Silicon wafer pre-cleaning treatment process
Through a silicon wafer pre-cleaning treatment process including wax removal agent, liquid cleaning and ultrasonic vibration, the problem of unstable surface roughness of the silicon wafer is solved, and higher quality silicon wafer surface cleaning and cost reduction are achieved.
Patent Information
- Application Number
- CN202411661597.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-03-28
AI Technical Summary
In the prior art, the surface roughness of the silicon wafer is unstable and the quality is poor, which affects the performance and reliability of semiconductor devices.
A pre-cleaning treatment process for silicon wafers is adopted, including removing wax agent on the surface of the silicon wafer, cleaning the liquid, cleaning with different concentration ratios, combining ultrasonic vibration and pure water cleaning to ensure that the surface of the silicon wafer reaches a high-quality clean state.
Effectively reduce the surface roughness of the silicon wafer to make it no more than 1.25A, improve the quality of the silicon wafer, and extend the use time of pure water and liquid during the cleaning process, reducing the cleaning cost.
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Figure CN119725076A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of silicon wafer cleaning, and in particular, relates to a silicon wafer pre-cleaning treatment process. Background Art
[0002] In May 2024, the global semiconductor industry sales reached US$49.1 billion, a year-on-year increase of 19% and a month-on-month increase of 4.1%, of which the Chinese market increased by 20.2% year-on-year. With the continuous improvement of my country's scientific and technological level, the current society is increasingly using semiconductor devices and large-scale integrated circuits, and at the same time, it has put forward higher and higher requirements on their surface quality.
[0003] Among them, surface roughness is one of the most important parameter indicators of semiconductor single crystal polishing wafers. The roughness of silicon wafers has a significant impact on the performance of semiconductor devices because it can affect electron mobility, threshold voltage and device reliability. In integrated circuit manufacturing, especially in advanced nodes, silicon wafers are required to have extremely high flatness and low roughness to ensure the accuracy of the patterning process and the performance of the final device. Therefore, how to reduce the surface roughness of silicon wafers to improve product competitiveness is a technical problem that needs to be solved in the existing semiconductor polishing wafer preparation process. Summary of the invention
[0004] The present application provides a silicon wafer pre-cleaning treatment process, which solves the technical problems of unstable silicon wafer surface roughness and poor quality in the prior art.
[0005] In order to solve at least one of the above technical problems, the technical solution adopted in this application is:
[0006] A silicon wafer pre-cleaning process comprises the following steps: firstly removing wax agent from the surface of the silicon wafer; then cleaning the silicon wafer with liquid medicine, and in the liquid medicine cleaning, cleaning the silicon wafer with liquid medicines of different concentration ratios in sequence.
[0007] Furthermore, the silicon wafer is dewaxed in a dewaxing tank, wherein the concentration ratio of the dewaxing agent to water is 1:100 and the dewaxing temperature is 35°C.
[0008] Furthermore, between wax removal and liquid cleaning, the silicon wafer is also cleaned with pure water. At the same time, during liquid cleaning, the silicon wafer is controlled to be continuously cleaned with liquid in two liquid tanks, and the liquid compositions in the two liquid tanks are the same.
[0009] Furthermore, in the chemical cleaning, the cleaning chemical components in the two chemical tanks include ammonia water and hydrogen peroxide, and the rest are deionized water; and the grade of all cleaning chemical solutions is UPSS or Grade 5.
[0010] Furthermore, in the first liquid medicine tank, the liquid medicine concentration ratio is ammonia water: hydrogen peroxide: deionized water = 1:4:100;
[0011] In the second chemical solution tank, the chemical solution concentration ratio is ammonia water: hydrogen peroxide: deionized water = 0.5:3:100.
[0012] Furthermore, the concentration of the medicine in all the medicine tanks is the same, which is 70° C.; and ultrasonic vibration is provided in all the medicine tanks, and the ultrasonic power is 900±6W.
[0013] Furthermore, in all solution tanks, the circulation flow rate of the cleaning solution was 16±2 L / min, and the solution was replaced every 12 hours; the rehydration cycle was to add 0.1 L of ammonia water and 0.2 L of hydrogen peroxide every 1 hour.
[0014] Furthermore, after the liquid cleaning, the silicon wafer is sequentially cleaned with pure water and then with pure water ultrasonic cleaning, wherein the working flow rate of the pure water is 15±2L / min; the non-working flow rate is 3±1L / min; during the pure water ultrasonic cleaning, the ultrasonic power is 900±6W.
[0015] Furthermore, before dewaxing the silicon wafer, the method further includes controlling the silicon wafer to be placed at a loading location to wait for material, including controlling the silicon wafer to be immersed in pure water, and the waiting time for material is no more than 6 hours.
[0016] Furthermore, after the liquid cleaning, the silicon wafer is also cleaned by slow pulling and then dried, wherein the solution in the slow pulling tank is pure water at a temperature of 30°C.
[0017] A silicon wafer pre-cleaning process designed in this application is adopted. This process is aimed at cleaning wafers with a diameter of 200mm and a thickness of 500-1000um. It can not only reduce the surface roughness of the silicon wafer and make the surface roughness of the silicon wafer no more than 1.25A, thereby improving the quality of the silicon wafer; it can also extend the use time of pure water and the used chemical solution in the cleaning process, thereby reducing the cleaning cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a flow chart of a silicon wafer pre-cleaning process in the present application;
[0019] Figure 2 It is the distribution structure diagram of all tanks in the whole pre-cleaning process;
[0020] Figure 3 It is a box-and-whisker diagram comparing the roughness of silicon wafers obtained by the processing technology of the present application and the existing processing technology;
[0021] Figure 4 It is a box plot comparing particles on the surface of a silicon wafer obtained by using the processing technology of the present application and the existing processing technology. DETAILED DESCRIPTION
[0022] The present application is described in detail below with reference to the accompanying drawings and specific embodiments.
[0023] This embodiment proposes a silicon wafer pre-cleaning process, such as Figure 1 As shown, the structures of each tank body corresponding to its process are as follows Figure 2 As shown, the processing steps include:
[0024] S1. Take out the polished silicon wafer and place it on the loading station to rest.
[0025] Specifically, the silicon wafers in this embodiment are all polished wafers with a diameter of 20mm and a thickness of 500-1000um. During the polishing process, a layer of wax will be coated on the surface of the silicon wafer to facilitate polishing. After polishing, the silicon wafer is placed in a pure water solution at the loading place to wait for material. The loading place is a pure water tank, and the silicon wafer is completely immersed in pure water, and the waiting time is no more than 6 hours. The purpose of standing in pure water is to prevent the silicon wafer from directly contacting the air. At the same time, the silicon wafer immersed in pure water can prevent metal particles from contaminating the surface of the silicon wafer, which is conducive to the subsequent cleaning of the silicon wafer surface.
[0026] S2. Remove wax from the surface of silicon wafer.
[0027] Before cleaning with the chemical solution, the wax on both sides of the silicon wafer is also removed. The silicon wafer is placed in a wax removal tank containing a wax remover. The concentration ratio of the wax remover to water is 1:100. Ultrasonic vibration is also provided in the wax removal tank to accelerate the removal of the wax on the surface of the silicon wafer. The temperature in the wax removal tank is 35°C.
[0028] Wax removers are generally organic solvents, such as toluene, acetone, anhydrous ethanol, etc. After removing the wax, the organic solvents remaining on the surface of the silicon wafer must be cleaned with pure water, which means that a pure water treatment process in a pure water tank is added between the wax removal tank and the liquid cleaning process in order to remove the organic solvents on the surface of the silicon wafer. In this pure water cleaning process, the working flow rate of pure water is 15±2L / min; its non-working flow rate is 3±1L / min.
[0029] S3, cleaning the surface of the silicon wafer with a chemical solution, and in the chemical solution cleaning, the silicon wafer is cleaned with chemical solutions of different concentration ratios in sequence.
[0030] After dewaxing and pure water treatment, the silicon wafer is directly subjected to liquid cleaning. In this embodiment, the liquid cleaning is SC1 liquid cleaning, which includes continuous cleaning of the silicon wafer in two liquid tanks, mainly for removing particles and organic matter. In the SC1 liquid cleaning process, two liquid tanks are provided, namely the first liquid tank and the second liquid tank. The liquids in the two liquid tanks are both alkaline liquids, with the same composition but different concentration ratios, so as to completely remove particles and organic matter on the surface of the silicon wafer.
[0031] In SC1 liquid cleaning, the cleaning liquid components in the two liquid tanks include ammonia water and hydrogen peroxide, and the rest are deionized water. In order to ensure the safety and reliability of the liquid components, the grade of these two alkaline cleaning liquids is required to be UPSS grade or Grade 5.
[0032] The concentration ratio of the drug solution in the first drug solution tank is ammonia water: hydrogen peroxide: deionized water = 1:4:100, and the concentration ratio of the drug solution in the second drug solution tank is ammonia water: hydrogen peroxide: deionized water = 0.5:3:100. The drug solution concentrations in the two drug solution tanks are the same, which is 70°C.
[0033] In order to further improve the cleaning effect of the two liquid tanks, ultrasonic vibration is provided in the first liquid tank and the second liquid tank, and the ultrasonic power is 900±6W, in order to improve the cleaning effect and reduce the surface roughness of the silicon wafer.
[0034] In the first and second liquid tanks, the circulation flow of the cleaning liquid is 16±2L / min; and they have the same liquid replacement cycle and liquid replenishment cycle. Among them, the liquid replacement cycle is to replace the liquid every 12 hours; the liquid replenishment cycle is to add 0.1L ammonia water and 0.2L hydrogen peroxide every 1 hour. The purpose is to ensure the purity and sustainability of the liquid. Hydrogen peroxide can form an oxide layer on the surface of the silicon wafer, which helps to reduce anisotropic corrosion in the subsequent cleaning process, thereby reducing the surface roughness. At the same time, the appropriate liquid temperature can further improve the cleaning effect of the silicon wafer surface roughness and ensure the quality of the silicon wafer surface after cleaning.
[0035] S4. Drying
[0036] After the SC1 liquid cleaning, the process also includes: firstly performing pure water cleaning in a pure water tank and a pure water ultrasonic cleaning in a pure water ultrasonic tank, then performing a slow pulling treatment in a slow pulling tank, and finally performing a high temperature drying treatment in a drying chamber.
[0037] Among them, when cleaning in the pure water tank and the pure water ultrasonic tank, the working flow rate of pure water is 15±2L / min; its non-working flow rate is 3±1L / min. At the same time, in the pure water ultrasonic tank, the ultrasonic power is 900±6W. Pure water cleaning and pure water ultrasonic cleaning can quickly remove alkaline solvents and residual metals or particles on the surface of silicon wafers.
[0038] During the slow pull cleaning process, the solution in the slow pull tank is pure water, and its temperature is 30°C. During the slow pull treatment, the working flow rate of pure water is also 15±2L / min; its non-working flow rate is also 3±1L / min. Afterwards, the silicon wafers after the slow pull treatment are dried in the drying chamber to obtain dry and clean silicon wafers.
[0039] During the entire cleaning process, ensure that the entire liquid cleaning process is carried out in a clean and closed environment, adjust the FFU (Fan Filter Unit) and exhaust system in the cleaning machine to coordinate with each other, and adjust the wind pressure direction to be discharged from the machine body to the outside to ensure the purity and safety of the internal environment of the cleaning machine.
[0040] In order to enable those skilled in the art to further understand the method of the present invention, the technical solution of the present invention will be explained in detail below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.
[0041] A wafer with a diameter of 200 mm and a thickness of 800 μm was selected and treated with different cleaning processes as follows:
[0042] Example 1
[0043] S1. Take out the polished silicon wafer and place it on the loading station to rest.
[0044] After polishing, the silicon wafer is placed in a pure water solution at the upper loading point to wait for material. The upper loading point is a pure water tank, and the silicon wafer is completely immersed in pure water, and the waiting time is 5 hours.
[0045] S2. Remove wax from the surface of silicon wafer.
[0046] Acetone was used as a wax remover with a concentration ratio of 1:100 to water. The temperature in the wax removal tank was controlled at 35°C, and ultrasonic vibration was performed while wax removal was performed. The wax removal time was 300s.
[0047] After removing the wax agent, the silicon wafer is controlled to be cleaned in a pure water solution tank, and the working flow rate of the pure water is 15L / min and the non-working flow rate is 3L / min.
[0048] S3, cleaning the surface of the silicon wafer with a chemical solution, and in the chemical solution cleaning, the silicon wafer is cleaned with chemical solutions of different concentration ratios in sequence.
[0049] In the first liquid tank, the concentration ratio of ammonia: hydrogen peroxide: deionized water is 1:4:100, and the liquid temperature is 70°C; and in the second liquid tank, the concentration ratio of ammonia: hydrogen peroxide: deionized water is 0.5:3:100, and the concentration is 70°C; and their grades are UPSS or Grade 5. Ultrasonic vibration is set in both liquid tanks, and its ultrasonic power is 900W.
[0050] In both the first and second chemical tanks, the circulation flow of the cleaning solution was 16 L / min, and the solution was replaced every 12 hours, and the replenishment cycle was 0.1 L of ammonia and 0.2 L of hydrogen peroxide every hour. The cleaning time in the first chemical tank was 300 s; the cleaning time in the second chemical tank was 300 s.
[0051] S4. Drying
[0052] After the liquid cleaning, the silicon wafer is sequentially cleaned with pure water and then with pure water ultrasonic cleaning. In both processes, the working flow rate of pure water is 15L / min, and the non-working flow rate is 3L / min. At the same time, in the pure water ultrasonic cleaning, the ultrasonic power is 900W. After two pure water cleanings, the alkaline solvent and residual metal or particulate matter on the surface of the silicon wafer can be quickly removed.
[0053] Then, a slow pulling treatment is performed at 30° C., and then the silicon wafer is dried to finally obtain a dry silicon wafer.
[0054] For the silicon wafers cleaned after the adjustment process, the roughness tester was used to test the surface roughness of the silicon wafers. The 9-point test method was used to obtain the values. Each silicon wafer was tested 3 times, and the test data was averaged. The data obtained are as follows: Figure 3 The box plot shown in the figure shows that the roughness of the silicon wafer obtained by the cleaning process of the present application is 0.85A; the lower the roughness, the better the surface quality of the silicon wafer. At the same time, the particle size on the silicon wafer is tested. In the SP2 normal test mode, the average value of the LLS-0.065 particles obtained is Figure 4 The box plot shown is 7.52, which shows that the auxiliary material has a longer life.
[0055] Example 2
[0056] S1. Take out the polished silicon wafer and place it on the loading station to rest.
[0057] After polishing, the silicon wafer is placed in a pure water solution at the upper loading point to wait for material. The upper loading point is a pure water tank, and the silicon wafer is completely immersed in pure water, and the waiting time is 4 hours.
[0058] S2. Remove wax from the surface of silicon wafer.
[0059] Acetone was used as a wax remover with a concentration ratio of 1:100 to water. The temperature in the wax removal tank was controlled at 35°C, and ultrasonic vibration was performed while wax removal was performed. The wax removal time was 300s.
[0060] After removing the wax agent, the silicon wafer is controlled to be cleaned in a pure water solution tank, and the working flow rate of the pure water is 15L / min and the non-working flow rate is 3L / min.
[0061] S3, cleaning the surface of the silicon wafer with a chemical solution, and in the chemical solution cleaning, the silicon wafer is cleaned with chemical solutions of different concentration ratios in sequence.
[0062] The ratio of the liquid in the first liquid tank and the second liquid tank is different from the data ratio in Example 1. In this embodiment, the concentration ratio of ammonia water: hydrogen peroxide: deionized water in the first liquid tank is 2:7:100, and the liquid temperature is 70°C. The concentration ratio of ammonia water: hydrogen peroxide: deionized water in the second liquid tank is 2:7:100, and the concentration is 70°C. And their grades are UPSS or Grade 5. Ultrasonic vibration is set in both liquid tanks, and its ultrasonic power is 900W.
[0063] In the first and second chemical tanks, the circulation flow rate of the cleaning chemical solution is 16 L / min, but the liquid replacement cycle and liquid replenishment cycle of the chemical solution are different from those in Example 1. In this embodiment, the first and second chemical tanks are replaced every 6 hours, and the liquid replenishment cycle is to replenish 0.1 L of ammonia water and 0.2 L of hydrogen peroxide every 0.5 hours. The cleaning time in the first and second chemical tanks is 300 seconds.
[0064] S4. Drying
[0065] After the liquid cleaning, the silicon wafer is sequentially cleaned with pure water and then with pure water ultrasonic cleaning. In both processes, the working flow rate of pure water is 15L / min, and the non-working flow rate is 3L / min. At the same time, in the pure water ultrasonic cleaning, the ultrasonic power is 900W. After two pure water cleanings, the alkaline solvent and residual metal or particulate matter on the surface of the silicon wafer can be quickly removed.
[0066] Then, a slow pulling treatment is performed at 30° C., and then the silicon wafer is dried to finally obtain a dry silicon wafer.
[0067] For the silicon wafers cleaned after the adjustment process, the roughness tester was used to test the surface roughness of the silicon wafers. The 9-point test method was used to obtain the values. Each silicon wafer was tested 3 times, and the test data was averaged. The data obtained are as follows: Figure 3 The box plot shown in the figure shows that the roughness of the silicon wafer obtained by the cleaning process of the present application is 1.11A. At the same time, the particle size on the silicon wafer is tested. In the SP2normal test mode, the average value of the LLS-0.065 particles obtained is Figure 4 The box plot shown, is 7.44.
[0068] Depend on Figure 3The example results in FIG. 2 show that the cleaning process of the present application can achieve a lower roughness value, which can not only improve the surface quality of silicon wafers, but also more effectively improve the competitiveness of silicon wafers of this size in the market. Moreover, the service life of the auxiliary materials using the cleaning process of the present application is improved compared with the existing data.
[0069] Depend on Figure 3 and Figure 4 As can be seen from the accompanying drawings, the roughness of Example 1 using the treatment process of the present application is greatly reduced compared with Comparative Example 2 of the current existing process, and the SP2 particle test result after cleaning is equivalent to the LLS-0.065 particle capacity, and the cost of hydrogen peroxide and ammonia water can be saved by 30%, and the cost of pure water can be saved by 10%.
[0070] A silicon wafer pre-cleaning process designed in this application is adopted. This process is aimed at cleaning wafers with a diameter of 200mm and a thickness of 500-1000um. It can not only reduce the surface roughness of the silicon wafer and make the surface roughness of the silicon wafer no more than 1.25A, thereby improving the quality of the silicon wafer; it can also extend the use time of pure water and the used chemical solution in the cleaning process, thereby reducing the cleaning cost.
[0071] The above detailed description of the embodiments of the present application is only a preferred embodiment of the present application and cannot be considered to limit the scope of implementation of the present application. All equivalent changes and improvements made within the scope of the present application should still fall within the scope of the patent coverage of the present application.
Claims
1. A silicon wafer pre-cleaning process, characterized in that the steps include: First, the wax agent on the surface of the silicon wafer is removed; then the silicon wafer is cleaned with a chemical solution, and during the chemical solution cleaning, the silicon wafer is cleaned with chemical solutions of different concentration ratios in sequence.
2. A silicon wafer pre-cleaning process according to claim 1, characterized in that: The silicon wafer is dewaxed in a dewax tank, wherein the concentration ratio of the dewax agent to water is 1:100 and the dewax temperature is 35°C.
3. A silicon wafer pre-cleaning process according to claim 1 or 2, characterized in that: After dewaxing, the silicon wafer is controlled to be continuously cleaned with chemical liquid in two chemical liquid tanks.
4. A silicon wafer pre-cleaning process according to claim 3, characterized in that: In the chemical cleaning, the cleaning chemical components of the two chemical tanks include ammonia water and hydrogen peroxide, and the rest are deionized water; and the grade of all cleaning chemicals is UPSS or Grade 5.
5. A silicon wafer pre-cleaning process according to claim 4, characterized in that: In the first liquid medicine tank, the liquid medicine concentration ratio is ammonia water: hydrogen peroxide: deionized water = 1:4:100; In the second chemical solution tank, the chemical solution concentration ratio is ammonia water: hydrogen peroxide: deionized water = 0.5:3:
100.
6. A silicon wafer pre-cleaning process according to claim 4 or 5, characterized in that: The concentration of the medicine in all the medicine tanks is the same, which is 70°C; and ultrasonic vibration is installed in all the medicine tanks, and its ultrasonic power is 900±6W.
7. A silicon wafer pre-cleaning process according to claim 6, characterized in that: In all solution tanks, the circulation flow rate of the cleaning solution is 16±2L / min, and the solution is replaced every 12h; the rehydration cycle is to add 0.1L ammonia water and 0.2L hydrogen peroxide every 1h.
8. A silicon wafer pre-cleaning process according to claim 7, characterized in that: After the liquid cleaning, the silicon wafer is sequentially cleaned with pure water and then with pure water ultrasonic cleaning. The working flow rate of the pure water is 15±2L / min, and the non-working flow rate is 3±1L / min. During the pure water ultrasonic cleaning, the ultrasonic power is 900±6W.
9. A silicon wafer pre-cleaning process according to any one of claims 1-2, 4-5, 7-8, characterized in that: Before dewaxing the silicon wafer, the process also includes controlling the silicon wafer to be placed at a loading location to wait for material, including controlling the silicon wafer to be immersed in pure water, and the waiting time for material is no more than 6 hours.
10. A silicon wafer pre-cleaning process according to claim 9, characterized in that: After the liquid cleaning, the silicon wafer is also cleaned by slow pulling and then dried, wherein the solution in the slow pulling tank is pure water at a temperature of 30°C.