On-wafer time-dependent high reproducibility nano-force tensile testing

Time-dependent mechanical investigations of on-wafer specimens are of interest for improving the reliability of thin metal film microdevices. This paper presents a novel methodology, addressing key challenges in creep and anelasticity investigations through on-wafer tensile tests, achieving highly reproducible force and specimen deformation measurements and loading states. The methodology consists of a novel approach for precise loading using a pinin- hole gripper and a high-precision specimen alignment system based on three-dimensional image tracking and optical profilometry resulting in angular alignment of < 0.1 mrad and near-perfect co-linearity. A compact test system enables in situ tensile tests of on-wafer specimens under light and electron microscopy. Precision force measurement over a range of 0.07 mu N to 250 mN is realized based on a simple drift-compensated elastically-hinged load cell with high-precision deflection measurement. The specimen deformation measurement, compensated for drift through image tracking, yields displacement reproducibility of < 6 nm. Proof of principle tensile experiments are performed on 5 mu m-thick aluminum-alloy thin film specimens, demonstrating reproducible Young's modulus measurement of 72.6 +/- 3.7 GPa. Room temperature creep experiments show excellent stability of the force measurement and underline the methodology's high reproducibility and suitability for time-dependent nanoforce tensile testing of on-wafer specimens.