Research Progress on Surface/Subsurface Damages of 4H Silicon Carbide Wafers

Abstract

Abstract: 4H silicon carbide (4H-SiC) substrate wafers without surface/subsurface damages and low surface roughness are ideal substrates for the development of power electronics and radio frequency (RF) microwave devices, which hold great promise in applications of new energy, rail transportation, smart grid and 5G communication. The processing of 4H-SiC substrate wafers includes slicing, grinding, lapping, polishing and cleaning. However, the surface damages (SDs) and subsurface damages (SSDs) introduced during the processing of 4H-SiC substrates affects the properties of 4H-SiC substrates and epitaxial layers, and thus the performance and reliability of devices based on 4H-SiC. This paper focuses on the formation and removal mechanisms of SDs/SSDs during the processing of 4H-SiC substrate wafers. Based on the detection method of SDs/SSDs, the morphologies and characterization approaches of SDs/SSDs are reviewed. Finally, three commonly used technologies for the removal SDs/SSDs, along with their technical advantages, development challenges and trends, are briefly discussed.

Key words: semiconductor, 4H-SiC, substrate wafer, surface/subsurface damage, wafer processing

CLC Number:

LI Guofeng, CHEN Hongyu, HANG Wei, HAN Xuefeng, YUAN Julong, PI Xiaodong, YANG Deren, WANG Rong. Research Progress on Surface/Subsurface Damages of 4H Silicon Carbide Wafers[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2023, 52(11): 1907-1921.

References

[1] 麦玉冰, 谢欣荣. 第三代半导体材料碳化硅(SiC)研究进展[J]. 广东化工, 2021, 48(9): 151-152+155.
MAI Y B, XIE X R. The research progress of the third generation semiconductor materials SiC[J]. Guangdong Chemical Industry, 2021, 48(9): 151-152+155 (in Chinese).
[2] DENG H, LIU N, ENDO K, et al. Atomic-scale finishing of carbon face of single crystal SiC by combination of thermal oxidation pretreatment and slurry polishing[J]. Applied Surface Science, 2018, 434: 40-48.
[3] 张银霞, 李大磊, 郜伟, 等. 硅片加工表面层损伤检测技术的试验研究[J]. 人工晶体学报, 2011, 40(2): 359-364.
ZHANG Y X, LI D L, GAO W, et al. Experimental investigation on the detection technique for surface layer damage of machined silicon wafers[J]. Journal of Synthetic Crystals, 2011, 40(2): 359-364 (in Chinese).
[4] 高玉飞, 葛培琪, 李绍杰, 等. 单晶硅线锯切片亚表层损伤层厚度预测与测量[J]. 中国机械工程, 2009, 20(14): 1731-1735.
GAO Y F, GE P Q, LI S J, et al. Prediction and measurement of subsurface damage thickness of silicon wafer in wire saw slicing[J]. China Mechanical Engineering, 2009, 20(14): 1731-1735 (in Chinese).
[5] SAKO H, YAMASHITA T, SUGIYAMA N, et al. Characterization of scraper-shaped defects on 4H-SiC epitaxial film surfaces[J]. Japanese Journal of Applied Physics, 2014, 53(5): 051301.
[6] 杨光, 刘晓双, 李佳君, 等. 4H碳化硅单晶中的位错[J]. 人工晶体学报, 2022, 51(9-10): 1673-1690.
YANG G, LIU X S, LI J J, et al. Dislocation in 4H silicon carbide single crystal[J]. Journal of Synthetic Crystals, 2022, 51(9-10): 1673-1690 (in Chinese).
[7] HUANG H, ZHANG Y X, XU X P. Experimental investigation on the machining characteristics of single-crystal SiC sawing with the fixed diamond wire[J]. The International Journal of Advanced Manufacturing Technology, 2015, 81(5): 955-965.
[8] WANG N C. Review on brittle material subsurface damage detection technology[J]. Journal of Mechanical Engineering, 2017, 53(9): 170.
[9] 张俊然, 朱如忠, 张玺, 等. 线锯切片技术及其在碳化硅晶圆加工中的应用[J]. 人工晶体学报, 2023, 52(3): 365-379.
ZHANG J R, ZHU R Z, ZHANG X, et al. Wire saw slicing and its application in silicon carbide wafers processing[J]. Journal of Synthetic Crystals, 2023, 52(3): 365-379 (in Chinese).
[10] 王肖烨. SiC单晶体超声线锯切割技术及实验研究[D]. 西安: 西安理工大学, 2013.
WANG X Y. Cutting technology and experimental study of SiC single crystal ultrasonic wire saw[D]. Xi'an: Xi'an University of Technology, 2013 (in Chinese).
[11] WANG P Z, GE P Q, GAO Y F, et al. Prediction of sawing force for single-crystal silicon carbide with fixed abrasive diamond wire saw[J]. Materials Science in Semiconductor Processing, 2017, 63: 25-32.
[12] ARIF M, ZHANG X Q, RAHMAN M, et al. A predictive model of the critical undeformed chip thickness for ductile-brittle transition in nano-machining of brittle materials[J]. International Journal of Machine Tools and Manufacture, 2013, 64: 114-122.
[13] 张银霞, 王健康, 郜伟, 等. 6H-SiC单晶片划痕形貌与残余应力研究[J]. 硅酸盐学报, 2019, 47(7): 964-971.
ZHANG Y X, WANG J K, GAO W, et al. Morphology and residual stress of 6H-SiC single crystal wafer induced by scratching[J]. Journal of the Chinese Ceramic Society, 2019, 47(7): 964-971 (in Chinese).
[14] ISHIKAWA Y, YAO Y Z, SUGAWARA Y, et al. Comparison of slicing-induced damage in hexagonal SiC by wire sawing with loose abrasive, wire sawing with fixed abrasive, and electric discharge machining[J]. Japanese Journal of Applied Physics, 2014, 53(7): 071301.
[15] GAO Y F, CHEN Y, GE P Q, et al. Study on the subsurface microcrack damage depth in electroplated diamond wire saw slicing SiC crystal[J]. Ceramics International, 2018, 44(18): 22927-22934.
[16] ISHIKAWA Y, SATO K, OKAMOTO Y, et al. Dislocation formation in epitaxial film by propagation of shallow dislocations on 4H-SiC substrate[J]. Materials Science Forum, 2012, 717/718/719/720: 383-386.
[17] 王亚茹, 李英杰, 邹莱, 等. RB-SiC金刚石磨粒柔性刻划材料去除及表面损伤行为[J]. 光学精密工程, 2022, 30(14): 1704-1715.
WANG Y R, LI Y J, ZOU L, et al. Material removal and surface damage behavior of diamond grain for flexible scribing RB-SiC[J]. Optics and Precision Engineering, 2022, 30(14): 1704-1715 (in Chinese).
[18] 李晶. 二维旋转超声辅助磨削-电解-放电展成加工机理及试验研究[D]. 扬州: 扬州大学, 2022.
LI J. Mechanism and experimental study of two-dimensional rotary ultrasonic-assisted grinding-electrolysis-discharge generating machining[D].Yangzhou: Yangzhou University, 2022 (in Chinese).
[19] 王超超, 张凤林, 欧阳承达, 等. 用于磨削6H-SiC晶片的陶瓷结合剂金刚石砂轮制备及磨削试验研究[J]. 工具技术, 2022, 56(12): 48-51.
WANG C C, ZHANG F L, OUYANG C D, et al. Preparation and grinding test of ceramic bonded diamond grinding wheel for grinding 6H-SiC wafer[J]. Tool Engineering, 2022, 56(12): 48-51 (in Chinese).
[20] 张玺, 朱如忠, 张序清, 等. 磨料形貌及分散介质对4H碳化硅晶片研磨质量的影响研究[J]. 人工晶体学报, 2023, 52(1): 48-55.
ZHANG X, ZHU R Z, ZHANG X Q, et al. Study on the influence of abrasive morphology and dispersion media on the grinding quality of 4H silicon carbide wafer[J]. Journal of Synthetic Crystals, 2023, 52(1): 48-55 (in Chinese).
[21] YAN Q S, CHEN S K, PAN J S, et al. Surface and subsurface damage characteristics and material removal mechanism in 6H-SiC wafer grinding[J]. Materials Research Innovations, 2014, 18(sup2): S2-742.
[22] LIU Y, LI B Z, KONG L F. Molecular dynamics simulation of silicon carbide nanoscale material removal behavior[J]. Ceramics International, 2018, 44(10): 11910-11913.
[23] AGARWAL S, RAO P V. Experimental investigation of surface/subsurface damage formation and material removal mechanisms in SiC grinding[J]. International Journal of Machine Tools and Manufacture, 2008, 48(6): 698-710.
[24] AGARWAL S, VENKATESWARA RAO P. Grinding characteristics, material removal and damage formation mechanisms in high removal rate grinding of silicon carbide[J]. International Journal of Machine Tools and Manufacture, 2010, 50(12): 1077-1087.
[25] GAO S, WANG H X, HUANG H, et al. Molecular simulation of the plastic deformation and crack formation in single grit grinding of 4H-SiC single crystal[J]. International Journal of Mechanical Sciences, 2023, 247: 108147.
[26] WU Z H, ZHANG L C, LIU W D. Structural anisotropy effect on the nanoscratching of monocrystalline 6H-silicon carbide[J]. Wear, 2021, 476: 203677.
[27] LIU C L, CHEN X, KE J Y, et al. Numerical investigation on subsurface damage in nanometric cutting of single-crystal silicon at elevated temperatures[J]. Journal of Manufacturing Processes, 2021, 68: 1060-1071.
[28] MENG B B, YUAN D D, XU S L. Study on strain rate and heat effect on the removal mechanism of SiC during nano-scratching process by molecular dynamics simulation[J]. International Journal of Mechanical Sciences, 2019, 151: 724-732.
[29] PAN J S, ZHANG X W, YAN Q S, et al. Experimental study of surface performance of monocrystalline 6H-SiC substrates in plane grinding with a metal-bonded diamond wheel[J]. The International Journal of Advanced Manufacturing Technology, 2017, 89(1): 619-627.
[30] ZHU D H, YAN S J, LI B Z. Single-grit modeling and simulation of crack initiation and propagation in SiC grinding using maximum undeformed chip thickness[J]. Computational Materials Science, 2014, 92: 13-21.
[31] YIN J F, BAI Q, GOEL S, et al. An analytical model to predict the depth of sub-surface damage for grinding of brittle materials[J]. CIRP Journal of Manufacturing Science and Technology, 2021, 33: 454-464.
[32] QIUSHENG Y, SENKAI C, JISHENG P. Surface and subsurface cracks characteristics of single crystal SiC wafer in surface machining[C]//AIP Conference Proceedings. Fethiye, Turkey. AIP Publishing LLC, 2015.
[33] WANG C C, FANG Q H, CHEN J B, et al. Subsurface damage in high-speed grinding of brittle materials considering kinematic characteristics of the grinding process[J]. The International Journal of Advanced Manufacturing Technology, 2016, 83(5): 937-948.
[34] WANG H R, CHEN H F, FU G L, et al. Relationship between grinding process and the parameters of subsurface damage based on the image processing[J]. The International Journal of Advanced Manufacturing Technology, 2016, 83(9/10/11/12): 1707-1715.
[35] GUO F L, SHAO C, CHEN X F, et al. Shape modulation due to sub-surface damage difference on N-type 4H-SiC wafer during lapping and polishing[J]. Materials Science in Semiconductor Processing, 2022, 152: 107124.
[36] WANG Z, WU Y L, DAI Y F, et al. Subsurface damage distribution in the lapping process[J]. Applied Optics, 2008, 47(10): 1417-1426.
[37] GAO S, LI H G, HUANG H, et al. Grinding and lapping induced surface integrity of silicon wafers and its effect on chemical mechanical polishing[J]. Applied Surface Science, 2022, 599: 153982.
[38] DOBRESCU T, DORIN A. A study of silicon wafers plane lapping process[J]. Annals of DAAAM & Proceedings. 2007: 229-231.
[39] TSAI M Y, WANG S M, TSAI C C, et al. Investigation of increased removal rate during polishing of single-crystal silicon carbide[J]. The International Journal of Advanced Manufacturing Technology, 2015, 80(9): 1511-1520.
[40] XIAO H, DAI Y F, DUAN J, et al. Material removal and surface evolution of single crystal silicon during ion beam polishing[J]. Applied Surface Science, 2021, 544: 148954.
[41] YAMAMURA K, TAKIGUCHI T, UEDA M, et al. Plasma assisted polishing of single crystal SiC for obtaining atomically flat strain-free surface[J]. CIRP Annals, 2011, 60(1): 571-574.
[42] HSIEH C H, CHANG C Y, HSIAO Y K, et al. Recent advances in silicon carbide chemical mechanical polishing technologies[J]. Micromachines, 2022, 13(10): 1752.
[43] 康健, 宣斌, 谢京江. 表面改性碳化硅基底反射镜加工技术现状[J]. 中国光学, 2013, 6(6): 824-833.
KANG J, XUAN B, XIE J J. Manufacture technology status of surface modified silicon carbide mirrors[J]. Chinese Optics, 2013, 6(6): 824-833 (in Chinese).
[44] WANG W T, LU X S, WU X K, et al. Chemical-mechanical polishing of 4H silicon carbide wafers[J]. Advanced Materials Interfaces, 2023, 10(13): 2202369.
[45] ZHOU Y, PAN G S, SHI X L, et al. XPS, UV-vis spectroscopy and AFM studies on removal mechanisms of Si-face SiC wafer chemical mechanical polishing (CMP)[J]. Applied Surface Science, 2014, 316: 643-648.
[46] ZHOU Y, PAN G S, SHI X L, et al. Chemical mechanical planarization (CMP) of on-axis Si-face SiC wafer using catalyst nanoparticles in slurry[J]. Surface and Coatings Technology, 2014, 251: 48-55.
[47] POWELL A R, SUMAKERIS J J, KHLEBNIKOV Y, et al. Bulk growth of large area SiC crystals[J]. Materials Science Forum, 2016, 858: 5-10.
[48] SASAKI M, MATSUHATA H, TAMURA K, et al. Synchrotron X-ray topography analysis of local damage occurring during polishing of 4H-SiC wafers[J]. Japanese Journal of Applied Physics, 2015, 54(9): 091301.
[49] MARTIN C, KERR T M, STEPKO W, et al. Sub-surface damage removal in fabrication & polishing of silicon carbide[C]. Proc of Int CS MANTECH Conference Miami, 2004.
[50] SAKO H, MATSUHATA H, SASAKI M, et al. Micro-structural analysis of local damage introduced in subsurface regions of 4H-SiC wafers during chemo-mechanical polishing[J]. Journal of Applied Physics, 2016, 119(13): 135702.
[51] PIROUZ J L DEMENET M H, HONG P. On transition temperatures in the plasticity and fracture of semiconductors[J]. Philosophical Magazine A, 2001, 81(5): 1207-1227.
[52] TSUKIMOTO S, ISE T, MARUYAMA G, et al. Local strain distribution and microstructure of grinding-induced damage layers in SiC wafer[J]. Journal of Electronic Materials, 2018, 47(11): 6722-6730.
[53] 王健, 郑非非, 董志刚, 等. 碳化硅磨削亚表面损伤检测方法[J]. 金刚石与磨料磨具工程, 2015, 35(4): 60-65.
WANG J, ZHENG F F, DONG Z G, et al. Detection method of subsurface damage of silicon carbide after grinding[J]. Diamond & Abrasives Engineering, 2015, 35(4): 60-65 (in Chinese).
[54] WANG J J, ZHANG C L, FENG P F, et al. A model for prediction of subsurface damage in rotary ultrasonic face milling of optical K9 glass[J]. The International Journal of Advanced Manufacturing Technology, 2016, 83(1/2/3/4): 347-355.
[55] CHEN J B, FANG Q H, LI P. Effect of grinding wheel spindle vibration on surface roughness and subsurface damage in brittle material grinding[J]. International Journal of Machine Tools and Manufacture, 2015, 91: 12-23.
[56] 王洪祥, 李成福, 朱本温, 等. 光学元件亚表面缺陷的损伤性检测方法[J]. 强激光与粒子束, 2014, 26(12): 122008.
WANG H X, LI C F, ZHU B W, et al. Destructive methods for detecting subsurface defects of fused silica optics[J]. High Power Laser and Particle Beams, 2014, 26(12): 122008 (in Chinese).
[57] 杨立峰, 王亚非. 声学显微镜及其进展[J]. 声学与电子工程, 2006(1): 50-53.
YANG L F, WANG Y F. Acoustic microscope and its progress[J]. Acoustics and Electronics Engineering, 2006(1): 50-53 (in Chinese).
[58] TROST M, HERFFURTH T, SCHMITZ D, et al. Evaluation of subsurface damage by light scattering techniques[J]. Applied Optics, 2013, 52(26): 6579-6588.
[59] 王春慧. 光学表面亚表层损伤检测技术研究[D]. 西安: 西安工业大学, 2010.
WANG C H. Research on subsurface damage detection technology of optical surface[D]. Xi’an: Xi’an Technological University, 2010 (in Chinese).
[60] POWELL J A, LARKIN D J. Process-induced morphological defects in epitaxial CVD silicon carbide[J]. Physica Status Solidi (b), 1997, 202(1): 529-548.
[61] CAMP D W, KOZLOWSKI M R, SHEEHAN L M, et al. Subsurface damage and polishing compound affect the 355-nm laser damage threshold of fused silica surfaces[C]//Laser-Induced Damage in Optical Materials: 1997. Proc SPIE 3244, Laser-Induced Damage in Optical Materials: 1997, Boulder, Co, USA. 1998, 3244: 356-364.
[62] ZHANG Y X, SU J X, GAO W, et al. Study on subsurface damage model of the ground monocrystallinge silicon wafers[J]. Key Engineering Materials, 2009, 416: 66-70.
[63] SAKO H, YAMASHITA T, TAMURA K, et al. Microstructural analysis of damaged layer introduced during chemo-mechanical polishing[J]. Materials Science Forum, 2014, 778/779/780: 370-373.
[64] MAEDA K, SUZUKI K, FUJITA S, et al. Defects in plastically deformed 6H SiC single crystals studied by transmission electron microscopy[J]. Philosophical Magazine A, 1988, 57(4): 573-592.
[65] DO E, KANEKO M, KIMOTO T. Expansion patterns of single Shockley stacking faults from scratches on 4H-SiC[J]. Japanese Journal of Applied Physics, 2021, 60(6): 068001.
[66] GAO S, KANG R K, GUO D M, et al. Study on the subsurface damage distribution of the silicon wafer ground by diamond wheel[J]. Advanced Materials Research, 2010, 126/127/128: 113-118.
[67] GENG W H, YANG G A, ZHANG X Q, et al. Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching[J]. Journal of Semiconductors, 2022, 43(10): 102801.
[68] WANG J H, ZHANG L, WANG H X, et al. Fused quartz subsurface damage detecting method based on confocal fluorescence microscopy[J]. Chinese Journal of Lasers, 2015, 42(4): 0406004.
[69] 白倩, 马浩, 殷景飞. 基于偏振激光共聚焦的研磨石英玻璃亚表面损伤检测[J]. 光学精密工程, 2021, 29(8): 1795-1803.
BAI Q, MA H, YIN J F. Polarized laser confocal technique for subsurface damage of lapped quartz glass[J]. Optics and Precision Engineering, 2021, 29(8): 1795-1803 (in Chinese).
[70] 崔辉, 刘世杰, 赵元安, 等. 全内反射显微技术探测亚表面缺陷新方法研究[J]. 光学学报, 2014, 34(6): 131-137.
CUI H, LIU S J, ZHAO Y A, et al. Study on total internal reflection microscopy for subsurface damage[J]. Acta Optica Sinica, 2014, 34(6): 131-137 (in Chinese).
[71] EVANS A G, MUMM D R, HUTCHINSON J W, et al. Mechanisms controlling the durability of thermal barrier coatings[J]. Progress in Materials Science, 2001, 46(5): 505-553.
[72] GU Y, ZHU W H, LIN J Q, et al. Subsurface damage in polishing process of silicon carbide ceramic[J]. Materials, 2018, 11(4): 506.
[73] LAMBROPOULOS J. From abrasive size to subsurface damage in grinding[C]//Optical Fabrication and Testing. Québec City, Canada. Washington DC: OSA, 2000: OMA6.
[74] KATSUNO T, WATANABE Y, HIROKAZU F, et al. New separation method of threading dislocations in 4H-SiC epitaxial layer by molten KOH etching[J]. Materials Science Forum, 2011, 679/680: 298-301.
[75] SCHULZ D, DOERSCHEL J, LECHNER M, et al. On mass transport and surface morphology of sublimation grown 4H silicon carbide[J]. Journal of Crystal Growth, 2002, 246(1/2): 31-36.
[76] YEO I G, EUN T H, KIM J Y, et al. Study on dislocation behaviors during PVT growth of 4H-SiC[J]. Materials Science Forum, 2019, 963: 64-67.
[77] SASAKI M, TAMURA K, SAKO H, et al. Analysis on generation of localized step-bunchings on 4H-SiC(0001)Si face by synchrotron X-ray topography[J]. Materials Science Forum, 2014, 778/779/780: 398-401.
[78] ZHANG N, CHEN Y, SANCHEZ E K, et al. The effect of 4H-SiC substrate surface scratches on chemical vapor deposition grown homo-epitaxial layer quality[J]. Materials Science Forum, 2009, 615/616/617: 109-112.
[79] DUDLEY M, ZHANG N, ZHANG Y, et al. Nucleation of c-axis screw dislocations at substrate surface damage during 4H-silicon carbide homo-epitaxy[J]. Materials Science Forum, 2010, 645/646/647/648: 295-298.
[80] SKOWRONSKI M. Degradation of hexagonal silicon carbide-based bipolar devices[C]//2005 International Semiconductor Device Research Symposium. December 7-9, 2005, Bethesda, MD, USA. IEEE, 2006: 138.
[81] MARTIN C, KERR D T M, STEPKO W, et al. Sub-surface damage removal in fabrication & polishing of silicon[J]. CS MANTECH Conference. 2004.
[82] MA G L, LI S J, LIU F L, et al. A review on precision polishing technology of single-crystal SiC[J]. Crystals, 2022, 12(1): 101.
[83] YU S A, HU J J, XU L L, et al. Highest quality and repeatability for single wafer 150 mm SiC CMP designed for high volume manufacturing[J]. Materials Science Forum, 2022, 1062: 229-234.
[84] RAMACHANDRAN V, BRADY M F, SMITH A R, et al. Preparation of atomically flat surfaces on silicon carbide using hydrogen etching[J]. Journal of Electronic Materials, 1998, 27(4): 308-312.
[85] SUKKAEW P, DANIELSSON Ö, OJAMÄE L. Growth mechanism of SiC CVD: surface etching by H₂, H atoms, and HCl[J]. The Journal of Physical Chemistry A, 2018, 122(9): 2503-2512.
[86] CHEN X F, ZHANG F S, YANG X L, et al. Reduction of dislocation density of SiC crystals grown on seeds after H₂ etching[J]. Materials Science Forum, 2017, 897: 19-23.
[87] SOUBATCH S, SADDOW S E, RAO S P, et al. Structure and morphology of 4H-SiC wafer surfaces after H₂-etching[J]. Materials Science Forum, 2005, 483/484/485: 761-764.
[88] ANZALONE R, PILUSO N, SALANITRI M, et al. Hydrogen etching influence on 4H-SiC homo-epitaxial layer for high power device[J]. Materials Science Forum, 2017, 897: 71-74.
[89] LI X, UL HASSAN J, KORDINA O, et al. Surface preparation of 4° off-axis 4H-SiC substrate for epitaxial growth[J]. Materials Science Forum, 2013, 740/741/742: 225-228.
[90] NIU Y X, TANG X Y, SANG L, et al. The influence of temperature on the silicon droplet evolution in the homoepitaxial growth of 4H-SiC[J]. Journal of Crystal Growth, 2018, 504: 37-40.
[91] TAWARA T, NAKAMURA S. Technology for controlling trench shape in SiC power MOSFETs [J]. Fuji Elect Rev, 2009, 55(2): 69-73.
[92] TORIMI S, NOGAMI S, KANEKO T. Development of a novel cap-free activation annealing technique of 4H-SiC by Si-vapor ambient annealing using TaC/Ta composite materials[J]. Materials Science Forum, 2014, 778/779/780: 673-676.
[93] YABUKI N, TORIMI S, NOGAMI S, et al. Development of “Si-vapor etching” and “Si vapor ambient anneal” in TaC/Ta composite materials[J]. Materials Science Forum, 2016, 858: 719-722.
[94] YAO Y Z, ISHIKAWA Y, SUGAWARA Y, et al. Removal of mechanical-polishing-induced surface damages on 4H-SiC by chemical etching and its effect on subsequent epitaxial growth[J]. Materials Science Forum, 2015, 821/822/823: 541-544.
[95] ZHANG Y, CHEN H, LIU D Z, et al. High efficient polishing of sliced 4H-SiC (0001) by molten KOH etching[J]. Applied Surface Science, 2020, 525: 146532.
[96] DOJIMA D, MAKI M, DANSAKO D, et al. Enhancement of dislocation contrasts in PL imaging from 4H-SiC bulkwafers by removing subsurface damage using sublimation etching[C]. 19th International Conference on Silicon Carbide and Related Materials, 2022: 2.