Deep plasma etching of piezoelectric PZT with SF6

Reactive ion etching with sulfur hexafluoride (SF6) gas has been employed to create deep structures in bulk samples of the piezoelectric material lead zirconate titanate, Pb(Zr,Ti)O-3 (PZT). SF6 is chosen for compatibility with dry etching, of silicon with a possibility for production of hybrid silicon-piezoelectric devices. Thick photoresist layers have been used to pattern PZT to a depth of 2 mum at a rate of 120 nm min(-1). The use of more durable nickel masks, formed by electroplating through the thick resist, leads to structures greater than 100 mum in height, with an average sidewall angle of similar to72degrees. The profile of the deep PZT structures is seen to depend on etch duration and the spacing; of structures, attributed to the redeposition of mask and etch products, respectively. The addition of nitrogen and argon to the SF6 plasma is shown to produce small improvements in the profiles. By combining gas addition with heating of the substrate PZT etch rates up to 200 nm min(-1) have been obtained. (C) 2001 American Vacuum Society.