Laser annealing for high-Q MEMS resonators

Keith L. Aubin, Maxim Zalalutdinov, Robert B. Reichenbach, Brian Houston, Alan T. Zehnder, Jeevak M. Parpia, Harold G. Craighead

Research output: Contribution to journalConference article

15 Scopus citations

Abstract

High frequency and high quality factor, Q, (defined as a half-width of the resonant peak) are the key factors that enable applications of microelectromechanical (MEMS) oscillators for supersensitive force detection or as elements for radio frequency signal processing. By shrinking the dimensions of MEMS resonators to the sub-micron range one increases the resonant frequency of the devices. Shrinking the devices, however, also increases the surface-to-volume ratio leading to a significant degradation of the quality factor (to below 5,000) due to the increased contribution of surface-related losses. We demonstrate that local annealing performed by focused low-power laser beams can improve the quality factor of MEMS resonators by more than an order of magnitude, which we attribute to the alteration of the surface state. Quality factors over 100,000 were achieved after laser annealing 3.1 MHz disc-type oscillators (radius R=10 micrometers, thickness h=0.25 micrometer) compared with a Q=6,000 for the as-fabricated device. The mushroom-type design of our resonator (a single-crystal silicon disc supported by a thin silicon dioxide pillar at the center) provides low heat loss. The combined power of a red HeNe laser (Pred=4mW) and a blue Ar+ ion laser (Pblue=5mW) focused on the periphery of the mushroom provides enough energy for surface modification. The post-treatment quality factor, exceeding 100,000 for MHz-range resonators, boosts the performance of MEMS to be comparable to that of lower frequency single-crystal quartz devices. The local nature of laser annealing, safe for surrounding electronics, is a crucial element for integration of MEMS resonators into an integrated circuit environment.

Original languageEnglish (US)
Pages (from-to)531-535
Number of pages5
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume5116 II
DOIs
StatePublished - 2003
EventSmart Sensors, Actuators, and MEMS - Maspalonas, Gran Canaria, Spain
Duration: May 19 2003May 21 2003

Keywords

  • Laser annealing
  • MEMS integration
  • Quality factor
  • Resonator
  • Surface losses

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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