Optimization of diamond nucleation and growth using MW-PACVD method

Abstract

An investigation was initiated to find the optimum process parameters which favour diamond nucleation and subsequent growth. The parameters examined were the reactor pressure, substrate temperature, gas flow rate and methane concentration; each factor was varied gradually in selected ranges. The experiments were carried out according to an optimization method which was developed from orthogonal designs. Using this method the experiments could be performed with a minimum number of tests. An analysis of variance was used to evaluate the results, and the trend of each factor was estimated. The diamond films were deposited on SiC substrates with a gas mixture of CH4H2 using a microwave plasma-enhanced chemical vapour deposition (MW-PACVD) system. A comparison of the results indicates that the conditions for the initial nucleation and film growth of diamond are different. The nucleation density strongly depends on the methane concentration and on the pressure. The growth rate of diamond is influenced mainly by the percentage of CH4. Neither the substrate temperature nor the flow rate has a significant effect on diamond nucleation and growth in the ranges studied.