Progress in silicon etching by in-situ dc microplasmas

This paper reports on the etching of Si using spatially confined SF/sub 6/ microplasmas that are generated by applying a DC bias across a metal-polyimide-metal electrode stack patterned on a sample substrate. The typical operating pressure and power density are in the range of 1-20 Torr and 1-10 W/cm/sup 2/, respectively. The plasma confinement can be varied from <100 /spl mu/m to >1 cm by variations in the electrode area, operating pressure, and power. Etch rates of 4-17 /spl mu/m/min have been achieved. The etch rate per unit power density increases with increasing pressure, while the plasma resistance decreases with increasing power density. In a shared anode configuration, which is suitable for small feature sizes, reducing the trench width from 106 /spl mu/m to 6 /spl mu/m reduces the etch rate by 14%. Numerical modeling is used to correlate variations in the local electric fields to measured trends in the etch rate and asymmetry in the etch profile.