Microtrench depth and width of SiON plasma etching

Silicon oxynitride films were etched in a C2F6 inductively coupled plasma. In all experiments, microtrenching occurred at the feet of the profile sidewall. The microtrenching was characterized in terms of maximum depth and width. Each characteristic was examined as a function of the process parameters, including radiofrequency source power, bias power, pressure, and C2F6 flow rate. Apart from the etch mechanisms, relationships between microtrenching and profile angle were also identified. Profile angle variation played an important role in understanding depth variation. The width of microtrenching increased with increasing the source or bias power. In contrast, increasing the C2F6 flow rate decreased the width. Effect of process parameters on microtrenching at various plasma conditions was characterized by using a statistical experimental design. Smaller depths and widths were obtained at lower source and bias powers. The main effect analysis revealed that the bias power had a considerable impact on both characteristics.