Atomic layer deposited alumina for micromachined resonators

In this work, atomic layer deposited (ALD) alumina (AI₂O₃) has been demonstrated as the structural material for a micro-resonator for the first time. An electrostatically actuated micro-bridge made of Cr and ALD AI₂O₃ was used as a resonator. The resonator was formed by simple wet- and dry-etching processes. The static displacement profile of the micro-resonator was then measured by an optical interferometer. A model of a pinned-pinned beam with axial stress of 250 MPa is used to fit the measured data. An optical method was used to measure the resonant frequency modes. The fundamental frequency of the resonator was measured around 200 kHz. Higher modes of resonance were also observed and fitted with the analytical model.