A nano-tensile tester for creep studies

Abstract

Free-standing metallic thin films are increasingly used as structural components in MEMS. In commercial devices, long-term reliability is essential, which requires determining time-dependent mechanical properties of these films. The uniaxial tensile test is a preferred method due to uncomplicated determination of the stress and strain state. However, at the MEMS-scale this method is not straightforward: specimen handling and loading, force and deformation measurement need careful consideration. Here we discuss the challenges of the application and measurement of nano-Newton forces, nanometer deformations and micro-radians rotation alignment ensuring negligible bending in on-chip tensile test structures during long periods. We then present a novel tensile-testing instrument with in-situ capabilities in SEM and Optical Profilometry. The design solutions to measure these small forces and deformations whilst ensuring a uniaxial stress state will be presented.