Scanning capacitance microscopy investigations of SiC structures

Abstract

We have applied scanning capacitance microscopy (SCM) to investigate SiC structures grown by vapour-phase epitaxy. The SCM technique is evaluated using n- and p-type doping staircase structures with doping concentrations ranging from 1016 to 1020cm−3. The n- and p-type doping was obtained by doping SiC with nitrogen and aluminium, respectively. The sample cross-sections for SCM were obtained by simple cleaving. For doping levels above 1017cm−3 the SCM data are consistent with doping data obtained independently from secondary ion mass spectroscopy (SIMS). Treating the samples with diluted hydrofluoric acid significantly improves the SCM signal for the low-doped regions. The SCM technique has been used to investigate doping redistribution in patterned regrowth of n- and p-type SiC around dry-etched mesas. In both cases, contrast variations were seen close to the mesa walls, indicative of doping variations; lower and higher incorporation for p- and n-type, respectively. The observations are shown to be consistent with the expected trends in dopant incorporation in the SiC material.