Mechanism of temperature-induced plastic deformation of amorphous dielectric films for MEMS applications

This paper presents a microstructure based mechanism which elucidates seams as a source of density change and voids as a source of plastic deformation, accompanied by a viscous flow. This theory was then applied to explain a series of experimental results that are related to thermal cycling as well as annealing of amorphous dielectric films, such as plasma enhanced physical vapor deposited (PECVD) silicon oxide (SiO_x) films, including stress hysteresis generation and reduction and coefficient of thermal expansion changes. In particular, the thickness effect was examined; PECVD SiO_x films with a thickness varying from 1 to 40 μm were studied, as certain demanding applications in MEMS require such thick films serving as heat/electrical insulation layers.