Cleaning method for effectively removing organic dirt of silicon carbide epitaxial wafer
Through the multi-step soaking and cleaning steps of the liquid, the problem of poor cleaning effect of silicon carbide epitaxial sheets is solved, and efficient removal of organic matter dirt is achieved, reducing rework frequency and cost, and improving production efficiency.
Patent Information
- Application Number
- CN202510553248.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-07-22
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
In the existing silicon carbide epitaxial sheet cleaning methods, the accumulation of organic impurities in the acetone solution leads to a decrease in the cleaning effect, resulting in an increase in residual organic matter on the wafer surface, affecting the quality and subsequent processes, and increasing the rework frequency and cost.
After soaking with alkaline solution, the acetone solution, SPM solution, ammonia solution and DHF solution are soaked in sequence, and combined with the QDR cleaning and purge and drying steps, the organic matter dirt is removed through multiple soaking and sonication of the solution.
Effectively remove organic matter dirt on the surface of silicon carbide epitaxial sheet, reduce the frequency of rework, reduce the cost of using medicine liquid, and improve production efficiency.
Smart Images
Figure CN120347016A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor cleaning, and particularly relates to a cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer. Background Art
[0002] After the film of the existing silicon carbide epitaxial wafer is removed, the cleaning is usually carried out by first soaking in an organic solvent (such as acetone) to effectively remove the residue of organic matter (acrylic adhesive) after the film is removed from the silicon surface of the silicon carbide, and then by wet cleaning to effectively remove impurities such as dust, metal ions and organic matter remaining on the silicon carbide epitaxial wafer wafer without damaging the surface characteristics and electrical characteristics of the wafer. However, after continuous cleaning operations for a period of time, a large amount of organic impurities will gradually accumulate in the acetone solution. This is because as the cleaning process continues, the acrylic acid dissolved in the acetone and other organic substances eluted from the silicon carbide surface will continuously increase. These organic impurities are mixed with each other in the acetone solution, changing the original chemical environment and solubility of the acetone solution. When the organic impurities in the acetone solution reach a certain concentration, its solubility for acrylic acid will decrease significantly. Especially in the case of large production demand, a large amount of silicon carbide materials need to be continuously cleaned, and the use frequency of the acetone solution is extremely high, which makes the accumulation speed of organic impurities faster and this disadvantage becomes more obvious. In this case, the removal effect of acrylic organic matter becomes worse, resulting in an increase in the acrylic organic matter remaining on the wafer surface, and then an increase in the particles on the wafer surface, affecting the quality and subsequent performance of the wafer. When the removal effect of acetone on organic matter is not ideal, some of the remaining organic matter will carbonize after being treated with SPM solution. This is because the SPM solution has strong oxidizing properties and can react with organic matter. Under conditions such as high temperature, hydrogen, oxygen and other elements in the organic matter are removed in the form of water, leaving carbon elements, thus carbonizing the organic matter. The carbonized substance has stable properties and dense structure, and is difficult to be cleaned by subsequent cleaning processes. This will not only form stubborn stains on the surface of the silicon carbide epitaxial wafer, affecting the flatness and smoothness of the surface, but may also interfere with subsequent precision processes such as lithography and etching, resulting in process deviation and reducing the yield of the product. Due to the above problems of poor cleaning effect, the rework frequency is higher. Each rework means that the equipment needs to be used again for cleaning operations, which will increase the running time of the equipment and accelerate the wear of the equipment, thus significantly increasing the equipment maintenance cost. At the same time, a large amount of cleaning liquid needs to be used again for rework, including acetone, SPM solution and other chemical solvents in the wet cleaning process, which undoubtedly increases the rework liquid input cost. In addition, rework operations require additional manpower for equipment operation, product transfer and quality inspection, etc., which further increases the personnel demand cost. Generally speaking, the increase in rework frequency will bring a heavy cost burden to the entire production process, reducing production efficiency and economic benefits.
[0003] Therefore, there is an urgent need for a cleaning method that can effectively remove the organic contaminants on the silicon carbide epitaxial wafer to solve the deficiencies in the existing technology. Summary of the Invention
[0004] In view of the above problems, the purpose of the present invention is to provide a cleaning method that can effectively remove the organic contaminants on the silicon carbide epitaxial wafer, which can effectively remove the organic contaminants on the silicon carbide epitaxial wafer, reduce the rework frequency, and improve the production efficiency.
[0005] To achieve the above purpose, the present invention provides a cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer, including the steps of: (1) Immerse the silicon carbide epitaxial wafer in an alkaline solution, and then perform the first QDR cleaning; (2) Immerse the silicon carbide epitaxial wafer treated in step (1) in an acetone solution, and then perform the second QDR cleaning; (3) Immerse the silicon carbide epitaxial wafer treated in step (2) in an SPM solution, and then perform the third QDR cleaning; (4) Immerse the silicon carbide epitaxial wafer treated in step (3) in an ammonia water solution, and then perform the fourth QDR cleaning; (5) Immerse the silicon carbide epitaxial wafer treated in step (4) in a DHF solution, and then perform the fifth QDR cleaning; (6) Blow-dry the silicon carbide epitaxial wafer treated in step (5).
[0006] Compared with the existing technology, the present invention first immerses the silicon carbide epitaxial wafer in an alkaline solution. During the immersion process, the acrylic organic film remaining after the film peeling of the silicon carbide epitaxial wafer reacts with the alkaline solution to generate acrylate, thereby effectively removing the remaining acrylic organic film on its surface. Then, the silicon carbide epitaxial wafer treated with the alkaline solution is successively immersed in an acetone solution, an SPM solution, an ammonia water solution, and a DHF solution, which can effectively reduce the organic content during the acetone solution treatment, thereby improving the immersion cleaning effect of the acetone solution on organic impurities and other impurities. And when the silicon carbide epitaxial wafer is treated with the SPM solution, the stubborn particles attached to its surface due to the carbonization of organic matter can be further reduced, thereby further improving the cleaning effect of the subsequent ammonia water solution and DHF solution on the silicon carbide epitaxial wafer. Therefore, the cleaning method of the present invention can effectively remove the organic contaminants on the silicon carbide epitaxial wafer, reduce the rework frequency and the cost of solution use, and improve the production efficiency.
[0007] As a preferred technical solution, the alkaline solution of the present invention is selected from at least one of sodium hydroxide solution and potassium hydroxide solution.
[0008] As a preferred technical solution, the concentration of the lye in the present invention is 5% to 10%.
[0009] As a preferred technical solution, the temperature of the lye immersion treatment in the present invention is 55°C to 75°C, and the time is 10 min to 20 min.
[0010] As a preferred technical solution, while the silicon carbide epitaxial wafer in the present invention is immersed in the acetone solution, megasonic treatment is also included, and the power of the megasonic treatment is 600 W to 800 W.
[0011] As a preferred technical solution, the temperature of the acetone solution immersion treatment in the present invention is 20°C to 40°C, and the time is 15 min to 30 min.
[0012] As a preferred technical solution, the SPM solution in the present invention is a mixed solution with a volume ratio of concentrated sulfuric acid: hydrogen peroxide = 3 to 7: 1 to 3.
[0013] As a preferred technical solution, the concentration of the concentrated sulfuric acid in the present invention is 90% to 100%, and the concentration of the hydrogen peroxide is 30% to 32%.
[0014] As a preferred technical solution, the temperature of the SPM solution immersion treatment in the present invention is 100°C to 140°C, and the time is 15 min to 30 min.
[0015] As a preferred technical solution, the ammonia water solution in the present invention is a mixed solution with a volume ratio of ammonia water solution: deionized water = 2.4 to 3.6: 8 to 9.
[0016] As a preferred technical solution, the concentration of the ammonia water solution in the present invention is 28% to 30%.
[0017] As a preferred technical solution, the temperature of the ammonia water solution immersion treatment in the present invention is 55°C to 75°C, and the time is 15 min to 30 min.
[0018] As a preferred technical solution, the DHF solution in the present invention is a mixed solution with a volume ratio of hydrofluoric acid solution: pure water = 1: 40 to 50.
[0019] As a preferred technical solution, the concentration of the hydrofluoric acid solution in the present invention is 44% to 54%.
[0020] As a preferred technical solution, the temperature of the DHF solution immersion treatment in the present invention is 20°C to 30°C, and the time is 5 to 10 min.
[0021] As a preferred technical solution, the rotation speed of the silicon carbide epitaxial wafer drying in the present invention is 1200 to 1500 rpm, and the drying time is 5 to 10 min.
[0022] As a preferred technical solution, the purging of the present invention includes purging with nitrogen.
[0023] As a preferred technical solution, the first QDR cleaning, the second QDR cleaning, the third QDR cleaning, the fourth QDR cleaning and the fifth QDR cleaning of the present invention specifically include placing the silicon carbide epitaxial wafer in a pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the functions of spraying, ultrasonic, bubbling, overflowing, fast forward and fast discharge of the pure water QDR tank.
[0024] As a preferred technical solution, the third QDR cleaning of the present invention includes first placing the silicon carbide epitaxial wafer in a pure water QDR tank and cleaning it at 50°C to 70°C for 5 to 15 minutes, and then cleaning it at 20°C to 30°C for 5 to 15 minutes.
[0025] As a preferred technical solution, the cleaning temperatures of the first QDR cleaning, the second QDR cleaning, the fourth QDR cleaning and the fifth QDR cleaning of the present invention are each independently selected from 20°C to 30°C, the cleaning times are each independently selected from 5 to 15 minutes, and the cycle periods are each independently selected from 3 to 4 times. Description of the Drawings
[0026] Figure 1 It is a surface particle number characterization diagram before cleaning the silicon carbide epitaxial wafer 1#; Figure 2 It is a surface particle number characterization diagram after cleaning the silicon carbide epitaxial wafer 1# by the cleaning method of the prior art; Figure 3 It is a surface particle number characterization diagram after cleaning the silicon carbide epitaxial wafer 1# by the cleaning method of Embodiment 1 of the present invention; Figure 4 It is a surface particle number characterization diagram before cleaning the silicon carbide epitaxial wafer 2#; Figure 5 It is a surface particle number characterization diagram after cleaning the silicon carbide epitaxial wafer 2# by the cleaning method of the prior art; Figure 6 It is a surface particle number characterization diagram after cleaning the silicon carbide epitaxial wafer 2# by the cleaning method of Embodiment 2 of the present invention; Detailed Embodiments The present invention discloses a cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer, including the steps: (1) Soak the silicon carbide epitaxial wafer in an alkali solution, and then perform the first QDR cleaning; (2) Soak the silicon carbide epitaxial wafer processed in step (1) in an acetone medicine solution, and then perform the second QDR cleaning; (3) Immerse the silicon carbide epitaxial wafer processed in step (2) in SPM solution, and then perform the third QDR cleaning; (4) Immerse the silicon carbide epitaxial wafer processed in step (3) in ammonia water solution, and then perform the fourth QDR cleaning; (5) Immerse the silicon carbide epitaxial wafer processed in step (4) in DHF solution, and then perform the fifth QDR cleaning; (6) Blow-dry the silicon carbide epitaxial wafer processed in step (5).
[0027] Specifically, before step (1), it also includes loading the silicon carbide epitaxial wafer after film removal into a PFA cassette with a capacity of 25 pcs, and then performing the subsequent cleaning process.
[0028] In step (1), the alkaline solution can be selected from at least one of sodium hydroxide solution and potassium hydroxide solution. Preferably, the alkaline solution is selected from sodium hydroxide solution. The concentration of the alkaline solution can be 5% - 10%. Specifically, the concentration of the alkaline solution can be, but is not limited to, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%. The temperature of the alkaline solution immersion treatment can be 55°C - 75°C. Specifically, the immersion treatment temperature can be, but is not limited to, 55°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 75°C. The time of the alkaline solution immersion treatment is 10 min - 20 min. Specifically, the time of the alkaline solution immersion treatment can be, but is not limited to, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min. In the present invention, by first immersing the silicon carbide epitaxial wafer after film removal in an alkaline solution with a concentration of 5% - 10% at 55°C - 75°C, under this condition, the alkaline solution can react with the organic matter film (acrylic acid type) remaining on the surface of the silicon carbide epitaxial wafer to obtain acrylate, thereby effectively removing the organic matter contamination of the silicon carbide epitaxial wafer, and at the same time, effectively avoiding the situation that impurities are difficult to remove due to the formation of carbides after subsequent treatment with SPM solution.
[0029] The first QDR cleaning involves placing the silicon carbide epitaxial wafer in a pure water QDR tank, and effectively removing particulate impurities (acrylate) and alkali solution residues on the surface of the silicon carbide epitaxial wafer through the functions of spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge in the pure water QDR tank. Among them, the cycle period is 3 or 4 times, and the cleaning temperature is 20°C to 30°C. As an example, the cleaning temperature can be, but is not limited to, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C. The cleaning time is 5 min to 15 min. As an example, the cleaning time can be, but is not limited to, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min. The power of the ultrasonic is 40 KHz to 80 KHz. As an example, the power of the ultrasonic can be, but is not limited to, 40 KHz, 45 KHz, 50 KHz, 55 KHz, 60 KHz, 65 KHz, 70 KHz, 75 KHz, 80 KHz.
[0030] In step (2), while the silicon carbide epitaxial wafer is being soaked in the acetone medicine solution, megasonic treatment is also included. The power of the megasonic treatment is 600 W to 800 W. Specifically, the power of the megasonic treatment can be, but is not limited to, 600 W, 650 W, 700 W, 750 W, 800 W. Under this condition, megasonic treatment can effectively remove particulate impurities on the surface of the silicon carbide epitaxial wafer without damaging its surface. The temperature for soaking the silicon carbide epitaxial wafer in the acetone medicine solution is 20°C to 40°C. Specifically, the temperature for soaking the silicon carbide epitaxial wafer in the acetone medicine solution can be, but is not limited to, 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C, 40°C. The time for soaking the silicon carbide epitaxial wafer in the acetone medicine solution is 15 min to 30 min. Specifically, the time for soaking the silicon carbide epitaxial wafer in the acetone medicine solution can be, but is not limited to, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min. In the present invention, megasonic treatment is carried out while the silicon carbide epitaxial wafer is being soaked in the acetone medicine solution, which can effectively remove residual organic substances and other particulate impurities on the surface of the silicon carbide epitaxial wafer without damaging its surface.
[0031] The second QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank, and effectively removing particulate impurities (acrylate) and alkali residue on the surface of the silicon carbide epitaxial wafer through functions such as spraying, ultrasonic wave, bubbling, overflow, fast forward and fast discharge. Among them, the circulation period is 3 or 4 times, and the cleaning temperature is 20°C to 30°C. As an example, the cleaning temperature can be but is not limited to 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C. The cleaning time is 5 min to 15 min. As an example, the cleaning time can be but is not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min. The power of the ultrasonic wave is 40 KHz to 80 KHz. As an example, the power of the ultrasonic wave can be but is not limited to 40 KHz, 45 KHz, 50 KHz, 55 KHz, 60 KHz, 65 KHz, 70 KHz, 75 KHz, 80 KHz..
[0032] In step (3), the SPM liquid medicine is a mixed solution with a volume ratio of concentrated sulfuric acid: hydrogen peroxide = 3 to 7: 1 to 3. Preferably, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 3:1 or 7:3. The concentration of concentrated sulfuric acid is 90% to 100%, and the concentration of hydrogen peroxide is 30% to 32%. The temperature for soaking treatment with the SPM liquid medicine is 100°C to 140°C. Specifically, the temperature for soaking treatment with the SPM liquid medicine can be but is not limited to 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C. The time for soaking treatment with the SPM liquid medicine is 15 min to 30 min. Specifically, the time for soaking treatment with the SPM liquid medicine can be but is not limited to 15 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min. The SPM liquid medicine has strong oxidizing property and can effectively remove organic substances, inorganic compounds, heavy metal ions such as Hg, Ge, etc. on the surface of the silicon carbide epitaxial wafer. In addition, the temperature for soaking treatment with the SPM liquid medicine in the present invention is 100°C to 140°C, and at this temperature, the oxidizing property of the SPM liquid medicine can be improved, thereby having a more excellent cleaning effect.
[0033] The third QDR cleaning process involves placing the silicon carbide epitaxial wafer in a pure water QDR tank and performing cleaning through the functions of spraying, ultrasonic vibration, bubbling, overflow, and fast forward and fast discharge of the pure water QDR tank. Specifically, the silicon carbide epitaxial wafer is first cleaned at 50°C to 70°C for 5 to 15 minutes, and then at 20°C to 30°C for 5 to 15 minutes. The stepwise temperature reduction cleaning can prevent fragmentation caused by thermal expansion and contraction. Moreover, the residual SPM solution on the surface of the silicon carbide epitaxial wafer has high activity in hot water, which is conducive to quickly cleaning the residual solution. Through its overflow, bubbling, spraying, and fast discharge functions, particulate impurities on the silicon carbide epitaxial wafer can be effectively removed, further cleaning its surface and avoiding contamination of subsequent solutions. Among them, the power of ultrasonic vibration is 40KHz to 80KHz. As an example, the power of ultrasonic vibration can be but is not limited to 40KHz, 45KHz, 50KHz, 55KHz, 60KHz, 65KHz, 70KHz, 75KHz, 80KHz.
[0034] In step (4), ultrasonic treatment is also included while performing the ammonia solution immersion treatment. The frequency of ultrasonic vibration is 40KHz to 150KHz. Specifically, the frequency of ultrasonic vibration can be but is not limited to 40KHz, 50KHz, 60KHz, 70KHz, 80KHz, 90KHz, 100KHz, 110KHz, 120KHz, 130KHz, 140KHz, 150KHz. The ammonia solution is a mixed solution with a volume ratio of ammonia water solution: deionized water = 2.4 to 3.6:8 to 9. Specifically, the volume ratio of ammonia water solution to deionized water can be but is not limited to 2.4:8, 2.4:8.5, 2.4:9, 3:8, 3:8.5, 3:9, 3.6:8, 3.6:8.5, 3.6:9. Preferably, the volume ratio of ammonia water solution to deionized water is 2.4:8 or 3.6:9. The concentration of the ammonia water solution is 28% to 30%. The temperature of the ammonia solution immersion treatment is 55°C to 75°C. Specifically, the temperature of the ammonia solution immersion treatment can be but is not limited to 55°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 75°C. The time of the ammonia solution immersion treatment is 15 minutes to 30 minutes. Specifically, the time of the alkali solution immersion treatment can be but is not limited to 15 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 30 minutes. Using the ammonia solution to perform ultrasonic cleaning on the silicon carbide epitaxial wafer under the condition of 55°C to 75°C can effectively strip cationic and particulate impurities on the wafer surface, and can also further remove minor organic pollutants and some metallized pollutants. At the same time, using an ammonia water solution with a concentration of 28% to 30% can effectively avoid the oxidation etching effect on the silicon carbide epitaxial wafer, which may cause the phenomenon of surface roughness.
[0035] The fourth QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank, and removing the particulate impurities and residual chemical solution on the surface of the silicon carbide epitaxial wafer through functions such as spraying, ultrasonic wave, bubbling, overflow, fast forward and fast discharge. Among them, the cleaning temperature is 20°C to 30°C. As an example, the cleaning temperature can be but is not limited to 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C. The cycle period is 3 to 4 times, and the cleaning time is 5 min to 15 min. As an example, the cleaning time can be but is not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min. The power of the ultrasonic wave is 40 KHz to 80 KHz. As an example, the power of the ultrasonic wave can be but is not limited to 40 KHz, 45 KHz, 50 KHz, 55 KHz, 60 KHz, 65 KHz, 70 KHz, 75 KHz, 80 KHz.
[0036] In step (5), the DHF chemical solution is a mixed solution with a volume ratio of hydrofluoric acid solution: pure water = 1:40 to 50. Specifically, the volume ratio of the hydrofluoric acid solution to pure water can be but is not limited to 1:40, 1:42, 1:44, 1:46, 1:48, 1:50. Preferably, the volume ratio of the hydrofluoric acid solution to pure water is 1:40 or 1:50. The concentration of the hydrofluoric acid solution is 49%. The temperature for the DHF chemical solution immersion treatment is 20°C to 30°C. Specifically, the temperature for the DHF chemical solution immersion treatment can be but is not limited to 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C. The time for the DHF chemical solution immersion treatment is 5 min to 10 min. Specifically, the time for the DHF chemical solution immersion treatment can be but is not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min. Through the DHF immersion treatment, the natural oxide film on the surface of the silicon carbide epitaxial wafer can be removed. Therefore, the metals attached to the natural oxide film will be dissolved into the cleaning solution, and at the same time, DHF inhibits the formation of the oxide film. Therefore, it is easy to remove metals such as Al, Fe, Zn, Ni on the surface of the silicon carbide epitaxial wafer, and DHF can also remove the metal hydroxides attached to the natural oxide film. When cleaning with DHF, when the natural oxide film is corroded, the silicon surface on the surface of the silicon carbide epitaxial wafer is hardly corroded.
[0037] The fifth QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank, and removing the particulate impurities and residual chemical liquid on the surface of the silicon carbide epitaxial wafer through functions such as spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge. Among them, the cleaning temperature is 20°C to 30°C. As an example, the cleaning temperature can be but is not limited to 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C. The cycle period is 3 to 4 times, and the cleaning time is 5 min to 15 min. As an example, the cleaning time can be but is not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min. The power of the ultrasonic is 40 KHz to 80 KHz. As an example, the power of the ultrasonic can be but is not limited to 40 KHz, 45 KHz, 50 KHz, 55 KHz, 60 KHz, 65 KHz, 70 KHz, 75 KHz, 80 KHz.
[0038] The cleaning temperature, cycle period, cleaning time and ultrasonic frequency of the first QDR cleaning, the second QDR cleaning, the fourth QDR cleaning and the fifth QDR cleaning can be the same or different.
[0039] In step (6), the purging and drying are carried out in a horizontal dryer. The purging includes purging with nitrogen. The rotation speed of drying is 1200 rpm to 1500 rpm. Specifically, the rotation speed of drying can be but is not limited to 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, 1400 rpm, 1450 rpm, 1500 rpm. The drying time is 5 min to 10 min. Specifically, the drying time can be but is not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min. The silicon carbide epitaxial wafer is dried at 1200 rpm - 1500 rpm, and high-purity nitrogen is used for purging during the drying process, which can effectively remove the particulate on the surface of the silicon carbide epitaxial wafer. Controlling the drying time within 5 min to 10 min can effectively avoid the attachment of other particulates on the surface due to too long drying time.
[0040] To better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the methods described in the following embodiments are further explanatory descriptions of the present invention and should not be regarded as limitations of the present invention.
[0041] Example 1 This embodiment provides a cleaning method for effectively removing organic dirt on a silicon carbide epitaxial wafer, including the steps: (1) Load the silicon carbide epitaxial wafer (1#) after film peeling into a PFA cassette with a capacity of 25 pcs. Soak the silicon carbide epitaxial wafer in an alkaline solution, and then perform the first QDR cleaning. Among them, the alkaline solution is a sodium hydroxide solution with a concentration of 6%, the temperature of the soaking treatment is 60 °C, the time of the soaking treatment is 18 min. The first QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cycle period is 4 times, the cleaning time is 10 min, the cleaning temperature is 25 °C, and the ultrasonic frequency is 50 KHz; (2) Soak the silicon carbide epitaxial wafer processed in step (1) in an acetone medicine solution, and perform megasonic treatment at the same time, and then perform the second QDR cleaning. Among them, the temperature of the soaking treatment is 28 °C, the time of the soaking treatment is 20 min, and the megasonic frequency is 650 W. The second QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cycle period is 3 times, the cleaning time is 15 min, the cleaning temperature is 25 °C, and the ultrasonic frequency is 55 KHz; (3) Soak the silicon carbide epitaxial wafer processed in step (2) in an SPM medicine solution, and then perform the third QDR cleaning. Among them, the SPM medicine solution is a mixed solution with a volume ratio of 98% concentrated sulfuric acid: 30% hydrogen peroxide = 3:1. The temperature of the soaking treatment is 115 °C, the time of the soaking treatment is 16 min. The third QDR cleaning includes first placing the silicon carbide epitaxial wafer in a pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank, and cleaning at 50 °C for 10 min first, and then cleaning at 20 °C for 5 min. The ultrasonic frequency is 55 KHz; (4) Soak the silicon carbide epitaxial wafer processed in step (3) in an ammonia water medicine solution, and perform ultrasonic treatment at the same time, and then perform the fourth QDR cleaning. Among them, the ammonia water medicine solution is a mixed solution with a volume ratio of 28% ammonia water solution: deionized water = 2.4:8. The temperature of the soaking treatment is 55 °C, the time is 15 min, the ultrasonic frequency during the soaking treatment is 60 KHz. The fourth QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cleaning temperature is 20 °C, the cycle period is 3 times, the cleaning time is 8 min, and the ultrasonic frequency is 55 KHz; (5) Immerse the silicon carbide epitaxial wafer processed in step (4) in DHF solution, and then perform the fifth QDR cleaning. The DHF solution is a mixed solution of 49% hydrofluoric acid solution and pure water with a volume ratio of 1:40. The temperature of the immersion treatment is 20 °C, and the time is 6 min. The fifth QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cleaning temperature is 20 °C, the cycle period is 3 times, the cleaning time is 8 min, and the ultrasonic frequency is 60 KHz; (6) Blow-dry the silicon carbide epitaxial wafer processed in step (5). The rotation speed for drying is 1280 rpm, and the drying time is 8 min. While drying, purge with high-purity nitrogen.
[0042] It can be seen from Figures 1 to 3 that by using the method of the present invention, the number of surface particles can be reduced from 1914 to 31, while only reduced to 246 by using the cleaning method of the prior art. Therefore, the cleaning method of the present invention can effectively improve the cleaning effect on the organic contamination of the silicon carbide epitaxial wafer compared with the existing cleaning method.
[0043] Example 2 This example provides a cleaning method for effectively removing organic contamination on a silicon carbide epitaxial wafer, including the steps: (1) Load the silicon carbide epitaxial wafer (2#) after film removal into a PFA cassette with a capacity of 25 pcs, immerse the silicon carbide epitaxial wafer in an alkaline solution, and then perform the first QDR cleaning. The alkaline solution is a sodium hydroxide solution with a concentration of 8%. The temperature of the immersion treatment is 70 °C, and the immersion treatment time is 11 min. The first QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cycle period is 4 times, the cleaning time is 10 min, the cleaning temperature is 25 °C, and the ultrasonic frequency is 50 KHz; (2) Immerse the silicon carbide epitaxial wafer processed in step (1) in acetone solution, and perform megasonic treatment at the same time, and then perform the second QDR cleaning. The temperature of the immersion treatment is 35 °C, the immersion treatment time is 25 min, and the megasonic frequency is 720 W. The second QDR cleaning includes placing the silicon carbide epitaxial wafer in a pure water QDR tank and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cycle period is 4 times, the cleaning time is 15 min, the cleaning temperature is 25 °C, and the ultrasonic frequency is 55 KHz; (3) Immerse the silicon carbide epitaxial wafer processed in step (2) in the SPM solution, and then perform the third QDR cleaning. The SPM solution is a mixed solution with a volume ratio of 98% concentrated sulfuric acid: 32% hydrogen peroxide = 7:3. The temperature of the immersion treatment is 130 °C, and the time of the immersion treatment is 25 min. The third QDR cleaning includes placing the silicon carbide epitaxial wafer in the pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. First, clean at 70 °C for 10 min, then clean at 30 °C for 5 min, and the ultrasonic frequency is 55 KHz; (4) Immerse the silicon carbide epitaxial wafer processed in step (3) in the ammonia water solution, and perform ultrasonic treatment at the same time, and then perform the fourth QDR cleaning. The ammonia water solution is a mixed solution with a volume ratio of 30% ammonia water solution: deionized water = 3.6:9. The temperature of the immersion treatment is 68 °C, and the time is 20 min. The ultrasonic frequency during the immersion treatment is 60 KHz. The fourth QDR cleaning includes placing the silicon carbide epitaxial wafer in the pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cleaning temperature is 20 °C, the cycle period is 3 times, the cleaning time is 8 min, and the ultrasonic frequency is 55 KHz; (5) Immerse the silicon carbide epitaxial wafer processed in step (4) in the DHF solution, and then perform the fifth QDR cleaning. The DHF solution is a mixed solution with a volume ratio of 49% hydrofluoric acid solution: pure water = 1:50. The temperature of the immersion treatment is 25 °C, and the time is 6 min. The fifth QDR cleaning includes placing the silicon carbide epitaxial wafer in the pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the spraying, ultrasonic, bubbling, overflow, fast forward and fast discharge functions of the pure water QDR tank. The cleaning temperature is 20 °C, the cycle period is 3 times, the cleaning time is 8 min, and the ultrasonic frequency is 60 KHz; (6) Blow-dry the silicon carbide epitaxial wafer processed in step (5). The rotation speed of the drying is 1380 rpm, and the drying time is 6 min. While drying, purge with high-purity nitrogen.
[0044] From Figures 4 to 6 the surface particle number characterization diagram, it can be seen that by using the method of the present invention, the surface particle number can be reduced from 821 to 45, while only reduced to 181 by using the cleaning method of the prior art. Therefore, the cleaning method of the present invention can effectively improve the cleaning effect.
[0045] 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 the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to the embodiments listed. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A cleaning method for effectively removing organic contaminants from a silicon carbide epitaxial wafer, comprising the steps: (1) soaking the silicon carbide epitaxial wafer in an alkaline solution, and then performing the first QDR cleaning; (2) soaking the silicon carbide epitaxial wafer treated in step (1) in an acetone solution, and then performing the second QDR cleaning; (3) soaking the silicon carbide epitaxial wafer treated in step (2) in an SPM solution, and then performing the third QDR cleaning; (4) soaking the silicon carbide epitaxial wafer treated in step (3) in an ammonia water solution, and then performing the fourth QDR cleaning; (5) soaking the silicon carbide epitaxial wafer treated in step (4) in a DHF solution, and then performing the fifth QDR cleaning; (6) purging and spin-drying the silicon carbide epitaxial wafer treated in step (5).
2. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, wherein The alkaline solution is selected from at least one of a sodium hydroxide solution and a potassium hydroxide solution, the concentration of the alkaline solution is 5% - 10%, the temperature of the alkaline solution soaking treatment is 55°C - 75°C, and the time is 10 min - 20 min.
3. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, wherein, When the silicon carbide epitaxial wafer is soaked in the acetone solution, megasonic treatment is also included. The power of the megasonic treatment is 600 W - 800 W, the temperature of the acetone solution soaking treatment is 20°C - 40°C, and the time is 15 min - 30 min.
4. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, wherein, The SPM solution is a mixed solution with a volume ratio of concentrated sulfuric acid: hydrogen peroxide = 3 - 7:1 - 3. Among them, the concentration of the concentrated sulfuric acid is 90% - 100%, the concentration of the hydrogen peroxide is 30% - 32%, the temperature of the SPM solution soaking treatment is 100°C - 140°C, and the time is 15 min - 30 min.
5. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, characterized in that, The ammonia water solution is a mixed solution with a volume ratio of ammonia water solution: deionized water = 2.4 - 3.6:8 - 9. Among them, the concentration of the ammonia water solution is 28% - 30%, the temperature of the ammonia water solution soaking treatment is 55°C - 75°C, and the time is 15 min - 30 min.
6. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, characterized in that, The DHF solution is a mixed solution with a volume ratio of hydrofluoric acid solution: pure water = 1:40 - 50. Among them, the concentration of the hydrofluoric acid solution is 44% - 54%, the temperature of the DHF solution soaking treatment is 20°C - 30°C, and the time is 5 min - 10 min.
7. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, characterized in that, The rotation speed of spin-drying the silicon carbide epitaxial wafer is 1200 rpm - 1500 rpm, and the spin-drying time is 5 min - 10 min. The purging includes purging with nitrogen.
8. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 1, wherein, The first QDR cleaning, the second QDR cleaning, the third QDR cleaning, the fourth QDR cleaning, and the fifth QDR cleaning specifically include placing the silicon carbide epitaxial wafer in a pure water QDR tank, and cleaning the silicon carbide epitaxial wafer through the functions of spraying, ultrasonic, bubbling, overflowing, and fast forward and fast discharge of the pure water QDR tank.
9. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 8, wherein, The third QDR cleaning includes first placing the silicon carbide epitaxial wafer in a pure water QDR tank and cleaning it at 50°C - 70°C for 5 - 15 min, and then cleaning it at 20°C - 30°C for 5 - 15 min.
10. The cleaning method for effectively removing organic contaminants on a silicon carbide epitaxial wafer according to claim 8, wherein The cleaning temperatures of the first QDR cleaning, the second QDR cleaning, the fourth QDR cleaning, and the fifth QDR cleaning are each independently selected from 20°C to 30°C, the cleaning times are each independently selected from 5 minutes to 15 minutes, and the cycle periods are each independently selected from 3 to 4 times.