Selective monitoring of basic chemicals

Abstract

A method is provided for the selective measurement and monitoring of multiple base chemicals in a processing solution. The method includes providing a processing solution containing multiple base chemicals and performing a first analytical method, such as measuring the conductivity of the solution mixture, in combination with a second analytical method, such as titrating or measuring pH of the solution. From such measurements, the concentration of one or more base chemicals can be selectively determined. In such a method, multiple bases in the same processing solution can be advantageously selectively and accurately measured and monitored.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to the analysis of process solutions, such as semiconductor process solutions, and more particularly to techniques for the measurement and monitoring of multiple base chemicals in such process solutions. [Background technology]

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 140,405, filed January 22, 2021, the contents of which are incorporated herein by reference in their entirety. Processing solutions are used in several industries, including the semiconductor industry, to produce products with desired properties. Such processing solutions may include, for example, base chemicals for use in materials processing. One group of base chemicals includes hydroxides, which may be represented as X-OH, where X may be a metal. Another group of base chemicals may be nitrogen-based, which may be represented as (R1-N-R2, R2, R3)+. In some cases, a particular base may have characteristics of both ammonium hydroxide (NH4OH) and tetramethylammonium hydroxide ((CH3)4N(OH)) or TMAH, for example.

[0003] Different base materials may provide different process characteristics in solution. Thus, combinations of multiple base chemicals may be utilized, for example, to provide products with specific characteristics. Process control may require accurate and selective measurement and monitoring of multiple bases in a solution mixture. Certain methods may provide for the continuous titration of two bases. However, such methods may require a relatively large difference in pK values ​​(e.g., a strong base and a weak base) and may be limited when two strong bases cannot be distinguished from each other in solution. Another method involves the continuous titration of two bases in the presence of a solvent. The solvent can manipulate the strength of the bases and, in some cases, force two different bases to have different properties. For example, one base may be a strong base and another a weak base. However, the use of flammable solvents may pose safety hazards and environmental hazards. Additional methods include ion chromatography and capillary electrophoresis, but they can be expensive, difficult to automate, and have relatively long analysis times. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 6,302,600 [Patent Document 2] U.S. Patent No. 5,472,516 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, a process that provides economical, safe, efficient, rapid, and accurate selective measurement and monitoring of multiple base chemicals in a processing solution, for example, two base chemicals in a solution mixture, is desirable. [Means for solving the problem]

[0006] The disclosed methods provide for the selective measurement and monitoring of multiple base chemicals in a processing solution, such as a semiconductor processing solution. Specifically, in certain embodiments, the present disclosure provides for the selective measurement and monitoring of multiple base chemicals by combining a first analytical method, such as titration or pH measurement, with a second analytical method, such as conductivity measurement. In such methods, multiple base chemicals in the same processing solution can be selectively and accurately measured and monitored. Furthermore, such methods provide an economical, safe, efficient, and rapid means for determining the foregoing.

[0007] An exemplary method for determining the concentration of at least one base chemical in a processing solution containing a first base chemical and a second base chemical is provided. The method includes performing a first analytical method including measuring the conductivity of the processing solution to provide a first measurement value, performing a second analytical method of the processing solution to provide a second measurement value, and determining the concentration of at least one of the first base chemical and the second base chemical based on the first and second measurements. The first base chemical is different from the second base chemical. The first analytical method is different from the second analytical method.

[0008] In certain embodiments, the second analytical method may include titrating the process solution.

[0009] In certain embodiments, the second analytical method may include measuring the pH of the treatment solution.

[0010] In certain embodiments, the first and second base chemicals can be strong bases.

[0011] In certain embodiments, the processing solution may be a semiconductor processing solution.

[0012] In certain embodiments, the first base chemical can be a hydroxide. In certain embodiments, the first base chemical can be sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH).

[0013] In certain embodiments, the second base chemical can be an amine compound. In certain embodiments, the second base chemical can be monoethylamine (MEA), ammonium hydroxide, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, methyltrihydroxyethylammonium hydroxide, phenyltrimethylammonium hydroxide, phenyltriethylammonium hydroxide, or benzyltrimethylammonium hydroxide.

[0014] In certain embodiments, the conductivity of the process solution may be measured at a constant temperature.

[0015] A method is provided for determining the concentration of at least one base chemical in a processing solution containing hydroxide and amine compounds. An exemplary method includes performing a first analytical method including measuring the conductivity of the processing solution to provide a first measurement value, performing a second analytical method of the processing solution to provide a second measurement value, and determining the concentration of at least one of the hydroxide and amine compounds based on the first and second measurements. The first analytical method is different from the second analytical method.

[0016] In certain embodiments, the second analytical method may include titrating the process solution.

[0017] In certain embodiments, the second analytical method may include measuring the pH of the treatment solution.

[0018] In certain embodiments, the hydroxide and amine compounds may be strong bases.

[0019] In certain embodiments, the processing solution may be a semiconductor processing solution.

[0020] In certain embodiments, the hydroxide can be sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH).

[0021] In certain embodiments, the amine compound can be monoethylamine (MEA), ammonium hydroxide, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, methyltrihydroxyethylammonium hydroxide, phenyltrimethylammonium hydroxide, phenyltriethylammonium hydroxide, or benzyltrimethylammonium hydroxide.

[0022] In certain embodiments, the conductivity of the process solution may be measured at a constant temperature. [Brief explanation of the drawings]

[0023] [Figure 1A] 1 shows results for the measured concentration (N) of sodium hydroxide (NaOH) from conductivity and titration measurements versus the expected concentration (N) of NaOH in the solution mixture according to Example 1. [Figure 1B] 1 shows the results for the measured concentration (N) of monoethylamine (MEA) from conductivity and titration measurements versus the expected concentration (N) of MEA in the solution mixture according to Example 1. [Figure 1C] 1 shows results for the measured concentration (N) of sodium hydroxide (NaOH) from conductivity and pH measurements versus the expected concentration (N) of NaOH in the solution mixture according to Example 1. [Figure 2A] 1 shows the results for the measured concentration (wt%) of base 1 (B) from conductivity and titration measurements versus the expected concentration (wt%) of base 1 (B) in the solution mixture according to Example 2. [Figure 2B] 1 shows the results for the measured concentration (wt%) of base 2 (TMAH) from conductivity and titration measurements versus the expected concentration (wt%) of base 2 (TMAH) in the solution mixture according to Example 2. [Figure 2C]1 shows the results for the measured concentration (wt%) of base 1 (B) by conductivity and pH measurements versus the expected concentration (wt%) of base 1 (B) in the solution mixture according to Example 2. [Figure 2D] 1 shows the results for the measured concentration (wt%) of base 2 (TMAH) by conductivity and pH measurements versus the expected concentration (wt%) of base 2 (TMAH) in the solution mixture according to Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present disclosure provides techniques for selectively measuring and monitoring multiple base chemicals in processing solutions, such as semiconductor processing solutions. In certain embodiments, the present disclosure provides for accurately determining the concentration of one or more base chemicals in a solution mixture by combining a first analytical method, such as titration or pH measurement, with a second analytical method, such as conductivity measurement. Thus, multiple base chemicals in the same processing solution can be advantageously selectively measured and monitored. In certain embodiments, the processing solution can include multiple strong bases.

[0025] The technical terms used in this disclosure are generally known to those skilled in the art. As used herein, the phrase "predetermined concentration" refers to a known, target, or optimal concentration for a component in solution.

[0026] As used herein, a "strong base" refers to a base that can be fully ionized in solution. In certain embodiments, a "strong base" as used herein refers to a base that can ionize a proton (H) from a molecule of a very weak acid in an acid-base reaction. + ) refers to a basic compound that can remove

[0027] As used herein, a "weak base" refers to a base that does not completely ionize in solution. In certain aspects, a "weak base" as used herein refers to an incompletely protonated basic compound.

[0028] As used herein, the terms "selective" or "selectively" refer to, for example, the specific monitoring, measurement, or determination of a particular or specific component property. For example, the selective measurement of a base chemical refers to the measurement of one particular or predetermined target base chemical from multiple base chemicals present in a solution.

[0029] As used herein, the terms "accurate" or "accurately" refer to, for example, a measurement or determination that is relatively close or near to an existing or true value, a standard or known measurement or value.

[0030] As used herein, the term "about" or "approximately" means within an acceptable range of error for a particular value, as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, the term "about" can mean within a 20% range, a 10% range, a 5% range, or a 1% range for a given value.

[0031] The methods of the present disclosure may be applied to various types of solutions, including process solutions, which in certain embodiments may be semiconductor process solutions.

[0032] In certain embodiments, the processing solution may include one or more base chemicals. Those skilled in the art will appreciate that a wide variety of base chemicals are suitable for use with the present disclosure. In certain embodiments, the one or more base chemicals may include a hydroxide. In certain embodiments, the hydroxide may include sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH). Those skilled in the art will appreciate that a wide variety of hydroxides are suitable for use with the present disclosure. In certain embodiments, the one or more base chemicals may include an amine compound. In certain embodiments, the amine compound may include monoethylamine (MEA), ammonium hydroxide, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, methyltrihydroxyethylammonium hydroxide, phenyltrimethylammonium hydroxide, phenyltriethylammonium hydroxide, benzyltrimethylammonium hydroxide, and the like. Those skilled in the art will appreciate that a wide variety of amine compounds are suitable for use with the present disclosure. In certain embodiments, the one or more base chemicals may include at least one strong base, and each of the one or more base chemicals in the processing solution may be a strong base. In certain embodiments, the one or more base chemicals may include at least one weak base, and each of the one or more base chemicals in the processing solution may be a weak base. In certain embodiments, the one or more base chemicals may include at least one weak base and at least one strong base in the processing solution.

[0033] In certain embodiments, the treatment solution may include multiple base chemicals. The multiple base chemicals may be different from one another. For example, in certain embodiments, the treatment solution may include a hydroxide and an amine compound. The hydroxide may be sodium hydroxide and the amine compound may be monoethylamine (MEA). Those skilled in the art will appreciate that a wide variety of combinations of base chemicals are suitable for use with the present disclosure.

[0034] The disclosed methods provide multiple analytical methods and measurements of a processing solution, for example, to advantageously and selectively measure multiple base chemicals in the same processing solution. In certain embodiments, conductivity, titration, and pH measurements of the processing solution may be determined. These measurements may be advantageously used to selectively determine the concentrations of multiple base chemicals in the processing solution. In certain embodiments, a first analytical method, such as a titration measurement, may be combined with a second analytical method, such as a conductivity measurement. Furthermore, in certain embodiments, a first analytical method, such as a pH measurement, may be combined with a second analytical method, such as a conductivity measurement.

[0035] In certain embodiments, the conductivity of the processing solution may be measured. For example, in certain embodiments, the conductivity of the processing solution may be measured by a conductivity meter. Each base species in the processing solution may contribute to the measured conductivity as: conductivity = a x (concentration of base 1, N) + b x (concentration of base 2, N). The coefficients (a) and (b) may be determined by measuring the conductivity of several standard solutions with known concentrations of base. In certain embodiments, the conductivity measurement may be performed at a constant temperature or temperature compensated. In certain embodiments, the conductivity measurement may be performed at room temperature, e.g., about 22°C.

[0036] In certain embodiments, one or more base chemicals may be titrated together as total base. For example, in certain embodiments, a total base titration may be performed by adding a titrant / acid having a known concentration to a fixed volume of an unknown base sample until an endpoint is reached. The endpoint may be determined, for example, by a pH indicator or pH electrode, and the titrant volume may be recorded. Total base (N) may be determined as Total Base (N) = Concentration of Titrant / Acid × Volume of Titrant / Volume of Unknown Base Sample. In certain aspects, each base species in the treatment solution may contribute to the measured total base (N) by titration as Total Base by Titration N = (Concentration of Base 1, N) + (Concentration of Base 2, N).

[0037] In certain embodiments, the pH of the processing solution may be measured. For example, in certain embodiments, the pH may be measured by a pH electrode. Each base species in the processing solution may contribute to the measured pH of the processing solution as pH = f1 (concentration of base 1, N) + f1 × (concentration of base 2, N), where f1 and f2 may be linear or logarithmic functions. For example, f(x) = n + mX, or f(x) = N + Mlog(x).

[0038] In certain aspects, one or more base chemicals can be measured by conductivity and titration measurements of the process solution. For example, in certain embodiments, the concentration of one or more base chemicals can be determined as Concentration(Base(i)) = Offset + Conductivity × Conductivity Slope(j) + Total Base × Total Base Slope(j).

[0039] In certain embodiments, the one or more base chemicals can be measured by conductivity and pH measurements of the processing solution. For example, the concentration of the one or more base chemicals can be determined as Concentration(Base(i)) = Offset + Conductivity × Conductivity Slope(j) + pH × pH Slope(j).

[0040] A method of the present disclosure provides for determining the concentration of at least one base chemical in a processing solution. The processing solution may include multiple base chemicals. In certain embodiments, the method may include providing a processing solution. The processing solution may include multiple base chemicals, e.g., a first base chemical and a second base chemical. In certain embodiments, a first analysis method of the processing solution may be performed to provide a first measurement value. The first analysis method may include measuring the conductivity of the processing solution. In certain embodiments, the method may include performing a second analysis method of the processing solution to provide a second measurement value. The second analysis method may include measuring or titrating the pH of the processing solution. The method may further include determining the concentration of at least one of the first and second base chemicals based on the first and second measurements. In certain embodiments, the first base chemical is different from the second base chemical. In certain embodiments, the first analysis method is different from the second analysis method.

[0041] The disclosed methods further provide for determining the concentration of at least one base chemical in the processing solution. In certain embodiments, the method may include providing a processing solution. The processing solution may include a hydroxide and an amine compound. A first analysis method of the processing solution may be performed to provide a first measurement value. The first analysis method may include measuring the conductivity of the processing solution. In certain embodiments, the method may include performing a second analysis method of the processing solution to provide a second measurement value. The second analysis method may include measuring or titrating the pH of the processing solution. The method may further include determining the concentration of at least one of the hydroxide and the amine compound based on the first and second measurements. In certain embodiments, the first analysis method is different from the second analysis method.

[0042] The presently disclosed subject matter will be better understood by reference to the following examples, which are merely illustrative of the presently disclosed subject matter and should not be construed as limiting the scope of the subject matter in any way. [Example]

[0043] The following examples are merely illustrative of the subject matter disclosed herein, and they should not be construed as limiting the scope of the subject matter in any way.

[0044] Example 1: Selective determination of sodium hydroxide (NaOH) and monoethylamine (MEA) in a solution mixture This example provides selective measurements of two different base chemicals, sodium hydroxide (NaOH) and monoethylamine (MEA), in a solution mixture. Both bases are strong (at least in the DIW basic matrix) and were titrated together as total base. Nine samples (Samples 1–9) were prepared as shown in Table 1. To selectively determine the concentrations of multiple bases in the solution mixture, the sample measurements were used in various calculations below. Total base (N) was measured by titrating 10 mL of the sample with 0.1 N hydrogen chloride (HCl). The endpoint was determined using a pH electrode, and the final volume of titrant (0.1 N HCl) was recorded. Total base (N) was calculated as titrant concentration (0.1 N) * final volume / sample volume (10 mL). The pH of the sample was measured using a pH electrode. The conductivity (mS / cm) of the sample was measured using a conductivity meter. The results are shown in Table 1.

[0045] The following calculations are equations for how each base species can contribute to the measurement signal (i.e., titration, conductivity, and pH). Total base by titration, N = (concentration of base 1 (NaOH), N) + (concentration of base 2 (MEA), N). Conductivity = a x (concentration of base 1 (NaOH), N) + b x (concentration of base 2 (MEA), N). The coefficients (a) and (b) were determined by conductivity measurements of several standard solutions with known concentrations of base. pH = f1 (concentration of base 1 (NaOH), N) + f1 × (concentration of base 2 (MEA), N), where f1 and f2 can be linear or logarithmic functions. For example, f(x) = n + mX, or f(x) = N + Mlog(x).

[0046] [Table 1]

[0047] The concentrations of NaOH and MEA in the solution were selectively determined from titration and conductivity measurements shown in Table 1.

[0048] The results for NaOH are shown in Table 2 and Figure 1A.

[0049] [Table 2]

[0050] The results for the MEAs are shown in Table 3 and Figure 1B.

[0051] [Table 3]

[0052] The concentration of NaOH in the solution was selectively determined from the pH and conductivity measurements shown in Table 1. The results are shown in Table 4 and Figure 1C.

[0053] [Table 4]

[0054] As shown in Tables 2-4 and Figures 1A-C, the disclosed method provides accurate and selective measurement and monitoring of multiple base chemicals in a solution mixture.

[0055] Calculation parameters The following calculation parameters (Equations 1-2 and Tables 4-5) were used to selectively determine the measured concentrations of multiple base chemicals in the solution mixture. Equation 1: Concentration(base(i)) = Offset + Conductivity × Conductivity Gradient(j) + Total Bases × Total Base Gradient(j)

[0056] [Table 5]

[0057] Equation 2: Concentration (NaOH) = Offset + Conductivity × Conductivity Gradient + pH × pH Gradient

[0058] [Table 6]

[0059] Example 2: Selective measurement of multiple bases (base 1 and base 2) in a solution mixture This example provides the selective measurement of two different base chemicals, Base 1 (B) and Base 2 (TMAH), in a commercially available formulation for cleaning semiconductor devices. Both bases were titrated together as the total base. Nine samples (Samples 10–18) were prepared as shown in Table 7. Sample measurements were used in various calculations below to selectively determine the concentrations of multiple bases in the solution mixture. Total base (N) was measured by titrating 1 mL of the sample with 0.1 N hydrogen chloride (HCl). The endpoint was determined with a pH electrode, and the final volume of titrant (0.1 N HCl) was recorded. Total base (N) was calculated as the titrant concentration (0.1 N) * final volume / sample volume (1 mL). The pH of the sample was measured with a pH electrode. The conductivity (mS / cm) of the sample was measured with a conductivity meter. The results are shown in Table 7.

[0060] The following calculations are equations for how each base species can contribute to the measurement signal (i.e., titration, conductivity, and pH). Total base by titration, N = (concentration of base 1 (B), N) + (concentration of base 2 (TMAH), N). Conductivity = a x (concentration of base 1 (B), N) + b x (concentration of base 2 (TMAH), N). The coefficients (a) and (b) were determined by conductivity measurements of several standard solutions with known concentrations of base. pH = f1 (concentration of base 1 (B), N) + f1 × (concentration of base 2 (TMAH), N), where f1 and f2 can be linear or logarithmic functions. For example, f(x) = n + mX, or f(x) = N + Mlog(x).

[0061] [Table 7]

[0062] The concentrations of base 1 (B) and base 2 (TMAH) in solution were selectively determined from titration and conductivity measurements shown in Table 7.

[0063] The results for base 1(B) are shown in Table 8 and Figure 2A.

[0064] [Table 8]

[0065] The results for base 2 (TMAH) are shown in Table 9 and Figure 2B.

[0066] [Table 9]

[0067] The concentrations of base 1 (B) and base 2 (TMAH) in the solution were selectively determined from the pH and conductivity measurements shown in Table 7.

[0068] The results for base 1(B) are shown in Table 10 and Figure 2C.

[0069] [Table 10]

[0070] The results for base 2 (TMAH) are shown in Table 11 and Figure 2D.

[0071] [Table 11]

[0072] As shown in Tables 8-11 and Figures 2A-D, the disclosed method provides accurate and selective measurement and monitoring of multiple base chemicals in a solution mixture.

[0073] Calculation parameters The following calculation parameters (Equations 3-4 and Tables 12-13) were used to selectively determine the measured concentrations of multiple base chemicals in the solution mixture. Equation 3: Concentration(base(i)) = Offset + Conductivity × Conductivity Gradient(j) + Total Bases × Total Base Gradient(j)

[0074] [Table 12]

[0075] Equation 4: Concentration(Base(i)) = Offset + Conductivity × Conductivity Gradient(j) + pH × pH Gradient(j)

[0076] [Table 13]

[0077] The description herein merely illustrates the principles of the disclosed subject matter. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in light of the teachings herein. Accordingly, the disclosure herein is intended to be illustrative, but not limiting, of the scope of the disclosed subject matter. Moreover, the principles of the disclosed subject matter may be embodied in various configurations and are not intended to be limited in any way to the specific embodiments presented herein.

[0078] In addition to the various embodiments shown and claimed, the disclosed subject matter is also directed to other embodiments having other combinations of the features disclosed and claimed herein. Thus, the specific features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter, such that the disclosed subject matter includes any suitable combination of the features disclosed herein. The foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to these disclosed embodiments.

[0079] It will be apparent to those skilled in the art that various modifications and variations can be made in the systems and methods of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter cover modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. 1. A method for determining a concentration of at least one base chemical in a processing solution comprising a first base chemical and a second base chemical, the method comprising: performing a first analytical method comprising measuring the conductivity of the process solution to provide a first measurement; performing a second analytical method including titrating the process solution and measuring pH to provide a second measurement; determining a concentration of at least one of the first base chemical and the second base chemical based on the first and second measurements, the first base chemical is different from the second base chemical, the first analytical method is different from the second analytical method, and the first measurement value and the second measurement value are selected to be a combination of the conductivity and the titration, or a combination of the conductivity and the pH; A method comprising:

2. 10. The method of claim 1, wherein the first base chemical and the second base chemical are strong bases.

3. The method of claim 1 , wherein the processing solution is a semiconductor processing solution.

4. The method of claim 1 , wherein the first base chemical comprises a hydroxide.

5. 5. The method of claim 4, wherein the first base chemical is sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH).

6. The method of claim 1 , wherein the second basic chemical comprises an amine compound.

7. 7. The method of claim 6, wherein the second base chemical is monoethylamine (MEA), ammonium hydroxide, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, methyltrihydroxyethylammonium hydroxide, phenyltrimethylammonium hydroxide, phenyltriethylammonium hydroxide, or benzyltrimethylammonium hydroxide.

8. The method of claim 1 , wherein the conductivity of the processing solution is measured at a constant temperature.

9. 1. A method for determining the concentration of at least one base chemical in a process solution containing hydroxide and amine compounds, comprising: performing a first analytical method comprising measuring the conductivity of the process solution to provide a first measurement; performing a second analytical method including titrating the process solution and measuring pH to provide a second measurement; determining a concentration of at least one of the hydroxide and the amine compound based on the first and second measurements; The first analysis method is different from the second analysis method, and the first measurement value and the second measurement value are selected to be a combination of the conductivity and the titration, or a combination of the conductivity and the pH; A method comprising:

10. 10. The method of claim 9, wherein the hydroxide and the amine compound are strong bases.

11. The method of claim 9 , wherein the processing solution is a semiconductor processing solution.

12. 10. The method of claim 9, wherein the hydroxide is sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH).

13. 10. The method of claim 9, wherein the amine compound is monoethylamine (MEA), ammonium hydroxide, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, methyltrihydroxyethylammonium hydroxide, phenyltrimethylammonium hydroxide, phenyltriethylammonium hydroxide, or benzyltrimethylammonium hydroxide.

14. The method of claim 9 , wherein the conductivity of the processing solution is measured at a constant temperature.

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