The Effect of Crystalline Orientation on Vibration Sensitivity of Silicon Micro-Resonators

Abstract

In this work the effect of crystalline orientation on the acceleration sensitivity of Silicon-based MEMS oscillators is experimentally studied for the first time. The thin-film piezoelectric-on-Silicon (TPoS) platform is utilized to implement the oscillators as it enables resonators with low-motional resistance and high Q. A single lateral-extensional-mode resonator design is fabricated in <100> and <110> orientations on a <100> Silicon wafer. The resonators are then used to assemble two oscillators operating at ~25MHz and ~27MHz respectively. The average acceleration sensitivity of the oscillator containing the <110> resonator is measured to be ~4×10 -10 at vibration frequencies up to 2700 Hz; an astonishing two orders of magnitude lower than that of the oscillator utilizing the <100> resonator. The acceleration sensitivity in these Silicon-based resonators is believed to stem from nonlinear elastic properties of Silicon, which is dependent on crystalline orientation as well as doping type/concentration. The Silicon substrate used in this work is Phosphorous-doped at ~5e19 cm -3 concentration.