Annealing temperature dependence of mechanical and structural properties of chromium-gold films on the silica glass substrate

Abstract

Efficient mechanical properties of thin gold films on dielectric substrates are essential in micro-electro-mechanical systems applications. Hence, the film performance should be optimized via thermal treatment. In this paper, gold films with a nominal thickness of 100 nm and a chromium adhesion layer of 10 nm are deposited on the fused glass substrate. Annealing temperature dependency of the mechanical and structural properties of chromium-gold films is carefully investigated. The surface, cross-sectional morphology, hardness, Young's modulus, adhesion, stress, and conductivity of the chromium-gold bilayer film are explored for the annealing temperature range from 100 °C to 700 °C. The results show that the transition point temperature varies for different properties. The transition point at 200 °C for the adhesion and resistivity can be attributed to the improvement of the crystalline state caused by annealing. When the annealing temperature reaches 300 °C, Young's modulus, and the hardness are reduced, and the residual stress is minimized. Significant diffusion of chromium atoms into the gold layer is observed for the annealing temperature of 400 °C, which alters the initial structure of the bilayer films and modifies film properties. Moreover, resistivity reaches a maximum value, and the internal stress starts to increase, which is caused by the diffusion of the chromium film. Consequently, the definite annealing temperature needs to be selected for the required film properties.