Investigation of E-Beam Evaporated Silicon Film Properties for MEMS Applications

PROJECT TITLE :

Investigation of E-Beam Evaporated Silicon Film Properties for MEMS Applications

ABSTRACT:

This paper investigates the crystallinity, microstructure, surface morphology, stress characteristics, and Young’s Modulus of ultrahigh vacuum (UHV) electron-beam (E-beam) evaporated silicon films with a low thermal budget. The films are evaporated at varied substrate temperatures starting from two hundred °C–625 °C, deposition rates ranging from fifty to four hundred nm/min, and annealed at 60zero °C for numerous durations. Some of the preliminary results were reported by Michael and Kwok. The results indicate that the film characteristics of the evaporated silicon films are significantly completely different from and higher fitted to microelectromechanical systems (MEMS) applications than low pressure chemical vapor deposition silicon films, commonly used for MEMS devices. The terribly attractive properties of UHV E-beam deposited silicon films are remarkably low residual stress (each average and gradient), very swish surface morphology, and thick layers at an occasional thermal budget with fairly large deposition rates. 2 different mechanisms are identified as accountable for initiating the formation of crystal grains in these films: 1) kinetic energy of evaporated silicon atoms; and a pair of) thermal energy from the substrate heating. The primary mechanism leads to fine columnar grains accountable for the graceful surface morphology and simply controllable low stress characteristics. The second mechanism ends up in coarse grain formation with a relatively higher proportion of (111) oriented grains. Cantilever beams of 30- $mu textm$ thickness have been fabricated from such films with rms roughness of <5 nm, residual stress of twenty MPa, and stress gradient of

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