Oscillator far-from-carrier phase noise reduction via nano-scale gap tuning of micromechanical resonators

Abstract

Substantial improvements in the far-from-carrier phase noise of oscillators referenced to stand-alone (as opposed to arrayed) capacitively transduced micromechanical disk resonators have been attained via the use of atomic layer deposition (ALD) to tune the electrode-to-resonator capacitive gaps. Specifically, ALD of about 30nm of hafnia (HfO 2 ) onto the surface of a released 60-MHz micromechanical disk resonator to reduce its effective resonator-to electrode gap size from 92nm to 32nm provides an increase in power handling leading to more than 15-20dB reduction in the far-from-carrier phase noise of an oscillator referenced to this resonator. This ALD-enabled nano-scale gap tuning provides a simple and effective method to satisfy increasing demands for higher short-term stability in frequency references for electronic applications.

A high-performance oscillator based on RF MEMS resonator and low-noise sustaining circuit for timing applications

“…The low phase noise benefits from ultra-low noise of the sustaining circuit and excellent performance of the MEMS resonator. The phase noise of the developed oscillators is compared with the reported MEMS oscillators [7,8,9,10]. …”

Achieving nanoscale horizontal separations in the standard 2 μm PolyMUMPS process

“…Finally, the oxide layer is wet-etched and we are left with the desired separation (step 'f'). Note that it is easily possible to have a sacrificial layer deposited right after the nitride to serve as a sacrificial layer for the first polysilicon layer, and for this sacrificial layer to be patterned so that the first structural layer is anchored to the nitride as previously done (Akgul et al 2009;Hsu et al 2001;Wang et al 2003).…”

Low Impedance ALD HfO2 Partially-Filled-Gap Flexural and Bulk MEMS Resonators Piezoresistively Detected for Distributed Mass Sensing

“…Capacitively transduced MEMS resonators have been proven to achieve resonance frequency times quality factor (f0xQ) products of the order of 10 13 [1], evidencing to be promising candidates to be used in communications [2] and environmental mass sensing applications [3]. Partially-filled-gap capacitive MEMS disks resonators were proposed in [4] to attain lower motional impedance, Rm, better electromechanical coupling and more robustness against electrodes-resonator collapse.…”

“…Partially-filled-gap capacitive MEMS disks resonators were proposed in [4] to attain lower motional impedance, Rm, better electromechanical coupling and more robustness against electrodes-resonator collapse. Similar devices have been proposed in [2] in order to overcome the power handling deficiencies of oscillators based on capacitively transduced disks.…”