Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

Wenhao Geng; Guang Yang; Xuqing Zhang; Xi Zhang; Yazhe Wang; Lihui Song; Penglei Chen; Yiqiang Zhang; Xiaodong Pi; Deren Yang; Rong Wang

doi:10.1088/1674-4926/43/10/102801

J. Semicond. > 2022, Volume 43 > Issue 10 > 102801

ARTICLES

Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

Wenhao Geng^{1, 2}, Guang Yang³, Xuqing Zhang^{1, 2}, Xi Zhang², Yazhe Wang², Lihui Song², Penglei Chen², Yiqiang Zhang⁴, Xiaodong Pi^{1, 2,}, Deren Yang^{1, 2} and Rong Wang^{1, 2,}

+ Author Affiliations

1. State Key Laboratory of Silicon Materials & School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
2. Institute of Advanced Semiconductors & Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices, Hangzhou Innovation Center, Zhejiang University, Hangzhou 311200, China
3. Key Laboratory of Optical Field Manipulation of Zhejiang Province, Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China
4. School of Materials Science and Engineering & College of Chemistry, Zhengzhou University, Zhengzhou 450001, China

Author Bio:

Wenhao Geng obtained his Ph.D. at University of Chinese Academy of Sciences in 2021. Currently he is a postdoc in Hangzhou Innovation Center of Zhejiang University. His research focuses on the origin and evolution of defects in semiconductor materials.

Xiaodong Pi received his Ph.D. degree at the University of Bath in 2004. He then carried out research at McMaster University and the University of Minnesota at Twin Cities. He joined Zhejiang University as an associate professor in 2008. He is now a professor in the State Key Laboratory of Silicon Materials, the School of Materials Science and Engineering and Hangzhou Innovation Center at Zhejiang University. His research mainly concerns group IV semiconductor materials and devices.

Deren Yang is an academician of Chinese Academy of Science, President of NingboTech University, director of Faculty of Engineering at Zhejiang University and chief scientist of Hangzhou Innovation Center of Zhejiang University. He received his Ph.D. in 1991, at Zhejiang University. In 1990s, he worked in Japan, Germany, and Sweden for several years as a visiting researcher. He has been engaged in research on silicon materials for microelectronic devices, solar cells, and nanodevices.

Rong Wang received her Ph.D. degree at Zhejiang University in 2014. She then carried out research at Taiyuan University of Technology and China Academy of Engineering Physics. She joined Hangzhou Innovation Center of Zhejiang University in 2020. Her research mainly focuses on wide-bandgap semiconductor physics.

Corresponding author: Xiaodong Pi, xdpi@zju.edu.cn; Rong Wang, rong_wang@zju.edu.cn

DOI: 10.1088/1674-4926/43/10/102801

Abstract: In this work, we propose to reveal the subsurface damage (SSD) of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching. Under UV illumination, SSD acts as a photoluminescence-black defect. The selective photo-chemical etching reveals SSD as the ridge-like defect. It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion. The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines, which are typical features of scratches. This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers. SSD is incorporated into 4H-SiC wafers during the lapping, rather than the chemical mechanical polishing (CMP).

Key words: 4H-SiC, subsurface damages, photo-chemical etching, molten-alkali etching

References

[1]	Huang R, Tao Y, Bai S, et al. Design and fabrication of a 3.3 kV 4H-SiC MOSFET. J Semiconduct, 2015, 36, 094002 doi: 10.1088/1674-4926/36/9/094002
[2]	Chatterjee A, Stevenson P, Franceschi S D, et al. Semiconductor qubits in practice. Nat Rev Phys, 2021, 3, 157 doi: 10.1038/s42254-021-00283-9
[3]	Gao F, Weber W J. Mechanical properties and elastic constants due to damage accumulation and amorphization in SiC. Phys Rev B, 2004, 69, 224108 doi: 10.1103/PhysRevB.69.224108
[4]	Liu X, Zhang J, Xu B, et al. Deformation of 4H-SiC: the role of dopants. Appl Phys Lett, 2022, 120, 052105 doi: 10.1063/5.0083882
[5]	Wang W, Zhang B, Shi Y, et al. Improvement in chemical mechanical polishing of 4H-SiC wafer by activating persulfate through the synergistic effect of UV and TiO₂. J Mater Process Tech, 2021, 295, 117150 doi: 10.1016/j.jmatprotec.2021.117150
[6]	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. Mater Sci Forum, 2014, 778–780, 398 doi: 10.4028/www.scientific.net/MSF.778-780.398
[7]	Sasaki M, Matsuhata H, Tamura K, et al. Synchrotron X-Ray topography analysis of local damage occurring during polishing of 4H-SiC wafers. Jpn J Appl Phys, 2015, 54, 091301 doi: 10.7567/JJAP.54.091301
[8]	Zhang Z, Cai H, Gan D, et al. A new method to characterize underlying scratches on SiC wafers. CrystEngComm, 2019, 21, 1200 doi: 10.1039/C8CE01700J
[9]	Zhang Y, Zhang L, Chen K, et al. Rapid subsurface damage detection of SiC using inductivity coupled plasma. Int J Extrem Manuf, 2021, 3, 035202 doi: 10.1088/2631-7990/abff34
[10]	Dudley M, Zhang N, Zhang Y, et al. Nucleation of c-axis screw dislocations at substrate surface damage during 4H-silicon carbide homo-epitaxy. Mater Sci Forum, 2010, 645–648, 295 doi: 10.4028/www.scientific.net/MSF.645-648.295
[11]	Ashida K, Dojima D, Torimi S, et al. Rearrangement of surface structure of 4° off-axis 4H-SiC (0001) epitaxial wafer by high temperature annealing in Si/Ar ambient. Mater Sci Forum, 2018, 924, 249 doi: 10.4028/www.scientific.net/MSF.924.249
[12]	Ashida K, Dojima D, Kutsuma Y, et al. Evaluation of polishing-induced subsurface damage of 4H-SiC (0001) by cross-sectional electron backscattered diffraction and synchrotron x-ray micro-diffraction. MRS Adv, 2016, 1, 3697 doi: 10.1557/adv.2016.433
[13]	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 Appl Phys, 2016, 119, 135702 doi: 10.1063/1.4945017
[14]	Xu Z, He Z, Song Y, et al. Topic review: application of Raman spectroscopy characterization in micro/nano-machining. Micromachines, 2018, 9, 361 doi: 10.3390/mi9070361
[15]	Li H, Cui C, Bian S, et al. Double-sided and single-sided polished 6H-SiC wafers with subsurface damage layer studied by Mueller matrix ellipsometry. J Appl Phys, 2020, 128, 235304 doi: 10.1063/5.0026124
[16]	Yin J, Bai Q, Zhang B. Methods for detection of subsurface damage: a review. Chin J Mech Eng, 2018, 31, 41 doi: 10.1186/s10033-018-0229-2
[17]	Wu L, Yu B, Zhang P, et al. Rapid identification of ultrathin amorphous damage on monocrystalline silicon surface. Phys Chem Chem Phys, 2020, 22, 12987 doi: 10.1039/D0CP01370F
[18]	Gao S, Kang R, Guo D, et al. Study on the subsurface damage distribution of the silicon wafer ground by diamond wheel. Adv Mat Res, 2010, 126–128, 113 doi: 10.4028/www.scientific.net/AMR.126-128.113
[19]	Zhou P, Xu S, Wang Z, et al. A load identification method for the grinding damage induced stress (GDIS) distribution in silicon wafers. Int J Mach Tools Manuf, 2016, 107, 1 doi: 10.1016/j.ijmachtools.2016.04.010
[20]	Sekhar H, Fukuda T, Kida Y, et al. The impact of damage etching on fracture strength of diamond wire sawn monocrystalline silicon wafers for photovoltaics use. Jpn J Appl Phys, 2018, 57, 126501 doi: 10.7567/JJAP.57.126501
[21]	Luo H, Li J, Yang G, et al. Electronic and optical properties of threading dislocations in n-type 4H-SiC. ACS Appl Electron Mater, 2022, 4, 1678 doi: 10.1021/acsaelm.1c01330
[22]	Liu J, Liu J, Liu C, et al. 3D dark-field confocal microscopy for subsurface defects detection. Opt Lett, 2020, 45(3), 660 doi: 10.1364/OL.384487
[23]	Youtsey C, Romano L T, Adesida I. Gallium nitride whiskers formed by selective photoenhanced wet etching of dislocations. Appl Phys Lett, 1998, 73(6), 10 doi: 10.1063/1.122005
[24]	Weyher J L, van Dorp D H, Kelly J J. Principles of electroless photoetching of non-uniformly doped GaN: kinetics and defect revealing. J Cryst Growth, 2015, 430, 21 doi: 10.1016/j.jcrysgro.2015.08.003
[25]	Lazar S, Weyher J L, Macht L, et al. Nanopipes in GaN: photo-etching and TEM study. Eur Phys J Appl Phys, 2004, 27, 275 doi: 10.1051/epjap:2004047
[26]	Weyher J L, Lazar S, Borysiuk J, et al. Defect-selective etching of SiC. Phys Stat Sol A, 2005, 202(4), 578 doi: 10.1002/pssa.200460432
[27]	Weyher J L. Defect sensitive etching of nitrides: appraisal of methods. Cryst Res Technol, 2012, 47(3), 333 doi: 10.1002/crat.201100421
[28]	Weyher J L, Smalc-Koziorowska J, Bańkowska M, et al. Photo-etching of GaN: revealing nano-scale non-homogeneities. J Cryst Growth, 2015, 426, 153 doi: 10.1016/j.jcrysgro.2015.05.031
[29]	Macht L, Kelly J J, Weyher J L, et al. An electrochemical study of photoetching of heteroepitaxial GaN: kinetics and morphology. J Cryst Growth, 2005, 273, 347 doi: 10.1016/j.jcrysgro.2004.09.029
[30]	Van Dorp D H, Weyher J L, Kelly J J. Anodic etching of SiC in alkaline solutions. J Micromech Microeng, 2007, 17, 50 doi: 10.1088/0960-1317/17/1/007
[31]	Harima H, Nakashima S, Uemura T. Raman scattering from anisotropic LO-phonon-plasmon-coupled mode in n-type 4H- and 6H-SiC. J Appl Phys, 1995, 78, 1996 doi: 10.1063/1.360174
[32]	Mahadik N A, Stahlbush R E, Qadri S B, et al. Structure and morphology of inclusions in 4 offcut 4H-SiC epitaxial layers. J Electron Mater, 2011, 40(4), 413 doi: 10.1007/s11664-011-1570-8
[33]	Katsuno M, Ohtani N, Takahashi J, et al. Mechanism of molten KOH etching of SiC single crystals: comparative study with thermal oxidation. Jpn J Appl Phys, 1999, 38, 4661 doi: 10.1143/JJAP.38.4661
[34]	Gao Y, Zhang Z, Bondokov R, et al. The effect of doping concentration and conductivity type on preferential etching of 4H-SiC by molten KOH. MRS Online Proceedings Library, 2004, 815, 6
[35]	Zhu B, Zhao D, Zhao H. A study of deformation behavior and phase transformation in 4H-SiC during nanoindentation process via molecular dynamics simulation. Ceram Int, 2019, 45, 5150 doi: 10.1016/j.ceramint.2018.10.261

Fig. 1. (Color online) (a) AFM image of the CMP-treated 4H-SiC wafer, (b) distribution and (c) density of defects of the CMP-treated 4H-SiC wafer, and (d) DIC and UV-PL images of the same PL-Black defect site [the black box in (b)] of the Si-face of the CMP-treated 4H-SiC wafer.

DownLoad: Full-Size Img PowerPoint

Fig. 2. (Color online) (a) Schematic diagram showing the setup of the photo-chemical etching of 4H-SiC. (b) The current of 4H-SiC during the photo-chemical etching under the UV and sunlight illumination.

DownLoad: Full-Size Img PowerPoint

Fig. 3. (a) Differential interference contrast (DIC) optical microscopy image, (b) SEM image, (c) AFM image, and (d) height of the ridge-like defect in the photo-chemically etched Si-face of 4H-SiC.

DownLoad: Full-Size Img PowerPoint

Fig. 4. (Color online) (a) Optical microscopy image, (b) Raman spectra, and Raman mappings based on the intensity of peaks located at (c) 204, (d) 776, and (e) 984 cm^–1 across the ridge-like defect in the photo-chemically etched Si-face of 4H-SiC.

DownLoad: Full-Size Img PowerPoint

Fig. 5. (Color online) (a) Schematic diagram of molten-KOH etching of the photo-chemically etched Si-face of 4H-SiC. (b, c) DIC images obtained with the molten-KOH etching with 3 and 30 min, respectively. The insets show the local SEM images in the red dotted boxes.

DownLoad: Full-Size Img PowerPoint

Fig. 6. (Color online) Cross-section schematic diagrams showing the Si-face of 4H-SiC after the (a) fine-lapping, (b) CMP, (c) photo-chemical etching and (d) molten-KOH etching.

DownLoad: Full-Size Img PowerPoint

[1]	Huang R, Tao Y, Bai S, et al. Design and fabrication of a 3.3 kV 4H-SiC MOSFET. J Semiconduct, 2015, 36, 094002 doi: 10.1088/1674-4926/36/9/094002
[2]	Chatterjee A, Stevenson P, Franceschi S D, et al. Semiconductor qubits in practice. Nat Rev Phys, 2021, 3, 157 doi: 10.1038/s42254-021-00283-9
[3]	Gao F, Weber W J. Mechanical properties and elastic constants due to damage accumulation and amorphization in SiC. Phys Rev B, 2004, 69, 224108 doi: 10.1103/PhysRevB.69.224108
[4]	Liu X, Zhang J, Xu B, et al. Deformation of 4H-SiC: the role of dopants. Appl Phys Lett, 2022, 120, 052105 doi: 10.1063/5.0083882
[5]	Wang W, Zhang B, Shi Y, et al. Improvement in chemical mechanical polishing of 4H-SiC wafer by activating persulfate through the synergistic effect of UV and TiO₂. J Mater Process Tech, 2021, 295, 117150 doi: 10.1016/j.jmatprotec.2021.117150
[6]	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. Mater Sci Forum, 2014, 778–780, 398 doi: 10.4028/www.scientific.net/MSF.778-780.398
[7]	Sasaki M, Matsuhata H, Tamura K, et al. Synchrotron X-Ray topography analysis of local damage occurring during polishing of 4H-SiC wafers. Jpn J Appl Phys, 2015, 54, 091301 doi: 10.7567/JJAP.54.091301
[8]	Zhang Z, Cai H, Gan D, et al. A new method to characterize underlying scratches on SiC wafers. CrystEngComm, 2019, 21, 1200 doi: 10.1039/C8CE01700J
[9]	Zhang Y, Zhang L, Chen K, et al. Rapid subsurface damage detection of SiC using inductivity coupled plasma. Int J Extrem Manuf, 2021, 3, 035202 doi: 10.1088/2631-7990/abff34
[10]	Dudley M, Zhang N, Zhang Y, et al. Nucleation of c-axis screw dislocations at substrate surface damage during 4H-silicon carbide homo-epitaxy. Mater Sci Forum, 2010, 645–648, 295 doi: 10.4028/www.scientific.net/MSF.645-648.295
[11]	Ashida K, Dojima D, Torimi S, et al. Rearrangement of surface structure of 4° off-axis 4H-SiC (0001) epitaxial wafer by high temperature annealing in Si/Ar ambient. Mater Sci Forum, 2018, 924, 249 doi: 10.4028/www.scientific.net/MSF.924.249
[12]	Ashida K, Dojima D, Kutsuma Y, et al. Evaluation of polishing-induced subsurface damage of 4H-SiC (0001) by cross-sectional electron backscattered diffraction and synchrotron x-ray micro-diffraction. MRS Adv, 2016, 1, 3697 doi: 10.1557/adv.2016.433
[13]	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 Appl Phys, 2016, 119, 135702 doi: 10.1063/1.4945017
[14]	Xu Z, He Z, Song Y, et al. Topic review: application of Raman spectroscopy characterization in micro/nano-machining. Micromachines, 2018, 9, 361 doi: 10.3390/mi9070361
[15]	Li H, Cui C, Bian S, et al. Double-sided and single-sided polished 6H-SiC wafers with subsurface damage layer studied by Mueller matrix ellipsometry. J Appl Phys, 2020, 128, 235304 doi: 10.1063/5.0026124
[16]	Yin J, Bai Q, Zhang B. Methods for detection of subsurface damage: a review. Chin J Mech Eng, 2018, 31, 41 doi: 10.1186/s10033-018-0229-2
[17]	Wu L, Yu B, Zhang P, et al. Rapid identification of ultrathin amorphous damage on monocrystalline silicon surface. Phys Chem Chem Phys, 2020, 22, 12987 doi: 10.1039/D0CP01370F
[18]	Gao S, Kang R, Guo D, et al. Study on the subsurface damage distribution of the silicon wafer ground by diamond wheel. Adv Mat Res, 2010, 126–128, 113 doi: 10.4028/www.scientific.net/AMR.126-128.113
[19]	Zhou P, Xu S, Wang Z, et al. A load identification method for the grinding damage induced stress (GDIS) distribution in silicon wafers. Int J Mach Tools Manuf, 2016, 107, 1 doi: 10.1016/j.ijmachtools.2016.04.010
[20]	Sekhar H, Fukuda T, Kida Y, et al. The impact of damage etching on fracture strength of diamond wire sawn monocrystalline silicon wafers for photovoltaics use. Jpn J Appl Phys, 2018, 57, 126501 doi: 10.7567/JJAP.57.126501
[21]	Luo H, Li J, Yang G, et al. Electronic and optical properties of threading dislocations in n-type 4H-SiC. ACS Appl Electron Mater, 2022, 4, 1678 doi: 10.1021/acsaelm.1c01330
[22]	Liu J, Liu J, Liu C, et al. 3D dark-field confocal microscopy for subsurface defects detection. Opt Lett, 2020, 45(3), 660 doi: 10.1364/OL.384487
[23]	Youtsey C, Romano L T, Adesida I. Gallium nitride whiskers formed by selective photoenhanced wet etching of dislocations. Appl Phys Lett, 1998, 73(6), 10 doi: 10.1063/1.122005
[24]	Weyher J L, van Dorp D H, Kelly J J. Principles of electroless photoetching of non-uniformly doped GaN: kinetics and defect revealing. J Cryst Growth, 2015, 430, 21 doi: 10.1016/j.jcrysgro.2015.08.003
[25]	Lazar S, Weyher J L, Macht L, et al. Nanopipes in GaN: photo-etching and TEM study. Eur Phys J Appl Phys, 2004, 27, 275 doi: 10.1051/epjap:2004047
[26]	Weyher J L, Lazar S, Borysiuk J, et al. Defect-selective etching of SiC. Phys Stat Sol A, 2005, 202(4), 578 doi: 10.1002/pssa.200460432
[27]	Weyher J L. Defect sensitive etching of nitrides: appraisal of methods. Cryst Res Technol, 2012, 47(3), 333 doi: 10.1002/crat.201100421
[28]	Weyher J L, Smalc-Koziorowska J, Bańkowska M, et al. Photo-etching of GaN: revealing nano-scale non-homogeneities. J Cryst Growth, 2015, 426, 153 doi: 10.1016/j.jcrysgro.2015.05.031
[29]	Macht L, Kelly J J, Weyher J L, et al. An electrochemical study of photoetching of heteroepitaxial GaN: kinetics and morphology. J Cryst Growth, 2005, 273, 347 doi: 10.1016/j.jcrysgro.2004.09.029
[30]	Van Dorp D H, Weyher J L, Kelly J J. Anodic etching of SiC in alkaline solutions. J Micromech Microeng, 2007, 17, 50 doi: 10.1088/0960-1317/17/1/007
[31]	Harima H, Nakashima S, Uemura T. Raman scattering from anisotropic LO-phonon-plasmon-coupled mode in n-type 4H- and 6H-SiC. J Appl Phys, 1995, 78, 1996 doi: 10.1063/1.360174
[32]	Mahadik N A, Stahlbush R E, Qadri S B, et al. Structure and morphology of inclusions in 4 offcut 4H-SiC epitaxial layers. J Electron Mater, 2011, 40(4), 413 doi: 10.1007/s11664-011-1570-8
[33]	Katsuno M, Ohtani N, Takahashi J, et al. Mechanism of molten KOH etching of SiC single crystals: comparative study with thermal oxidation. Jpn J Appl Phys, 1999, 38, 4661 doi: 10.1143/JJAP.38.4661
[34]	Gao Y, Zhang Z, Bondokov R, et al. The effect of doping concentration and conductivity type on preferential etching of 4H-SiC by molten KOH. MRS Online Proceedings Library, 2004, 815, 6
[35]	Zhu B, Zhao D, Zhao H. A study of deformation behavior and phase transformation in 4H-SiC during nanoindentation process via molecular dynamics simulation. Ceram Int, 2019, 45, 5150 doi: 10.1016/j.ceramint.2018.10.261

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Received: 26 March 2022 Revised: 20 April 2022 Online: Uncorrected proof: 24 June 2022Published: 01 October 2022

Article Navigation > Journal of Semiconductors > 2022 > 43(10): 102801

Wenhao Geng, Guang Yang, Xuqing Zhang, Xi Zhang, Yazhe Wang, Lihui Song, Penglei Chen, Yiqiang Zhang, Xiaodong Pi, Deren Yang, Rong Wang. 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. doi: 10.1088/1674-4926/43/10/102801 ****W H Geng, G Yang, X Q Zhang, X Zhang, Y Z Wang, L H Song, P L Chen, Y Q Zhang, X D Pi, D R Yang, R Wang. Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching[J]. J. Semicond, 2022, 43(10): 102801. doi: 10.1088/1674-4926/43/10/102801

Citation:

W H Geng, G Yang, X Q Zhang, X Zhang, Y Z Wang, L H Song, P L Chen, Y Q Zhang, X D Pi, D R Yang, R Wang. Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching[J]. J. Semicond, 2022, 43(10): 102801. doi: 10.1088/1674-4926/43/10/102801

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Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

DOI: 10.1088/1674-4926/43/10/102801

Wenhao Geng^{1, 2},
Guang Yang³,
Xuqing Zhang^{1, 2},
Xi Zhang²,
Yazhe Wang²,
Lihui Song²,
Penglei Chen²,
Yiqiang Zhang⁴,
Xiaodong Pi^{1, 2,},
Deren Yang^{1, 2},
Rong Wang^{1, 2,}

1.
State Key Laboratory of Silicon Materials & School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
2.
Institute of Advanced Semiconductors & Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices, Hangzhou Innovation Center, Zhejiang University, Hangzhou 311200, China
3.
Key Laboratory of Optical Field Manipulation of Zhejiang Province, Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China
4.
School of Materials Science and Engineering & College of Chemistry, Zhengzhou University, Zhengzhou 450001, China

More Information

Wenhao Geng：obtained his Ph.D. at University of Chinese Academy of Sciences in 2021. Currently he is a postdoc in Hangzhou Innovation Center of Zhejiang University. His research focuses on the origin and evolution of defects in semiconductor materials
Xiaodong Pi：received his Ph.D. degree at the University of Bath in 2004. He then carried out research at McMaster University and the University of Minnesota at Twin Cities. He joined Zhejiang University as an associate professor in 2008. He is now a professor in the State Key Laboratory of Silicon Materials, the School of Materials Science and Engineering and Hangzhou Innovation Center at Zhejiang University. His research mainly concerns group IV semiconductor materials and devices
Deren Yang：is an academician of Chinese Academy of Science, President of NingboTech University, director of Faculty of Engineering at Zhejiang University and chief scientist of Hangzhou Innovation Center of Zhejiang University. He received his Ph.D. in 1991, at Zhejiang University. In 1990s, he worked in Japan, Germany, and Sweden for several years as a visiting researcher. He has been engaged in research on silicon materials for microelectronic devices, solar cells, and nanodevices
Rong Wang：received her Ph.D. degree at Zhejiang University in 2014. She then carried out research at Taiyuan University of Technology and China Academy of Engineering Physics. She joined Hangzhou Innovation Center of Zhejiang University in 2020. Her research mainly focuses on wide-bandgap semiconductor physics
Corresponding author: xdpi@zju.edu.cn; rong_wang@zju.edu.cn
Received Date: 2022-03-26
Revised Date: 2022-04-20

Available Online: 2022-06-24

Abstract

Abstract

In this work, we propose to reveal the subsurface damage (SSD) of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching. Under UV illumination, SSD acts as a photoluminescence-black defect. The selective photo-chemical etching reveals SSD as the ridge-like defect. It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion. The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines, which are typical features of scratches. This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers. SSD is incorporated into 4H-SiC wafers during the lapping, rather than the chemical mechanical polishing (CMP).
- 4H-SiC,
- subsurface damages,
- photo-chemical etching,
- molten-alkali etching

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References(35)

References

[1]	Huang R, Tao Y, Bai S, et al. Design and fabrication of a 3.3 kV 4H-SiC MOSFET. J Semiconduct, 2015, 36, 094002 doi: 10.1088/1674-4926/36/9/094002
[2]	Chatterjee A, Stevenson P, Franceschi S D, et al. Semiconductor qubits in practice. Nat Rev Phys, 2021, 3, 157 doi: 10.1038/s42254-021-00283-9
[3]	Gao F, Weber W J. Mechanical properties and elastic constants due to damage accumulation and amorphization in SiC. Phys Rev B, 2004, 69, 224108 doi: 10.1103/PhysRevB.69.224108
[4]	Liu X, Zhang J, Xu B, et al. Deformation of 4H-SiC: the role of dopants. Appl Phys Lett, 2022, 120, 052105 doi: 10.1063/5.0083882
[5]	Wang W, Zhang B, Shi Y, et al. Improvement in chemical mechanical polishing of 4H-SiC wafer by activating persulfate through the synergistic effect of UV and TiO₂. J Mater Process Tech, 2021, 295, 117150 doi: 10.1016/j.jmatprotec.2021.117150
[6]	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. Mater Sci Forum, 2014, 778–780, 398 doi: 10.4028/www.scientific.net/MSF.778-780.398
[7]	Sasaki M, Matsuhata H, Tamura K, et al. Synchrotron X-Ray topography analysis of local damage occurring during polishing of 4H-SiC wafers. Jpn J Appl Phys, 2015, 54, 091301 doi: 10.7567/JJAP.54.091301
[8]	Zhang Z, Cai H, Gan D, et al. A new method to characterize underlying scratches on SiC wafers. CrystEngComm, 2019, 21, 1200 doi: 10.1039/C8CE01700J
[9]	Zhang Y, Zhang L, Chen K, et al. Rapid subsurface damage detection of SiC using inductivity coupled plasma. Int J Extrem Manuf, 2021, 3, 035202 doi: 10.1088/2631-7990/abff34
[10]	Dudley M, Zhang N, Zhang Y, et al. Nucleation of c-axis screw dislocations at substrate surface damage during 4H-silicon carbide homo-epitaxy. Mater Sci Forum, 2010, 645–648, 295 doi: 10.4028/www.scientific.net/MSF.645-648.295
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Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

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Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

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Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

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Identification of subsurface damage of 4H-SiC wafers by combining photo-chemical etching and molten-alkali etching

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