A diode based on silicon carbide thick film epitaxial wafer and its preparation method

Abstract

The present invention relates to the technical field of semiconductor devices, and in particular to a diode based on a silicon carbide thick film epitaxial wafer and a preparation method thereof. The present invention prepares a diode based on a silicon carbide thick film epitaxial wafer through processes such as cleaning, depositing a silicon dioxide layer, etching, ion implantation, high-temperature annealing, ion activation, re-depositing a silicon dioxide layer, and sputtering ions. The diode is further prepared by adjusting growth condition parameters such as the carbon-silicon ratio during epitaxial growth to control the morphology of large pit defects on the surface of the silicon carbide thick film epitaxial wafer, so that the large pit defects are controlled to be long strips, thereby reducing the electric field focusing effect and improving the gate oxide stability of related devices. In addition, a photoresist containing nanoparticles is used in the preparation process. The nanoparticles can generate photogenerated carriers under light and can also capture electrons, thereby greatly improving the responsiveness of the device. Therefore, the diode prepared by the present invention has a wider application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a diode based on a silicon carbide thick film epitaxial wafer and a preparation method thereof. Background Art

[0002] In the field of semiconductor devices, diodes, as fundamental electronic components, are widely used in various circuits, including rectification, detection, and voltage regulation. In recent years, the rapid development of power electronics technology has placed higher demands on diodes' high-temperature stability, high-frequency response speed, and voltage resistance. Silicon carbide, due to its excellent physical and chemical properties, such as high hardness, high melting point, high thermal conductivity, and excellent chemical stability, has become an ideal material for manufacturing high-performance diodes. Diode products based on silicon carbide already exist, and these products often use silicon carbide single crystal wafers as a substrate, using epitaxial growth techniques to form structures such as PN junctions.

[0003] However, existing silicon carbide diodes often use relatively thin epitaxial layers. For example, patent document CN109509706B discloses a method for fabricating a silicon carbide diode and a silicon carbide diode produced using this method. The growth process for thin epitaxial layers is more complex and costly than for thicker epitaxial layers. However, the thick-film epitaxial wafers produced using existing technology often exhibit large inverted conical pit defects on their surfaces. The electric field concentration effect at the tip of these large pit defects can adversely affect the gate oxide stability of the diode.

[0004] Therefore, according to the above-mentioned related technologies, there is an urgent need to develop a diode based on silicon carbide thick film epitaxial wafer and a preparation method thereof. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a diode based on a silicon carbide thick film epitaxial wafer and a preparation method thereof, so as to solve the problem of poor gate oxide stability of diodes prepared by the prior art.

[0006] Based on the above objectives, the present invention provides a diode based on a silicon carbide thick film epitaxial wafer and a method for preparing the same.

[0007] A method for preparing a diode based on a silicon carbide thick film epitaxial wafer, the method comprising the following steps:

[0008] Step S1. Clean the silicon carbide thick film epitaxial wafer with piranha solution 3-5 times, blow dry it with nitrogen, and then grow a layer of silicon dioxide with a thickness of 100-200nm to obtain a deposited wafer;

[0009] Step S2. Mask the deposited sheet with a photoresist, remove the photoresist, and then perform plasma etching to a depth of 3-5 μm to obtain an etched sheet;

[0010] Step S3: Send the wafer to the ion implanter to perform Al + Ion implantation, followed by deposition of a 1-3 μm thick layer of silicon dioxide, followed by treatment at 1000-1100°C for 15-20 minutes in a nitrogen atmosphere to obtain an activated sheet;

[0011] Step S4. Depositing a 5-8 μm thick layer of silicon dioxide on the surface of the activation sheet, and then sputtering a 3-5 μm thick layer of nickel on the back side, and rapidly annealing to obtain an ohmic contact sheet;

[0012] Step S5. Etch the front surface of the ohmic contact sheet to a depth of 5-10 μm using a large P-area aperture plate, then perform photolithography using a large P-area metal definition plate, then sputter a boron ion film in the large P-area, and finally peel off and perform rapid annealing to obtain a large P-area aperture sheet.

[0013] Step S6. Depositing a layer of SiO2 and Si3N4 with a thickness of 3-5 μm on the surface of the sheet, and then etching to a depth of 3-5 μm using an active area aperture plate to obtain an active area aperture sheet;

[0014] Step S7. Use the Schottky area aperture plate to etch the active area aperture plate to a thickness of 5-10μm, then sputter a layer of 13-15μm thick Ti metal, and then use the anode metal definition plate to etch to a depth of 1-2μm. Finally, complete the patterning of the front metal by wet etching to obtain a diode.

[0015] Preferably, the method for preparing the silicon carbide thick film epitaxial wafer is as follows:

[0016] A1. With a doping concentration of 10 17 -10 19 cm -3 Using nitrogen as a doping gas, epitaxial growth is performed on a silicon carbide substrate for 3-40 minutes at a temperature of 1520-1690° C., a chamber pressure of 60-130 mbar, a carbon-silicon ratio of 1.00-1.03, and a growth rate of 3-20 μm / h to obtain a buffer layer attachment sheet;

[0017] A2. With a doping concentration of 10 14 -10 16 cm -3Nitrogen is used as the doping gas, and the growth time is 7-60 minutes on the buffer layer attachment sheet at a temperature of 1520-1690°C, a chamber pressure of 60-130mbar, a carbon-silicon ratio of 1.00-1.03, and a growth rate of 10-100μm / h to obtain a silicon carbide thick film epitaxial wafer. By keeping the growth temperature and chamber pressure of the buffer layer and the pressure-resistant layer unchanged, silicon carbide epitaxial wafers with large surface pit defects of different morphologies can be produced by adjusting the carbon-silicon ratio of the pressure-resistant layer. When the carbon-silicon ratio is set in the range of 1.0-1.03, the large surface pit defects of the epitaxial wafer produced are long strips, and the morphology is as follows. Figure 1 shown.

[0018] Preferably, the thickness of the buffer layer attachment sheet is 0.5-2 μm; the thickness of the silicon carbide thick film epitaxial wafer is 20-100 μm.

[0019] Preferably, the preparation method of the photoresist is as follows:

[0020] Step B1. Sodium hydroxide and 2-chloro-4-hydroxybenzaldehyde were added to water, heated to 75-80 ° C, 3-chloro-1,2-propylene glycol was added and reacted for 12-15h, hydrochloric acid and water were added, and then reacted at 75-80 ° C for 1-1.5h, ethyl acetate was added, washed, dried, and purified to obtain grafted benzaldehyde;

[0021] Step B2. Benzil, ammonium acetate, and acetic acid were added to the grafted benzaldehyde in sequence, heated to 85-90°C, and reacted for 16-20 hours. Saturated aqueous sodium chloride solution was then added, and the mixture was neutralized to neutrality. A yellow precipitate was obtained by filtration.

[0022] Step B3. Dissolve the yellow precipitate with tetrahydrofuran and add aqueous sodium hydroxide solution. Heat to 70-75 ° C and react for 1-1.5 hours. Take the organic layer, evaporate, wash and dry to obtain a white powder.

[0023] Step B4. Potassium ferrocyanide and potassium hydroxide were added to water and mixed, followed by addition of dichloromethane and white powder. The reaction was continued for 12-15 hours, and the organic layer was washed, evaporated, and dried to obtain a light yellow powder.

[0024] Step B5. Add light yellow powder, ethyl acetate, dibutyltin dilaurate, isophorone diisocyanate, perfluorooctanesulfonyl fluoride, tert-butylhydroquinone and nanoparticles to polyethylene glycol, react for 5-10 minutes and then filter to obtain a photoresist.

[0025] Preferably, the mass ratio of sodium hydroxide, 2-chloro-4-hydroxybenzaldehyde, 3-chloro-1,2-propylene glycol, hydrochloric acid and ethyl acetate in step B1 is 7.68-7.75:10-10.5:15.6-16:18-25:45-50.

[0026] Preferably, the mass ratio of the grafted benzaldehyde, benzil, ammonium acetate, and acetic acid in step B2 is 7.5-8.5:8.5-9:26.5-27:100-110.

[0027] Preferably, the mass ratio of potassium ferrocyanide, potassium hydroxide, white powder and dichloromethane in step B4 is 7.8-7.9:2.65-2.7:2-2.5:465-470.

[0028] Preferably, the mass ratio of the polyethylene glycol, light yellow powder, ethyl acetate, dibutyltin dilaurate, isophorone diisocyanate, tert-butylhydroquinone and nanoparticles in step B5 is 0.1-0.2: 0.08-0.15: 5-10: 0.05-0.1: 0.1-0.19: 0.1-0.2: 0.3-0.5.

[0029] Preferably, the molecular weight of the polyethylene glycol in step B5 is 400-500.

[0030] Preferably, the preparation method of the nanoparticles is as follows:

[0031] Step C1. Dissolve 0.3-0.5 g of CsPbBr3 in 3-5 mL of n-hexane, then add 9-15 mL of methyl acetate. Centrifuge at 7000-7500 rpm for 5-10 min. Repeat the dissolution and centrifugation of the precipitate 3-5 times, and collect the supernatant.

[0032] Step C2. The supernatant was placed in a dark environment at 0-4°C for 45-50 hours, then centrifuged at 5000-5500 rpm for 3-5 minutes, and then distilled under reduced pressure to dryness. 10-20 mL of chloroform was added and stirred to obtain a dispersion.

[0033] Step C3. To the dispersion, 0.1-0.2 g of quaterthiophene-diketopyrrole, 0.02-0.05 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 0.01-0.03 g of trimethylpropylene tris(3-mercaptopropionic acid) were sequentially added, stirred, and then dropped onto glass. The mixture was then dried and irradiated with ultraviolet light to form a thin film on the glass plate.

[0034] Step C4. The film is placed in a quartz mortar for wet grinding to collect the powder, which is then ultrasonicated in chloroform for 30-45 minutes. The powder is then filtered through a 0.1-0.2 μm filter and the filtrate is dried to obtain nanoparticles.

[0035] Beneficial effects of the present invention:

[0036] The present invention provides a diode based on a silicon carbide thick-film epitaxial wafer and a preparation method thereof. The present invention controls the morphology of large pit defects on the surface of the silicon carbide thick-film epitaxial wafer by adjusting growth condition parameters such as the carbon-silicon ratio during epitaxial growth, so that the large pit defects are controlled to be long strips, thereby reducing the electric field concentration effect and improving the gate oxide stability of related devices. In addition, a photoresist containing nanoparticles is used in the preparation process. The nanoparticles can generate photogenerated carriers and capture electrons under light, thereby greatly improving the responsiveness of the device. Therefore, the diode prepared by the present invention has a wider application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is a scanning electron microscope image of the silicon carbide thick film epitaxial wafer of the present invention;

[0039] Figure 2 This is a scanning electron microscope image of the silicon carbide thick film epitaxial wafer prepared in Comparative Example 1. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0041] The sources and properties of some of the raw materials used in the present invention are as follows:

[0042] 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide was purchased from Hubei Chengfeng Chemical Co., Ltd., CAS: 75980-60-8; 2-chloro-4-hydroxybenzaldehyde was purchased from Hubei Hengjingrui Chemical Co., Ltd., CAS: 56962-11-9; benzil was purchased from Wuhan Xingzhongcheng Technology Co., Ltd., CAS: 134-81-6; ammonium acetate was purchased from Wuhan Jixin Yibang Biotechnology Co., Ltd., CAS: 631-61-8; potassium ferricyanide was purchased from Hubei Chengfeng Chemical Co., Ltd., CAS: 13746-66-2; Dichloromethane was purchased from Shandong Zhengxing New Materials Co., Ltd., CAS: 75-09-2; polyethylene glycol with a molecular weight of 400-500 was purchased from Changzhou Guxu Chemical Co., Ltd., CAS: 25322-68-3; dibutyltin dilaurate was purchased from Wuhan Jiyesheng Chemical Co., Ltd., CAS: 77-58-7; isophorone diisocyanate was purchased from Hubei Kewode Chemical Co., Ltd., CAS: 4098-71-9; tert-Butylhydroquinone was purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd., CAS: 1948-33-0.

[0043] Example 1: A method for preparing a diode based on a silicon carbide thick film epitaxial wafer is as follows:

[0044] S1. With a doping concentration of 10 17 cm -3 Using nitrogen as the doping gas, epitaxial growth was performed on a silicon carbide substrate for 3 minutes at a temperature of 1520°C, a chamber pressure of 60 mbar, a carbon-silicon ratio of 1, and a growth rate of 3 μm / h to obtain a buffer layer attachment sheet with a thickness of 0.5 μm;

[0045] S2. With a doping concentration of 10 14 cm -3 Using nitrogen as the doping gas, the silicon carbide thick film epitaxial wafer with a thickness of 20 μm was grown on the buffer layer attachment wafer at a temperature of 1520°C, a chamber pressure of 60 mbar, a carbon-silicon ratio of 1, and a growth rate of 10 μm / h for 7 minutes.

[0046] S3. Dissolve 0.3 g of CsPbBr3 in 3 mL of n-hexane, then add 9 mL of methyl acetate. Centrifuge at 7000 rpm for 5 min. Repeat the dissolution and centrifugation three times to collect the supernatant.

[0047] S4. The supernatant was incubated in a dark environment at 0°C for 45 h, then centrifuged at 5000 rpm for 3 min, and then distilled to dryness under reduced pressure. 10 mL of chloroform was added and stirred to obtain a dispersion.

[0048] S5. To the dispersion were added 0.1 g of tetrathiophene-diketopyrrole, 0.02 g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 0.01 g of trimethylpropylene tris(3-mercaptopropionic acid), stirred, and then dropped onto glass, followed by drying and ultraviolet irradiation to form a thin film on the glass plate;

[0049] S6. The film was wet-ground in a quartz mortar to collect the powder, which was then sonicated in chloroform for 30 min. The resulting solution was filtered through a 0.1 μm filter and dried to obtain nanoparticles.

[0050] S7. Add 7.68g of sodium hydroxide and 10g of 2-chloro-4-hydroxybenzaldehyde to water, heat to 75 ° C, add 15.6g of 3-chloro-1,2-propylene glycol and react for 12h, then add 18g of hydrochloric acid and water, and then react at 75 ° C for 1h, then add 45g of ethyl acetate, wash, dry, and purify to obtain grafted benzaldehyde;

[0051] S8. To 7.5 g of grafted benzaldehyde were added 8.5 g of benzil, 26.5 g of ammonium acetate, and 100 g of acetic acid, heated to 85 ° C and reacted for 16 h, followed by addition of saturated sodium chloride aqueous solution, and then neutralized to neutrality, and filtered to obtain a yellow precipitate;

[0052] S9. The yellow precipitate was dissolved in tetrahydrofuran and then an aqueous sodium hydroxide solution was added. The temperature was raised to 70°C and the reaction was allowed to react for 1 hour. The organic layer was evaporated, washed, and dried to obtain a white powder.

[0053] S10. Add 7.5g of potassium ferrocyanide and 2.65g of potassium hydroxide to water, mix well, add 465g of dichloromethane and 2g of white powder, react for 12h, take the organic layer, wash, evaporate and dry to give a light yellow powder;

[0054] S11. To 0.1 g of polyethylene glycol having a molecular weight of 400-500, 0.08 g of light yellow powder, 5 g of ethyl acetate, 0.05 g of dibutyltin dilaurate, 0.1 g of isophorone diisocyanate, 0.1 g of tert-butylhydroquinone and 0.3 g of nanoparticles were added, and the mixture was reacted for 5 min and filtered to obtain a photoresist;

[0055] S12. The silicon carbide thick film epitaxial wafer was cleaned three times with piranha solution, dried with nitrogen, and then a 100 nm thick layer of silicon dioxide was grown to obtain a deposited wafer;

[0056] S13. Mask the deposited film with a photoresist, remove the photoresist, and perform plasma etching to a depth of 3 μm to obtain an etched film;

[0057] S14. Send the wafer into the ion implanter and perform Al +Ion implantation was followed by deposition of a 1 μm thick layer of silicon dioxide, which was then treated at 1000°C for 15 min in a nitrogen atmosphere to obtain an activated sheet;

[0058] S15. A 5 μm thick layer of silicon dioxide is deposited on the surface of the active sheet, and then a 3 μm thick layer of nickel is sputtered on the back side and rapidly annealed to obtain an ohmic contact sheet;

[0059] S16. Etch the front surface of the ohmic contact sheet to a depth of 5 μm using a large P-area aperture plate. Then, perform photolithography using a large P-area metal definition plate. Then, sputter a boron ion film on the large P-area. Finally, peel off and perform rapid annealing to obtain a large P-area aperture sheet.

[0060] S17. A 3 μm thick layer of SiO2 and Si3N4 is deposited on the surface of the sheet, and then etched to a depth of 3 μm using an active area aperture plate to obtain an active area aperture sheet;

[0061] S18. Etch the active area aperture plate to a thickness of 5 μm using a Schottky area aperture plate. Then, sputter a 13 μm thick layer of Ti metal. Etch to a depth of 1 μm using an anode metal definition plate. Finally, pattern the front metal by wet etching to complete the diode.

[0062] Example 2: A method for preparing a diode based on a silicon carbide thick film epitaxial wafer is as follows:

[0063] S1. With a doping concentration of 10 18 cm -3 Using nitrogen as the doping gas, epitaxial growth was carried out on a silicon carbide substrate for 20 minutes at a temperature of 1600°C, a chamber pressure of 100 mbar, a carbon-silicon ratio of 1.02, and a growth rate of 12 μm / h to obtain a buffer layer attachment sheet with a thickness of 1 μm;

[0064] S2. With a doping concentration of 10 15 cm -3 The silicon carbide thick film epitaxial wafer with a thickness of 50 μm was grown on the buffer layer attachment wafer for 30 minutes using nitrogen as the doping gas at a temperature of 1600°C, a chamber pressure of 100 mbar, a carbon-silicon ratio of 1.02, and a growth rate of 50 μm / h.

[0065] S3. Dissolve 0.4 g of CsPbBr3 in 4 mL of n-hexane, then add 11 mL of methyl acetate and centrifuge at 7300 rpm for 8 min. Repeat the dissolution and centrifugation of the precipitate four times, and collect the supernatant after centrifugation.

[0066] S4. The supernatant was incubated in the dark at 2°C for 48 h, then centrifuged at 5300 rpm for 4 min, and then distilled to dryness under reduced pressure. 15 mL of chloroform was added and stirred to obtain a dispersion.

[0067] S5. To the dispersion were added 0.15 g of tetrathiophene-diketopyrrole, 0.04 g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 0.02 g of trimethylpropylene tris(3-mercaptopropionic acid), stirred, and then dropped onto glass, followed by drying and ultraviolet irradiation to form a thin film on the glass plate;

[0068] S6. The film was wet-ground in a quartz mortar to collect the powder, which was then sonicated in chloroform for 40 min. The resulting solution was filtered through a 0.15 μm filter and dried to obtain nanoparticles.

[0069] S7. Add 7.70g of sodium hydroxide and 10.3g of 2-chloro-4-hydroxybenzaldehyde to water, heat to 78 ° C, add 15.8g of 3-chloro-1,2-propylene glycol and react for 20h, then add 22g of hydrochloric acid and water, and then react at 78 ° C for 1.3h, then add 48g of ethyl acetate, wash, dry, and purify to obtain grafted benzaldehyde;

[0070] S8. To 8 g of grafted benzaldehyde were added 8.8 g of benzil, 26.8 g of ammonium acetate, and 105 g of acetic acid, heated to 88 ° C and reacted for 18 h, followed by addition of saturated sodium chloride aqueous solution, and then neutralized to neutrality, and filtered to obtain a yellow precipitate;

[0071] S9. The yellow precipitate was dissolved in tetrahydrofuran and then an aqueous sodium hydroxide solution was added. The temperature was raised to 73°C and the reaction was continued for 1.3 hours. The organic layer was evaporated, washed, and dried to obtain a white powder.

[0072] S10. Add 7.8g of potassium ferrocyanide and 2.68g of potassium hydroxide to water, mix well, add 468g of dichloromethane and 2.3g of white powder, react for 13h, take the organic layer, wash, evaporate, and dry to give a light yellow powder;

[0073] S11. To 0.15 g of polyethylene glycol having a molecular weight of 400-500, 0.12 g of a light yellow powder, 8 g of ethyl acetate, 0.08 g of dibutyltin dilaurate, 0.15 g of isophorone diisocyanate, 0.15 g of tert-butylhydroquinone and 0.4 g of nanoparticles were added, and the mixture was reacted for 8 min and filtered to obtain a photoresist;

[0074] S12. The silicon carbide thick film epitaxial wafer was cleaned four times with piranha solution, dried with nitrogen, and then a 150 nm thick layer of silicon dioxide was grown to obtain a deposited wafer;

[0075] S13. Mask the deposited sheet with a photoresist, remove the photoresist, and perform plasma etching to a depth of 4 μm to obtain an etched sheet;

[0076] S14. Send the wafer into the ion implanter and perform Al + Ion implantation was followed by deposition of a 2 μm thick layer of silicon dioxide, which was then treated at 1050°C for 18 min in a nitrogen atmosphere to obtain an activated sheet;

[0077] S15. A 7 μm thick layer of silicon dioxide is deposited on the surface of the active sheet, and then a 4 μm thick layer of nickel is sputtered on the back surface and rapidly annealed to obtain an ohmic contact sheet;

[0078] S16. Etch the front surface of the ohmic contact sheet to a depth of 8 μm using a large P-area aperture plate. Then, perform photolithography using a large P-area metal definition plate. Then, sputter a boron ion film on the large P-area. Finally, peel off and perform rapid annealing to obtain a large P-area aperture sheet.

[0079] S17. A 4 μm thick layer of SiO2 and Si3N4 is deposited on the surface of the sheet, and then etched to a depth of 4 μm using an active area aperture plate to obtain an active area aperture sheet;

[0080] S18. Etch the active area aperture sheet to a thickness of 8 μm using a Schottky area aperture plate. Then, sputter a 14 μm thick layer of Ti metal. Etch to a depth of 1.5 μm using an anode metal definition plate. Finally, pattern the front metal by wet etching to complete the diode.

[0081] Example 3: A method for preparing a diode based on a silicon carbide thick film epitaxial wafer is as follows:

[0082] S1. With a doping concentration of 10 19 cm -3 Using nitrogen as the doping gas, epitaxial growth was performed on a silicon carbide substrate for 40 minutes at a temperature of 1690°C, a chamber pressure of 130 mbar, a carbon-silicon ratio of 1.03, and a growth rate of 20 μm / h to obtain a buffer layer attachment sheet with a thickness of 2 μm.

[0083] S2. With a doping concentration of 10 16 cm -3 The silicon carbide thick film epitaxial wafer with a thickness of 100 μm was grown on the buffer layer attachment wafer for 60 min using nitrogen as the doping gas at a temperature of 1690°C, a chamber pressure of 130 mbar, a carbon-silicon ratio of 1.03, and a growth rate of 100 μm / h.

[0084] S3. Dissolve 0.5 g of CsPbBr3 in 5 mL of n-hexane, then add 15 mL of methyl acetate. Centrifuge at 7500 rpm for 10 min. Repeat the dissolution and centrifugation of the precipitate five times, and collect the supernatant.

[0085] S4. The supernatant was incubated in the dark at 4°C for 50 h, then centrifuged at 5500 rpm for 5 min, and then distilled to dryness under reduced pressure. 20 mL of chloroform was added and stirred to obtain a dispersion.

[0086] S5. 0.2 g of quaternary thiophene-diketopyrrole, 0.05 g of 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 0.03 g of trimethylpropylene tris(3-mercaptopropionic acid) were sequentially added to the dispersion, stirred, and then dropped onto glass, followed by drying and ultraviolet irradiation to form a thin film on the glass plate;

[0087] S6. The film was wet-ground in a quartz mortar to collect the powder, which was then sonicated in chloroform for 45 minutes. The resulting solution was filtered through a 0.2 μm filter and dried to obtain nanoparticles.

[0088] S7. Add 7.75g of sodium hydroxide and 10.5g of 2-chloro-4-hydroxybenzaldehyde to water, heat to 80 ° C, add 16g of 3-chloro-1,2-propylene glycol and react for 25h, then add 25g of hydrochloric acid and water, and then react at 80 ° C for 1.5h, then add 50g of ethyl acetate, wash, dry, and purify to obtain grafted benzaldehyde;

[0089] S8. To 8.5 g of grafted benzaldehyde were added 9 g of benzil, 27 g of ammonium acetate, and 110 g of acetic acid, heated to 90 ° C and reacted for 20 h, followed by addition of a saturated aqueous sodium chloride solution, and then neutralized to neutrality, and filtered to obtain a yellow precipitate;

[0090] S9. The yellow precipitate was dissolved in tetrahydrofuran and then an aqueous sodium hydroxide solution was added. The temperature was raised to 75°C and the reaction was continued for 1.5 hours. The organic layer was evaporated, washed, and dried to obtain a white powder.

[0091] S10. Add 8g of potassium ferrocyanide and 2.7g of potassium hydroxide to water, mix well, add 470g of dichloromethane and 2.5g of white powder, react for 15h, take the organic layer, wash, evaporate and dry to give a light yellow powder;

[0092] S11. To 0.2 g of polyethylene glycol having a molecular weight of 400-500, 0.15 g of a light yellow powder, 10 g of ethyl acetate, 0.1 g of dibutyltin dilaurate, 0.19 g of isophorone diisocyanate, 0.2 g of tert-butylhydroquinone and 0.5 g of nanoparticles were added, and the mixture was reacted for 10 min and filtered to obtain a photoresist;

[0093] S12. The silicon carbide thick film epitaxial wafer was cleaned with piranha solution five times, dried with nitrogen, and then a 200 nm thick layer of silicon dioxide was grown to obtain a deposited wafer;

[0094] S13. Mask the deposited sheet with a photoresist, remove the photoresist, and perform plasma etching to a depth of 5 μm to obtain an etched sheet;

[0095] S14. Send the wafer into the ion implanter and perform Al + Ion implantation was followed by deposition of a 3 μm thick layer of silicon dioxide, which was then treated at 1100°C for 20 min in a nitrogen atmosphere to obtain an activated sheet;

[0096] S15. Depositing an 8 μm thick layer of silicon dioxide on the surface of the active sheet, and then sputtering a 5 μm thick layer of nickel on the back side, and rapidly annealing to obtain an ohmic contact sheet;

[0097] S16. Etch the front surface of the ohmic contact sheet to a depth of 10 μm using a large P-area aperture plate. Then, perform photolithography using a large P-area metal definition plate. Then, sputter a boron ion film on the large P-area. Finally, peel off and perform rapid annealing to obtain a large P-area aperture sheet.

[0098] S17. A 5 μm thick layer of SiO2 and Si3N4 is deposited on the surface of the sheet, and then etched to a depth of 5 μm using an active area aperture plate to obtain an active area aperture sheet;

[0099] S18. Use the Schottky area aperture plate to etch the active area aperture plate to a thickness of 10 μm, then sputter a layer of 15 μm thick Ti metal, and then use the anode metal definition plate to etch to a depth of 2 μm. Finally, complete the patterning of the front metal by wet etching to obtain a diode.

[0100] Comparative Example 1:

[0101] S1. With a doping concentration of 10 17 cm -3 Using nitrogen as the doping gas, epitaxial growth was performed on a silicon carbide substrate for 3 minutes at a temperature of 1520°C, a chamber pressure of 60 mbar, a carbon-silicon ratio of 1.06, and a growth rate of 3 μm / h to obtain a buffer layer attachment sheet with a thickness of 0.5 μm;

[0102] S2. With a doping concentration of 10 14 cm -3Nitrogen is used as the doping gas, and the growth is carried out on the buffer layer attachment sheet for 7 minutes at a temperature of 1520°C, a chamber pressure of 60mbar, a carbon-silicon ratio of 1.06, and a growth rate of 10μm / h to obtain a silicon carbide thick film epitaxial wafer with a thickness of 20μm. The growth temperature and chamber pressure of the buffer layer and the pressure-resistant layer are kept the same as those in Example 1. By adjusting the carbon-silicon ratio of the pressure-resistant layer, silicon carbide epitaxial wafers with large surface pit defects of different morphologies can be produced. When the carbon-silicon ratio is set in the range of 1.03-1.06, the large surface pit defects of the produced epitaxial wafer are inverted cones, and the morphology is as follows. Figure 2 As shown. Existing technologies often directly extend the epitaxial growth time based on the process recipe for thin (5-12μm) silicon carbide epitaxial wafers to produce thick silicon carbide film (20-100μm) epitaxial wafers. The resulting epitaxial wafers have numerous large inverted cone-shaped pit defects similar to those in this comparative example. However, the electric field concentration effect at the tip of these large pit defects can adversely affect the gate oxide stability of the device.

[0103] Comparative Example 2:

[0104] Compared with Example 1, this comparative example only replaced the "light yellow powder" added in the photoresist preparation process with "photosensitizer 1". The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a photoresist was obtained; wherein the CAS number of photosensitizer 1 is 1886-13-1;

[0105] Comparative Example 3:

[0106] This comparative example is compared with Example 1 except that "tert-butylhydroquinone" is not added during the preparation of the photoresist. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a photoresist is obtained.

[0107] Comparative Example 4:

[0108] This comparative example is compared with Example 1 only in that "nanoparticles" are not added during the preparation of the photoresist. The remaining steps and parameters are the same, and this comparative example will not be repeated. Finally, a photoresist is obtained;

[0109] Performance test of photoresist:

[0110] The photoresists prepared in Examples 1 to 3 and Comparative Examples 2 to 4 were laminated under the conditions of a hot pressing roller temperature of 100°C, a laminating speed of 1.0-3.0 m / min, and a laminating pressure of 0.3-0.5 MPa. The film temperature was 40-60°C, the film thickness was 35-40 μm, and the film was placed for 15 minutes and then heated at 35 mJ / cm 2 After exposure for 15 minutes, the irradiation temperature was set at 30℃ and the pressure was 1.5mJ / cm 2, the developing point is 50%, the developing speed is 1m / min, and the developing is carried out for 1 minute. Finally, the developing speed is 1m / min, and the developing speed is 1m / min. The ... 2 The film was stripped at 1m / min for 1min to obtain a dry film;

[0111] Determination of hardness:

[0112] According to ASTM D2240 "Standard Test Method for Durometer Hardness", specimens with a width of 15 mm, a length of 150 mm, and a thickness of 6 mm were prepared, and the Shore hardness of the dry films prepared in Examples 1 to 3 and Comparative Examples 2 to 4 was tested using a Shore durometer (LX-A, Wenzhou, China).

[0113] Determination of tensile strength:

[0114] Referring to GB / T 1040.3-2006 "Test for Tensile Properties of Plastics," strip specimens with a width of 15 mm and a length of 150 mm and parallel markings at 50 mm intervals were prepared by cutting. The tensile strength (MPa) of the dry films prepared in Examples 1-3 and Comparative Examples 2-4 was tested using a universal testing machine (Instron® 6800) at a speed of 50 mm / min.

[0115] Determination of elongation at break:

[0116] Referring to GB / T 1040.3-2006 "Test for Tensile Properties of Plastics," strip specimens with a width of 15 mm and a length of 150 mm and parallel markings at 50 mm intervals were prepared by cutting. The elongation at break (%) of the dry films prepared in Examples 1-3 and Comparative Examples 1-4 was tested using a universal testing machine (Instron® 6800) at a speed of 50 mm / min.

[0117] Determination of adhesion:

[0118] According to ASTM D3359-17, "Evaluation of Adhesion by Tape Test," the dry film on the printed circuit board was cut into an x-shape, and pressure-sensitive tape was applied to the cut. The tape was then removed, and the adhesion was evaluated using a scale of 0 to 5, with 0 being the strongest adhesion and 5 being the weakest. The adhesion of the dry films prepared in Examples 1 to 3 and Comparative Examples 1 to 4 was tested using an adhesion tester (QFH-HG600, Huaguo Precision Instruments). The test results are shown in Table 1.

[0119] Table 1

[0120] project Adhesion / Grade hardness Elongation at break / % Tensile strength / MPa Example 1 0 59 343.54 38.62 Example 2 0 60 346.45 34.17 Example 3 0 60 332.17 33.54 Comparative Example 2 1 34 167.33 17.71 Comparative Example 3 0 58 329.65 34.43 Comparative Example 4 0 56 297.39 31.22

[0121] Data Analysis:

[0122] As can be seen from Table 1, the photoresist prepared by the present invention has higher adhesion, hardness, elongation at break and tensile strength;

[0123] This may be because the light yellow powder added to the photoresist prepared by the present invention can not only copolymerize with components such as polyethylene glycol, isocyanate, and nanoparticles on the substrate surface to form a network-like cross-linked polyurethane, thereby improving the adhesion, hardness, elongation at break, and tensile strength of the photoresist, thereby making the dry film more complete and reducing its impact on the quality of the diode; the addition of tert-butylhydroquinone will cause the polymer in the photoresist after exposure to be decomposed into a linear structure with stronger solubility, and the active ingredients will lose their composite activity, making the photoresist more easily dissolved after organic solvent development, but its addition will not have a significant effect on the adhesion, hardness, elongation at break, and tensile strength of the dry film even if no exposure is performed. Therefore, the unexposed area will remain intact on the substrate after development, and the formed photolithographic pattern will also have higher clarity; and the nanoparticles will not only generate photogenerated carriers and capture electrons after exposure, thereby producing in-situ grating regulation of the semiconductor conductive channel and greatly improving the responsiveness of the diode, but will also cross-link with other components in the photoresist, further improving the tensile strength and elongation at break of the photoresist.

[0124] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0125] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a diode based on a silicon carbide thick film epitaxial wafer, characterized in that: The preparation method comprises the following steps: Step S1. Clean the silicon carbide thick film epitaxial wafer with piranha solution 3-5 times, blow dry it with nitrogen, and then grow a layer of silicon dioxide with a thickness of 100-200nm to obtain a deposited wafer; Step S2. Mask the deposited sheet with a photoresist, remove the photoresist, and then perform plasma etching to a depth of 3-5 μm to obtain an etched sheet; Step S3: Send the wafer to the ion implanter to perform Al + Ion implantation, followed by deposition of a 1-3 μm thick layer of silicon dioxide, followed by treatment at 1000-1100°C for 15-20 minutes in a nitrogen atmosphere to obtain an activated sheet; Step S4. Depositing a 5-8 μm thick layer of silicon dioxide on the surface of the activation sheet, and then sputtering a 3-5 μm thick layer of nickel on the back side, and rapidly annealing to obtain an ohmic contact sheet; Step S5. Etch the front surface of the ohmic contact sheet to a depth of 5-10 μm using a large P-area aperture plate, then perform photolithography using a large P-area metal definition plate, then sputter a boron ion film in the large P-area, and finally peel off and perform rapid annealing to obtain a large P-area aperture sheet. Step S6. Depositing a layer of SiO2 and Si3N4 with a thickness of 3-5 μm on the surface of the sheet, and then etching to a depth of 3-5 μm using an active area aperture plate to obtain an active area aperture sheet; Step S7. Etching the active area aperture sheet to a thickness of 5-10 μm using a Schottky area aperture plate, then sputtering a 13-15 μm thick layer of Ti metal, and then etching to a depth of 1-2 μm using an anode metal definition plate. Finally, patterning the front metal by wet etching to obtain a diode; The preparation method of the silicon carbide thick film epitaxial wafer is as follows: Step A1: Nitrogen is used as the doping gas, and the doping concentration of nitrogen is 10 17 -10 19 cm -3 , epitaxially growing on a silicon carbide substrate for 3-40 minutes at a temperature of 1520-1690° C., a chamber pressure of 60-130 mbar, a carbon-silicon ratio of 1.00-1.03, and a growth rate of 3-20 μm / h to obtain a buffer layer attachment sheet; Step A2. Using nitrogen as the doping gas, grow on the buffer layer attachment sheet for 7-60 minutes at a temperature of 1520-1690°C, a chamber pressure of 60-130 mbar, a carbon-silicon ratio of 1.00-1.03, and a growth rate of 10-100 μm / h to obtain a silicon carbide thick film epitaxial wafer.

2. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 1, characterized in that: The thickness of the buffer layer attachment sheet is 0.5-2 μm; the thickness of the silicon carbide thick film epitaxial wafer is 20-100 μm.

3. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 1, wherein: The preparation method of the photoresist is as follows: Step B1. Sodium hydroxide and 2-chloro-4-hydroxybenzaldehyde were added to water, heated to 75-80 ° C, 3-chloro-1,2-propylene glycol was added and reacted for 12-15h, hydrochloric acid and water were added, and then reacted at 75-80 ° C for 1-1.5h, ethyl acetate was added, washed, dried, and purified to obtain grafted benzaldehyde; Step B2. Benzil, ammonium acetate, and acetic acid were added to the grafted benzaldehyde in sequence, heated to 85-90°C, and reacted for 16-20 hours. Saturated aqueous sodium chloride solution was then added, and the mixture was neutralized to neutrality. A yellow precipitate was obtained by filtration. Step B3. Dissolve the yellow precipitate with tetrahydrofuran and add aqueous sodium hydroxide solution. Heat to 70-75 ° C and react for 1-1.5 hours. Take the organic layer, evaporate, wash and dry to obtain a white powder. Step B4. Potassium ferrocyanide and potassium hydroxide were added to water and mixed, followed by addition of dichloromethane and white powder. The reaction was continued for 12-15 hours, and the organic layer was washed, evaporated, and dried to obtain a light yellow powder. Step B5. Add light yellow powder, ethyl acetate, dibutyltin dilaurate, isophorone diisocyanate, perfluorooctanesulfonyl fluoride, tert-butylhydroquinone and nanoparticles to polyethylene glycol, react for 5-10 minutes and then filter to obtain a photoresist.

4. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 3, wherein: The mass ratio of sodium hydroxide, 2-chloro-4-hydroxybenzaldehyde, 3-chloro-1,2-propylene glycol, hydrochloric acid and ethyl acetate in step B1 is 7.68-7.75:10-10.5:15.6-16:18-25:45-50.

5. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 3, wherein: The mass ratio of the grafted benzaldehyde, benzil, ammonium acetate and acetic acid in step B2 is 7.5-8.5:8.5-9:26.5-27:100-110.

6. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 3, wherein: The mass ratio of potassium ferrocyanide, potassium hydroxide, white powder and dichloromethane in step B4 is 7.8-7.9:2.65-2.7:2-2.5:465-470.

7. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 3, wherein: The mass ratio of polyethylene glycol, light yellow powder, ethyl acetate, dibutyltin dilaurate, isophorone diisocyanate, tert-butylhydroquinone and nanoparticles in step B5 is 0.1-0.2: 0.08-0.15: 5-10: 0.05-0.1: 0.1-0.19: 0.1-0.2: 0.3-0.

5.

8. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 3, wherein: The molecular weight of the polyethylene glycol in step B5 is 400-500.

9. The method for preparing a diode based on a silicon carbide thick film epitaxial wafer according to claim 3, wherein: The preparation method of the nanoparticles is as follows: Step C1. Dissolve 0.3-0.5 g of CsPbBr3 in 3-5 mL of n-hexane, then add 9-15 mL of methyl acetate. Centrifuge at 7000-7500 rpm for 5-10 min. Repeat the dissolution and centrifugation of the precipitate 3-5 times, and collect the supernatant. Step C2. The supernatant was placed in a dark environment at 0-4°C for 45-50 hours, then centrifuged at 5000-5500 rpm for 3-5 minutes, and then distilled under reduced pressure to dryness. 10-20 mL of chloroform was added and stirred to obtain a dispersion. Step C3. To the dispersion, 0.1-0.2 g of quaterthiophene-diketopyrrole, 0.02-0.05 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 0.01-0.03 g of trimethylpropylene tris(3-mercaptopropionic acid) were sequentially added, stirred, and then dropped onto glass. The mixture was then dried and irradiated with ultraviolet light to form a thin film on the glass plate. Step C4. The film is placed in a quartz mortar for wet grinding to collect the powder, which is then ultrasonicated in chloroform for 30-45 minutes. The powder is then filtered through a 0.1-0.2 μm filter and the filtrate is dried to obtain nanoparticles.

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