Study of the Yielding and Strain Hardening Behavior of a Copper Thin Film on a Silicon Substrate Using Microbeam Bending

Abstract

ABSTRACTRecently a new microbeam bending technique utilizing triangular beams was introduced. For this geometry, the film on top of the beam deforms uniformly when the beams are deflected, unlike the standard rectangular geometry in which the bending is concentrated at the support. The yielding behavior of the film can be modeled using average stress-strain equations to predict the stress-strain relation for the film while attached to its substrate. This model has also been used to show that the gradint of stress and strain through the thickness of the film, which occurs during beam bending, does not obscure the measurement of the yield stress in our analysis.Utilizing this technique, the yielding and strain hardening behavior of bare Cu thin films has been investigated. The Cu film was thermally cycled from room temperature to 500 °C, and from room temperature to –196°C. The film was tested after each cycle. The thermal cycles were performed to examine the effect of thermal processing on the stress-strain behavior of the film.