Determining thermal expansion coefficients of thin films using micromachined cantilevers

In this research, the coefficient of thermal expansion (CTE) of thin films was studied through analytical and experimental approaches using micromachined beams. Both single layer and bilayer micromachined cantilevers (microcantilevers) were exploited in measuring the thermal expansion of the thin films. It was obtained that both single and bilayer micromachined cantilevers would exhibit an out of plane deflection after subjected to temperature changes. Thus the thermal expansion of thin film materials can be determined using optical interferometric techniques on these heat-deformed microcantilevers. The contributions of the proposed techniques are that they can be used to increase the sensitivity and accuracy of CTE measurements. Furthermore, the distribution of the thin film CTE across the entire substrate can also be determined through the proposed approaches. Since the microcantilever structure used in this study is very simple, both modeling and fabrication processes are simplified. Thus the proposed technique can be applied to supplement other techniques used in determining the CTE of thin films. (C) 1999 Elsevier Science S.A. All rights reserved.