TEM investigation of silicon carbide wafers with reduced micropipe density

A technique to reduce the micropipe density in SiC substrates by first filling in the defects and then growing an LPE layer on the filled material has been developed by TDI. LPE growth in SiC is known to result in poor surface morphology, namely step-bunching due to the off-axis substrate orientation. Chemical vapor deposition (CVD) growth experiments on SiC substrates with reduced micropipe density using a cold-wall CVD reactor resulted in a significant improvement in the surface morphology. Although preliminary device results are encouraging, the exact nature of the filled micropipes nor the impact of growing CVD epitaxial layers on LPE SiC had not been fully characterized. We have preformed transmission electron microscopy (TEM) measurements to evaluate the crystallographic properties of the CVD/LPE and LPE/substrate interface. It was observed that no new dislocations were nucleated at the LPE/CVD interface. Although a micropipe was not located in the samples characterized, a tilt of 1.5° was observed between the LPE layer and the substrate. In addition, dislocations were observed to propagate through the LPE layer from the substrate which are most likely the 1C close-core screw dislocations common to SiC hexagonal substrates.