Determination method of peroxide in ultra-clean hydrofluoric acid for semiconductor industry
The titration and detection of hydrofluoric acid was solved by the standard potassium permanganate titration solution of the problem that peroxide in hydrofluoric acid affects the cleaning effect of silicon wafers, and the accurate detection and control of peroxide content was achieved to ensure the optimization of the cleaning effect.
Patent Information
- Application Number
- CN202411736279.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-03-04
AI Technical Summary
In the semiconductor industry, the peroxides present in hydrofluoric acid will affect the cleaning effect of silicon wafers, and the existing standards do not involve the detection of peroxides, resulting in poor cleaning effect.
The hydrofluoric acid solution to be tested was titrated using the standard potassium permanganate titration solution until the solution turned light pink. The titration was stopped. By calculating the consumption of the standard potassium permanganate titration solution, the peroxide content in the hydrofluoric acid to be tested was obtained.
This method can accurately detect the peroxide content in hydrofluoric acid to ensure that it is less than 10ppm, so as not to affect the subsequent cleaning effect of the silicon wafer.
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Abstract
Description
Technical Field
[0001] The invention belongs to the field of ultra-clean hydrofluoric acid detection, in particular to a method for determining peroxides in ultra-clean hydrofluoric acid used in the semiconductor industry. Background Art
[0002] In the industrial production process of hydrofluoric acid, fluorite and sulfuric acid are often used to react to generate anhydrous hydrogen fluoride, in which the main impurities are fluorosilicic acid, sulfur dioxide and water. These impurities are removed by distillation, but the conventional distillation method is not enough to significantly and effectively reduce the arsenic impurity content in anhydrous hydrogen fluoride. Arsenic exists in the form of arsenic trifluoride (AsF3), which is difficult to remove by co-distillation with anhydrous hydrogen fluoride. Since hydrofluoric acid is used for cleaning and corrosion in large-scale integrated circuits, the presence of arsenic impurities has a serious impact on the performance of electronic devices. Therefore, reducing the arsenic content in hydrofluoric acid is the main problem in the hydrofluoric acid purification process. There are many arsenic removal methods reported in the literature, including sulfide method, electrolysis method, ion exchange method, oxidation method, etc. Among them, the oxidation method uses fluorine gas, potassium permanganate, ammonium persulfate and other arsenic oxides to remove pentavalent arsenate. Hydrofluoric acid is widely used as one of the more common cleaning liquid raw materials in the semiconductor industry, but in the actual production process, there will be poor cleaning effects, such as leaving spots after cleaning, thereby affecting the cleaning efficiency. Summary of the invention
[0003] The present invention postpones the situation that the cleaning effect is not good or even spots appear in the actual cleaning process. It is found that after the hydrofluoric acid is introduced into the fluorine gas during the arsenic removal process, due to the reaction between the hydrofluoric acid and water, the main reaction is: 2F2+2H2O=4HF+O2, hydrogen fluoride and oxygen are generated, and a small amount of hydrogen peroxide, oxygen difluoride and ozone are generated by the side reaction. If fluorine gas is used to remove arsenic, peroxides will exist in the finished hydrofluoric acid. After research, it is found that the presence of peroxides will affect the cleaning effect of subsequent silicon wafers. However, all standards for hydrofluoric acid (EL grade, UP, UPS, UPSS) used in the semiconductor industry do not involve the detection of peroxides, that is, there is no requirement for peroxides. Therefore, the presence of peroxides affects the cleaning effect of subsequent silicon wafers. The present invention provides a method for determining peroxides in ultra-clean hydrofluoric acid for the semiconductor industry to solve the above-mentioned defects.
[0004] The present invention is achieved through the following technical solutions:
[0005] A method for determining peroxides in ultra-clean hydrofluoric acid for use in the semiconductor industry comprises the following steps:
[0006] Step 1: Weigh 10 g of the hydrofluoric acid to be tested and add it into a PFA bottle with a cap to prepare a hydrofluoric acid solution to be tested;
[0007] Step 2: Use a microburette to add potassium permanganate standard titrant to the hydrofluoric acid solution to be tested in a PFA bottle with a cap until the solution turns light pink and then stop titrating;
[0008] Step 3: Calculate the consumption of potassium permanganate standard titration solution according to the volume change before and after the use of potassium permanganate standard titration solution, thereby converting the mass of peroxide in the hydrofluoric acid to be measured and dividing it by the mass of the hydrofluoric acid to be measured to obtain the peroxide content in the hydrofluoric acid to be measured, and determine whether the peroxide content in the hydrofluoric acid to be measured meets the standard.
[0009] As described above, in the method for determining peroxides in ultra-clean hydrofluoric acid for use in the semiconductor industry, in the step 1, 10 g of the hydrofluoric acid to be tested is weighed and added to a 250 ml PFA bottle with a lid into which 20 ml of ultra-pure water has been added in advance, and then 10 ml of ultra-pure water is added along the bottle wall while rinsing the inner wall. After the addition is completed, the hydrofluoric acid solution to be tested is shaken to obtain.
[0010] According to the method for determining peroxides in ultra-clean hydrofluoric acid for the semiconductor industry, in the step 2, potassium permanganate standard titration solution is added dropwise until the solution turns light pink, then the dropping is stopped, the solution is shaken well, and the solution is allowed to stand for 1 minute. If the solution does not fade, the titration endpoint is considered to be reached. If the solution fades, the dropping is continued until the solution is stopped, the solution is shaken well, and the solution is allowed to stand for 1 minute. If the solution does not fade, the titration endpoint is considered to be reached.
[0011] The above-mentioned method for determining peroxides in ultra-clean hydrofluoric acid for the semiconductor industry is characterized in that the concentration of the potassium permanganate standard titration solution is lower than 0.02 mol / L.
[0012] In the above-mentioned method for determining peroxides in ultra-clean hydrofluoric acid for use in the semiconductor industry, the qualified standard for the content of peroxides in the hydrofluoric acid to be determined in step three is less than 10 ppm.
[0013] In the above method for determining peroxides in ultra-clean hydrofluoric acid for use in the semiconductor industry, the mass of the peroxide is calculated using the molecular weight of hydrogen peroxide as the overall molecular weight of the peroxide.
[0014] The advantages of the present invention are as follows: the present invention can conveniently obtain the peroxide content in the hydrofluoric acid to be tested by titrating the peroxide in the hydrofluoric acid solution to be tested with potassium permanganate titration solution, and at the same time, according to experimental verification, when the peroxide content (in terms of hydrogen peroxide) in the hydrofluoric acid to be tested is less than 10 ppm, it will not affect the subsequent cleaning effect of the silicon wafer. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.
[0016] Figure 1 Schematic diagram of a silicon wafer after a silicon wafer cleaning verification test using the cleaning solution of group 1# of the present invention;
[0017] Figure 2 Schematic diagram of a silicon wafer after a silicon wafer cleaning verification test using the cleaning solution of group 2 of the present invention;
[0018] Figure 3 Schematic diagram of a silicon wafer after a silicon wafer cleaning verification test using the cleaning solution of group 3# of the present invention;
[0019] Figure 4 Schematic diagram of a silicon wafer after a silicon wafer cleaning verification test using the cleaning solution of group 4 of the present invention;
[0020] Figure 5 This is a schematic diagram of a silicon wafer after a silicon wafer cleaning verification test using the cleaning solution of group 5# of the present invention;
[0021] Figure 6 It is a schematic diagram of a silicon wafer after a silicon wafer cleaning verification test using the cleaning solution of group 6 of the present invention. DETAILED DESCRIPTION
[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0023] A method for determining peroxides in ultra-clean hydrofluoric acid for use in the semiconductor industry comprises the following steps:
[0024] Step 1: Weigh 10g of the hydrofluoric acid to be tested. In the step 1, weigh 10g of the hydrofluoric acid to be tested and add it to a 250ml PFA bottle with a cover into which 20ml of ultrapure water has been added in advance. Then add 10ml of ultrapure water along the bottle wall while rinsing the inner wall. After the addition is completed, shake well to obtain the hydrofluoric acid solution to be tested. After the addition is completed, shake well to obtain the hydrofluoric acid solution to be tested.
[0025] Step 2: Use a microburette to add potassium permanganate standard titrant (concentration less than 0.02 mol / L) to the hydrofluoric acid solution to be tested in a 250 ml PFA bottle with a cap until the solution turns light pink. Stop adding, shake well, and let stand for 1 min. If it does not fade, it is considered the titration end point. If it fades, continue adding until the solution stops adding, shake well, and let stand for 1 min. If it does not fade, it is considered the titration end point.
[0026] Step 3: Calculate the consumption of potassium permanganate standard titration solution according to the volume change before and after the use of potassium permanganate standard titration solution, thereby converting the mass of peroxide (in terms of hydrogen peroxide) in the hydrofluoric acid to be measured and dividing it by the mass of the hydrofluoric acid to be measured to obtain the peroxide content in the hydrofluoric acid to be measured and determine whether the peroxide content in the hydrofluoric acid to be measured meets the standard. The qualified standard of the peroxide content in the hydrofluoric acid to be measured (in terms of hydrogen peroxide) is less than 10ppm.
[0027] Verification test
[0028] Peroxide determination method spike recovery
[0029] The hydrofluoric acid that has been detected to contain no peroxide is prepared into hydrofluoric acid solutions according to the method of the present invention, and 1500 mg, 500 mg, 50 mg, 10 mg and 5 mg of hydrogen peroxide are added respectively and numbered 1#, 2#, 3#, 4# and 5# in sequence, shaken well, and titrated with potassium permanganate standard titration solution (concentration of 0.01 mol / L) until it turns light pink. The end point is that the peroxide detection content and the recovery rate are calculated respectively. The results are shown in Table 1.
[0030]
[0031]
[0032] Table 1
[0033] From the data in Table 1, it can be seen that the recovery rate of the present invention is between 98.7% and 111.5%, which proves that the present invention can more accurately detect the peroxide content in hydrofluoric acid, thereby avoiding the impact of subsequent cleaning effects on subsequent silicon wafers due to inaccurate peroxide content detection.
[0034] Precision of peroxide determination method
[0035] The same sample solution was titrated six times under the same conditions, and the results are shown in Table 2.
[0036] Sample number to be tested 1 time 2 times 3 times 4 times 5 times 6 times RSD% 1# 1500 1509 1544 1498 1600 1550 2.57 2# 500 522 504 549 543 512 3.91 3# 50 52 49 51 52 50 2.39 4# 10.0 10.1 11.0 9.9 10.1 9.8 4.26 5# 5 5.2 5.3 4.9 5.1 5.6 4.79
[0037] Table 2
[0038] As can be seen from the data in Table 2, the relative standard deviation of the peroxide (calculated as hydrogen peroxide) data is less than 5%, which meets the requirement of RSD<5%, thereby avoiding the impact of subsequent silicon wafer cleaning effects due to inaccurate peroxide (calculated as hydrogen peroxide) content detection.
[0039] Silicon wafer cleaning verification test
[0040] Subsequent cleaning solutions were prepared for hydrofluoric acid with different peroxide contents and silicon wafer cleaning tests were performed. The peroxide contents of the six groups of hydrofluoric acid to be tested are shown in Table III.
[0041] 1# 2# 3# 4# 5# 6# Peroxide / ppm 1500 500 50 10 5 0
[0042] Table 3
[0043] According to the ratio of 150 ml hydrochloric acid, 100 ml hydrofluoric acid and 100 ml ultrapure water, 6 groups of hydrofluoric acid with different peroxide (calculated as hydrogen peroxide) contents were prepared into 6 groups of corresponding cleaning solutions, and then put into 500 ml beakers respectively, stirred evenly and set aside.
[0044] Put the 6 groups of prepared cleaning solutions into the fume hood, take an appropriate amount of silicon wafers to be cleaned, soak them in the cleaning solution for 10 minutes, then slowly pull out the cleaning solution and observe the cleaning degree of the silicon wafers (the results are shown in the figure below). Figure 1-Figure 6 ). Figure 1-Figure 3 They are hydrofluoric acid samples 1#, 2# and 3#. It can be seen that after cleaning the three groups of samples, there are water droplets on the surface of the silicon wafer, the color is dark, and the impurities are not completely removed; Figure 4 and Figure 5 These are hydrofluoric acid samples 4# and 5#. It can be seen that after the silicon wafers are cleaned and pulled out of water, there are fewer water droplets on the surface of the silicon wafers, the color is obviously not dark, and the impurities on the surface of the silicon wafers are completely removed. The results are better than the cleaning effects of the first three groups of samples. Figure 6 This is hydrofluoric acid sample #6. It can be seen that after the silicon wafer is cleaned and pulled out of water, there are fewer water droplets on the surface of the silicon wafer, the color is obviously not dark, and the impurities on the surface of the silicon wafer are completely removed. The result is better than the cleaning effect of the first five samples.
[0045] The above results show that when hydrofluoric acid with different peroxide (calculated as hydrogen peroxide) contents is used to clean silicon wafers, the peroxide (calculated as hydrogen peroxide) content has a greater impact on the effect of hydrofluoric acid cleaning silicon wafers; it can also be verified that when the peroxide (calculated as hydrogen peroxide) content is below 10ppm, there is no obvious negative impact on the cleaning effect of silicon wafers. Therefore, the determination requirements for peroxide (calculated as hydrogen peroxide) should be added to the quality standards of electronic grade and ultra-clean hydrofluoric acid, and the peroxide (calculated as hydrogen peroxide) content should be specified to be below 10ppm, so as to ensure the subsequent cleaning effect of silicon wafers.
[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for determining peroxides in ultra-clean hydrofluoric acid for the semiconductor industry, characterized in that: The steps include: Step 1: Weigh 10 g of the hydrofluoric acid to be tested and add it into a PFA bottle with a cap to prepare a hydrofluoric acid solution to be tested; Step 2: Use a microburette to add potassium permanganate standard titrant to the hydrofluoric acid solution to be tested in a PFA bottle with a cap until the solution turns light pink and then stop titrating; Step 3: Calculate the consumption of potassium permanganate standard titration solution according to the volume change before and after the use of potassium permanganate standard titration solution, thereby converting the mass of peroxide in the hydrofluoric acid to be measured and dividing it by the mass of the hydrofluoric acid to be measured to obtain the peroxide content in the hydrofluoric acid to be measured, and determine whether the peroxide content in the hydrofluoric acid to be measured meets the standard.
2. The method for determining peroxide in ultra-clean hydrofluoric acid for the semiconductor industry according to claim 1, characterized in that: In the step 1, 10 g of the hydrofluoric acid to be tested is weighed and added to a 250 ml PFA bottle with a lid into which 20 ml of ultrapure water has been added in advance, and then 10 ml of ultrapure water is added along the bottle wall while rinsing the inner wall. After the addition is completed, the hydrofluoric acid solution to be tested is shaken well.
3. The method for determining peroxide in ultra-clean hydrofluoric acid for semiconductor industry according to claim 1, characterized in that: In the step 2, potassium permanganate standard titration solution is added dropwise until the solution turns light pink. Then, the addition is stopped, the solution is shaken well, and the solution is allowed to stand for 1 minute. If the solution does not fade, the titration endpoint is considered to be reached. If the solution fades, the addition is continued until the solution is stopped, the solution is shaken well, and the solution is allowed to stand for 1 minute. If the solution does not fade, the titration endpoint is considered to be reached.
4. The method for determining peroxide in ultra-clean hydrofluoric acid for semiconductor industry according to claim 1, characterized in that: The concentration of the potassium permanganate standard titration solution is lower than 0.02 mol / L.
5. The method for determining peroxide in ultra-clean hydrofluoric acid for semiconductor industry according to claim 1, characterized in that: The qualified standard of the peroxide content in the hydrofluoric acid to be tested in step 3 is less than 10 ppm.
6. A method for determining peroxides in ultra-clean hydrofluoric acid for semiconductor industry according to any one of claims 1 to 5, characterized in that: When calculating the mass of the peroxide, the molecular weight of hydrogen peroxide is used as the overall molecular weight of the peroxide.