Properties of amorphous AlCuY alloy metallizations

Abstract

Amorphous metal alloys are ideally suited for interconnects in micro-electromechanical systems (MEMS) because of their resistance against migration and diffusion, and their stability in chemically aggressive environments, which should both lead to a substantial improvement of lifetime and reliability of robust sensors. Amorphous aluminium alloy metallizations are especially promising for surface acoustic wave (SAW) sensors, where the interconnects are exposed to considerable mechanical strains. In this work, first experimental results for amorphous 400 nm Al/sub 84/Cu/sub 4/Y/sub 12/ alloy thin films deposited on single crystal LiTaO/sub 3/ piezoelectric substrates at room temperature (R.T.) by ultra-high vacuum (UHV) electron beam evaporation will be presented. The composition of the films was validated by Rutherford backscattering (RBS) spectroscopy, and their amorphous structure was confirmed by X-ray diffraction (XRD) analysis. The roughness and hardness of the metallization, both important parameters for wire bonding, were investigated by scanning probe microscopy (SPM) and depth-sensing nanoindentation. The electrical resistivity was determined by four-point probe measurements. The amorphous films were annealed in UHV, and their crystallization temperature T/sub x/ was investigated by XRD.