Study Of Homoepitaxial Growth On On-Axis4H-SiC Substrates And Characterication Methods

SiC homoepitaxy is a key process for the growth of device quality layers. Theactive layer of a device is commonly grown on an off-axis4H-SiC substrate with8degrees off-cut typically along the <1120> direction. The use of off-axis substratescan avoid the formation of3C-SiC in epilayers through step-flow growth. But it alsocauses material losses and the replication of basal plane dislocations （BPDs） from thesubstrate into the epilayer. The BPDs are reported to result in degradation of SiCbipolar devices. This thesis mainly focuses on the on-axis homoepitaxial growth on4H-SiC substrates and material characterization.Homoepitaxial growth is performed on3-inch （0001） Si-face on-axis4H-SiCsubstrates using a horizontal hot-wall chemical vapor depositon system. The mainimportant process parameters and growth mechanics are studied. In-situ surfacepreparation, starting growth parameters and growth temperature are found to play avital role to inherit the stacking sequence of the substrate.Several characterization methods are used to investigate the epilayer grown bythe optimal growth process. The eiplayer shows a step surface with a few triangulardefects intersecting in the area close to the edge under the Nomarki contrastmicroscope. The RMS is0.484measured by AFM. The single-crystal SiCpolytypes are characterized by Raman scattering spectroscopy and only1%triangular3C-SiC inclusions are found on the whole3-inch homoepitaxial layer. The FWHW ofrocking curve is58.3aresec measured by X-ray diffraction（XRD）. The dopingconcentration is1.17×10¹⁶cm^-3measured by Hg prob C-V test. Structure defects areinvestigated by molten KOH etching and the result shows that BPDs from thesubstrate into the epilayer are completely eliminated using the on-axis4H-SiChomoepitaxial growth.