Detection And Analysis Of Defects In 4H-SiC Epitaxial Layer

The defects of the 4H-SiC homoepitaxial material have been detected and analyzed by means of chemical etching and scanning electron microscopy. The objective of the investigation is to determine a reproducible etching technique for 4H-SiC, and characterize the type, distribution, density and other parameters of the defects in 4H-SiC homoepitaxial layer. The main research results are as follows:First, the chemical etching process of 4H-SiC is determined, with which a better observation results could be achieved. The parameters of chemical etching are determined by orthogonal experiment, which include etching temperature of 470℃, etching time of 30min, and etching agent KOH with analytically pure. In this case, the etching technique is reproducible, and etching patterns are clear enough. The purpose of detection of the dislocations is achieved.Second, the etching morphology of TED, TSD, BPD and dislocation arrays formed by TED, BPD are analyzed. It is noted that little lattice distortion is produced by stacking fault and the boundary of stacking fault is partial dislocation. So it is not a good way to detect the existence of stacking fault by chemical etching.Third, the dislocation density is calculated by counting the etching pits. No micropipe is found, indicating that its density has fallen to a relatively low level. The density of TED, TSD and BPD are 2.99×105cm-2, 2.4×103cm-2, 1.13×104cm-2 separately, being consistent with the literatures reported.Characterization method of defects in silicon carbide by chemical etching and optimal process parameters are obtained.