A new residual stress measurement method using ultra-wide micromachined bilayer cantilevers

Abstract

A new method is proposed to improve thin-film stress measurement using micromachined bilayer cantilevers. Our previous studies demonstrated that the width does affect the bilayer cantilever deflection, and the effect of width disappears as the width exceeds a critical value, which is usually far larger than the bilayer cantilever length. The existing methods, which employ the narrow micromachined bilayer cantilever to measure the residual stresses, do not consider the width effect, and hence may generate some uncertainties in their measurement results. To remove these uncertainties, a cantilever with a very large width is introduced and used in this proposed method. Its corresponding model, based on the plate theory, has been derived and applied to this new measurement procedure. Following the measurement procedure suggested in this paper would provide measurement results more reliable than the traditional ones which use the narrow bilayer cantilever in determining the stresses of thin films.