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 α- and γ- crystalline phases simultaneously. Stress in Al
2
O
3
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 °C. To show the feasibility of this material for MEMS applications, 2 μm 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.