Fracture analysis of thick plasma-enhanced chemical vapor deposited oxide films for improving the structural integrity of power MEMS

In this paper, we present the characterization of the residual stress and modeling of the fracture behavior of thick silane-based plasma-enhanced chemical vapor deposited oxide films. The motivation for this paper is to elucidate the factors contributing to the fracture of the oxide films and to optimize the fabrication process so as to maintain the structural integrity of power microelectromechanical systems. It is found that the film stresses strongly depend on the processing history. Thermal stress and micropore annihilation are identified as the major mechanisms to control the mechanical behavior of the oxide films. After high temperature annealing, all non-thermal stress mechanisms essentially vanish and the mechanical behaviors are completely dominated by the thermal stress. Finally, linear elastic fracture mechanics is used to explore the relationship between the critical surface flaw size, film thickness, and the crack propagation temperatures. Based on these results, a series of engineering solutions are proposed in order to improve the structural integrity.