晶格畸变检测仪研究碳化硅晶片中位错缺陷分布

利用晶格畸变检测仪研究了SiC晶片位错分布情况,通过对熔融KOH腐蚀后的SiC晶片进行全片或局部扫描,从而得到完整SiC晶片或局部区域的位错分布。与LEXT OLS4000 3D激光共聚焦显微镜扫描腐蚀图进行比较,晶格畸变检测仪扫描腐蚀图可以将晶片上位错腐蚀坑信息完全呈现出来,且根据腐蚀坑呈现的颜色及尺寸大小,可以分辨出三种不同类型的穿透型位错,其中黑点腐蚀坑对应螺位错,小尺寸白点腐蚀坑对应刃位错,大尺寸白点腐蚀坑对应混合型位错。采用晶格畸变测试仪研究了4英寸(101.6 mm)N型4H-SiC晶体不同生长时期的位错密度及分布情况,结果表明随着晶体生长,位错密度呈现逐渐降低的趋势,生长后期晶片的总位错密度降为生长前期晶片总位错密度的近1/3,有利于反馈位错缺陷在SiC晶体生长过程中的延伸和转化特性信息,以指导SiC晶体生长工艺改进。

Dislocation Distribution in SiC Wafers Studied by Lattice Distortion Detector

The dislocation distribution of SiC wafers was studied by lattice distortion detector. The dislocation distribution of the whole SiC wafer or a local area was obtained by scanning the SiC wafers etched by molten KOH. Compared with the scanning corrosion mapping of the LEXT OLS4000 3D laser confocal microscope, the scanning corrosion mapping of the lattice distortion detector can fully display the dislocation etch pit information. According to the color and size of the etch pits, three types of threading dislocations were identified, in which black spot corrosion pits correspond to screw dislocations (TSD), small size white spot corrosion pits correspond to edge dislocations (TED), and large size white spot corrosion pits correspond to mixed type dislocations (TMD). The lattice distortion detector was used to study the dislocation density and distribution of 4-inch (101.6 nm) N-type 4H-SiC crystal at different growth stages. The results reveal that as the crystal grows, the dislocation density shows a gradual decrease trend. The total dislocation density of the wafer in the later stage of growth is reduced to nearly 1/3 of the total dislocation density of the wafer in the early stage of growth. TED occupies the largest proportion in the wafer and decreases the fastest during the growth process. TSD and BPD occupy a small proportion in the wafer, and the density gradually decreases. The results of 0004 rocking curves indicate high crystalline quality and virtually flat basal planes. It is helpful to feed back the information of the propagation and transformation characteristics of dislocation defects during the SiC crystal growth process, so as to guide the improvement of the SiC crystal growth process.