Impurity Removal from 6H-SiC Using Field Enhanced Diffusion by Optical Activation Method

This paper presents results of impurity removal from 6H-SiC wafers. A new chemical reactor has been tested for Field Enhanced Diffusion by Optical Activation (FEDOA) purification (reversed diffusion) of SiC films. Different conditions have been used to purify SiC samples including temperature variation, electrical field variation, variations in electrical current and optical activation. A 5 mW (630-680 nm) laser was used for optical activation. It was observed that optical activation has a major effect on ion drift rates. It was also observed that the magnitude of the electrical current enhanced ion drift rates as well by a postulated current drag mechanism. I-V characteristic curves were obtained to verify changes in the electrical properties of the samples. SIMS was used to analyze the concentrations of impurities in the SiC samples before and after treatment. It has been demonstrated that the field enhanced diffusion by optical activation method can remove impurities such as N and B from SiC films. As a result, the electrical properties of the 6H-SiC wafers have been significantly improved during treatment especially in cases where a laser is emplaced.