copper waste - CCW) from semiconductor production facilities, as well as a 25:1 mixture of SCW and CCW, were analyzed and found to contain the contaminants listed in Table 1 below: Table 1 - SCW and CCW wastewater analysis

[0040] Tests were conducted to determine whether the amount of copper present in a 25:1 mixture of SCW and CCW was sufficient to catalyze the production of sufficient hydroxyl radicals to decompose the 1,2,4-triazole present in the mixture. Details of the test conditions and results are presented in Table 2 below: Table 2 - Decomposition of azoles using a Fenton-like reaction in SCW:CCW mixtures

[0041] The pH of the blended sample (962 mL SCW + 38 mL CCW) was 3.0. A cumulative dose of 1,680 mg / L of H2O2 produced a 90% TOC removal rate and a residual azole level of 0.38 mg / L (99% removal) within a 120-minute reaction time. These results were achieved without the addition of iron and demonstrate that copper, already present in wastewater streams from semiconductor manufacturing facilities, can be used as a catalyst for Fenton-like reactions to successfully remove organic pollutants, including azoles, from those same wastewater streams.

[0042] The words and terms used herein are for descriptive purposes and should not be considered limiting. As used herein, the term "more than one / plurality" refers to two or more items or components. The terms "comprising," "including," "carrying," "having," "containing," and "involving," whether in the written description or in the claims and the like, are open-ended terms, meaning "including but not limited to." Therefore, the use of such terms is intended to encompass the items listed thereafter and their equivalents, as well as additional items. With respect to the claims, only the transitional terms "consisting of" and "consisting essentially of" are closed transitional terms or semi-closed transitional terms, respectively. The use of ordinal terms such as "first," "second," "third," and the like in the claims that modify claim elements does not, by itself, imply any priority, precedence, or order of one claim element relative to another claim element, or the temporal order in which the acts of the method are performed, but rather serves merely as a marker to distinguish one claim element having a certain name from another element having the same name (but using ordinal terms) to distinguish the claim elements.

Claims

1. A method for removing one or more azoles from wastewater of a semiconductor production facility, the method comprising: obtaining copper from the wastewater; as well as An oxidizing agent is introduced into the wastewater to generate hydroxyl radicals from the oxidizing agent to react with the one or more azoles, wherein the copper catalyzes the generation of the hydroxyl radicals from the oxidizing agent.

2. The method of claim 1 , further comprising maintaining the pH of the wastewater at a level at which the copper catalyzes the production of the hydroxyl radicals from the oxidant.

3. The method of claim 1, further comprising obtaining the wastewater from a copper chemical mechanical polishing (CMP) operation of the semiconductor fabrication facility.

4. The method of claim 1 , wherein removing the one or more azoles from the wastewater comprises removing one or more of 1,2,4-triazole, pyrazole, benzotriazole, 5-methyl-1H-benzotriazole (toluenetriazole), or 3-amino-1,2,4-triazole from the wastewater.

5. The method of claim 1, wherein introducing the oxidizing agent into the wastewater comprises introducing hydrogen peroxide into the wastewater.

6. The method of claim 5, further comprising obtaining the hydrogen peroxide from a waste stream from the semiconductor fabrication facility.

7. The method of claim 1, wherein the copper is present in the wastewater in the form of copper sulfate.

8. A system for removing one or more azoles from copper-containing wastewater from a semiconductor manufacturing facility, the system comprising: a container fluidly connectable to a wastewater source; an oxidant source configured to introduce an oxidant into the wastewater in the vessel, the copper catalyzing generation of hydroxyl radicals from the oxidant to react with the one or more azoles; and A pH adjusting chemical source is configured to introduce a pH adjusting chemical into the wastewater in the container.

9. The system according to claim 8, further comprising: a pH monitor disposed within the container; as well as A controller is configured to control the pH adjusting chemical source to introduce the pH adjusting chemical into the wastewater in the container in an amount and at a rate sufficient to maintain the pH of the wastewater at a level at which the copper catalyzes the generation of hydroxyl radicals from the oxidant.

10. The system of claim 8, wherein the wastewater comprises one or more of 1,2,4-triazole, pyrazole, benzotriazole, 5-methyl-1H-benzotriazole (toluenetriazole), or 3-amino-1,2,4-triazole, and the system is configured to decompose the one or more of 1,2,4-triazole, pyrazole, benzotriazole, toluenetriazole, or 3-amino-1,2,4-triazole using the hydroxyl radical.

11. The system of claim 8, wherein the wastewater is copper chemical mechanical polishing (CMP) wastewater at the semiconductor fabrication facility.

12. The system of claim 8, wherein the copper is in the form of copper sulfate.

13. The system of claim 8, wherein the oxidant source is a source of hydrogen peroxide.

14. The system of claim 13, wherein the source of hydrogen peroxide comprises a waste stream from the semiconductor fabrication facility.

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