Characterization of 6H-SiC surfaces after ion implantation and annealing using positron annihilation spectroscopy and atomic force microscopy

Abstract

Systematic slow positron implantation spectroscopy (SPIS) and atomic force microscopy studies of various 6H-SiC samples are presented to clarify the role of conductivity type, crystal quality, ion implantation (B+,Al+, and N+), and annealing (1.650 °C) in the formation of continuous long furrows running in one direction across the wafer surface. It is found that the observed changes in surface morphology are primarily the result of step bunching during thermal activation and thus occur regardless of conductivity type, crystal quality, and type of ion implantation. On terraces separating the step bunches, stripelike islands with a discrete height in the nanometer range have been observed which may have some link with the ion implantation chosen. SPIS results clearly indicate the formation of vacancy clusters in n-type material which are connected with the mobility of nitrogen in the samples at elevated temperatures. It is found that defect profiling by SPIS is not influenced by the changes in surface morphology observed due to annealing.