Wafer‐level vacuum‐encapsulated silicon resonators with arc‐welded electrodes

Abstract

This work presents wafer-level vacuum-encapsulated silicon resonators that utilise movable electrodes and arc welding in order to achieve deep sub-micron transduction gaps. The devices are fabricated using micro-electro-mechanical systems (MEMS) integrated design for inertial sensors (MIDIS) process, a commercial pure-play MEMS process, offered by Teledyne DALSA Semiconductor Inc.. The default minimum transduction gap in the MIDIS process is 1.5 μm. Here, the work introduces a technique to permanently reduce the transduction gap of the resonator using localised arc welding to a designed width of ∼200 nm. The prototype Lamé mode resonators are encapsulated in an ultra-clean 10 mTorr vacuum cavity that ensures long-term stability. The quality factor was measured to be 1.37 million at a resonance frequency of 6.89 MHz. With the narrower gap, the motional resistance of the resonators is reduced by a factor of ten times.