Authors: R.G. DeAnna, J. Mitchell, C.A. Zorman and M. Mehregany
Affilation: U.S. Army Research Laboratory, United States
Pages: 253 - 256
Keywords: silicon carbide, MEMS, ANSYS, membrane, FEM
Finite-element modeling (FEM) of 3C-SiC thin-film membranes on Si substrates was used to determine the residual stress and center deflection with applied pressure. The anisotropic, three-dimensional model includes the entire 3C-SiC membrane and Si substrate with appropriate material properties and boundary conditions. Residual stress due to the thermal-expansion-coefficient mismatch between the 3C-SiC film and Si substrate was included in the model. Both before- and after-etching, residual stresses were calculated. In-plane membrane stress and normal deflection with applied pressure were also calculated. FEM results predict a tensile residual stress of 259 MPa in the 3C-SiC membrane before etching. This decreases to 247 MPa after etching the substrate below the membrane. The residual stress experimentally measured on samples made at Case Western Reserve University was 280 MPa on post-etched membranes. This is excellent agreement when an additional 30-40 MPa of residual stress to account for lattice mismatch is added to the FEM results.