Tribological reliability of MEMS multilayered thin films

Tribological behaviours of polysilicon and layered metals/polysilicon microstructures are needed to design reliable microelectromechanical systems (MEMS). Nanomechanical characterisation of bulk materials of polysilicon and thin films of polysilicon/chromium/gold was carried out in this study. Scratch resistance of these materials were measured using a nano test system. The deformation mechanisms of these materials during nanoscratching were found to be strongly dependent on the loading conditions. In the case of constant load, the scratch depth is proportional to the applied load. Nanoscratch tests with linearly ramping loads suggests that two deformation regimes can be defined; an elasto-plastic regime at low loads, and a fully plastic regime at high loads. Abrupt change of the scratch depth for (Au/Cr/P- Si) tri film revealed the existence of unwanted porosities in the deposited metal films.