An apparatus for the measurement of internal stress and thermal expansion coefficient of metal oxide films

A measuring apparatus based on a phase shifting interferometry technique to determine the mechanical properties of metal oxide films was presented. Th in films were prepared by ion-beam sputter deposition at low substrate temp erature. Quantitative determination of the mechanical properties such as th e internal stress, biaxial elastic modulus, and thermal expansion coefficie nt of metal oxide films were investigated. A phase shifting Twyman-Green in terferometer with the phase reduction algorithm was setup to measure the te mperature-dependent stress in thin films. Two types of circular glass plate s, with known Young's moduli, Poisson's ratios, and thermal expansion coeff icients, were used as coating substrate. The temperature-dependent stress b ehavior of the metal oxide films was obtained by heating samples in the ran ge from room temperature to 70 degreesC. The stresses of thin films deposit ed on two different substrates were plotted against the stress measurement temperature, showing a linear dependence. Four oxide films were reported fo r their film stresses and thermal expansion coefficients. (C) 2001 American Institute of Physics.