湿法腐蚀研究PVT法生长的SiC单晶中的位错

Research on Dislocation of SiC Crystal Grown by the PVT Using Wet Etching Technology

采用湿法腐蚀对不同电阻率的4H-SiC衬底进行腐蚀。观察发现，对于同一类型缺陷，低电阻率衬底的缺陷腐蚀坑尺寸比高电阻率衬底的小1～2倍，证明氮元素掺杂的低电阻率SiC衬底的腐蚀速率更低。通过显微镜观察腐蚀后的衬底，对六边形的螺位错（TSD）、近圆形的刃位错（TED）和贝壳形的基平面位错（BPD）腐蚀坑进行了分析。对比了TSD与微管腐蚀坑形貌的区别，虽然两种缺陷腐蚀坑都具有六边形形貌，但微管腐蚀坑尺寸比TSD腐蚀坑大1．4倍左右。通过对位错密度的统计，发现目前4H-SiC衬底中主要的位错为TED和BPD，而TSD密度相对较低，仅为420cm^-2。

4H-SiC substrates with different resisitivity were etched using wet etching method. It is found that the etching pit size of the same type defect in the low-resistivity substrate is about 1 to 2 times smaller than that in the high-resistiviy substrate. This proves that the etching speed of the low-resistivity substrate with N doping is slower than that of the high-resistivity substrate. The hexagonal threading screw dislocation （TSD）, approximately rounded threading edge dislocation （TED）, and scalloped basal plane dislocation （BPD） were analyzed by observing the etched substrates using the microscope. The differences of the TSD and micropipe etching pits were compared. Although both of the TSD and micropipe etching pits exhibit hexagon, the etching pit size of micropipe is about 1.4 times larger than that of the TSD. The dislocation density was calculated by statistic analysis. The TED and BPD are the main dislocations in 4H-SiC substrates, and the TSD density is relatively low with the value of 420 cm-2