Article
Chemistry, Multidisciplinary
Guanglei Zhong, Xuejian Xie, Desheng Wang, Xinglong Wang, Li Sun, Xianglong Yang, Yan Peng, Xiufang Chen, Xiaobo Hu, Xiangang Xu
Summary: A novel Al doping method using p-type SiC powder was proposed for the growth of p-type SiC crystals. The continuity and utilization rate of Al element were greatly improved by using p-type SiC powder, leading to a significant reduction in resistivity and improvement in resistivity uniformity of the crystals.
Article
Materials Science, Ceramics
Xiaozhe Yang, Xu Yang, Haiyang Gu, Kentaro Kawai, Kenta Arima, Kazuya Yamamura
Summary: This paper proposes a slurryless, highly efficient polishing method called ultrasonic vibration assisted electrochemical mechanical polishing (UAECMP) for achieving subnanometer surface roughness on 4H-SiC wafers. The performance of UAECMP was evaluated and compared to ordinary electrochemical mechanical polishing and mechanical polishing. The results showed that UAECMP achieved a significantly higher material removal rate and that ultrasonic vibration played a crucial role in increasing the anodic oxidation rate. However, increasing the ultrasonic vibration amplitude also led to an increase in surface roughness, suggesting the need for a combined UAECMP and ECMP process.
CERAMICS INTERNATIONAL
(2022)
Article
Materials Science, Ceramics
Xiaozhe Yang, Xu Yang, Zhuangde Jiang, Kazuya Yamamura
Summary: Slurryless electrochemical mechanical polishing (ECMP) is a high-efficiency and high-precision method that can be applied to SiC wafers. In this study, a novel selective ECMP method using porous material impregnated with electrolyte was proposed and verified. The study investigated the effects of porous material pore size, applied voltage, current density, and oxidation time on the selective anodic oxidation performance.
CERAMICS INTERNATIONAL
(2023)
Article
Engineering, Electrical & Electronic
Jiaxu Gao, Tao Ju, Liguo Zhang, Xiang Kan, Rongkun Ji, Wenbo Tang, Dan Fang, Zhipeng Wei, Xuan Zhang, Baoshun Zhang, Zhongming Zeng
Summary: In this work, dislocation etch pits by molten KOH etching in 4H-SiC epilayers doped by ion implantation were characterized. The sizes and shapes of dislocation etch pits were studied in the range of implanted nitrogen concentration from 2 x 1019 cm-3 to 4 x 1019 cm-3 and implanted aluminum concentration from 1 x 1018 cm-3 to 1 x 1019 cm-3. It was found that the etch rates at dislocations followed a trend of n+ < n- < p- ≈ p+ while the threading dislocation etch pits showed the anisotropic etching characteristic of hexagonal shape in all samples. The characteristics of dislocation etch pits in n+-4H-SiC samples were analyzed based on the effect of preferential N occupation at dislocations.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Electrochemistry
Xiaozhe Yang, Xu Yang, Kazuya Yamamura
Summary: The effects of electrolyte type and concentration on anodic oxidation and ECMP of SiC wafers were investigated. The results showed that the anodic oxidation rate is mainly influenced by conductivity, while the type of electrolyte has little effect. The anodic oxidation rate initially increases and then decreases with increasing electrolyte concentration, while the anodic oxidation uniformity of the SiC surface increases. The material removal rate and surface roughness obtained by ECMP both decrease with increasing electrolyte concentration.
ELECTROCHIMICA ACTA
(2024)
Article
Chemistry, Analytical
Peng Li, Julong Yuan, Minghui Zhu, Jianxing Zhou, Binghai Lyu
Summary: In this study, shear rheological polishing was used to improve the polishing efficiency of 4H-SiC wafers by polishing the Si surface. The effects of four critical parameters (abrasive particle size, abrasive particle concentration, polishing speed, and polishing pressure) on the Si surface polishing were analyzed using the Taguchi method. The wear particle size had the most significant influence on the surface roughness, followed by polishing pressure and abrasive concentration.
Article
Engineering, Electrical & Electronic
Fenglin Guo, Chen Shao, Xiufang Chen, Xiejian Xie, Xianglong Yang, Xiaobo Hu, Xiangang Xu
Summary: The technology enhancement of obtaining 4H-SiC wafers with a concave Si face shape has improved the performance of GaN-on-SiC. It is crucial to control the wafer shape in order to maintain the quality of deposited films. The study found that the varying shapes of SiC wafers are caused by surface damage and intrinsic stress, with intrinsic stress being dominant.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2022)
Article
Engineering, Manufacturing
Linfeng Zhang, Dong Lu, Hui Deng
Summary: Electrochemical etching can alter the carrier distribution along the polar plane and cause severe surface oxidation on the Ga-face. The etched surface morphology can be divided into protrusions and pits depending on excessive carrier density, and the pre-etched surface exhibits better ductility and desirable surface quality.
JOURNAL OF MANUFACTURING PROCESSES
(2022)
Article
Electrochemistry
Xiaozhe Yang, Xu Yang, Haiyang Gu, Kentaro Kawai, Kenta Arima, Kazuya Yamamura
Summary: Slurryless electrochemical mechanical polishing is effective for polishing SiC wafers, but the charge utilization efficiency needs to be controlled within a certain range to avoid significant reduction in material removal rate.
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
(2022)
Article
Engineering, Multidisciplinary
Xu Yang, Xiaozhe Yang, Kazufumi Aoki, Kazuya Yamamura
Summary: Silicon carbide (SiC) is a promising semiconductor material for power devices, and slurryless electrochemical mechanical polishing (ECMP) is a promising technology for polishing SiC wafers. This study investigated the ECMP of Si and C faces of 4-inch 4H-SiC wafers, comparing the anodic oxidation property, polishing characteristics, and mechanism. The results showed that two-step slurryless ECMP achieved high precision and efficiency, obtaining Si and C faces with low roughness and peak-to-valley (PV) value less than 2 μm.
PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY
(2023)
Article
Engineering, Electrical & Electronic
Rui Li, Kaimin Zhang, Yi Zhang, Zhenzhen Zhang, Peixuan Ji, Chengqian Shi, Danni Hao, Yipeng Zhang, Ramiro Moro, Yanqing Ma, Lei Ma
Summary: The study investigated the effects of processing parameters on the hydrogen etching of 4H-SiC (0001) and developed a new two-step etching method with a specifically designed crucible, achieving high efficiency in realizing atomically uniform SiC surface morphology with over 70% coverage of the sample surface.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2022)
Article
Physics, Applied
Yuanchao Huang, Rong Wang, Yiqiang Zhang, Deren Yang, Xiaodong Pi
Summary: One of the major challenges of 4H-silicon carbide (4H-SiC) is the difficulty in preparing low resistivity p-type single crystal. This study investigates the compensation of native defects and self-compensation in Al-doped 4H-SiC and finds that V-C(2+) acts as one of the dominant compensating centers. The passivation of V-C(2+) and quenching can effectively enhance the hole concentration of Al-doped 4H-SiC.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Analytical
Gaoling Ma, Shujuan Li, Xu Liu, Xincheng Yin, Zhen Jia, Feilong Liu
Summary: The novel polishing technique combining plasma electrolytic processing and mechanical polishing (PEP-MP) effectively polishes single-crystal 4H-SiC surfaces, resulting in a scratch-free and damage-free surface with reduced roughness. The hardness of the single-crystal 4H-SiC surface is significantly decreased after plasma electrolytic processing, while the material removal rate of PEP-MP is about 21.8 μm/h.
Article
Chemistry, Physical
Fei Cao, Yang-xi Xu, Jin-chi Sui, Xing-ji Li, Jian-qun Yang, Ying Wang
Summary: This paper investigates the electrical and structural properties of Cu/Ti/Al ohmic contacts to p-type 4H-SiC with different annealing temperatures and Cu layer thicknesses. The results show that the Cu/Ti/Al contact forms ohmic contact with a contact resistivity of 1.0×10-4 Ω·cm2 after annealing at 800 degrees C. The surface roughness and number of pits on the sample surface increase with the increase of annealing temperature.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Physical
Xiaozhe Yang, Xu Yang, Kentaro Kawai, Kenta Arima, Kazuya Yamamura
Summary: The study investigated factors affecting the anodic oxidation rate of SiC and found that electrolyte temperature, surface damage, doping concentration, and strain all have a promotional effect on SiC anodic oxidation. The relationship between strain on the SiC surface and anodic oxidation rate was quantitatively studied by a strain-controllable anodic oxidation device, showing that both compressive and tensile strains increase the anodic oxidation rate of SiC. The study is expected to guide the improvement of ECMP efficiency and contribute to its practical application.
APPLIED SURFACE SCIENCE
(2021)