In situ bias current monitoring of nucleation for epitaxial diamonds on 3C-SiC/Si substrates

Heteroepitaxial diamond on Si substrates can offer large-area, low-cost diamond wafers for many practical applications. Bias-enhanced nucleation (BEN) has been shown to be one of the best process methods for diamond heteroepitaxy. However, the precise control of the nucleation is difficult because the optimized nucleation time is sensitive to both plasma and substrate conditions. In this study, we performed in situ monitoring for epitaxial diamond nucleation on 3C-SiC/Si substrates that detected the bias current during the BEN process. The bias current was found to decrease at the beginning of the BEN process and then increase during diamond formation. An increase in the bias current of 10% led to epitaxial diamond nucleation with a nucleation density of 10(10) cm(-2). We found from an analytical model that the nucleation occurs at a constant rate in this region. Similar characteristics were obtained on both (001)- and (111)-oriented substrates. This technique was based on the difference between the secondary electron emission coefficient of diamond and that of the material underneath. Thus, this method would be applicable to optimizing the epitaxial diamond nucleation on other substrates or buffer layers in addition to the 3C-SiC/Si studies here.