A further extension of the microbridge testing method was developed by deriving a closed formula of deflection versus load, which is applied at an arbitrary position on the microbridge beam. Testing a single beam at various positions under small deformation allows us to characterize simultaneously Young’s modulus and residual stress of the beam....[ Read more ]

A further extension of the microbridge testing method was developed by deriving a closed formula of deflection versus load, which is applied at an arbitrary position on the microbridge beam. Testing a single beam at various positions under small deformation allows us to characterize simultaneously Young’s modulus and residual stress of the beam.

The developed method was used to characterize the mechanical properties of brittle GaN thin films on patterned-Si (111) substrates grown by metal organic chemical vapor deposition (MOCVD). The microbridge samples were fabricated by using the microelectromechanical fabrication technique and tested with a nanoindentation system. Young’s modulus and residual stress of the 1.1 μm GaN film were determined to be 287 ± 190 GPa and 851 ± 155 MPa, respectively. In addition, alternative measurements of the residual stress, Young’s modulus and hardness of the GaN films, were conducted with micro-Raman spectroscopy and the nanoindentation test, yielding the corresponding values of 847 ± 46 MPa, 269.0 ± 7.0 GPa and 17.8 ± 1.1 GPa.

The developed method was also used to determine the mechanical properties of 4.18μm Parylene-C thin film on silicon substrate deposited by chemical vapor deposition (CVD) at room temperature. The Young’s modulus and residual stress was determined to be 3.49±0.23 GPa and 43.3±4.1 MPa, respectively.

The viscoelasticity of the 4.4 μm polymer was investigated by nanoDMA, which gave the storage modulus, loss modulus and loss tangent in the frequency range of 10~250Hz. In addition, microbridge tests were conducted on Parylene-C films with different thicknesses to examine whether there is size effect existed.