Materials Science Forum, Vol.457-460, 1523-1526, 2004
Characterization of polycrystalline SiC thin films for MEMS applications using surface micromachined devices
This paper details the characterization of polycrystalline SiC (poly-SiC) thin films using surface micromachined devices. The films were deposited in a large-volume, low-pressure chemical vapor deposition (LPCVD) furnace on 100mm-diameter silicon (Si) wafers using dichlorosilane (SiH2O2) and acetylene (C2H2) as precursors. The lowest average residual stresses across the wafers were obtained for films deposited at 900degreesC, a pressure of 2 torr, and flow rates of SiH2O2 and C2H2 at 35 sccm and 180 sccm (5% in H-2), respectively. Wafer curvature measurements for similar to2 gm-thick films indicated tensile stresses ranging from 4 to 55 MPa across the boat. A variety of micromachined structures including lateral resonant structures, stress pointers and cantilevers were fabricated. The average Young's modulus was found to be 403 GPa. Residual stress measurements were consistent with those obtained using a wafer curvature technique. Interferometric measurements of cantilever beams indicated stress gradients with an upper bound of 52 MPa/mum.