Treatment of organic-containing wastewater using modified Fenton's reagent

Abstract

The disclosed method for removing one or more azoles from wastewater of a semiconductor manufacturing facility includes obtaining copper from the wastewater and introducing an oxidizing agent into the wastewater to generate hydroxyl radicals from the oxidizing agent and react with the one or more azoles, wherein the copper catalyzes the generation of hydroxyl radicals from the oxidizing agent.

Description

[Technical Field]

[0001] Aspects and embodiments disclosed herein relate to systems and methods for the treatment of wastewater, such as copper chemical mechanical polishing (CMP) wastewater containing organic contaminants such as azoles. The methods disclosed herein provide for the destruction of organic contaminants in the wastewater using a modified Fenton's reagent. Summary of the Invention

[0002] According to one embodiment, there is provided a method for removing one or more azoles from wastewater of a semiconductor fabrication facility, the method comprising the steps of obtaining copper from the wastewater and introducing an oxidizing agent into the wastewater to generate hydroxyl radicals from the oxidizing agent and react with one or more azoles, wherein the copper catalyzes the generation of hydroxyl radicals from the oxidizing agent, thereby removing the one or more azoles from the wastewater of the semiconductor fabrication facility.

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

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

[0005] In some embodiments, the step of removing one or more azoles from the wastewater comprises 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, the step of introducing an oxidizing agent to the wastewater comprises introducing hydrogen peroxide to the wastewater.

[0007] In some embodiments, the method further comprises obtaining 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 comprising: a vessel fluidly connectable to a source of wastewater; an oxidant source configured to introduce an oxidant to the wastewater in the vessel, where copper catalyzes the production of hydroxyl radicals from the oxidant to react with the one or more azoles; and a pH-adjusting chemical source configured to introduce a pH-adjusting chemical to the wastewater in the vessel.

[0010] In some embodiments, the system includes a pH monitor disposed within the vessel; and a controller configured to control a pH adjusting chemical source to introduce a pH adjusting chemical into the wastewater in the vessel 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 oxidizing agent. Further provided are:

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

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

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

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

[0015] In some embodiments, the hydrogen peroxide source comprises a waste stream from a semiconductor manufacturing facility.

[0016] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component is designated by a like numeral. For clarity, not all components may be labeled. [Brief explanation of the drawings]

[0017] [Figure 1] 1 illustrates an example of a system disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0018] The chemical mechanical polishing (CMP) planarization process involves removing and / or etching semiconductor wafers during the manufacturing process using a polishing slurry containing oxidizers, abrasives, complexing agents, and additives. 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 in combination with the polishing pad to the silicon wafer on the planarization table. Oxidizers and etchants are introduced to control material removal. Deionized water rinses are generally used to remove debris from the silicon wafer. UPW, demineralized water, and polishing water from reverse osmosis (RO) can also be used to rinse silicon wafers in semiconductor manufacturing facility equipment.

[0019] An oxidizer, hydrogen peroxide (H2O2), is typically used to help dissolve copper from the microchips, so levels of about 300 ppm or more of hydrogen peroxide (H2O2) may also be present in the by-product polishing slurry wastewater.

[0020] In the manufacturing process of semiconductor devices, the CMP step for polishing copper surfaces when mounting copper wiring generates a large amount of wastewater containing copper corrosion inhibitors, and therefore, treatment of the wastewater is desirable to prevent the release of undesirable pollutants into the environment.

[0021] Among copper corrosion inhibitors, azole-type copper corrosion inhibitors in particular have excellent corrosion inhibitory effects. However, azole-type copper corrosion inhibitors usually have a chemically stable structure and are not easily biodegradable. For this reason, in the treatment of wastewater containing azole-type copper corrosion inhibitors discharged from processes, the azole-type copper corrosion inhibitors are decomposed using an oxidizing agent with high oxidizing power, such as ozone, ultraviolet light, or hydrogen peroxide, or an advanced oxidation process using a combination of these oxidizing agents, and the treated water is then discharged or recovered.

[0022] However, as mentioned above, because azole-type copper corrosion inhibitors are chemically stable, even when a highly oxidizing agent such as ozone is used, the oxidative decomposition of the azole-type copper corrosion inhibitor requires the addition of a large amount of the oxidizing agent, which poses a significant problem from the viewpoint of cost. In particular, in recent years, with the increasing integration of semiconductor devices, the number of fine polishing steps has increased, and the amount of polishing wastewater discharged has also increased. Therefore, the increased cost due to the increased capacity of wastewater treatment facilities has become a problem.

[0023] Fenton's reagent is often used to treat organic compounds. It can be produced by adding 10 parts peroxide to 1 part ferrous peroxide (ferrous sulfate) for every 0.3 parts of organic compound. Fenton's reagent is effective in treating some azoles, such as pyrazoles. However, laboratory tests have shown that other forms of azoles, such as 1,2,4-triazoles, are not degraded by exposure to Fenton's reagent.

[0024] As mentioned above, azoles are often used as corrosion inhibitors in facilities that manufacture computer chips. These facilities also typically have high copper-containing wastewater from the CMP process, which is treated and disposed of at the facility's expense after use. In one embodiment, azole compounds in the wastewater are treated and decomposed by substituting a waste copper stream for iron in the Fenton reagent. Testing has shown that 1,2,4-triazole, 1H-benzotriazole, and methylbenzotriazole:4,5-tolyltriazole can all be treated using the copper-substituted Fenton reagent. In one test, waste hydrogen peroxide (containing the azole to be treated) and waste copper sulfate, which can be used in place of iron sulfate in the Fenton reaction, were used to produce an oxidant-containing solution that effectively decomposed the azole.

[0025] In some embodiments, copper replaces iron in a modified Fenton reaction, or what is referred to herein as a Fenton-like reaction. Waste copper streams from semiconductor manufacturing facilities plants can be used as the copper source.

[0026] As mentioned above, wastewater from semiconductor manufacturing facilities or other industrial sources can contain high levels of azoles, for example, from about 20 mg / L up to about 200 mg / L or more, which are used as corrosion inhibitors for copper during wafer planarization and polishing processes. Wastewater from these processes can also contain heavy metals, additional organic compounds such as alcohols, and / or surfactants such as ammonium salts and inorganic abrasives such as colloidal silica, all of which should be removed before discharge. These additional contaminants can be present at levels of about 0.01 wt% to about 1 wt%. The wastewater also has high background total organic carbon (TOC) concentrations, with total azoles comprising a portion of the TOC. For example, oxidizers such as hydrogen peroxide (HO), commonly used to dissolve copper from microchips, can be present in CMP wastewater at concentrations exceeding 1,000 mg / L or 0.1 wt%.

[0027] Although azoles are not currently regulated by U.S. regulatory agencies at maximum contaminant levels (MCLs), they may present adverse environmental impacts when discharged into open waterways. Recent evidence indicates bioaccumulation of azoles in fish and toxicity in naturally occurring algal blooms, necessitating their removal from process waters prior to discharge.

[0028] As described in U.S. Patent No. 8,801,937, the entire disclosure of which is incorporated herein by reference, azole compounds are widely used in the semiconductor industry as corrosion inhibitors for copper during silicon wafer processing. 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, and any of their derivatives, amine salts, metals, etc. Examples of azole derivatives include compounds having a condensed ring such as an azole ring and a benzene ring, such as indazole, benzimidazole, benzotriazole, and benzothiazole, as well 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 alkylaminosulfonylbenzotriazoles. and derivatives thereof, such as arylbenzotriazole, mercaptobenzotriazole, hydroxybenzotriazole, nitrobenzotriazole (e.g., 4-nitrobenzotriazole), halobenzotriazole (e.g., 5-chlorobenzotriazole), hydroxyalkylbenzotriazole, hydrobenzotriazole, aminobenzotriazole, (substituted aminomethyl)tolyltriazole, carboxybenzotriazole, N-alkylbenzotriazole, bisbenzotriazole, naphthatriazole, mercaptobenzothiazole, and aminobenzothiazole, as well as amine salts and metal salts thereof.

[0029] One embodiment of a system for treating azole-containing wastewater from a semiconductor production facility is shown schematically in Figure 1. A semiconductor production facility 110 typically contains hundreds of unit operations, three of which are shown in Figure 1. The unit operations shown in Figure 1 are a copper CMP unit operation 120, a unit operation 130 that produces high-concentration dissolved copper-containing wastewater, such as a copper plating operation, and a unit operation 140 that produces high-concentration hydrogen peroxide-containing wastewater, such as one of the wafer cleaning unit operations within the 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 is used to catalyze the production of hydroxyl radicals from hydrogen peroxide. The hydroxyl radicals oxidatively decompose the organic contaminants, converting them into more harmless byproducts, such as nitrogen dioxide (NO2 / NO3), carbon dioxide, and water.

[0030] Wastewater from CMP unit operation 120 is directed to vessel 150, e.g., by pump P1. An oxidant, e.g., hydrogen peroxide from oxidant source 160, is added to the wastewater in vessel 150, e.g., using another pump P4, in an amount and rate sufficient to maintain a desired concentration of hydrogen peroxide in the vessel, e.g., 300 mg / L or greater, to promote the degradation of organic compounds in the wastewater. In some embodiments, the addition of oxidant from oxidant source 160 can be supplemented by the addition of hydrogen peroxide-containing wastewater from unit operation 140, e.g., using pump P3. If the hydrogen peroxide-containing wastewater from unit operation 140 contains sufficient hydrogen peroxide, it can be used as the sole source of hydrogen peroxide to be added to the wastewater in vessel 150.

[0031] In other embodiments, persulfates, such as ammonium persulfate, potassium persulfate, and / or sodium persulfate, may be utilized as the oxidizing agent. The aspects and embodiments disclosed herein are not limited by the type of oxidizing agent added to the treatment system. Peroxides generate hydroxyl and hydroperoxyl radicals when reacting with dissolved copper in vessel 150, and persulfates generate persulfate radicals.

[0032] A pH adjusting chemical source 170, e.g., a sulfuric acid and / or sodium hydroxide source, may add pH adjusting agents to the wastewater in 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., 2-4 or about 3, and promote the decomposition reaction of organic compounds in the wastewater.

[0033] The wastewater from CMP unit operation 120 may contain sufficient copper, for example, in the form of copper sulfate, to catalyze the production of hydroxyl radicals from hydrogen peroxide in vessel 150 in a Fenton-like reaction in which one or more organic species in the wastewater in vessel 150 are decomposed. Decomposition by-products of organic contaminants, such as nitrogen dioxide (NO2 / NO3) and carbon dioxide, may be vented from vessel 150 via vent V. The one or more organic species may include one or more azoles, such as 1,2,4-triazole, 1H-benzotriazole, or methylbenzotriazole:4,5-tolyltriazole, which may be present in the wastewater from CMP unit operation 120. The Fenton-like reagent used to decompose the azoles may contain 500 mg / L to 3,000 mg / L of an oxidant, such as hydrogen peroxide or persulfate, in a mixture of 50 mg / L to 300 mg / L of a soluble copper compound, such as copper sulfate (Cu 2+ )) to form the compound.

[0034] The Fenton-like reaction can proceed according to the following chemical formulas (1) to (3). JPEG2026505269000002.jpg39127

[0035] Cu 2+ Oxide of Cu 3+ The persulfates and hydroxyl radicals, hydroperoxyl radicals, and persulfate radicals formed by the reduction of azoles react with the azoles in the CMP wastewater and decompose into primarily nitrogen dioxide (NO2 / NO3), carbon dioxide, and water. Without wishing to be bound by theory, the decomposition of nitrogenous organic molecules such as azoles may proceed according to the reaction shown in equation (4). JPEG2026505269000003.jpg12127

[0036] One or more sensors or monitors, e.g., temperature, pH, ORP, chemical concentration sensors, etc., collectively referred to as "S," may be provided in contact with the wastewater in vessel 150. The one or more sensors S may be in communication with controller 190. Controller 190 may be a conventional computer, e.g., equipped with an Intel Core® processor and running a conventional operating system, such as any version of Microsoft Windows®, and may be programmed to perform the functions disclosed herein. If desired, the controller may be or include a specially programmed controller, such as an application-specific integrated circuit (ASIC), programmed to perform the functions disclosed herein. Controller 190 is programmed or configured to control pH-adjusting chemical source 170 to introduce pH-adjusting chemical into vessel 150 in an amount and at a rate sufficient to maintain the pH of the wastewater in the vessel at a level at which copper catalyzes the production of hydroxyl radicals from the oxidizing agent. Controller 190 may also control the operation of any of pumps P1-P6, such as those controlling the removal of wastewater from CMP unit operation 120, oxidant from oxidant source 160, hydrogen peroxide-containing wastewater from unit operation 140, and treated wastewater from vessel 150.

[0037] In some embodiments, the wastewater from CMP unit operation 120 may not contain enough copper to catalyze the production of sufficient hydroxyl radicals to degrade the organic contaminants in the wastewater from CMP unit operation 120 to the desired low levels. Therefore, additional copper may be added to the wastewater in vessel 150 via pump P2 operated by controller 190, for example, from a unit operation 130 having wastewater containing high concentrations of dissolved copper.

[0038] As disclosed herein, the wastewater from which organic compounds have been degraded and removed by the Fenton-like reaction in vessel 150 may be discharged from the vessel and directed, for example, by pump P6, to post-treatment system 180. Post-treatment system 180 may be used to remove residual copper and other unwanted components from the partially treated wastewater discharged from vessel 150 using methods known to those skilled in the art, producing treated water that may be discharged to the environment, recycled, or sent for further treatment or disposal.

[0039] Aspects and embodiments disclosed herein also relate to methods for removing one or more azoles from wastewater from a semiconductor production facility, such as wastewater from a chemical mechanical polishing unit operation using a Fenton-like reagent. Removing one or more azoles from the wastewater can include removing one or more of 1,2,4-triazole, 1H-benzotriazole, or methylbenzotriazole:4,5-tolyltriazole from the wastewater. The method can include obtaining copper from the wastewater. The wastewater from the chemical mechanical polishing unit operation may already contain sufficient copper in the form of copper sulfate or other copper compounds, so that additional copper supplementation may not be necessary. The method can further include introducing an oxidizing agent into the wastewater, generating hydroxyl radicals from the oxidizing agent to react with one or more azoles, where the copper catalyzes the generation of hydroxyl radicals from the oxidizing agent. The pH of the wastewater can be maintained at a level at which the copper catalyzes the generation of hydroxyl radicals from the oxidizing agent. Introducing the oxidizing agent into the wastewater can include introducing hydrogen peroxide into the wastewater. In some embodiments, hydrogen peroxide may be obtained from waste products from semiconductor manufacturing facilities. [Example]

[0040] Analysis of CMP slurry wastewater (slurry copper wastewater: SCW) and wastewater with high concentrations of Cu (concentrated copper waste: CCW), as well as a 25:1 mixture of SCW and CCW, from a semiconductor manufacturing facility, has revealed the presence of the contaminants listed in Table 1 below.

[0041] [Table 1]

[0042] Tests were conducted to determine whether copper in a 25:1 mixture of SCW and CCW was present in sufficient amounts to catalyze the production of enough hydroxyl radicals to decompose the 1,2,4-triazole present in the mixture. Test conditions and results are detailed in Table 2 below.

[0043] [Table 2]

[0044] The pH of the combined sample (962 mL SCW + 38 mL CCW) was 3.0. A cumulative HO dose of 1,680 mg / L over a 120-minute reaction time resulted in 90% TOC removal and 0.38 mg / L azole residual (99% removal). These results were achieved without added iron, demonstrating that copper, already present in wastewater streams from semiconductor manufacturing facilities, can be utilized as a catalyst in a Fenton-like reaction to effectively remove organic pollutants, including azoles, from the same wastewater stream.

[0045] The phrases and terms used herein are for descriptive purposes and should not be construed as limiting. As used herein, the term "plurality" refers to two or more items or components. Terms such as "comprise," "include," "hold," "have," "contain," "involve," and the like, whether in the specification or claims, are open-ended terms, i.e., meaning "including, but not limited to." Thus, the use of such terms is intended to encompass the subsequently listed items and their equivalents, as well as additional items. Only the transitional phrases "consisting of" and "consisting essentially of," respectively, are closed or semi-closed transitional phrases in the claims. The use of ordinal numbers such as "first," "second," and "third" to modify claim elements in the claims does not, in and of itself, imply that one claim element has a priority, precedence, or order in which method actions are performed relative to other claim elements, but is used merely as a label to distinguish one claim element having a particular name from another element having the same name (but using an ordinal number).

Claims

1. 1. A method for removing one or more azoles from wastewater from a semiconductor manufacturing facility, comprising: obtaining copper from the wastewater; introducing an oxidizing agent into the wastewater to generate hydroxyl radicals from the oxidizing agent to react with the one or more azoles; 10. A method for removing one or more azoles from wastewater from a semiconductor manufacturing facility, wherein the copper catalyzes the production of the hydroxyl radical from the oxidizing agent.

2. 10. The method of claim 1, further comprising maintaining the pH of the wastewater at a level where the copper catalyzes the production of the hydroxyl radicals from the oxidizing agent.

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

4. 10. 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 (tolutriazole), or 3-amino-1,2,4-triazole from the wastewater.

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

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

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

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

9. a pH monitor disposed within the vessel; a controller configured to control the pH adjusting chemical source to introduce the pH adjusting chemical into the wastewater in the vessel 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 from the oxidizing agent; The system of claim 8 further comprising:

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

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

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

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

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

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