A novel method for determining Young´s modulus of thin films by micro-strain gauges

This work presents a novel method for determining Young´s modulus of thin films with compact micromachined test structures and without using any extra load. The test structures comprise of a pair of micro-strain gauges and a cantilever beam. An analytical model is derived to extract the Young´s modulus of test structures. Notably, both Young´s modulus and residual stress can be simultaneously determined; thus we can correlate Young´s modulus and residual stress. The micromachined test structures employed in the measurement are made of low-pressure chemical-vapor deposition (LPCVD) undoped polycrystalline silicon films. A conventional surface-sacrificial layer micromachining technique with one mask is used to fabricate the structures. The obtained Young´s modulus is reduced a little as residual stress increases. The average value of the obtained Young´s modulus is 169 G Pa, and the residual stress calibrated from the strain gauge is 211 MPa.