AVS 52nd International Symposium
    MEMS and NEMS Monday Sessions
       Session MN-MoM

Paper MN-MoM11
Vacuum Packaging MEMS Devices

Monday, October 31, 2005, 11:40 am, Room 207

Session: Processing & Characterization of Materials for MEMS & NEMS
Presenter: A.C. Greenwald, Ion Optics, Inc.
Authors: R. Patel, Ion Optics, Inc.
M.U. Pralle, Ion Optics, Inc.
E.A. Johnson, Ion Optics, Inc.
A.C. Greenwald, Ion Optics, Inc.
Correspondent: Click to Email
MEMS devices have unique packaging considerations to allow for mechanical motion. Vacuum packaging is required to reduce atmospheric drag for high frequency motion, to reduce thermal convection, etc. To achieve stable low pressures material selection is of paramount importance. Low temperature options are not suitable for very long-term reliability so that sealing materials are limited to impervious ceramics or metallic composites. Ion Optics has developed a MOEMS infrared gas sensor using photonic crystal technology.@footnote 1@ Operation requires a high temperature thermally isolated filament and vacuum packaging. Experiments in vacuum packaging this device have been performed for both single die in leadless chip carriers (LCC) and with wafer level packaging (WLP). Both low-melting point solders and ceramic frits have been tested for sealing. Different getter materials to reduce initial pressure and improve long-term reliability were also tested. The electrical performance of the heater is a sensitive function of package pressure.@footnote 2@ Devices were calibrated prior to sealing and then used as gauges to measure internal package pressure during the sealing and operation. Pressures down to 10mtorr were achieved. Process optimization studies included time-temperature profiles for bake-out using an RGA to study gas evolution from package and chip materials. Additional post-sealing studies broke packages in a sealed chamber and measured evolved gas composition and volume. Despite pre-bakeout at over 200C, water vapor was the highest volume gas retained/evolved, followed by oxygen, carbon dioxide and nitrogen. The minimum pressures attained in WLP were lower than that for LCC. @FootnoteText@ @footnote 1@ Nicholas Moelders, et. al., Mat. Res. Soc. Symp. Proc. Vol. 729, paper U5.2(2003).@footnote 2@ Nicholas Moelders et. al., Mat. Res. Soc. Symp. Proc. Vol. 782 paper A5.32(2004).