Fabrication and characterization of U-shaped beams for the determination of Young's modulus modification due to Joule heating of polysilicon microstructures

The modification of Young's modulus is determined before and after the Joule heating generated by a current passing through polysilicon microstructures. U-shaped overhanging polysilicon beams are specially designed and fabricated to prevent both the heat transfer to substrate and the deformation by thermal expansion. The Joule heating is performed to the beams by applying a current of 5 to approximately 20 mA for 5 to approximately 10 seconds. The measured resonant frequencies shift up or down after the Joule heating, which is due to the deflection change of beams. The modification of the Young's modulus is very small, which means that material properties after the reshaping are not changed much.