Fabrication of amorphous carbon cantilever structures by isotropic and anisotropic wet etching methods

摘要

free-standing amorphous (a-c) cantilever structures were successfully fabricated by a single photolithography step. The relatively thick( ~ 1 mum), smooth (T_rms ~ 0.75 nm), low stress (<300 MPa) a-C films tha exhibit low friction (< ~0.08) adn wear rate (order of 10~-9 mm~3/Nm) were deposifted by filtered cathodic vacuum are (FCVA) deposition system, in conjunction with high substrate pulse biasing (5KV, 600 Hz and 25mus). The undercutting of the cantilever was carried out, both by isotropic (in a solution mixture fo 40% HF(1 part) and 70% HNO_3 (3 parts)) as well as anisotropic (in 40 wt.%KOH) Si wet etching methods. The study reveals that it is not viable tofabricate perfect free-standing a -C cantilever structure by isotropic wet etching. However, by controlling the etching duration/rate, it is possible to fabricate the as-designed free-standing cantlever structures by anisotropic wet etching method. The SEM imaes of the free-standing a-C cantilever structures do not show any bulging, and which clearly shows that the intrinsic stress in the film is low enough to be used for the fabrication of micro-electro-mechanical system (MEMS) devices, such as micro-motors and gears.