Fracture strength and fatigue of polysilicon determined by a novel thermalactuator

A novel thermal actuator for the determination of polysilicon fracture stre ngth and investigation of its fatigue is presented. The actuator consists o f two narrow beams, which expand due to electrical heating, and a cold plat e to which a short fracture beam is attached. Because of its small dimensio ns, the actuator can be used for on-wafer testing, This method is suitable for tensile and compressive material. Using different types of fracture bea ms fracture strengths were compared for uniaxial tension and bending test. Using Weibull statistics, the fracture strength for polysilicon has been fo und to be (2.9 +/- 0.5) GPa in tensile tests and (3.4 +/- 0.5) GPa in bendi ng tests. In fatigue investigations, we observe that fracture strength decr eases slowly with time to 2.2 GPa after 10(6) cycles.