TEM investigation of silicon carbide wafers with reduced micropipe density

A technique to reduce the micropipe density in SiC substrates by first fill ing 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 surfac e morphology, namely step-bunching due to the off-axis substrate orientatio n. Chemical vapor deposition (CVD) growth experiments on SiC substrates wit h reduced micropipe density using a cold-wall CVD reactor resulted in a sig nificant 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 chara cterized, We have preformed transmission electron microscopy (TEM) measurem ents to evaluate the crystallographic properties of the CVD/LPE and LPE/sub strate interface. It was observed that no new dislocations were nucleated a t the LPE/CVD interface. Although a micropipe was not located in the sample s characterized, a tilt of 1.5 degrees was observed between the LPE layer a nd the substrate. In addition, dislocations were observed to propagate thro ugh the LPE layer from the substrate which are most likely the 1C close-cor e screw dislocations common to SiC hexagonal substrates.