An oxidizing liquid for reducing the content of easily oxidized substances (SO2) in electronic grade sulfuric acid and a preparation method thereof

Abstract

The present invention relates to an oxidizing liquid for reducing the content of easily oxidized substances (SO2) in electronic-grade sulfuric acid and a preparation method thereof. An oxidizing liquid for reducing the content of easily oxidized substances (SO2) in electronic-grade sulfuric acid, the main components of which include 1-30% of hydrogen peroxide and 0.01-30% of inorganic acid accounting for the total weight of the oxidizing liquid, and the balance is water. The content of easily oxidized substances (SO2) in electronic-grade sulfuric acid is an important indicator, and its level directly affects the quality of electronic-grade sulfuric acid. By using a hydrogen peroxide-based oxidizing liquid, the content of easily oxidized substances (SO2) in electronic-grade sulfuric acid can be reduced, and because the reaction product is sulfuric acid, other impurities will not be introduced.

Description

Technical Field

[0001] The present invention belongs to the field of electronic chemicals, and specifically relates to a method for reducing the easily oxidized substances (SO 2 ) content of oxidizing liquid and its preparation method. Background Art

[0002] Electronic grade sulfuric acid, also known as ultrapure sulfuric acid, is an ultra-clean high-purity reagent. It is mainly used for cleaning, photolithography, and corrosion of silicon wafers, as well as corrosion and electroplating cleaning of printed circuit boards. Electronic grade sulfuric acid has been used for cleaning silicon wafers for more than 40 years. It is an indispensable key basic chemical reagent in the semiconductor industry and one of the eight most commonly used chemical reagents.

[0003] From the birth of the first transistor at Bell Labs on December 23, 1947 to today, semiconductor technology has experienced 70 years of rapid development following Moore's Law, with a generation of progress every two years and the size reduced to half of the original. As early as fifteen years ago, semiconductors entered the sub-micron era, and now they have entered the nano era, with the semiconductor 14nm process already in mass production. In such a precise semiconductor process, the purity of sulfuric acid used for cleaning, photolithography, and corrosion is also very high, and the content of easily oxidized substances is also one of the important indicators in electronic-grade sulfuric acid.

[0004] If the content of oxidizable substances in electronic-grade sulfuric acid is too high, it will affect the preparation of the "piranha" solution in the semiconductor industry, affect its final ratio, and make it fail to achieve the expected cleaning effect, which will eventually lead to a decrease in product yield. For suppliers of electronic-grade sulfuric acid, too high a content of oxidizable substances will also affect the sales of their electronic-grade sulfuric acid. Summary of the invention

[0005] The present invention aims to solve the problem that oxidizable substances (SO 2 ) content is too high, the purpose is to provide a method to add electronic grade sulfuric acid to reduce its easily oxidized substances (SO 2 ) content of oxidizing liquid and its preparation method.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0007] A method for reducing the easily oxidized substances (SO 2 ) content, the main components of which include 1-30% hydrogen peroxide and 0.01-50% inorganic acid, accounting for 1-30% of the total weight of the oxidizing liquid, and the balance is water; the oxidizing liquid will not introduce other impurities into the electronic grade sulfuric acid.

[0008] In the above scheme, the hydrogen peroxide raw material is UPSS grade 30-35% hydrogen peroxide.

[0009] In the above scheme, the inorganic acid is electronic grade sulfuric acid with a concentration of ≥98%.

[0010] In the above scheme, the water is ultrapure water with a resistivity of 15-18 MΩ*cm (25°C).

[0011] In the above scheme, the preparation method of the oxidant is: placing a container containing ultrapure water in an ice water bath, slowly adding electronic grade sulfuric acid to the ultrapure water, and after the solution is cooled, adding hydrogen peroxide to the solution, and mixing evenly to obtain an oxidizing solution.

[0012] In the above scheme, the material of the container containing ultrapure water is one of PFA, PTFE, and HDPE, and the amount of metal ion precipitation is ≤30w / 10 -9 .

[0013] In the above scheme, the concentration of the electronic grade sulfuric acid is ≥98%, and the acid temperature is ≤80°C.

[0014] Beneficial effects of the present invention

[0015] (1) First, electronic grade sulfuric acid is added to ultrapure water, and then UPSS grade hydrogen peroxide is added. On the one hand, the concentration of hydrogen peroxide is reduced. The lower the concentration, the slower the decomposition rate of hydrogen peroxide. On the other hand, adding electronic grade sulfuric acid to ultrapure water provides an acidic environment for hydrogen peroxide, and hydrogen peroxide is more stable in an acidic environment. The present invention improves the stability of hydrogen peroxide from two aspects, so that the oxidizing liquid will not decompose violently due to a large amount of heat release when added to concentrated sulfuric acid, thereby ensuring that the oxidizing liquid reduces the easily oxidized substances (SO 2 ) content.

[0016] (2) Because the oxidizable substances (SO 2 ) is at the ppm level. By conversion, the amount of oxidizing liquid added is extremely small relative to the amount of electronic-grade sulfuric acid in the storage tank. Therefore, the addition of oxidizing liquid will not affect the concentration of electronic-grade sulfuric acid in the storage tank. Hydrogen peroxide reacts with sulfur dioxide to produce sulfuric acid. Moreover, the raw materials used in the oxidizing liquid are all electronic-grade ultra-pure reagents. Therefore, the addition of oxidizing liquid will not introduce other impurities into the electronic-grade sulfuric acid, thus ensuring the quality of the electronic-grade sulfuric acid.

[0017] (3) For the semiconductor industry, the content of easily oxidized substances in electronic-grade sulfuric acid is reduced, making the ratio of cleaning liquid and etching liquid containing electronic-grade sulfuric acid more accurate, and the cleaning and etching effects are more in line with expectations, thereby improving product quality. For electronic-grade sulfuric acid manufacturers, electronic-grade sulfuric acid with a low content of easily oxidized substances undoubtedly has a better market and better sales. DETAILED DESCRIPTION

[0018] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0019] Example 1

[0020] An oxidizing liquid for reducing the content of easily oxidized substances (SO2) in electronic grade sulfuric acid is prepared by the following method:

[0021] (1) Select ultrapure reagents according to the following mass percentages: ultrapure water 90%, electronic grade sulfuric acid 1%, 30% UPSS grade hydrogen peroxide 9%.

[0022] (2) Place the container containing ultrapure water in an ice water bath, slowly add 1% by mass electronic grade sulfuric acid into the ultrapure water and mix well.

[0023] (3) After the solution is cooled, add 9% by mass of 30% UPSS grade hydrogen peroxide to the solution and mix well to obtain the oxidizing solution.

[0024] Example 2

[0025] A method for reducing the easily oxidized substances (SO 2 ) content of the oxidizing liquid, prepared by the following method:

[0026] (1) Select ultrapure reagents according to the mass percentage of each raw material: ultrapure water 50%, electronic grade sulfuric acid 30%, 30% UPSS grade hydrogen peroxide 20%.

[0027] (2) Place the container containing ultrapure water in an ice water bath, slowly add 30% by mass electronic grade sulfuric acid into the ultrapure water and mix well.

[0028] (3) After the solution is cooled, add 20% by mass of 30% UPSS grade hydrogen peroxide to the solution and mix well to obtain the oxidizing solution.

[0029] Example 3

[0030] The electronic grade sulfuric acid storage tank has a storage capacity of 20 m 3 The acid temperature is 60℃, and the sample is tested after even circulation. The oxidizable substances (SO 2 ) content was 4.6 ppm. 3 L of the oxidizing solution prepared in Example 1 was pumped into the electronic-grade sulfuric acid storage tank by a metering pump, and the electronic-grade sulfuric acid in the storage tank was circulated for 12 hours by a liner circulation pump, and then the circulated electronic-grade sulfuric acid sample was taken to test the content of easily oxidized substances. The test results showed that the content of easily oxidized substances was 0.32 ppm, and the metal ion indicators were all less than 500 ppt. This indicates that the oxidizing solution is effective in reducing the content of easily oxidized substances (SO 2) content has a significant effect and will not introduce other impurities.

[0031] Example 4

[0032] The electronic grade sulfuric acid storage tank has a storage capacity of 24 m3 of electronic grade sulfuric acid. 3 , the acid temperature is 40 ℃, and after even circulation, sampling and testing are carried out. The oxidizable substances (SO 2 ) content was 3.2 ppm. 2.6 L of the oxidizing solution prepared in Example 1 was pumped into the electronic-grade sulfuric acid storage tank by a metering pump, and the electronic-grade sulfuric acid in the storage tank was circulated for 16 h by a liner circulation pump, and then the circulated electronic-grade sulfuric acid sample was taken to test the content of easily oxidized substances. The test results showed that the content of easily oxidized substances was 0.29 ppm, and the metal ion indicators were all less than 500 ppt. This indicates that the oxidizing solution is effective in reducing the content of easily oxidized substances (SO 2 ) content has a significant effect and will not introduce other impurities.

[0033] Example 5

[0034] The electronic grade sulfuric acid storage tank has a storage capacity of 16 m3 of electronic grade sulfuric acid. 3 The acid temperature is 55 °C. After the circulation is even, the sample is tested and the oxidizable substances (SO 2 ) content was 4.2 ppm. 1 L of the oxidizing solution prepared in Example 2 was pumped into the electronic-grade sulfuric acid storage tank by a metering pump, and the electronic-grade sulfuric acid in the storage tank was circulated for 12 hours by a liner circulation pump, and then the circulated electronic-grade sulfuric acid sample was taken to test the content of easily oxidized substances. The test results showed that the content of easily oxidized substances was 0.44 ppm, and the metal ion indicators were all less than 500 ppt. This indicates that the oxidizing solution is effective in reducing the content of easily oxidized substances (SO 2 ) content has a significant effect and will not introduce other impurities.

[0035] Example 6

[0036] The electronic grade sulfuric acid storage tank has a storage capacity of 28 m3 of electronic grade sulfuric acid. 3 , the acid temperature is 65 ℃, and after even circulation, sampling and testing are carried out. The oxidizable substances (SO 2 ) content was 3.8 ppm. 1.6 L of the oxidizing solution prepared in Example 2 was pumped into the electronic-grade sulfuric acid storage tank by a metering pump, and the electronic-grade sulfuric acid in the storage tank was circulated for 15 h using an inner liner circulation pump. Then, the circulated electronic-grade sulfuric acid sample was taken to test the content of easily oxidized substances. The test results showed that the content of easily oxidized substances was 0.53 ppm, and the metal ion indicators were all less than 500 ppt. This indicates that the oxidizing solution is effective in reducing the content of easily oxidized substances (SO 2) content has a significant effect and will not introduce other impurities.

[0037] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the invention.

Claims

1. A method for reducing the content of easily oxidizable substances SO2 in electronic grade sulfuric acid, characterized in that: Follow these steps: The electronic grade sulfuric acid storage tank has a storage capacity of 20m3 of electronic grade sulfuric acid. 3 , the acid temperature is 60℃, and sampling is carried out after uniform circulation. It is measured that the content of easily oxidized material SO2 in the electronic-grade sulfuric acid in the storage tank is 4.6ppm. 3L of oxidizing liquid is pumped into the electronic-grade sulfuric acid storage tank through a metering pump, and the electronic-grade sulfuric acid in the storage tank is circulated for 12h using an inner liner circulation pump. Then, the electronic-grade sulfuric acid sample after circulation is taken for testing the content of easily oxidized material; the composition of the oxidizing liquid is 90% ultrapure water, 1% electronic-grade sulfuric acid, and 9% 30% UPSS-grade hydrogen peroxide according to the mass percentage of each raw material. The test results show that the content of easily oxidized material is 0.32ppm, the metal ion indicators are all less than 500ppt, and the concentration of electronic-grade sulfuric acid in the oxidizing liquid is ≥98%.

2. A method for reducing the content of easily oxidizable substances SO2 in electronic grade sulfuric acid, characterized in that: Follow these steps: The electronic grade sulfuric acid storage tank has a storage capacity of 24m3 of electronic grade sulfuric acid. 3 , the acid temperature is 40℃, and sampling is carried out after uniform circulation. The content of easily oxidized substances SO2 in the electronic-grade sulfuric acid in the storage tank is measured to be 3.2 ppm. 2.6L of oxidizing liquid is pumped into the electronic-grade sulfuric acid storage tank through a metering pump, and the electronic-grade sulfuric acid in the storage tank is circulated for 16 hours using an inner liner circulation pump. Then, the electronic-grade sulfuric acid sample after circulation is taken for testing the content of easily oxidized substances; the composition of the oxidizing liquid is 90% ultrapure water, 1% electronic-grade sulfuric acid, and 9% 30% UPSS-grade hydrogen peroxide according to the mass percentage of each raw material. The test results show that the content of easily oxidized substances is 0.29 ppm, the metal ion indicators are all less than 500ppt, and the concentration of electronic-grade sulfuric acid in the oxidizing liquid is ≥98%.

3. A method for reducing the content of easily oxidizable substances SO2 in electronic grade sulfuric acid, characterized in that: Follow these steps: The electronic grade sulfuric acid storage tank has a storage capacity of 16m3 of electronic grade sulfuric acid. 3 , the acid temperature is 55°C, and sampling is performed after uniform circulation. The content of easily oxidized material SO2 in the electronic-grade sulfuric acid in the storage tank is measured to be 4.2 ppm. 1L of oxidizing liquid is pumped into the electronic-grade sulfuric acid storage tank through a metering pump, and the electronic-grade sulfuric acid in the storage tank is circulated for 12 hours using an inner liner circulation pump. Then, the electronic-grade sulfuric acid sample after the circulation is taken for testing the content of easily oxidized material; the composition of the oxidizing liquid is 50% ultrapure water, 30% electronic-grade sulfuric acid, and 20% 30% UPSS-grade hydrogen peroxide according to the mass percentage of each raw material. The test results show that the content of easily oxidized material is 0.44 ppm, the metal ion indicators are all less than 500ppt, and the concentration of electronic-grade sulfuric acid in the oxidizing liquid is ≥98%.

4. A method for reducing the content of easily oxidizable substances SO2 in electronic grade sulfuric acid, characterized in that: Follow these steps: The electronic grade sulfuric acid storage tank has a storage capacity of 28m3 of electronic grade sulfuric acid. 3 The acid temperature is 65°C. After uniform circulation, sampling and testing are carried out. The content of easily oxidized substances SO2 in the electronic-grade sulfuric acid in the storage tank is measured to be 3.8ppm. 1.6L of oxidizing solution is pumped into the electronic-grade sulfuric acid storage tank through a metering pump. The electronic-grade sulfuric acid in the storage tank is circulated for 15h using an inner liner circulation pump. Then, the electronic-grade sulfuric acid sample after circulation is taken for testing the content of easily oxidized substances. The composition of the oxidizing solution is 50% ultrapure water, 30% electronic-grade sulfuric acid, and 20% 30% UPSS-grade hydrogen peroxide according to the mass percentage of each raw material. The test results show that the content of easily oxidized substances is 0.53ppm, the metal ion indicators are all less than 500ppt, and the concentration of electronic-grade sulfuric acid in the oxidizing solution is ≥98%.

5. The method for reducing the content of easily oxidized substances SO2 in electronic grade sulfuric acid according to any one of claims 1 to 4, characterized in that: The ultrapure water is ultrapure water with a resistivity of 15-18 MΩ*cm at 25°C.

6. The method for reducing the content of easily oxidized substances SO2 in electronic grade sulfuric acid according to any one of claims 1 to 4, characterized in that: The preparation method of the oxidizing solution is to place a container containing ultrapure water in an ice water bath, slowly add electronic grade sulfuric acid to the ultrapure water, and after the solution is cooled, add hydrogen peroxide to the solution, and mix well to obtain the oxidizing solution.