Measurement of elastic modulus, Poisson ratio, and coefficient of thermal expansion of on-wafer submicron films

A bending beam method has been developed to measure the elastic modulus E, the coefficient of thermal expansion (CTE) and the Poisson ratio nu for on- wafer dielectric films with thicknesses in the submicron range. The method was demonstrated for 0.5 mu m thick silicon dioxide films made from tetraet hylorthosilane (TEOS). First, the biaxial elastic modulus E/(1-nu) and CTE were measured on blanket TEOS on Si and GaAs substrates and found to be 77 GPa and 1.0 ppm/degrees C, respectively. The Poisson ratio n was determined by combining the finite element calculation and the experimental result of the thermal stresses of TEOS fine lines on the Si substrate. The Poisson r atio of TEOS was determined to be 0.24 and, as a consequence, the Young's m odulus was 59 GPa. Fourier transform infrared spectra were obtained for TEO S films on the Si and GaAs substrates to ensure that the chemical structure of the film is independent of the substrate. (C) 1999 American Institute o f Physics. [S0021-8979(99)05809-0].