Improvement of process parameters for polycrystalline silicon carbide low pressure chemical vapor deposition on 150 mm silicon substrate using monomethylsilane as precursor

摘要

This work shows a systematic approach using design of experiments (DoE) for the integration of the deposition process for polycrystalline 3C-SiC from 100 mm to 150 mm wafers in a vertical low pressure chemical vapor deposition furnace. The approach aims at developing n-doped SiC thin films on silicon substrates with low stress and low resistivity showing high uniformity of growth rate across boat and wafer. The 3C-SiC films are prepared using monomethylsilane (MMS) as the main precursor, dichlorosilane (DCS) as an additional Si source, ammonia (NH_3) as dopant and hydrogen (H_2) as diluting gas. The experimental parameters are temperature, pressure, DCS flow and NH3 flow. Flow rates of MMS and H_2 are kept constant, resulting in a two factorial DoE approach of 16 experiments. The analyzed response parameters are thickness, stress, and resistivity, including the thickness uniformity across boat and wafer. A strong influence of NH_3 (dopant) is found on the deposition rate, resistivity and stress of the film. Increasing the NH_3 flow from 1 to 2 sccm leads to a decrease in the deposition rate by a factor of three. The improved 3C-SiC film with the intended parameters obtained within the experiments showed a resistivity as low as 75 mΩ cm and a low stress of 306 MPa with the lowest deposition temperature of 775 ℃.