A cleaning process for gallium antimonide wafers

Abstract

The application belongs to the field of semiconductor substrate manufacturing, and discloses a cleaning process of a gallium antimonide wafer. The process comprises the following steps: placing a polished and waxed wafer in hot concentrated sulfuric acid and then in cold concentrated sulfuric acid for immersion treatment; placing the wafer in S1 cleaning solution for cleaning treatment, wherein the S1 cleaning solution is a tetramethylammonium hydroxide solution; placing the wafer in S2 cleaning solution for cleaning treatment, wherein the S2 cleaning solution is a mixture of hydrofluoric acid, hydrochloric acid and water; placing the wafer in S3 cleaning solution for cleaning treatment, wherein the S3 cleaning solution is a mixture of nitric acid and water; placing the wafer in S4 cleaning solution for cleaning treatment, wherein the S4 cleaning solution is hydrogen peroxide; placing the wafer in S5 cleaning solution for cleaning treatment, wherein the S5 cleaning solution is a mixture of phosphoric acid and water; placing the wafer in S6 cleaning solution for cleaning treatment, wherein the S6 cleaning solution is a mixture of sulfuric acid and water; and drying. The cleaning process can improve the yield of products and reduce production costs.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor substrate manufacturing and relates to a cleaning process for gallium antimonide wafers. Background Technology

[0002] Gallium antimonide wafers are a key basic material for uncooled mid-to-long-wave infrared detectors and focal plane arrays of type II superlattice. Uncooled mid-to-long-wave infrared detectors have advantages such as lightweight, long life, high sensitivity and high reliability, and have good application prospects in the field of infrared technology.

[0003] The fabrication process of gallium antimonide (GaS) substrate wafers generally includes cutting, edge grinding, lapping, polishing, and cleaning. Cleaning is crucial for further improving the flatness, roughness, and cleanliness of the polished surface, reducing residual particles and impurities to meet the requirements of subsequent epitaxial growth. Cleaning the GaS wafer is one of the most critical processes. After cleaning, the surface quality of the GaS wafer directly affects the performance of GaS-based devices. Besides ensuring the substrate material's performance quality meets customer requirements, the surface quality of the substrate wafer must also meet the customer's usage requirements.

[0004] The existing cleaning process has the following problems: after cleaning, it will corrode the wafer surface, resulting in more particles and excessive roughness on the wafer surface. It will also form a thick oxide film on the wafer surface. At the same time, uncontrollable white fog defects will be generated on the wafer surface, causing the surface impurity content to exceed the standard and fail to meet the requirements, resulting in low overall yield and high production cost. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention aims to provide a cleaning process for gallium antimonide wafers with high yield and low production cost. This cleaning process ensures the cleanliness of the wafer surface, while not damaging the roughness of the wafer after polishing, reducing the oxide layer thickness, controlling surface haze, and effectively controlling the surface impurity content.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A cleaning process for gallium antimonide wafers includes the following steps:

[0008] (1) The polished and wax-removed wafers were successively immersed in hot concentrated sulfuric acid and cold concentrated sulfuric acid;

[0009] (2) The wafer processed in step (1) is placed in S1 cleaning solution for cleaning treatment, wherein S1 cleaning solution is tetramethylammonium hydroxide solution;

[0010] (3) The wafer processed in step (2) is placed in S2 cleaning solution for cleaning treatment, wherein the S2 cleaning solution is a mixture of hydrofluoric acid, hydrochloric acid and water;

[0011] (4) The wafer processed in step (3) is placed in S3 cleaning solution for cleaning treatment, wherein S3 cleaning solution is a mixture of nitric acid and water;

[0012] (5) The wafer processed in step (4) is placed in S4 cleaning solution for cleaning treatment, wherein S4 cleaning solution is hydrogen peroxide;

[0013] (6) The wafer processed in step (5) is placed in S5 cleaning solution for cleaning, wherein S5 cleaning solution is a mixture of phosphoric acid and water;

[0014] (7) The wafer processed in step (6) is placed in S6 cleaning solution for cleaning, wherein S6 cleaning solution is a mixture of sulfuric acid and water;

[0015] (8) Dry the wafer after step (7).

[0016] The cleaning process of this invention creatively introduces S1, S2, S3, S4, S5 and S6 cleaning solutions to clean gallium antimonide wafers: Step (1) concentrated sulfuric acid is used to remove organic matter from the crystal surface; Step (2) an alkaline solution, such as tetramethylammonium hydroxide, is used to remove organic matter and metal ions; In Step (3), the cleaning agent mixes hydrochloric acid and hydrofluoric acid together, reducing the corrosiveness of hydrofluoric acid while ensuring the removal efficiency of silicon dioxide; Step (4) a strong oxidizing acid is set, which has a good removal effect on most metal elements; Step (5) a strong oxidizing agent solution is set to effectively remove inorganic impurities; In Step (6), the cleaning agent can effectively remove silicon dioxide from the wafer surface and reduce the thickness of the oxide layer; In Step (7), the cleaning agent further reduces the oxidation rate and prevents the white fog phenomenon; In Step (8), the wafer is dried.

[0017] Furthermore, in step (1):

[0018] Hot concentrated sulfuric acid treatment: soaking for 10-30 seconds; temperature 50-70℃; sulfuric acid concentration 70-98%;

[0019] Cold concentrated sulfuric acid treatment: soak for 10~30s; temperature 30~45℃; sulfuric acid mass concentration 70~98%.

[0020] Furthermore, in step (2), the pH value of the tetramethylammonium hydroxide solution is ≥12.5; the cleaning temperature is 20~30℃; and the cleaning time is 30~60s.

[0021] Further, in step (3), the volume ratio of hydrofluoric acid, hydrochloric acid and water in the S2 cleaning solution is 10~15:25~30:60~70; the mass concentration of the hydrofluoric acid used is ≥48.8%; the mass concentration of the hydrochloric acid used is ≥36%; and the cleaning time is 30~60s.

[0022] Further preferred methods include using hydrofluoric acid with a mass concentration of 48.8-49.2% and hydrochloric acid with a mass concentration of 36.0-38.0%.

[0023] Furthermore, in step (4), the volume ratio of nitric acid to water in the S3 cleaning solution is 2~5:10~15; the mass concentration of the nitric acid used is ≥69%; and the cleaning time is 30~60s.

[0024] Further optimization is to use a nitric acid concentration of 69.0~72.0%.

[0025] Furthermore, in step (5), the mass concentration of hydrogen peroxide in the S4 cleaning solution is ≥30.0%; the cleaning time is 30~60s.

[0026] Further preferred is that the mass concentration of hydrogen peroxide used is 30.0~32.0%.

[0027] Further, in step (6) and step (7), the volume ratio of phosphoric acid to water in the S5 cleaning solution is 1~5:5~9; the mass concentration of the phosphoric acid used is ≥85.0%; and the cleaning time is 30~60s.

[0028] Further, in step (7), the volume ratio of sulfuric acid to water in the S6 cleaning solution is 1~5:90~100; the mass concentration of the sulfuric acid used is ≥70%; and the cleaning time is 10~30s.

[0029] Further optimization is to use sulfuric acid with a mass concentration of 70% to 98%.

[0030] Further, the rinsing process in steps (1) to (8) specifically involves: placing the wafer in a water tank and simultaneously rinsing the water tank with a water gun to maintain an overflow state; the overflow water volume is 10~60L / min.

[0031] Furthermore, in steps (3) to (7), the cleaning temperature is below 25°C.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The cleaning process of the present invention, by introducing cleaning solutions S1, S2, S3, S4, S5, and S6, can effectively remove metal compound ions, organic particles, heavy metals, and inorganic impurities from the surface of gallium antimonide wafer substrates, ensuring the cleanliness of the wafer surface. At the same time, it does not damage the roughness of the wafer after polishing, reduces the oxide layer thickness, controls surface haze, and effectively controls the surface impurity content. Ultimately, it achieves the goal of optimizing and improving the substrate surface quality to meet customer needs.

[0034] (2) The cleaning process of the present invention can improve the product yield and reduce production costs. Detailed Implementation

[0035] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments in the specification, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0037] The component concentrations used in the various embodiments and comparative examples of this invention are as follows:

[0038] Hydrogen peroxide, with a mass concentration of 48.8%;

[0039] Sulfuric acid, with a mass concentration of 96%;

[0040] Nitric acid, with a mass concentration of 69.0%;

[0041] Hydrochloric acid, with a mass concentration of 36.0%;

[0042] Hydrofluoric acid, with a mass concentration of 48.8%;

[0043] Phosphoric acid, with a mass concentration of 85.0%;

[0044] Tetramethylammonium hydroxide solution, pH 12.5.

[0045] Example 1

[0046] This embodiment discloses a cleaning process for gallium antimonide wafers, including the following steps:

[0047] (1) Select 50 gallium antimonide 6-inch wafers that have been polished and waxed using the wax polishing process, and immerse them in sulfuric acid at 65°C for 20 seconds and in sulfuric acid at 30°C for 20 seconds in sequence. Place them in a water tank and simultaneously use a water gun to rinse the water bowl to keep the water overflowing. Cleaning time: 60 seconds.

[0048] (2) The wafer treated in step (1) is placed in a tetramethylammonium hydroxide solution for cleaning. The cleaning temperature is 25°C and the cleaning time is 40s. During the cleaning process, the wafer is rotated continuously to ensure that the surface of the wafer is evenly coated with liquid. Then, the wafer is rinsed with a water gun to keep the water bowl overflowing. The rinsing time is 60s.

[0049] (3) The wafer processed in step (2) is placed in the S2 cleaning solution for cleaning. The volume ratio of hydrofluoric acid, hydrochloric acid and water in the S2 cleaning solution is 15:25:60. The cleaning time is 30s and the cleaning temperature is 25℃. During the cleaning process, the wafer is rotated continuously to ensure that the wafer surface is evenly coated with liquid. Then the wafer is placed in a rinsing tank for rinsing for 60s.

[0050] (4) The wafer after step (3) is placed in S3 cleaning solution for cleaning. The volume ratio of nitric acid to water in S3 cleaning solution is 2:10. The cleaning time is 30s and the cleaning temperature is 25℃. During the cleaning process, the wafer is rotated continuously to make the wafer surface uniformly coated with liquid. Then the wafer is rinsed with a water gun to keep the water bowl in a state of overflow. The rinsing time is 60s.

[0051] (5) The wafer after step (4) is placed in S4 cleaning solution for cleaning. S4 cleaning solution is hydrogen peroxide with a mass concentration of 48.8%. The cleaning time is 30s. The cleaning temperature is 25℃. During the cleaning process, the wafer is rotated continuously to make the wafer surface uniformly coated with liquid. Then the wafer is rinsed with a water gun to keep the water bowl in an overflow state. The rinsing time is 60s.

[0052] (6) The wafer after step (5) is placed in S5 cleaning solution for cleaning. The volume ratio of phosphoric acid to water in S5 cleaning solution is 3:7. The cleaning time is 30s. The cleaning temperature is 25℃. During the cleaning process, the wafer is rotated continuously to make the wafer surface uniformly coated with liquid. Then the wafer is rinsed with a water gun to keep the water bowl in a state of overflow. The rinsing time is 60s.

[0053] (7) The wafer after step (6) is placed in S6 cleaning solution for cleaning. The volume ratio of sulfuric acid to water in S6 cleaning solution is 2:100. The cleaning time is 30s. The cleaning temperature is 25℃. During the cleaning process, the wafer is rotated continuously to make the wafer surface uniformly coated with liquid. Then the wafer is rinsed with a water gun to keep the water bowl in a state of overflow. The rinsing time is 60s.

[0054] (8) After each wafer is cleaned and dried, it is placed in a cartridge box that has been dried with nitrogen. After passing the inspection, it can be packaged and shipped.

[0055] Comparative Example 1

[0056] This comparative example discloses a cleaning process for gallium antimonide wafers, including the following steps:

[0057] (1) Select nine 3-inch gallium antimonide wafers that have been polished and waxed using the wax polishing process, and immerse them in hot sulfuric acid at 65°C for 5 seconds.

[0058] (2) Soak in cold sulfuric acid at room temperature for 3 seconds, put it in a water bowl, and rinse the water bowl with a water gun at the same time to keep the water overflowing. Cleaning time: 45 seconds.

[0059] (3) Use citric acid with a mass concentration of 99.8% and soak it in a mixed solution of citric acid and deionized water at 4℃ with a volume ratio of 1:30 for 30 seconds. During the soaking process, rotate the wafer clamp continuously to make the wafer surface evenly coated with liquid and rinse it with a water gun. Cleaning time: 30 seconds.

[0060] (4) Use ammonia water with a mass concentration of 28%, soak in a mixed solution of ammonia water and hydrogen peroxide at room temperature with a volume ratio of 3:7 for 30 seconds, rinse with a water gun, and clean for 30 seconds.

[0061] (5) Soak in a mixed solution of sulfuric acid and deionized water at room temperature for 45 seconds.

[0062] (6) After each wafer is cleaned and dried, it is placed in a cartridge box that has been dried with nitrogen. After passing the inspection, it can be packaged and shipped.

[0063] Examples 2-5

[0064] To verify the cleaning effect, Examples 2-5 were consistent with Example 1.

[0065] Comparative Examples 2-5

[0066] To compare the cleaning effects, Comparative Examples 2-5 were kept consistent with Comparative Example 1.

[0067] The cleaned wafers from Examples 1-5 and Comparative Examples 1-5 were tested, and the results are shown in Table 1. The specific test process is as follows:

[0068] Two cleaned gallium antimonide wafer substrates were randomly selected from each experimental group. The number of bright spots and the Haze value within the 0.15μm filter range on the gallium antimonide wafer substrate were detected using a Tencor machine. The average value of each experimental group was taken.

[0069] Two cleaned gallium antimonide wafer substrates were randomly selected from each experimental group. The thickness of the oxide layer on the gallium antimonide wafer substrate was measured using an ellipsometry, and the average value was taken for each experimental group.

[0070] Two cleaned gallium antimonide wafer substrates were randomly selected from each experimental group, and the silicon content on the gallium antimonide wafer substrates was tested by TOF-SIMS surface analysis. The average value of each experimental group was taken.

[0071] The criterion for judging the yield rate is: check the surface of each wafer with a strong light to see if there are scratches, damage, chemicals, etc.

[0072] Table 1

[0073]

[0074] It can be seen that the gallium antimonide wafer cleaning process of this application can effectively improve the cleaning effect on the wafer surface.

[0075] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A cleaning process for gallium antimonide wafers, characterized in that, Includes the following steps: (1) The polished and wax-removed wafers were successively immersed in hot concentrated sulfuric acid and cold concentrated sulfuric acid; (2) The wafer processed in step (1) is placed in cleaning solution S1 for cleaning treatment. The cleaning solution S1 is a tetramethylammonium hydroxide solution with a pH value ≥12.

5. The cleaning treatment temperature is 20~30℃ and the cleaning treatment time is 30~60s. (3) The wafer processed in step (2) is placed in S2 cleaning solution for cleaning. The S2 cleaning solution is a mixture of hydrofluoric acid, hydrochloric acid and water. The volume ratio of hydrofluoric acid, hydrochloric acid and water in the S2 cleaning solution is 10~15:25~30:60~70. The mass concentration of hydrofluoric acid used is ≥48.8%. The mass concentration of hydrochloric acid used is ≥36%. The cleaning time is 30~60s. (4) The wafer processed in step (3) is placed in S3 cleaning solution for cleaning. The S3 cleaning solution is a mixture of nitric acid and water. The volume ratio of nitric acid to water in the S3 cleaning solution is 2~5:10~15. The mass concentration of the nitric acid used is ≥69%. The cleaning time is 30~60s. (5) The wafer processed in step (4) is placed in S4 cleaning solution for cleaning treatment. The S4 cleaning solution is hydrogen peroxide with a mass concentration ≥30.0%; the cleaning treatment time is 30~60s. (6) The wafer processed in step (5) is placed in S5 cleaning solution for cleaning. The S5 cleaning solution is a mixture of phosphoric acid and water. The volume ratio of phosphoric acid to water in the S5 cleaning solution is 1~5:5~9. The mass concentration of the phosphoric acid used is ≥85.0%. The cleaning time is 30~60s. (7) The wafer processed in step (6) is placed in S6 cleaning solution for cleaning. S6 cleaning solution is a mixture of sulfuric acid and water. The volume ratio of sulfuric acid to water in S6 cleaning solution is 1~5:90~100. The mass concentration of sulfuric acid used is ≥70%. The cleaning time is 10~30s. (8) Dry the wafer after step (7).

2. The cleaning process as described in claim 1, characterized in that, In step (1): Hot concentrated sulfuric acid treatment: soak for 10~30s; temperature 50~70℃; sulfuric acid mass concentration 70~98%.

3. The cleaning process as described in claim 1, characterized in that, In step (1): Cold concentrated sulfuric acid treatment: soak for 10~30s; temperature 30~45℃; sulfuric acid mass concentration 70~98%.

4. The cleaning process according to any one of claims 1 to 3, characterized in that, In steps (1) to (8), a water rinsing process is set between adjacent steps. The rinsing process is as follows: the wafer is placed in a water tank, and the water tank is rinsed with a water gun to keep the water overflowing. The overflow water volume is 10~60L / min.

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