JP6168184B1 - Method and apparatus for measuring oxidant concentration, and electronic material cleaning apparatus - Google Patents

Abstract

A method for measuring an oxidant concentration in a sulfuric acid solution containing a metal and an oxidant can be accurately and efficiently measured without being affected by impurities such as metal, and can be easily brought online. I will provide a. SOLUTION: A sulfuric acid solution containing a metal and an oxidizing agent is mixed with a potassium iodide solution, UV absorbance at a wavelength of 200 to 600 nm is measured, and the oxidizing agent concentration of the sulfuric acid solution is determined based on the measurement result. To do. Impurities such as metals by adding a potassium iodide (KI) solution to a sulfuric acid solution containing a metal and an oxidizing agent, and selectively reacting an oxidizing substance in the sulfuric acid solution with KI to cause yellow coloration by liberated iodine. UV sensitivity becomes higher than that, and the UV absorbance can be measured with high accuracy by reducing the influence of impurities such as metals. [Selection] Figure 1

Description

  The present invention relates to a method and apparatus for measuring an oxidant concentration in a sulfuric acid solution containing a metal and an oxidant, and an electronic material cleaning apparatus using the apparatus.

  In semiconductor manufacturing processes, sulfuric acid-based oxidizer solutions such as SPM (mixed solution of sulfuric acid and hydrogen peroxide solution), SOM (ozone blowing sulfuric acid), and electrolytic sulfuric acid are used for resist removal, metal etching, and the like. In resist removal and metal etching using a sulfuric acid-based oxidant solution, the effect of the concentration of the oxidant in the sulfuric acid-based oxidant solution on the processing effect is large. For this reason, measurement and management of the oxidant concentration of the sulfuric acid-based oxidant solution are important requirements.

Conventionally, as a method for measuring the oxidant concentration in SPM or electrolytic sulfuric acid, the following methods can be mentioned.
(1) Method by measuring ultraviolet (UV) absorbance: The UV absorbance of a solution to be measured is measured, and the oxidizing agent is quantified from the measured value (Patent Document 1).
(2) Method of adding potassium iodide and titrating with sodium thiosulfate: Adding potassium iodide solution to the solution to be measured, mixing, titrating the released iodine with sodium thiosulfate, and quantifying the oxidizing agent from the result (Hereinafter referred to as “KI titration method”) (Patent Documents 2 and 3).

International Publication WO2015 / 012041 Pamphlet JP 2008-164504 A JP 2011-75467 A

When cleaning the wafer with sulfuric acid solution containing oxidizing agent such as SPM or electrolytic sulfuric acid, and recovering the cleaning waste liquid and regenerating and reusing the oxidizing substance, the eluate such as metal from the wafer remains in the cleaning waste liquid. There is a risk that it will be mixed into the regenerated cleaning liquid.
In the method for quantifying an oxidant by measuring UV absorbance in Patent Document 1, if a metal is mixed in the solution to be measured, the UV absorbance is affected by the metal, and the oxidant concentration cannot be accurately quantified.
Since the KI titration methods of Patent Documents 2 and 3 require a titration operation, the operation is complicated. Further, in wafer cleaning, immediate monitoring of the oxidant concentration is important, and online monitoring is required, but it is difficult to make online with this technology.

  The present invention can measure the oxidant concentration in a sulfuric acid solution containing a metal and an oxidant accurately and efficiently without being affected by impurities such as metal, and the oxidant concentration can be easily brought online. It is an object of the present invention to provide a measuring method, a measuring apparatus, and an electronic material cleaning apparatus using the measuring method and measuring apparatus.

As a result of intensive studies to solve the above problems, the present inventor measured the absorbance after adding and mixing a potassium iodide solution to a sulfuric acid solution, without being affected by impurities such as mixed metals. It was confirmed that the oxidant concentration in the solution can be measured easily and with high accuracy.
The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] A method for measuring an oxidant concentration of a sulfuric acid solution containing a metal and an oxidant, wherein a mixing step of mixing the sulfuric acid solution and a potassium iodide solution, and a wavelength of 250 to 400 nm of the obtained mixed solution and the absorbance measurement step of measuring either the absorbance, possess a quantitative step of quantifying the oxidizing agent concentration of the sulfuric acid solution based on the measurement result of the absorbance, a sulfuric acid solution SPM or electrolytic sulfuric, sulfuric acid The oxidant concentration of the solution is 0.001 to 1 mol / L, the sulfuric acid concentration is more than 20% by weight, and the sulfuric acid solution is a cleaning liquid for the electronic material or a cleaning drainage used for cleaning the electronic material, A part of the cleaning liquid or the cleaning waste liquid circulating from the cleaning liquid feeding system for supplying the cleaning liquid to the electronic material cleaning process or the cleaning drainage discharge system for discharging the cleaning waste liquid from the electronic material cleaning process. The oxidant concentration is separated by the flow method A method of measuring an oxidant concentration that is measured online with an absorptiometer, wherein the electronic material is a semiconductor wafer having a metal exposed on at least a part of a surface, and the sulfuric acid solution is preliminarily prepared prior to the mixing step. Including a dilution step of adjusting the sulfuric acid concentration to 20% by weight or less at a set dilution rate, and in the quantification step, an oxidant concentration for calculating the oxidant concentration of the sulfuric acid solution based on the measurement result of the absorbance and the dilution rate Measuring method.

[ 2 ] An apparatus for measuring an oxidant concentration of a sulfuric acid solution containing a metal and an oxidant, a mixing means for mixing the sulfuric acid solution and a potassium iodide solution, and a wavelength of 250 to 400 nm of the obtained mixed liquid and absorbance measurement means for measuring either the absorbance, possess a quantitative means for quantifying the oxidizing agent concentration of the sulfuric acid solution based on the measurement result of the absorbance, a sulfuric acid solution SPM or electrolytic sulfuric, sulfuric acid The oxidant concentration of the solution is 0.001 to 1 mol / L, the sulfuric acid concentration is more than 20% by weight, and the sulfuric acid solution is a cleaning liquid for the electronic material or a cleaning drainage used for cleaning the electronic material, A part of the cleaning liquid or cleaning waste liquid circulating from the cleaning liquid supply system for supplying the cleaning liquid to the electronic material cleaning means or the cleaning drainage discharge system for discharging the cleaning waste liquid from the electronic material cleaning means Having a sorting means for sorting, An oxidant concentration measuring apparatus in which the oxidant concentration of the cleaning liquid or cleaning waste liquid separated by the collecting means is measured on-line with a flow-type absorptiometer, wherein the electronic material has a metal on at least a part of its surface. An exposed semiconductor wafer, including dilution means for adjusting the sulfuric acid solution to a sulfuric acid concentration of 20% by weight or less at a preset dilution ratio prior to mixing by the mixing means. An oxidant concentration measuring device that calculates the oxidant concentration of the sulfuric acid solution based on the result and the dilution factor .

[ 3 ] An electronic material cleaning apparatus , comprising: electronic material cleaning means that is a semiconductor wafer having a metal exposed on at least a part of a surface thereof ; and the oxidizing agent concentration measuring device according to [2] .

[ 4 ] In [ 3 ], a regenerating unit that regenerates the cleaning drainage used for cleaning by the cleaning unit, and a circulating unit that circulates the liquid regenerated by the regenerating unit as a cleaning liquid to the cleaning unit. Electronic material cleaning device characterized by the above.

According to the measuring method and measuring apparatus for the oxidant concentration of the present invention, the oxidant concentration in a sulfuric acid solution containing a metal and an oxidant such as a sulfuric acid-based oxidant solution mixed with a metal used in the cleaning process of the electronic material. Can be measured easily and stably with high accuracy without being influenced by impurities such as metals, and online continuous monitoring can be easily performed.
Therefore, even when a metal or resist resulting from wafer cleaning is mixed by cleaning a semiconductor wafer with a sulfuric acid oxidizing solution such as SPM or electrolytic sulfuric acid, the sulfuric acid oxidizing agent is not affected by impurities such as metal. The concentration of the oxidizing agent in the solution can be accurately measured.
According to the electronic material cleaning apparatus of the present invention, this measurement technique is used when cleaning waste liquid from a sulfuric acid-based oxidant solution is recovered and the oxidant in the sulfuric acid-based oxidant solution is regenerated and reused for cleaning. Thus, the oxidant concentration in the cleaning liquid can be accurately monitored, and efficient cleaning can be performed with the cleaning liquid having a predetermined oxidant concentration.

It is a systematic diagram which shows an example of embodiment of the measuring apparatus of the oxidizing agent density | concentration of this invention. It is a systematic diagram which shows the example of application of the measuring apparatus of the oxidizing agent density | concentration of this invention. It is a systematic diagram which shows an example of embodiment of the electronic material washing | cleaning apparatus of this invention. It is a systematic diagram which shows the other example of embodiment of the electronic material cleaning apparatus of this invention. It is a systematic diagram which shows another example of embodiment of the electronic material cleaning apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

[mechanism]
In the present invention, a potassium iodide (KI) solution is added to a sulfuric acid solution containing a metal and an oxidizing agent, and an oxidizing agent (oxidizing substance) such as peroxodisulfuric acid in the sulfuric acid solution is selected as KI in the following reaction formula. By making yellow color with iodine (I ₂ ) liberated by reaction, the UV sensitivity of reaction products caused by oxidizing substances is higher than that of impurities such as metals, and the effect of metals is reduced and high accuracy is achieved. The absorbance due to the oxidizing substance can be measured.
H ₂ SO ₅ + 2KI → I ₂ (pale yellow) + K ₂ SO ₄ + H ₂ O
H ₂ S ₂ O ₈ + 4KI → 2I ₂ (pale yellow) + 2K ₂ SO ₄ + H ₂
H ₂ O ₂ + H ₂ SO ₄ + 2KI → I ₂ (light yellow) + K ₂ SO ₄ + 2H ₂ O

[Sulfuric acid solution containing metal and oxidizing agent]
In the present invention, the sulfuric acid solution to be measured for the oxidant concentration contains a metal and an oxidant and is not particularly limited. However, the present invention is a semiconductor wafer in which the metal is exposed on at least a part of the surface. This is useful for measuring the oxidant concentration of sulfuric acid-based oxidant solutions such as electrolytic sulfuric acid, SPM, and SOM containing metals as impurities. In particular, the present invention provides a cleaning process in the case of cleaning a semiconductor wafer using such a sulfuric acid-based oxidant solution as a cleaning liquid, recovering the cleaning waste liquid, regenerating the oxidant, and reusing it as a cleaning liquid. This is effective when the oxidant concentration in the cleaning liquid supplied to the cleaning liquid or the cleaning waste liquid discharged from the cleaning process is measured online to control the concentration.

[Mixing of potassium iodide solution]
As the potassium iodide solution, an aqueous potassium iodide solution of about 10 to 200 g / L can be used from the viewpoint of handleability.
The amount of potassium iodide solution added to the sulfuric acid solution to be measured is appropriately determined depending on the oxidant concentration in the sulfuric acid solution.
The potassium iodide solution is added so that the amount of KI added is about 5 to 20 times (volume ratio) with respect to oxidizing substances such as peroxysulfuric acid, hydrogen peroxide, and ozone in the sulfuric acid solution to be measured. It is preferable.

  In addition, since there is a problem of foaming if the sulfuric acid concentration of the sulfuric acid solution to which the potassium iodide solution is added is too high, if the sulfuric acid concentration of the sulfuric acid solution to be measured is high, the sulfuric acid concentration with water (pure water or ultrapure water) It is preferable to add the potassium iodide solution after diluting and mixing so as to be 20 wt% or less, for example, 5 to 15 wt%. In this case, dilution is performed to a preset dilution factor, and the oxidant concentration is calculated based on the measured absorbance value and the dilution factor. In addition, although this dilution is performed before mixing of a potassium iodide solution, dilution water can also be added and mixed with a potassium iodide solution.

[Absorbance measurement]
A sulfuric acid solution containing a metal and an oxidizing agent is diluted as necessary, and after adding and mixing a potassium iodide solution, the absorbance at any wavelength of 200 to 600 nm is measured. This measurement wavelength is preferably 200 to 500 nm, more preferably 250 to 400 nm.
The absorbance can be measured using a commercially available absorptiometer.

[Quantification of oxidant concentration]
For example, the following method can be employed to quantify the oxidizing agent concentration from the absorbance measurement result.
Prepare many types of standard sample solutions with different oxidizing agent concentrations at the same sulfuric acid concentration as the sulfuric acid solution to be measured, measure the absorbance after adding and mixing potassium iodide solution in advance for this standard sample solution, Prepare a calibration curve for absorbance and oxidant concentration. The measured value of the absorbance of the sulfuric acid solution to be measured is applied to this calibration curve to determine the oxidant concentration.

  Regarding the quantification of the oxidant concentration by absorbance, if the oxidant concentration is low, the measurement error tends to increase. Conversely, if the oxidant concentration is high, the absorbance exceeds the measurement range and cannot be followed. The calibration relationship between absorbance and absorbance disappears. Therefore, the liquid to be measured of the present invention has an oxidizing agent concentration of about 0.001 to 1 mol / L as a measuring concentration, that is, as an oxidizing agent concentration of a sulfuric acid solution containing a metal and an oxidizing agent before dilution for measuring the oxidizing agent concentration. Preferably there is.

Usually, since the sulfuric acid concentration and oxidizing agent concentration of electrolytic sulfuric acid, SPM, and SOM used for cleaning a semiconductor wafer are in the following ranges, the present invention can be effectively applied.
Electrolytic sulfuric acid: sulfuric acid concentration = 10 to 96% by weight
Oxidant concentration = 0.001 to 1 mol / L
SPM: sulfuric acid concentration = 10 to 96% by weight
Oxidant concentration = 0.01-10 mol / L
SOM: sulfuric acid concentration = 10 to 96% by weight
Oxidant concentration = 0.001 to 1 mol / L

[Online measurement]
The measurement of the oxidant concentration according to the present invention can also be performed in a batch system in which the sulfuric acid solution to be measured and the potassium iodide solution are mixed in the mixing tank and then the absorbance of the mixed solution is measured. However, by using a flow-type absorptiometer and mixing them in a line, it is easy to go online.

  With reference to FIG. 1, the measuring apparatus of the oxidizing agent density | concentration of this invention which employ | adopted this line mixing is demonstrated.

In this oxidant concentration measuring apparatus, pure water for dilution is introduced into the sample solution introduction pipe 11 to the flow type absorptiometer ₁ having the pump P _1, and the pipe 11 is supplied with the process from the semiconductor wafer cleaning step. by sulfuric acid solution containing a metal and an oxidizing agent such as oxidizing agent containing sulfuric acid based cleaning liquid is injected from the pipe 12 having a pump P _2, the oxidizing agent containing sulfuric acid based cleaning liquid is diluted with pure water.

Potassium iodide pipe 13 is connected, to the diluted oxidant containing sulfuric acid based cleaning solution having a pump P ₃ for injecting a potassium iodide solution on the downstream side of the injection point of the oxidizing agent containing sulfuric acid based cleaning fluid The solution is injected. This potassium iodide solution is a solution in which a high-concentration potassium iodide solution from a pipe 14 having a pump P ₄ is injected into a pipe 13 into which pure water is introduced and diluted to adjust the concentration.

  The liquid after the potassium iodide solution has been injected is further mixed by the line mixer 2, and then the mixed liquid is introduced into the flow type absorptiometer 1 to measure the absorbance. Since the liquid after the measurement contains potassium iodide and cannot be used as a cleaning liquid, it is discharged out of the system.

  With this oxidant concentration measuring device, a predetermined amount of potassium iodide solution is added to a sulfuric acid solution diluted to a predetermined concentration range by adjusting the flow rate of pure water, sulfuric acid solution and potassium iodide solution in each pipe. Absorbance can be measured with the flow-type absorptiometer 1 after addition and mixing. For example, by incorporating this into a semiconductor wafer cleaning apparatus, the cleaning liquid supplied to the cleaning process or the cleaning waste discharged from the cleaning process can be measured. The concentration of the oxidant in the liquid can be measured quickly and accurately.

The flow rate of each pipe is not particularly limited,
Pipe 11: 5 to 2000 times the flow rate of pipe 12 at 0.5 to 200 ml / min Pipe 12: 0.1 to 50 ml / min
Pipe 13: The flow rate of pipe 12 can be 200 to 10,000 times higher at 20 to 1000 ml / min.

[Application example]
FIG. 2 shows an example in which the oxidant concentration measuring apparatus of the present invention is applied to a cleaning liquid production system by electrolysis of a sulfuric acid solution. In FIG. 2, the electrolytic solution is supplied from the storage tank 20 to the electrolytic cell 23 through the pipe 22 including the pump 21, and the electrolytic treatment liquid is circulated to the storage tank 20 through the pipe 24, the gas-liquid separator 25, and the pipe 26. The On the downstream side of the pump 21 of the pipe 22, a sorting pipe 27 for sorting a part of the electrolyte solution is provided, and a part of the electrolyte solution is separated from the pipe 22, and the oxidizing agent of the present invention. It is sent to an oxidant concentration measurement unit 28 which is a concentration measuring device, and the oxidant concentration is measured. The liquid after the measurement is discharged out of the system through the pipe 29.
In this cleaning liquid manufacturing system, a cleaning liquid made of electrolytic sulfuric acid having a desired oxidizing agent concentration is manufactured by adjusting the electrolysis conditions of the electrolytic cell 23 based on the measurement result of the oxidizing agent concentration in the oxidizing agent concentration measuring unit 28. be able to.

[Electronic material cleaning equipment]
Next, an electronic material cleaning apparatus using the oxidant concentration measuring apparatus of the present invention will be described with reference to FIGS.
3 to 5 are system diagrams showing an embodiment of an electronic material cleaning apparatus to which the oxidant concentration measuring apparatus of the present invention is applied.

  FIG. 3 shows an application of the oxidant concentration measuring device of the present invention to a batch type washing machine using SPM as a washing liquid, and the washing liquid in the storage tank 30 is fed to the washing machine 32 via a pipe 31 and washed. The drainage liquid is circulated to the storage tank 30 through a pipe 36 having a pump 34 and a heat exchanger 35. The pipe 31 is branched by a sorting pipe 37 for separating a part of the cleaning liquid supplied to the cleaning machine 32 as a sample liquid, and the cleaning liquid sorted by this pipe 37 has the oxidant concentration of the present invention. Is supplied to the oxidant concentration measurement unit 38, which measures the oxidant concentration, and the measured sample solution is discharged out of the system through the pipe 39.

  FIG. 4 shows a batch type washing machine using electrolytic sulfuric acid as a cleaning liquid, and the oxidant concentration measuring device of the present invention is applied. The electrolytic sulfuric acid in the storage tank 40 is connected to pipes 42 and 43 having a pump 41 as a cleaning liquid. Then, it is supplied to the washing machine 44, and the drainage of the washing is discharged through a pipe 46 having a pump 45, a part is circulated to the washing machine 44 through a pipe 48 having a heater 47, and the rest has a cooler 49. It returns to the storage tank 40 through the pipe 50.

  The electrolytic sulfuric acid (sulfuric acid solution) in the storage tank 40 is supplied to the electrolyzer 55 through a pipe 53 including a pump 51 and a cooler 52, and peroxodisulfuric acid is generated by electrolysis in the electrolyzer 55 to generate peroxodisulfuric acid. The sulfuric acid solution containing is returned to the storage tank 40 through the pipe 56. The storage tank 40 is provided with a pure water supply pipe 57 and a concentrated sulfuric acid supply pipe 58.

  A part of the electrolytic sulfuric acid in the storage tank 40 is taken out from the pipe 59 and sent to the oxidant concentration measurement unit 60 which is the oxidant concentration measurement device of the present invention to measure the oxidant concentration. The sample solution is discharged out of the system through the pipe 61.

  FIG. 5 shows an example in which the oxidant concentration measuring device of the present invention is applied to a single wafer cleaning machine using electrolytic sulfuric acid as a cleaning solution, and the same members as those shown in FIG. is there.

  In the figure, reference numeral 70 denotes a decomposition tank for oxidizing and decomposing residual organic substances such as resist contained in the cleaning waste liquid discharged from the single wafer cleaning machine 80 through the pipe 71 with the oxidizing agent contained in the cleaning waste liquid. Is.

The electrolytic sulfuric acid in the storage tank 40 is fed from the pipe 42 provided with the pump 41 to the single wafer cleaning machine 80 through the filter 72 and the heater 73 as in FIG. The cleaning effluent used for cleaning the semiconductor wafer in the single wafer cleaning machine 80 is supplied to the decomposition tank 70 through the pipe 71, and the cleaning effluent processed in the decomposition tank 70 is supplied to the pump 45 and the cooler 49. It returns to the storage tank 40 through the piping 50 provided. The electrolytic treatment of the electrolytic sulfuric acid in the storage tank 40 and the measurement of the oxidant concentration are performed in the same manner as the treatment in FIG.
A part of the cleaning drainage is discharged out of the system through a pipe 74 branched from the pipe 71 as appropriate.

  As shown in FIGS. 3 to 5, by applying the oxidant concentration measuring device of the present invention to the electronic material cleaning device and measuring the oxidant concentration of the sulfuric acid-based oxidant solution as the cleaning solution, the cleaning solution is oxidized. By detecting the agent concentration on-time during cleaning and adjusting the oxidant concentration of the cleaning liquid as necessary, efficient cleaning can be performed with a cleaning liquid having an appropriate oxidant concentration.

Hereinafter, the present invention will be described more specifically with reference to examples.
In the following, if the error in the measurement result of the oxidant concentration of the sample solution before and after the addition of the metal is 40% or less, the measurement method is evaluated as “◯”. Evaluated as “x”.
Further, an ultraviolet-visible spectrophotometer manufactured by JASCO Corporation is used as a flow-type absorptiometer, a Ti standard solution (10000 ppm) is used as a Ti source to be added to a sample solution, and a Co standard solution (10000 ppm) is used as a Co source. Was used after appropriately diluted.

[Comparative Example 1]
Electrolytic sulfuric acid (sulfuric acid concentration 92% by weight, charged oxidant concentration 0.01 mol / L) was introduced into a flow-type absorptiometer at 1 L / min, and the absorbance at a wavelength of 253 nm was measured. Was quantified. The oxidizing agent concentration was 0.01 mol / L.
Next, a solution in which Ti source and Co source are added to this electrolytic sulfuric acid so as to be Ti 10 mg / L and Co 10 mg / L is prepared, the absorbance at a wavelength of 253 nm is measured, and the oxidant concentration after the metal addition is quantified. did. The oxidant concentration was 0.08 mol / L, and the error in the measured concentration with respect to that before the metal addition was 700% (= {(0.08−0.01) /0.01} × 100).
These results are shown in Table 1.

[Comparative Example 2]
SPM (liquid obtained by mixing 96% by weight sulfuric acid and 30% by weight hydrogen peroxide water in a ratio of 40: 1 (weight ratio)) (hereinafter referred to as “SPM40: 1”) was used as a sample liquid in the same manner as in Comparative Example 1. Thus, the oxidant concentration before and after the metal addition was determined, and the results are shown in Table 1.

[Comparative Example 3]
Using SOM (liquid in which ozone was blown into 92% by weight sulfuric acid) as a sample liquid, the oxidant concentration before and after the metal addition was determined in the same manner as in Comparative Example 1, and the results are shown in Table 1.

[Comparative Example 4]
Using the same sample solution as in Comparative Example 1, the oxidant concentration before and after the metal addition was determined by the KI titration method, and the results are shown in Table 1.

[Examples 1-7]
The electrolytic sulfuric acid having the sulfuric acid concentration and the oxidant concentration shown in Table 1 is used as a sample solution, and the electrolytic sulfuric acid of the sample solution is 1 mL / min from the pipe 12 and the pipe 11 is flowed at 400 mL / min in the flow type shown in FIG. After injecting into pure water and mixing and diluting, 75 g / L potassium iodide aqueous solution is injected at a rate of 5 mL / min from the pipe 13 and mixed. The mixture is introduced into the flow-type absorptiometer 1 and absorbs at a wavelength of 290 nm. Was measured, and the oxidant concentration before the metal addition was quantified.
The potassium iodide aqueous solution is obtained by diluting 375 g / L potassium iodide 1 mL / min from the pipe 14 with 4 mL / min ultrapure water from the pipe 13.

Next, the solution prepared so that the sulfuric acid concentration and the oxidant concentration were the same and the Ti and Co concentrations were as shown in Table 1 was used as a sample solution, and the oxidant concentration after the metal addition was determined in the same manner as described above.
These results are shown in Table 1.

[Example 8]
Using SPM 40: 1 as the sample solution, the oxidant concentration before and after the metal addition was determined in the same manner as in Example 3, and the results are shown in Table 1.

[Example 9]
The sample liquid was SPM (liquid obtained by mixing 96 wt% sulfuric acid and 30 wt% hydrogen peroxide water at a ratio of 4: 1 (weight ratio)) (hereinafter referred to as “SPM 4: 1”) in the same manner as in Example 3. Thus, the oxidant concentration before and after the metal addition was determined, and the results are shown in Table 1.

[Example 10]
Using SOM (liquid in which ozone was blown into 92% by weight sulfuric acid) as a sample liquid, the oxidant concentration before and after the metal addition was determined in the same manner as in Example 3, and the results are shown in Table 1.

[Example 11]
Not the flow method but the following batch method, the oxidant concentration was measured for the sample solution before and after the metal addition as in Example 3, and the results are shown in Table 1.
Batch type measurement is performed by adding 400 mL of ultrapure water, 1 mL of electrolytic sulfuric acid and 5 mL of 75 g / L potassium iodide solution to a beaker and mixing them with an absorptiometer (UV-Vis spectrophotometer manufactured by JASCO Corporation). The measurement was performed by measuring the absorbance at a wavelength of 290 nm.

As is apparent from Table 1, in the conventional UV measurement method (Comparative Examples 1 to 3), the operation is simple, but the measurement error is large due to the influence of the metal in the sample solution. Although there is no measurement error in the KI titration method (Comparative Example 4), the operation is complicated.
On the other hand, according to the present invention, the oxidizing agent concentration in sulfuric acid solutions such as electrolytic sulfuric acid, SPM, SOM, etc. having various oxidizing agent concentrations, sulfuric acid concentrations, and metal concentrations can be easily operated by both flow and batch methods. It is possible to measure accurately without being affected by metal.
In the above examples, the absorbance at a wavelength of 290 nm was measured, but similar measurement results could be obtained in the measurement of absorbance at wavelengths of 300 nm, 350 nm, and 355 nm.

DESCRIPTION OF SYMBOLS 1 Flow type absorptiometer 2 Line mixer 20 Reservoir 23 Electrolysis cell 25 Gas-liquid separator 28 Oxidant concentration measurement unit 30 Reservoir 32 Washer 38 Oxidant concentration measurement unit 40 Reservoir 44 Washer 47 Heater 49, 52 Cooler 55 Electrolytic device 60 Oxidant concentration measurement unit 70 Decomposition tank 72 Filter 73 Heater 80 Single wafer cleaning machine

Claims (4)

A method for measuring an oxidant concentration of a sulfuric acid solution containing a metal and an oxidant,
A mixing step of mixing the sulfuric acid solution and the potassium iodide solution;
An absorbance measurement step of measuring the absorbance of any one of wavelengths 250 to 400 nm of the obtained mixed solution;
It possesses a quantitative step of quantifying the oxidizing agent concentration of the sulfuric acid solution based on the measurement result of the absorbance,
The sulfuric acid solution is SPM or electrolytic sulfuric acid,
The sulfuric acid solution has an oxidizing agent concentration of 0.001 to 1 mol / L and a sulfuric acid concentration of more than 20% by weight;
The sulfuric acid solution is a cleaning liquid for the electronic material or a cleaning waste liquid used for cleaning the electronic material, and a cleaning liquid supply system for supplying the cleaning liquid to the cleaning process for the electronic material, or a cleaning process for the electronic material This is a method for measuring the oxidant concentration by separating a part of the circulated cleaning liquid or cleaning effluent from the cleaning effluent discharge system, and measuring the oxidant concentration online with a flow-type absorptiometer. There,
The electronic material is a semiconductor wafer in which metal is exposed on at least a part of the surface;
Prior to the mixing step, including a dilution step of adjusting the sulfuric acid solution to a sulfuric acid concentration of 20% by weight or less at a preset dilution rate,
In the quantification step, an oxidizing agent concentration measuring method for calculating an oxidizing agent concentration of the sulfuric acid solution based on the measurement result of the absorbance and the dilution factor . An apparatus for measuring an oxidant concentration of a sulfuric acid solution containing a metal and an oxidant,
Mixing means for mixing the sulfuric acid solution and the potassium iodide solution;
An absorbance measuring means for measuring the absorbance of any one of wavelengths 250 to 400 nm of the obtained mixed solution;
It possesses a quantitative means for quantifying the oxidizing agent concentration of the sulfuric acid solution based on the measurement result of the absorbance,
The sulfuric acid solution is SPM or electrolytic sulfuric acid,
The sulfuric acid solution has an oxidizing agent concentration of 0.001 to 1 mol / L and a sulfuric acid concentration of more than 20% by weight;
The sulfuric acid solution is an electronic material cleaning liquid or a cleaning waste liquid used for cleaning the electronic material, and a cleaning liquid supply system that supplies the cleaning liquid to the electronic material cleaning means, or the electronic material cleaning means The cleaning liquid or the cleaning waste liquid separated from the cleaning drainage discharge system for discharging the cleaning drainage from the cleaning liquid or the cleaning drainage separated by the sorting means. An oxidant concentration measuring apparatus in which the oxidant concentration of the oxidant is measured on-line with a flow-type absorptiometer,
The electronic material is a semiconductor wafer in which metal is exposed on at least a part of the surface;
Prior to mixing by the mixing means, including a diluting means for adjusting the sulfuric acid solution to a sulfuric acid concentration of 20% by weight or less at a preset dilution rate;
An apparatus for measuring an oxidant concentration , wherein the quantification means calculates the oxidant concentration of the sulfuric acid solution based on the measurement result of the absorbance and the dilution rate . An electronic material cleaning apparatus comprising: electronic material cleaning means that is a semiconductor wafer having a metal exposed on at least a part of a surface thereof; and the oxidizing agent concentration measuring device according to claim 2 . According to claim 3, and comprising: a reproducing means for reproducing the washing drainage used for washing in the washing unit, and a circulation means for circulating said cleaning means liquid reproduced by the reproducing means as the cleaning liquid Electronic material cleaning equipment.

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