RF magnetron sputtered aluminum oxide films for MEMS

In the present work, aluminum oxide (AL₂O₃) films have been investigated as an alternative structural material for micro-electro-mechanical-systems (MEMS). The AL₂O₃ films were prepared by RF magnetron sputtering process and characterized. These were used as structural layers for fabricating basic microstructure elements such as cantilever beams, micro-bridges etc. XRD study of films revealed that annealing of films significantly changed their crystal structure and formed both alpha- and gamma- crystalline phases simultaneously. Stress in AL₂O₃ film deposited at optimized parameters, was measured to be compressive in nature. Atomic force microscopy (AFM) revealed the RMS value of the surface roughness of as-deposited films to be 1.04 nm, which increased to 5.49 nm on post-deposition annealing at 1000 degC. To show the feasibility of this material for MEMS applications, 2 mum thick single cantilever beams as well as array of cantilever beams were fabricated successfully using bulk micromachining process. These basic microstructures can be used in different applications for MEMS.