Fabrication of electro-thermally driven tunable plate with Au/SiO2 bimorph beams

This paper presents the design and fabrication of MEMS based electro-thermally actuated square membrane/plate with gold and silicon dioxide bimorph beams. The main objective of this work is to generate a suspended bimorph structure for tunable cavity filters and resonators. A surface micromachining process has been employed in which bimorph structure is suspended by removing underneath sacrificial layer of photoresist through dry and wet etching. A major fabrication challenge is the release of square plate bimorph structure. Increase in temperature during subsequent processing steps cause excessive baking of photoresist. The possible reason of the hard sacrificial resist is baking beyond its thermal budget. Active layer of silicon dioxide utilized as a reinforcing layer during release. In the proposed process, over etched silicon dioxide and presence of sacrificial resist leads to process failure. Controlled thermal budget of sacrificial resist is essential for fully suspended structure.