Characterization of UHV E-beam Evaporated Low-Stress Thick Silicon Film for MEMS Application

Abstract

Abstract This paper investigates various deposition and subsequent processing conditions on UHV e-beam evaporated silicon to obtain low stress film. They include substrate temperature, deposition rate, annealing, thermal oxidation and post-oxidation annealing. Film stress is measured for each condition and cantilever beams made from the films are released for evaluating stress-gradient. Films are also deposited on sloped step structures to observe step and corner coverage. The results indicate that as-deposited evaporated silicon exhibits tensile stress at substrate temperatures below 400C and compressive stress as substrate temperature is increased above 400C for a 100 nm/min deposition rate. For evaporated amorphous silicon films, performing thermal oxidation at 900C and annealing at elevated temperatures has been found to be effective in reducing film stress. For fully crystallized poly-silicon films, however, annealing at 1000C without thermal oxidation seems to be the more effective way of reducing stress in the film.