Nanosized Vacuum Gap Electromechanical Devices with Integrated Piezoelectric Actuator

Abstract

Fabrication of aluminium vacuum gap capactior based electromechanical devices was investigated, where the bottom electrode is fixed, and the top electrode is free to move. To avoid collapse of the top electrode, imultaneous oxidation of both sides of the top electrodes was ensured by deposition of silicon protection layer without breaking vacuum, intended to be removed with the release process of the membrane with XeF2 gas. Furthermore, the vertical stress gradient was controlled by optimising the sputter deposition parameters for the aluminium top electrode to 50W and 3 µbar for 100nm. These techniques brought the fabrication yield of capacitors with radii of 7 µm to 90%, while for larger capacitors with radii up to 30 µm, the yield only decreased to 50%. A cryostat at 400 mK and a built in piezoactuator were used to prove electromechanical coupling.