Titanium isotropic and anisotropic etching for MEMS applications

Titanium (Ti) exhibits several advantages for the fabrication of biomedical microelectromechanical systems (bio-MEMS), due to its remarkable properties such as good corrosion resistance and biocompatibility. Recent advances in titanium micromachining have made it possible to create such microsystems. Motivated by this opportunity, in this paper we present our efforts to advance Ti MEMS technology through a novel fluorine-based reactive ion etching (RIE) process. Bulk Ti was etched in an inductively coupled plasma using a mixture of sulfur hexafluoride, oxygen, and argon. The RIE process parameters, such as reactive gas flow ratios, total gas flow rate and self-bias voltage, were carefully studied and optimized to achieve fast etch rates for creating titanium trenches of different width. The obtained etching characteristics can be interpreted in terms of competitive effects between simultaneous etching and oxidation of the Ti surface by atomic F and O, respectively.