Brim Effect of Negative Bias-Enhanced Nucleation of Diamond Film on Silicon Substrate

Diamond nucleation improved by negative bias-enhanced technology on Si (100) substrate has been investigated on a microwave plasma enhanced chemical vapor deposition (MPCVD) apparatus using a gas mixture of methane and hydrogen. The results show that the bias voltage has a significant effect on the uniformity of the nucleation density and the concentration of the methane mainly relevant to the nucleation time. There is an obvious brim effect of the nucleation when the size of the silicon substrate is less than that of the Mo substrate holder. The nucleation density of the side is higher than that of the center on the substrate when the bias voltage is lower than -150 V. The nucleation density of the side decrease significantly with the bias voltage when the bias voltage is lower than -150 V. There are nearly no nuclei on the side of silicon when the bias voltage is -200 V. This effect may be contributed to the electron emission of the diamond on Mo substrate holder. The concentration of the methane has little effect on the nucleation density at a fixed bias voltage. Increasing the methane concentration is useful for decreasing the nucleation time.