Evaporated Thick Polysilicon Film With Low Stress and Low Thermal Budget

Abstract

In this letter, we report on the use of e-beam evaporation under ultrahigh vacuum conditions to deposit smooth, low stress, and thick polysilicon films for low thermal budget applications. The film stress, surface morphology, and crystallographic characteristics have been investigated at various deposition temperatures, deposition rates, and annealing temperatures. Cantilever beams formed from such films have been released and characterized for the stress gradient and Young's modulus. The results show that crystallized grains start forming in the evaporated films below 400°C substrate temperatures and the stress levels in the film can be easily controlled and minimized. Residual stress of 20 MPa and a stress gradient of only 1.6 MPa/μm have been obtained for a 10 μm film deposited at 500°C and annealed at 600°C.