Anisotropic inductively coupled plasma etching of silicon with pure SF 6

Abstract

A conventional reactive ion etching (RIE) system was modified into an inductively coupled plasma (ICP)-like reactor by inserting a planar aluminium coil into the reactor chamber. In this way, RF power can be applied independently to this antenna and to the lower electrode. Monocrystalline silicon was etched in this reactor with pure SF 6 plasmas at 10 m Torr pressure. The etch rate increases with SF 6 flow in the 2–6 sccm flow range. When applying RF power to the antenna, the silicon etch rate increases, for some processes by more than 100%, when compared to the ordinary RIE processes. At the same time, the anisotropy of the etching increases, probably due to an increased polymerisation. If no power is applied to the coil, the etch rate is 0.4 μm/min, and the anisotropy is 0.45. Applying 200 W of power to the coil, increases the etch rate to 1.4 μm/min and the anisotropy to more than 0.9. These characteristics make this process interesting for microelectronic and micromechanical applications.