Analysis of Residual Stress Gradient in MEMS Multi-layer Structure

Abstract

Residual stress and its gradient through the thickness are among the most important properties of as-deposited films. Recently, a new mechanism based on a revised Thomas-Fermi-Dirac (TFD) model was proposed for the origin of intrinsic stress in solid films, giving the first order approximation of the stress gradient. The electron density at the boundary of the atoms (EDBA) defined by TFD model is taken as a dominating parameter inducing the stress. This paper applies the TFD model to multi-layer case, which is a typical structure in MEMS devices. The theoretical calculations suggest possibilities to control and reduce the residual stress.