Fracture strength and fatigue of polysilicon determined by a novel thermal actuator [MEMS]

A novel thermal actuator for the determination of polysilicon fracture strength and investigation of its fatigue is presented. The actuator consists of two narrow beams, which expand due to electrical heating, and a cold plate to which a short fracture beam is attached. Because of its small dimensions, the actuator can be used for on-wafer testing. This method is suitable for tensile and compressive material. Using different types of fracture beams fracture strengths were compared for uniaxial tension and bending test. Using Weibull statistics, the fracture strength for polysilicon has been found to be (2.9/spl plusmn/0.5) GPa in tensile tests and (3.4/spl plusmn/0.5) GPa in bending tests. In fatigue investigations, we observe that fracture strength decreases slowly with time to 2.2 GPa after 10/sup 6/ cycles.