Non-tilting out-of-plane mode high-Q mechanical silicon oscillator

Abstract

A single-crystal silicon oscillator with a non-tilting out-of-plane vibrational mode and high-quality factor for the mechanical resonance was designed, fabricated and characterized. The finite-element method (FEM) was utilized before the fabrication process to simulate the oscillator behavior and give guidance in optimizing the design. At low pressure p =10−3 mbar and at room temperature, the resonance frequency and Q value were measured to be f0 = 26 526 Hz and Q = 100 000, respectively. The measured resonance frequency was in a good agreement with the simulated one, f0,FEM = 26 787 Hz. The actual mode pattern was verified by measurements and compared with the simulation result. An interferometric laser beam was scanned over the oscillator surface and position-dependent oscillation amplitudes were stored with the phase-sensitive detection. The oscillation was proved to occur effectively in a pure non-tilting out-of-plane mode. We propose to use this kind of micromechanical probe in various measurement schemes, where one needs to approach the surface with a single non-torsional plane. In addition, such an oscillator can be utilized as an optical mirror so that the optical mode can be kept the same when moving the mirror.