Doped polycrystalline 3C-SiC films with low stress for MEMS: part II. Characterization using micromachined structures

Abstract

Surface micromachined resonators, stress pointers and cantilevers were used to characterize nitrogen doped polycrystalline 3C-SiC (poly-SiC) films for their suitability as structural materials for MEMS applications. The films were deposited on 100 mm diameter silicon (Si) and silicon dioxide (SiO2) wafers using dichlorosilane (SiH2Cl2) and acetylene (C2H2) as precursors and ammonia (NH3) as the dopant source gas in a high throughput, low-pressure chemical vapor deposition furnace. The average Young's modulus was found to be 330 GPa for the films with the best combination of resistivity and residual stress. The device level tensile stress and stress gradient measured by stress pointers and cantilevers indicated that the residual tensile stresses were significantly affected by doping gas flow rate and deposition pressure. The best films deposited on SiO2 exhibited an average tensile stress of 74.2 MPa and an average stress gradient of 222 MPa µm−1.