Surface Modification and High-Resolution Nondistractive Analysis toward Dislocation-free SiC Growth

对无位错碳化硅（SiC）生长进行了表面改性和高分辨率无损分析。用电子束感应电流（EBIC）方法对生长层中的晶体缺陷进行了非破坏性观察。由于SiC晶片的缺陷密度超过10000 cm ^-2，因此很难检测出其晶体缺陷。为了获得高分辨率的EBIC映射图像，检查了电子束的加速电压和EBIC信号的收集肖特基电极的金属。在10 kV加速电压和镍电极下，获得了0.5μm高分辨率的清晰EBIC图像。根据EBIC信号的变化，讨论了SiC中晶体缺陷的行为。在外延层与衬底界面处，一些向[11-20]方向延伸的基面位错被分解为穿线位错。本文认为，在外延生长过程中，表面改性（处理）氦可以转化SiC中的位错。在氯气和氧气的混合气体中，采用热腐蚀方法对SiC表面进行了改性。4 H型SiC（0001）Si面在950℃时的典型刻蚀速率为0.5μm/h。腐蚀坑的形状是一个扭曲的六边形，和晶体缺陷的种类，如螺旋，边缘和基面位错可以很容易地分类由腐蚀坑的大小。通过使用表面改性的SiC衬底，减少了外延层中的基面位错。

Surface modification and high-resolution nondestructive analysis toward dislocation-free silicon carbide (SiC) growth were carried out. Crystal defects in grown layers were observed nondestructively by an electron beam induced current (EBIC) method. It is difficult to detect crystal defects in commercially available SiC wafers due to the high defect density over 10000cm^-2. To obtain a high resolution EBIC mapping image, an accelerating voltage of the electron beam and the metal of collection Schottky electrode of an EBIC signal were examined. The clear mapping EBIC image with a high resolution of 0.5μm was realized at the accelerating voltage of 10kV and the nickel electrode. In addition, behaviors of crystal defects in SiC were discussed based on the change of EBIC signals. Some basal-plane dislocations extended to the [11-20] direction were resolved to the threading dislocations at the interface between the epilayer and wafer substrate. It is considered that the dislocations in SiC can be converted by the surface modification (treatment) helium the epitaxial growth. SiC surfaces were modified by a thermal etching method in a mixed gas of chlorine and oxygen. A typical etching rate of a 4H-type SiC (0001) Si face was 0.5μm/h at 950℃ Many pits appeared after the modification, and they were corresponding to the crystal defects. A shape of the etch pits was a distorted hexagon, and the kind of crystal defects such as screw, edge and basal-plane dislocations could be classified easily by the size of etch pits. Basal-plane dislocations in the epilayer were reduced by the use of surface modified SiC substrate.