On-wafer characterization of thermomechanical properties of dielectric thin films by a bending beam technique

A bending beam technique has been developed for on-wafer characterization o f thermomechanical properties of dielectric thin films including Young's mo dulus (E), the coefficient of thermal expansion (CTE), and the Poisson rati o (nu). The biaxial modulus E/(1-nu) and CTE were determined by measuring t he thermal stresses of the dielectric film as a function of temperature on two different substrates. The Poisson ratio and Young's modulus were determ ined by measuring the temperature dependence of the thermal stress of perio dic line structures of the dielectric film. Three dielectric thin films wer e selected for this study, consisting of silica made from tetraethylorthosi lane (TEOS), hydrogen silsesquioxane (HSQ), and biphenyltetracarboxylic dia nhydride-p-phenylene diamine (BPDA-PDA). The deduced biaxial modulus and CT E are 77 GPa and 1.0 ppm/degrees C for TEOS, 7.07 GPa and 20.5 ppm/degrees C for HSQ, and 11.1 GPa and 3.4 ppm/degrees C for BPDA-PDA. The Poisson rat io is determined to be 0.24 and Young's modulus is 59 GPa for the TEOS film . The error limit and the valid range of E/(1-nu) and CTE for applying this technique are also discussed. (C) 2000 American Institute of Physics. [S00 21-8979(00)08717-X].