Annealing temperature dependent strength of polysilicon measured using a novel tensile test structure

Polysilicon is commonly used as a structural material of MEMS after being deposited at a temperature below 600/spl deg/C and annealed at a temperature around 1000/spl deg/C to remove the residual stress. On the other hand, polysilicon can be also deposited at a temperature higher than 600/spl deg/C. We have examined the strength of polysilicon films obtained with different processing temperatures using a new efficient tensile test structure with plural specimens bridging the gap of a silicon substrate. Films deposited at 560/spl deg/C had the highest strength when annealed at 850/spl deg/C. Films deposited at 625/spl deg/C and annealed at 1050/spl deg/C were weaker than those deposited at 560/spl deg/C and annealed at 1050/spl deg/C.