Thermally assisted ion beam etching of polytetrafluoroethylene-a new technique for high aspect ratio etching of MEMS

In micromechanics, the etching of high aspect ratio structures in polymers is a prime technology. Normally, oxygen-based reactive ion etching or the LIGA technique are used to achieve this goal. This paper reintroduces a different idea to create deep trenches at high etch speed: the ion beam etching of Teflon. Because of its extraordinary properties the etch selectivity with respect to most other materials is over 1000. A model is proposed to explain the high etch rate and selectivity. Generally, the etching ions are highly energetic and material from different sources is sputtered on top of the sample. The high selectivity, high anisotropy, and sputtering of material are thought to be responsible for the forming of micrograss during etching a sample. Ways are given to decrease or increase this grass. The high potential of this technique will be discussed and applications will be shown. Especially, the use of etched Teflon for direct moulding is believed to become the main use of this technique.