Finite-Element Modeling of Residual Stress in SiC Diaphragms

摘要

Finite-element modeling of the residual stress due to expansion-coefficient mismatch between a 3C-SiC film and Si substrate is presented. The change in residual stress after bulk etching of the silicon substrate to create a suspended diaphragm is also presented. 1, 2, or 3 μm-thick 3C-SiC films are grown at 1600 K on a 100 mm diameter, 500 μm-thick, (100) Si substrate using atmospheric pressure chemical vapor deposition (APCVD) in a cold-wall, vertical-geometry, RF-induction-heated reactor. An axisymmetric, finite-element analysis (FEA) of the cooling and etching process is presented using the ANSYS54 finite-element package. The etching process is modeled by removing the Si elements in the etched region after cooling from film-growth to room temperature. The results show that residual stress in the diaphragm decreases from 3 to 8 percent after etching.