Application of aluminum oxide and ta-C thin films deposited at room temperature by PLD in RF-MEMS fabrication

Aluminium oxide and tetrahedral amorphous carbon thin films are deposited at room temperature using pulsed laser deposition (PLD) and their mechanical and electrical properties are investigated. As examples, the hardness of aluminium oxide films is found about 6.8 GPa and the Young's modulus 130 GPa, while the hardness of tetrahedral amorphous carbon (ta-C) layers reaches 45 GPa and its Young's modulus 650 GPa. These results allow considering the introduction of these materials in the fabrication of radio-frequency micro-electro-mechanical system (RF-MEMS). Aluminium oxide is used in RF-MEMS fabrication as well as dielectric material or structural material and nickel-doped ta-C allows the realization of localised, high value, planar, easily patterned resistances, leading to significant improvement of insertion losses of MEMS switches on electronic devices. At present, the use of ta-C thin films as structural material in RF-MEMS is limited by their high internal compressive stress.