Study On The Method Of Defect Density Control In4H-SiC Epitaxial Growth

Compared with Si, SiC power devices have excellent operating characteristics athigh temperatures, and lower switching losses. As a new generation of low-losscomponents, it is expected to make the power electronic systems much moreminiaturized and efficient. Quality of SiC epitaxial layer directly determines theperformance of SiC power devices, and the defect density is a key parameter incharacterizing the quality of the epitaxial layer. In this paper, we investigated theinfluence of C/Si, growth temperature and pressure on the density of triangle defect,basal plane dislocations, threading screw dislocations and threading edge dislocations.The main results are as follows:(1) Surface defects are effectively reduced with reducing the proportion of carbonatoms in the4H-SiC epitaxial growth process. Reducing the proportion of carbonatoms, will reduce the probability of3C-SiC nucleation. The triangle defect densitydecreases from450.69cm-2to44.6cm-2with C/Si ratio decreased from1.3to1. But thelower C/Si will cause the increase of background doping concentration in epitaxiallayer, which is not conducive to the preparation of high-power devices.(2) The epitaxial surface defects are reduced with the increase the temperature ofthe epitaxial growth because multi-type3C-SiC is difficult to form at the hightemperature. When the temperature increased from1520℃to1600℃, the triangledefect density decreased from107.1cm-2to17.8cm-2.But Severe step-bunching isobserved and the RMS rise to2.224nm when temperature go up to1600℃.(3) The surface defects are reduced at the lower pressure in the epitaxial growthprocess. The abnormal nucleations at the beginning of growth are suppressed becausethe Atoms have lower free energy on the surface under low pressure.When the pressuredecreases from100mbar to40mbar, triangle defect density decreases from75.8cm-2to8.9cm-2.