Abstract
An on-wafer characterization technique has been developed to determine the thermomechanical properties of a thin film. The thin film is deposited on an anisotropic substrate with in-plane principal directions of elasticity. The mismatch of thermomechanical properties between the substrate and the thin film causes the bilayer structure to deflect. Measuring this deflection and fitting it with a surface equation gives curvatures of the bilayer structure. The relationships between curvatures and thermomechanical properties are derived from equilibrium conditions. The results of a sensitivity analysis suggest the adoption the Poisson's ratio of bulk material such that the Young's modulus and the coefficient of thermal expansion (CTE) of the thin film can be found from fitted principal curvatures. An aluminum thin film deposited on an ST-cut quartz substrate at high temperature is employed for verification. The Young's modulus and CTE of the aluminum film are found to be 81.25 GPa and 25.52 ppm/°C, respectively. Data analysis shows that the characterization of Young's modulus and CTE is much more sensitive to principal curvatures than the Poisson's ratio.