Process for cleaning and drying silicon carbide wafer
By using a mixture of isopropanol and nitrogen and the Marangori effect during the silicon carbide wafer drying process, the water stain residues and particulate matter exceeding the standard caused by traditional drying methods are solved, and efficient drying and cleaning effects are achieved.
Patent Information
- Application Number
- CN202411910679.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-03-28
AI Technical Summary
The traditional silicon carbide wafer drying method can easily lead to liquid residues such as water stains, resulting in excess of the particle quantity.
A process is adopted to dry the mixture of isopropanol and nitrogen in the drying tank, and to remove water stains by using the surface tension gradient difference through the Marangori effect, combined with optimized process parameters such as upward movement speed, distance and gas flow rate, rapid drying is achieved.
Effectively remove watermarks, condensed particles and metal particles on the surface of silicon carbide wafers, reduce water stain residues and particulate attachment, and improve cleaning pass rate.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a process for cleaning and drying a silicon carbide wafer. Background Art
[0002] Silicon carbide wafer refers to the silicon wafer used to make silicon semiconductor circuits. Its original material is silicon. High-purity polycrystalline silicon is dissolved and doped with silicon crystal seeds, and then slowly pulled out to form cylindrical single crystal silicon. After grinding, polishing and slicing, the silicon crystal rod forms a silicon carbide wafer, that is, a silicon carbide wafer.
[0003] When silicon carbide is processed into thin slices and goes through similar manufacturing processes as silicon carbide wafers, such as grinding and polishing, it becomes a silicon carbide wafer, which is mainly used to manufacture semiconductor devices with special performance requirements such as high power, high frequency, and high temperature.
[0004] During the manufacturing process of silicon carbide wafers, silicon carbide wafers will be contaminated due to contact with various organic matter, particles and metals, so they need to be cleaned and dried. Cleaning and drying are two matching steps. Silicon carbide wafers must be taken out of the cleaning equipment in a dry state to avoid surface oxidation and water stains.
[0005] The traditional method of drying silicon carbide wafers is to use rotary drying, which removes water stains attached to the surface of silicon carbide wafers through centrifugal force generated at high speed. However, due to the difference in the material of silicon carbide wafers and the influence of surface conditions, this drying method sometimes causes liquid residues such as water stains, which will cause the number of particles in the entire silicon carbide wafer to exceed the standard. Summary of the invention
[0006] The object of the present invention is to provide a process for cleaning and drying a silicon carbide wafer, wherein the process of the present invention can effectively remove impurities such as watermarks, condensed particles and metal particles remaining on the surface of the silicon carbide wafer after RCA cleaning.
[0007] The present invention provides a process for cleaning and drying a silicon carbide wafer, comprising the following steps:
[0008] A) placing the cleaned silicon carbide wafer with a plug in a drying tank filled with water so that the silicon carbide wafer is completely immersed in the water;
[0009] B) using the support mechanism at the bottom of the drying tank to push the silicon carbide wafer up from the initial position, pushing the silicon carbide wafer out of the liquid surface at a first upward speed, and spraying a mixed gas of isopropyl alcohol and nitrogen on the surface of the silicon carbide wafer to dry it, after the silicon carbide wafer moves up to the first position, continuing to push the silicon carbide wafer up at a second upward speed, after the silicon carbide wafer rises to the second position, continuing to push the silicon carbide wafer up at a third upward speed, rising to the third position, and completing the drying of the silicon carbide wafer;
[0010] The first upward movement speed is 0.5-1.5 mm / s, and the first position is moved up by 170-180 mm relative to the initial position of the silicon carbide wafer; the second upward movement speed is 0.1-0.3 mm / s, and the second position is moved up by 195-205 mm relative to the initial position of the silicon carbide wafer; the third upward movement speed is 1-2 mm / s, and the third position is moved up by 220-230 mm relative to the initial position of the silicon carbide wafer;
[0011] The flow rate of the mixed gas of isopropanol and nitrogen is 80-100 LPM; the temperature of the mixed gas of isopropanol and nitrogen is 200-280° C.; the pressure of the mixed gas of isopropanol and nitrogen is 1-2 kPa;
[0012] C) drain the water in the drying tank and spray nitrogen on the surface of the plug to dry it;
[0013] D) The wafer is moved down into the plug, and a mixed gas of isopropyl alcohol and nitrogen is used to simultaneously purge the wafer and the plug to obtain a dry wafer.
[0014] Preferably, in the mixed gas of isopropanol and nitrogen used in step B), the volume fraction of isopropanol is 50-70%;
[0015] In the mixed gas of isopropanol and nitrogen used in step D), the volume fraction of isopropanol is 50-70%.
[0016] Preferably, during the drying process of the plug in step C), the flow rate of the nitrogen is 50 to 100 LPM; the temperature of the nitrogen is 220 to 280° C., and the pressure of the nitrogen is 0.5 to 1.5 kPa.
[0017] Preferably, in the process of drying the plug in step C), the drying time of the plug is 500 to 1000 seconds.
[0018] Preferably, in step D), the flow rate of the mixed gas of isopropanol and nitrogen is 60-100 LPM, the temperature is 250-300° C., and the pressure is 2-4 kPa.
[0019] Preferably, during the purging process in step D), nitrogen is introduced into the drying tank to maintain a nitrogen atmosphere in the drying tank, and the flow rate of the nitrogen is 80 to 120 LPM; the temperature of the nitrogen is 200 to 280° C., and the pressure of the nitrogen is 1 to 280 kPa.
[0020] Preferably, the purging time in step D) is 20 to 50 seconds.
[0021] Preferably, before drying the silicon carbide wafer, a mixed gas of isopropyl alcohol and nitrogen and nitrogen are introduced into the drying tank to clean the drying tank.
[0022] Preferably, during the cleaning process of the drying tank, the flow rate of the nitrogen is 50 to 80 LPM; the temperature of the nitrogen is 200 to 280° C., and the pressure of the nitrogen is 0.5 to 4 kPa.
[0023] Preferably, the flow rate of the mixed gas of isopropanol and nitrogen is 60-100 LPM; the temperature of the mixed gas of isopropanol and nitrogen is 20-25° C.; and the pressure of the mixed gas of isopropanol and nitrogen is 1-2 kPa.
[0024] The present invention provides a process for cleaning and drying a silicon carbide wafer, comprising the following steps: A) placing a cleaned silicon carbide wafer with a plug in a drying tank filled with water, so that the silicon carbide wafer is completely immersed in water; B) using a support mechanism at the bottom of the drying tank to push the silicon carbide wafer up, pushing the silicon carbide wafer out of the liquid surface at a first upward speed, and spraying a mixed gas of isopropyl alcohol and nitrogen on the surface of the silicon carbide wafer to dry it, after the silicon carbide wafer moves up to a first position, the silicon carbide wafer is continuously pushed up at a second upward speed, after the silicon carbide wafer is raised to a second position, the silicon carbide wafer is continuously pushed up at a third upward speed, and rises to a third position to complete the drying of the silicon carbide wafer; the first upward speed is 0.5-1.5 mm / s, and the first position is 0.5-1.5 mm / s relative to the initial position of the silicon carbide wafer. The position is moved up by 170 to 180 mm; the second upward speed is 0.1 to 0.3 mm / s, and the second position is moved up by 195 to 205 mm relative to the initial position of the silicon carbide wafer; the third upward speed is 1 to 2 mm / s, and the third position is moved up by 220 to 230 mm relative to the initial position of the silicon carbide wafer; the flow rate of the mixed gas of isopropyl alcohol and nitrogen is 60 to 100 LPM; the temperature of the mixed gas of isopropyl alcohol and nitrogen is 200 to 280°C; the pressure of the mixed gas of isopropyl alcohol and nitrogen is 1 to 2 kPa; C) drain the water in the drying tank, spray nitrogen on the surface of the plug for drying; D) move the wafer down to the plug, use the mixed gas of isopropyl alcohol and nitrogen to simultaneously purge the wafer and the plug to obtain a dry wafer. The present invention utilizes the Marangoni effect and the surface tension gradient difference of the silicon carbide wafer to remove the water attached to the surface of the silicon carbide wafer, and effectively reduces the possibility of residual water stains and particulate matter attached to the surface of the silicon carbide wafer. By improving the process parameters such as the speed, distance, IPA / N2 flow rate and nitrogen temperature of the wafer movement, a mixed liquid formed by liquid isopropyl alcohol and heated nitrogen is provided for the rapid drying of the silicon carbide wafer cleaning, and effectively removes impurities such as watermarks, condensed particles and metal particles remaining on the surface of the wafer after RCA cleaning. In addition, the present invention dries the jam and the wafer separately by optimizing the process parameters, and the dirty particles and metal impurities on the surface of the silicon carbide wafer after packaging and transportation are greatly reduced compared with before optimization, effectively improving the qualified rate of silicon carbide wafer cleaning. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.
[0026] Figure 1 This is a schematic diagram of the process flow of cleaning and drying a silicon carbide wafer in the present invention;
[0027] Figure 1 In the figure, 1 is a silicon carbide wafer, 2 is a plug, 3 is a top knife structure, 4 is a drying tank, 5 is a first position, 6 is a second position, and 7 is a third position;
[0028] Figure 2 The particle situation on the surface of the silicon carbide wafer after drying in Example 1 of the present invention;
[0029] Figure 3 The metal impurities on the surface of the silicon carbide wafer after drying in Example 1 of the present invention;
[0030] Figure 4 The particle situation on the surface of the dried silicon carbide wafer after packaging and transportation in Example 1 of the present invention;
[0031] Figure 5 is the metal impurity content on the surface of the dried silicon carbide wafer after packaging and transportation in Example 1 of the present invention;
[0032] Figure 6 This is the watermark residue on the surface of the silicon carbide wafer after drying by the spin-drying process in Comparative Example 6 of the present invention. DETAILED DESCRIPTION
[0033] The present invention provides a process for cleaning and drying a silicon carbide wafer, comprising the following steps:
[0034] A) placing the cleaned silicon carbide wafer with a plug in a drying tank filled with water so that the silicon carbide wafer is completely immersed in the water;
[0035] B) using the support mechanism at the bottom of the drying tank to push the silicon carbide wafer up, pushing the silicon carbide wafer out of the liquid surface at a first upward speed, and spraying a mixed gas of isopropyl alcohol and nitrogen on the surface of the silicon carbide wafer to dry it, after the silicon carbide wafer moves up to the first position, continuing to push the silicon carbide wafer up at a second upward speed, after the silicon carbide wafer rises to the second position, continuing to push the silicon carbide wafer up at a third upward speed, rising to the third position, and completing the drying of the silicon carbide wafer;
[0036] The first upward movement speed is 0.5-1.5 mm / s, and the first position is moved up by 170-180 mm relative to the initial position of the silicon carbide wafer; the second upward movement speed is 0.1-0.3 mm / s, and the second position is moved up by 195-205 mm relative to the initial position of the silicon carbide wafer; the third upward movement speed is 1-2 mm / s, and the third position is moved up by 220-230 mm relative to the initial position of the silicon carbide wafer;
[0037] The flow rate of the mixed gas of isopropanol and nitrogen is 80-100 LPM; the temperature of the mixed gas of isopropanol and nitrogen is 200-280° C.; the pressure of the mixed gas of isopropanol and nitrogen is 1-2 kPa;
[0038] C) drain the water in the drying tank and spray nitrogen on the surface of the plug to dry it;
[0039] D) The wafer is moved down into the plug, and a mixed gas of isopropyl alcohol and nitrogen is used to simultaneously purge the wafer and the plug to obtain a dry wafer.
[0040] In the present invention, the "wafer" refers to a silicon carbide wafer.
[0041] The present invention preferably cleans the drying tank filled with water before the silicon carbide wafer and the plug enter the drying tank to provide a whole drying atmosphere for drying. The present invention cleans the drying tank by introducing high-purity nitrogen and a mixed gas of isopropanol and nitrogen into the drying tank.
[0042] In the present invention, the flow rate of the nitrogen is preferably 50-80 LPM, more preferably 60-80 LPM, such as 50 LPM, 55 LPM, 60 LPM, 65 LPM, 70 LPM, 75 LPM, 80 LPM, preferably a range value with any of the above values as the upper or lower limit; the temperature of the nitrogen is preferably 200-280°C, more preferably 210-270°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, preferably a range value with any of the above values as the upper or lower limit; the pressure of the nitrogen is 0.5-4 kPa, more preferably 1-3 kPa;
[0043] The flow rate of the mixed gas of isopropanol and nitrogen is 60-100LPM, more preferably 70-80LPM, such as 60LPM, 65LPM, 70LPM, 75LPM, 80LPM, 85LPM, 90LPM, 95LPM, 100LPM, preferably a range value with any of the above values as the upper or lower limit; the temperature of the mixed gas of isopropanol and nitrogen is 20-25°C, more preferably 22-23°C; the pressure of the mixed gas of isopropanol and nitrogen is 1-2kPa.
[0044] After the drying tank is cleaned, the present invention immerses all the silicon carbide wafers with the plug in water, uses the support mechanism at the bottom of the drying tank to push the silicon carbide wafer up, pushes the silicon carbide wafer out of the liquid surface at a first upward speed, and sprays a mixed gas of isopropyl alcohol and nitrogen on the surface of the silicon carbide wafer to dry it. After the silicon carbide wafer moves up to the first position, the silicon carbide wafer is continuously pushed up at a second upward speed. After the silicon carbide wafer is raised to the second position, the silicon carbide wafer is continuously pushed up at a third upward speed and raised to the third position, thereby completing the drying of the silicon carbide wafer.
[0045] In the present invention, the silicon carbide wafer with a plug is a cleaned silicon carbide wafer, and the plug undergoes the same cleaning process as the silicon carbide wafer. The present invention places the silicon carbide wafer with a plug in a drying tank through a fixing device at the top, and the supporting mechanism at the bottom of the drying tank can move upward so as to push the silicon carbide wafer up. Specifically, in one embodiment of the present invention, the supporting mechanism at the bottom of the drying tank can be a top knife structure, and the plug remains stationary during the process of the top knife structure pushing the silicon carbide wafer upward.
[0046] In the present invention, during the drying process of the silicon carbide wafer, the volume fraction of isopropanol in the mixed gas of isopropanol and nitrogen is preferably 50-70%, more preferably 60-65%; the flow rate of the mixed gas of isopropanol and nitrogen is preferably 80-100LPM, more preferably 80-90LPM, such as 80LPM, 85LPM, 90LPM, 95LPM, 100LPM, preferably a range value with any of the above numerical values as the upper or lower limit; the temperature of the mixed gas of isopropanol and nitrogen is preferably 200-280°C, more preferably 210-270°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, preferably a range value with any of the above numerical values as the upper or lower limit; the pressure of the mixed gas of isopropanol and nitrogen is 1-2kPa.
[0047] In the present invention, the position of the silicon carbide wafer in the drying tank before it moves up is taken as the initial position. The present invention utilizes a supporting mechanism at the bottom of the drying tank to push the silicon carbide wafer up from the initial position, and pushes the silicon carbide wafer out of the liquid surface at a first speed. During this process, the first speed is maintained to move upward at a constant speed until it moves up to the first position.
[0048] In the present invention, the first speed is preferably 0.5-1.5 mm / s, more preferably 1-1.2 mm / s, such as 0.5 mm / s, 0.6 mm / s, 0.7 mm / s, 0.8 mm / s, 0.9 mm / s, 1 mm / s, 1.1 mm / s, 1.2 mm / s, 1.3 mm / s, 1.4 mm / s, 1.5 mm / s, preferably a range value with the above-mentioned any numerical value as the upper or lower limit; the first position is moved up by 170-180 mm relative to the initial position of the silicon carbide wafer, more preferably 173-178 mm, such as 170 mm, 171 mm, 172 mm, 173 mm, 174 mm, 175 mm, 176 mm, 177 mm, 178 mm, 179 mm, 180 mm, preferably a range value with the above-mentioned any numerical value as the upper or lower limit.
[0049] After the silicon carbide wafer moves up to the first position, the present invention continues to push the silicon carbide wafer upward at a uniform speed at a second speed until it moves up to the second position.
[0050] In the present invention, the second speed is preferably 0.1-0.3 mm / s, more preferably 0.15-0.25 mm / s, such as 0.1 mm / s, 0.15 mm / s, 0.2 mm / s, 0.25 mm / s, 0.3 mm / s, and preferably a range value with any of the above values as the upper or lower limit; the second position is moved up by 195-205 mm relative to the initial position of the silicon carbide wafer, more preferably 198-202 mm, such as 195 mm, 196 mm, 197 mm, 198 mm, 199 mm, 200 mm, 201 mm, 202 mm, 203 mm, 204 mm, 205 mm, and preferably a range value with any of the above values as the upper or lower limit.
[0051] After the silicon carbide wafer moves up to the second position, the present invention continues to push the silicon carbide wafer upward at a uniform speed at a third speed until it moves up to the third position.
[0052] In the present invention, the third upward movement speed is preferably 1-2mm / s, more preferably 1.2-1.8mm / s, such as 1mm / s, 1.1mm / s, 1.2mm / s, 1.3mm / s, 1.4mm / s, 1.5mm / s, 1.6mm / s, 1.7mm / s, 1.8mm / s, 1.9mm / s, 2mm / s, preferably a range value with any of the above values as the upper or lower limit; the third position is moved up by 220-230mm relative to the initial position of the silicon carbide wafer, more preferably 222-228mm, such as 220mm, 221mm, 222mm, 223mm, 224mm, 225mm, 226mm, 227mm, 228mm, 229mm, 230mm, preferably a range value with any of the above values as the upper or lower limit.
[0053] In the present invention, during the three-stage upward movement of the silicon carbide wafer, the flow rate, pressure and temperature of isopropyl alcohol and nitrogen are preferably kept unchanged, and the upward movement distances of the first position, the second position and the third position refer to the vertical distances between the same point (such as the center of a circle) on the silicon carbide wafer at two positions (such as the first position and the initial position).
[0054] After the silicon carbide wafer is dried, the present invention drains the water in the drying tank to expose the plug, and uses high-purity nitrogen to spray and dry the plug.
[0055] In the present invention, during the drying process of the plug, the flow rate of the nitrogen is preferably 50-100LPM, more preferably 60-80LPM, such as 50LPM, 55LPM, 60LPM, 65LPM, 70LPM, 75LPM, 80LPM, 85LPM, 90LPM, 95LPM, 100LPM, preferably a range value with any of the above values as the upper or lower limit; the temperature of the nitrogen is preferably 220-280°C, more preferably 230-260°C, such as 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, preferably a range value with any of the above values as the upper or lower limit; the pressure of the nitrogen is preferably 0.5-1.5kPa, more preferably 0.8-1.2kPa.
[0056] In the present invention, the jam drying time is preferably 500-1000s, more preferably 600-800s, such as 500s, 550s, 600s, 650s, 700s, 750s, 800s, 850s, 900s, 950s, 1000s, preferably a range value with any of the above values as the upper or lower limit.
[0057] After the plug is dried, the present invention moves the silicon carbide wafer in the third position down into the plug, and uses a mixed gas of isopropyl alcohol and nitrogen to simultaneously purge the wafer and the plug to remove residual cleaning liquid, impurity particles, etc. on their surfaces to obtain a dry wafer.
[0058] In the present invention, during the purge process, the flow rate of the mixed gas of isopropanol and nitrogen is preferably 60-100LPM, more preferably 70-80LPM, such as 60LPM, 65LPM, 70LPM, 75LPM, 80LPM, 85LPM, 90LPM, 95LPM, 100LPM, preferably a range value with any of the above values as the upper or lower limit, the temperature is preferably 250-300°C, more preferably 250-280°C, such as 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, preferably a range value with any of the above values as the upper or lower limit; the pressure is preferably 2-4kPa.
[0059] In the present invention, during the purging process, nitrogen is introduced into the drying tank to maintain a nitrogen atmosphere in the drying tank. The flow rate of the nitrogen is preferably 80 to 120 LPM, more preferably 90 to 110 LPM, such as 80 LPM, 85 LPM, 90 LPM, 95 LPM, 100 LPM, 105 LPM, 110 LPM, 115 LPM, 120 LPM, preferably a range value with any of the above values as the upper or lower limit; the temperature of the nitrogen is 200 to 280°C, more preferably 210 to 270°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, preferably a range value with any of the above values as the upper or lower limit; the pressure of the nitrogen is preferably 1 to 280 kPa, more preferably 1 to 200 kPa. Such as 1kPa, 10kPa, 50kPa, 100kPa, 150kPa, 200kPa, 250kPa, 280kPa, preferably a range value with any of the above values as the upper limit or lower limit.
[0060] In the present invention, the purging time is preferably 20 to 50 seconds, more preferably 30 to 40 seconds.
[0061] The present invention provides a process for cleaning and drying a silicon carbide wafer, comprising the following steps: A) placing a cleaned silicon carbide wafer with a plug in a drying tank filled with water, so that the silicon carbide wafer is completely immersed in water; B) using a support mechanism at the bottom of the drying tank to push the silicon carbide wafer up, pushing the silicon carbide wafer out of the liquid surface at a first upward moving speed, and spraying a mixed gas of isopropyl alcohol and nitrogen on the surface of the silicon carbide wafer to dry it, after the silicon carbide wafer moves up to a first position, the silicon carbide wafer is continuously pushed up at a second upward moving speed, after the silicon carbide wafer is raised to a second position, the silicon carbide wafer is continuously pushed up at a third upward moving speed, and rises to a third position to complete the drying of the silicon carbide wafer; the first upward moving speed is 0.5-1.5 mm / s, and the first position is moved up relative to the initial position of the silicon carbide wafer. 170~180mm; the second upward speed is 0.1~0.3mm / s, and the second position is moved up by 195~205mm relative to the initial position of the silicon carbide wafer; the third upward speed is 1~2mm / s, and the third position is moved up by 220~230mm relative to the initial position of the silicon carbide wafer; the flow rate of the mixed gas of isopropyl alcohol and nitrogen is 60~100LPM; the temperature of the mixed gas of isopropyl alcohol and nitrogen is 200~280℃; the pressure of the mixed gas of isopropyl alcohol and nitrogen is 1~2kPa; C) drain the water in the drying tank, spray the mixed gas of isopropyl alcohol and nitrogen on the surface of the plug for drying; D) move the round wafer down to the plug, use the mixed gas of isopropyl alcohol and nitrogen to purge the round wafer and the plug at the same time to obtain a dry round wafer. The present invention utilizes the Marangoni effect and the surface tension gradient difference of the silicon carbide wafer to remove the water attached to the surface of the silicon carbide wafer, and effectively reduces the possibility of residual water stains and particulate matter attached to the surface of the silicon carbide wafer. By improving the process parameters such as the speed, distance, IPA / N2 flow rate and nitrogen temperature of the wafer movement, a mixed liquid formed by liquid isopropyl alcohol and heated nitrogen is provided for the rapid drying of the silicon carbide wafer cleaning, and effectively removes impurities such as watermarks, condensed particles and metal particles remaining on the surface of the wafer after RCA cleaning. In addition, the present invention dries the jam and the wafer separately by optimizing the process parameters, and the dirty particles and metal impurities on the surface of the silicon carbide wafer after packaging and transportation are greatly reduced compared with before optimization, effectively improving the qualified rate of silicon carbide wafer cleaning.
[0062] In order to further illustrate the present invention, a process for cleaning and drying a silicon carbide wafer provided by the present invention is described in detail below in conjunction with an embodiment, but it should not be construed as limiting the scope of protection of the present invention.
[0063] Example 1
[0064] like Figure 1As shown, a mixed gas of isopropanol and nitrogen and nitrogen are introduced into the drying tank to clean the drying tank; the flow rate of nitrogen is 50LPM; the temperature is 280°C, and the pressure is 0.8kPa; the flow rate of the mixed gas of isopropanol and nitrogen is 80LPM; the temperature is 25°C; and the pressure is 1kPa.
[0065] After cleaning, the RCA cleaned connected stuck silicon carbide wafer is placed in a drying tank filled with water so that the silicon carbide wafer is completely immersed in water. Figure 1 As shown in Figure b;
[0066] The top knife at the bottom of the drying tank is used to push the silicon carbide wafer up from the initial position, and the silicon carbide wafer is pushed out of the liquid surface at a speed of 1 mm / s. At the same time, a mixed gas of isopropyl alcohol and nitrogen (the volume ratio of isopropyl alcohol to nitrogen is 1:1) is sprayed on the surface of the silicon carbide wafer. The mixed gas flow rate is 80 LPM, the temperature is 280 ° C, and the pressure is 1 kPa. After the silicon carbide wafer moves up 175 mm, it is pushed up at a speed of 0.2 mm / s. After the silicon carbide wafer continues to rise to 200 mm, it is pushed up at a speed of 1.5 mm / s. It continues to rise to 220 mm to complete the drying of the silicon carbide wafer. Figure 1 As shown in Figures c and d.
[0067] After the silicon carbide wafer is dried, the water in the drying tank is drained, and high-purity nitrogen is sprayed on the surface of the plug. The flow rate of nitrogen is 80LPM; the temperature of the nitrogen is 280℃, and the pressure of the nitrogen is 0.8kPa; the plug drying time is 750s. Figure 1 As shown in Figure e.
[0068] After the plug is dried, the wafer is moved down to the plug, and the wafer and the plug are purged simultaneously with a mixed gas of isopropanol and nitrogen (the volume ratio of isopropanol to nitrogen is 1:1), with a mixed gas flow rate of 75 LPM, a temperature of 280°C, and a pressure of 4 kPa; high-purity nitrogen is introduced during the purging process, with a nitrogen flow rate of 100 LPM; the nitrogen temperature is 280°C, and the nitrogen pressure is 1 kPa; the purging time is 30 seconds. Figure 1 As shown in Figure f.
[0069] The silicon carbide wafer obtained in Example 1 was subjected to the following characterization tests:
[0070] Characterization test
[0071] (1) Analysis of particles and residual chemical solution on the surface of silicon carbide wafers
[0072] The Candela 8520 inspection system uses proprietary optical technology to test the surface particles and chemical residues of silicon carbide wafers. The test results are shown in Figure 2, Figure 4 .
[0073] (2) Analysis of metal impurities on the surface of silicon carbide wafers
[0074] ICPMS (inductively coupled plasma mass spectrometry) combines the high temperature (8000K) ionization characteristics of ICP with the sensitive and fast scanning advantages of quadrupole mass spectrometer to form a new and powerful elemental analysis, isotope analysis and morphological analysis technology. It tests the metal impurity content on the surface of silicon carbide wafers. The test results are shown in Figure 3 , Figure 5 .
[0075] Comparative Example 1
[0076] The silicon carbide wafer is dried according to the method in Example 1, except that the flow rate of the mixed gas of isopropanol and nitrogen during the drying process of the silicon carbide wafer is reduced by 5 L / min to 75 LPM.
[0077] Comparative Example 2
[0078] The silicon carbide wafer was dried according to the method in Comparative Example 1, except that the temperature of the nitrogen during the purge process was increased by 5° C. to 285° C.
[0079] Comparative Example 3
[0080] The silicon carbide wafer was dried according to the method in Comparative Example 2, except that the first speed of moving the silicon carbide wafer upward was 2 mm / s.
[0081] Comparative Example 4
[0082] The silicon carbide wafer was dried according to the method in Comparative Example 3, except that the first position of the silicon carbide wafer was 185 mm, and the second position was 190 mm.
[0083] Comparative Example 5
[0084] The silicon carbide wafer was dried according to the method in Comparative Example 3, except that the first position of the silicon carbide wafer was 165 mm, and the second position was 210 mm.
[0085] The silicon carbide wafers obtained in Example 1 and Comparative Examples 1 to 5 were subjected to watermark detection, and the results are shown in Table 1:
[0086] Table 1 Watermarks on silicon carbide wafers in the examples and comparative examples
[0087]
[0088] Comparative Example 6
[0089] The spin drying process is used to dry the silicon carbide wafer. The specific steps are as follows:
[0090] The specific operation steps of the spin-drying process are as follows: flush the wafer and the plug with water for 60 seconds at a rotation speed of 650±50rpm, then fill them with nitrogen and destaticize them for 20 seconds at a rotation speed of 1100±100rpm, then heat the nitrogen to 75±5℃ for 480s at a rotation speed of 1150±150rpm, and finally heat the spin-drying chamber while heating the nitrogen, the internal temperature of the chamber is 60℃, the spin-drying time is 600s, and the rotation speed is 650rpm.
[0091] In summary, when drying by spin drying (such as Example 6), since the spin drying process only uses N2 for drying, the effect of removing watermarks and dirt on the surface of the silicon carbide wafer is not ideal; and using the process parameters in Examples 1 to 5, drying the plug and the chip at the same time cannot effectively remove the watermark on the chip surface; through the method in the present application, such as the process in Example 1, the plug and the chip are dried separately, and the dirty particles and metal impurities on the surface of the silicon carbide wafer after packaging and transportation are greatly reduced compared to before optimization, effectively improving the cleaning pass rate of the silicon carbide wafer.
[0092] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A process for cleaning and drying a silicon carbide wafer, comprising the following steps: A) placing the cleaned silicon carbide wafer with a plug in a drying tank filled with water so that the silicon carbide wafer is completely immersed in the water; B) using the support mechanism at the bottom of the drying tank to push the silicon carbide wafer up from the initial position, pushing the silicon carbide wafer out of the liquid surface at a first upward speed, and spraying a mixed gas of isopropyl alcohol and nitrogen on the surface of the silicon carbide wafer to dry it, after the silicon carbide wafer moves up to the first position, continuing to push the silicon carbide wafer up at a second upward speed, after the silicon carbide wafer rises to the second position, continuing to push the silicon carbide wafer up at a third upward speed, rising to the third position, and completing the drying of the silicon carbide wafer; The first upward movement speed is 0.5-1.5 mm / s, and the first position is moved up by 170-180 mm relative to the initial position of the silicon carbide wafer; the second upward movement speed is 0.1-0.3 mm / s, and the second position is moved up by 195-205 mm relative to the initial position of the silicon carbide wafer; the third upward movement speed is 1-2 mm / s, and the third position is moved up by 220-230 mm relative to the initial position of the silicon carbide wafer; The flow rate of the mixed gas of isopropanol and nitrogen is 80-100 LPM; the temperature of the mixed gas of isopropanol and nitrogen is 200-280° C.; the pressure of the mixed gas of isopropanol and nitrogen is 1-2 kPa; C) drain the water in the drying tank and spray nitrogen on the surface of the plug to dry it; D) The wafer is moved down into the plug, and a mixed gas of isopropyl alcohol and nitrogen is used to simultaneously purge the wafer and the plug to obtain a dry wafer.
2. The process according to claim 1, characterized in that In the mixed gas of isopropanol and nitrogen used in step B), the volume fraction of isopropanol is 50-70%; In the mixed gas of isopropanol and nitrogen used in step D), the volume fraction of isopropanol is 50-70%.
3. The process according to claim 1, characterized in that During the drying process of the plug in step C), the flow rate of the nitrogen is 50 to 100 LPM; the temperature of the nitrogen is 220 to 280° C., and the pressure of the nitrogen is 0.5 to 1.5 kPa.
4. The process according to claim 1, characterized in that In the process of drying the plug in step C), the drying time of the plug is 500 to 1000 seconds.
5. The process according to claim 1, characterized in that In step D), the flow rate of the mixed gas of isopropanol and nitrogen is 60-100 LPM, the temperature is 250-300° C., and the pressure is 2-4 kPa.
6. The process according to claim 1, characterized in that During the purging process in step D), nitrogen is introduced into the drying tank to maintain a nitrogen atmosphere in the drying tank, and the flow rate of the nitrogen is 80 to 120 LPM; the temperature of the nitrogen is 200 to 280° C., and the pressure of the nitrogen is 1 to 280 kPa.
7. The process according to claim 1, characterized in that The purging time in step D) is 20 to 50 seconds.
8. The process according to claim 1, characterized in that Before drying the silicon carbide wafer, a mixed gas of isopropyl alcohol and nitrogen and nitrogen are introduced into the drying tank to clean the drying tank.
9. The process according to claim 8, characterized in that During the cleaning process of the drying tank, the flow rate of the nitrogen gas is 50 to 80 LPM; the temperature of the nitrogen gas is 200 to 280° C., and the pressure of the nitrogen gas is 0.5 to 4 kPa.
10. The process according to claim 8, characterized in that The flow rate of the mixed gas of isopropanol and nitrogen is 60-100 LPM; the temperature of the mixed gas of isopropanol and nitrogen is 20-25° C.; the pressure of the mixed gas of isopropanol and nitrogen is 1-2 kPa.