Thin Film Aluminum Alloy for Movable Electrical Circuit

A Micro Electro-Mechanical System (MEMS) consist of a movable silicon substrate and static glass substrate. Two substrates are joined using an anodic bonding technique at 693 K for 1 h. A conductive thin film is deposited on to the silicon to provide the required electrical circuit. Thin film aluminum alloy is an appropriate material for MEMS, because it has low electrical resistance and is easy to etch using conventional acid techniques. Both electrical characteristics and mechanical characteristics of aluminum alloy film affect the MEMS device performance. Annealing at over 693 K will cause re-crystalization of the grain structure and hence the annealed aluminum alloy thin film has a large grain structure. With the addition of nitrogen and oxygen into the aluminum alloy, the grain growth will be inhibited during annealing, resulting in a fine grain structure of the annealed thin film. The dynamic hardness of the film with fine grain structure was approximately 1100 MPa and that of large one is 640 MPa, respectively. Both aluminum alloy thin films have been applied to yaw rate sensors. The static output of the sensors with the fine grain aluminum alloy thin film has been stable, but while those with coarse grain aluminum alloy thin film was found to be unstable.