Development of ultra-stable MEMS oscillators with 10⁻¹¹-level frequency stability via dual-mode temperature compensation

This thesis investigates the long-term frequency stability limits of encapsulated silicon MEMS resonators and develops two clock architectures to achieve high-precision, low-drift operation suitable for timing applications. The study is based on an encapsulated, heavily boron-doped Lamé-mode resonator, which provides a stable, aging-free mechanical platform by isolating the device from environmental perturbations. Building on this platform, we evaluate how temperature variations and electronics-induced phase drift fundamentally limit the achievable stability of MEMS-based clocks. The first architecture is a single-mode ovenized clock in which the resonator is mounted on a temperature-regulated copper chuck. Although this configuration achieves excellent short-term stability—reaching a minimum modified Allan deviation of 42 parts-per-trillion (ppt) at 85 seconds—its long-term performance is limited by the mismatch between the resonator temperature and that measured by an external temperature sensor. To overcome this limitation, a dual-mode clock is developed in which the resonator’s two distinct modes serve simultaneously as the clock mode and intrinsic temperature sensor. The ratio of their frequencies provides a monotonic measure of the true resonator temperature, enabling precise heater control without external sensing. A TCXO-style compensation scheme further suppresses electronics-induced phase drift in the frequency-tracking loop. Together, these techniques yield long-term stability remaining below 100 ppt up to 12 hours averaging time—suitable for the high precision timing application. The findings demonstrate that once environmental effects are removed, the stability of MEMS clocks becomes limited not by the mechanical device but by the frequency-tracking electronics. Developing an electronics-independent frequency tracking method will be essential for fully revealing the intrinsic stability limits of MEMS resonators.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Kim, Jintark

Contributors dc:contributor

• Bahl, Gaurav

• MEMS clock
• MEMS resonator

Statement dc:rights

• Copyright 2025 Jintark Kim

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132806

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132806