4H-SiC外延层中BPD向TED转化的深度及分布特征

Depth and Distribution Characteristics of BPD to TED Conversion in 4H-SiC Epitaxial Layers

采用熔融KOH腐蚀法和化学机械抛光技术对低掺杂4H-SiC外延层进行处理,通过共聚焦激光显微镜和偏光显微镜对基晶面位错(BPD)转化为贯穿型刃位错(TED)的过程进行光学表征,对比BPD与TED的腐蚀坑坑壁斜率变化找到转化点,测量了15个BPD-TED转化点的转化深度,发现93%的转化发生在1μm以内的缓冲层中,仅7%发生在1μm以上的漂移层中,并且平均转化深度为0.59μm,表明BPD-TED的转化主要发生在衬底/外延层的交界处,在外延生长初期就已完成转化。BPD-TED的转化研究,对于理解和优化SiC晶体外延生长具有重要意义。

Low-doped 4H-SiC epitaxial layers were treated using molten KOH etching and chemical mechanical polishing techniques.The conversion process of basal plane dislocations(BPDs)into threading edge dislocations(TEDs)was optically characterized by confocal laser microscopy and polarizing microscopy.By comparing the slope variations of BPDs and TEDs etch pits,the conversion points were identified and the conversion depths of 15 BPD-TED conversion points were measured.The results show that 93%of conversion occurs in the buffer layer within 1μm,and only 7%occurs in the drift layer above 1μm,with an average conversion depth of 0.59μm.These findings indicate that the conversion of BPDs to TEDs mainly occurs at the interface between the substrate and the epitaxial layer and is completed at the beginning of the epitaxial growth.This study is of great significance for understanding and optimizing SiC crystal epitaxial growth.