A Practical Approach for Determination of Thermal Stress and Temperature-Dependent Material Properties in Multilayered Thin Films

Multilayered thin
films are essential to most microelectro-mechanical
systems (MEMSs). The reliability and predictability of the behavior
of such systems, especially when intended for usage at high temperatures
or in harsh environments, demand the consideration of thermo-mechanical
properties of the individual films of the multilayer arrangement during
the design stage. This paper introduces a newly derived analytical
model for the convenient indirect determination of the temperature-dependent
Young’s modulus and the thermally induced stress of individual
layers within a multilayered thin film system, i.e., a multilayer-adapted
Stoney equation. It is based on sample curvature measurement and requires
data from only a single experiment. Experimental and numerical investigations
of the new models are carried out using a five-layered sample of a
RuAl metallization system developed for wireless high-temperature
acoustic sensing. The results highlight the usability of the new model
in practical MEMS analysis, enabling insights into complex layer stacks
by overcoming current experimental limitations.