Plasma Etching of Deep High-Aspect Ratio Features Into Silicon Carbide

This paper reports research performed on developing and optimizing a process recipe for the plasma etching of deep high-aspect ratio features into silicon carbide (SiC) material using an inductively-coupled plasma reactive-ion etch process. We performed a design of experiments (DOE) wherein the etch recipe parameters having the most impact on the etch process were varied over fixed ranges of predetermined values, while the other etch recipe process parameters were unchanged. Subsequently, the etched samples were analyzed so as to quantify the etch outcomes. Using the experimental data collected during the DOE, we then performed multiple regression analysis on this data to determine optimal etch tool parameters in order to achieve desired etch results. We have demonstrated the ability to etch very deep features into silicon carbide of more than 150 microns, having nearly vertical sidewalls and with aspect ratios of over 12 to 1 using the optimized etch process. The ability to fabricate deep high-aspect ratio features into SiC has important implications for a number of micro-electro-mechanical applications, particularly those involving harsh environments. The etch technology developments presented herein are applicable to SiC substrates and material layers in crystalline form, as well as to SiC in polycrystalline or amorphous forms.