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

Paper MN-MoM2
Characterization of Nanoscale Wear Processes in Polysilicon-Based MEMS Devices using AFM and PEEM-NEXAFS Spectromicroscopy

Monday, October 31, 2005, 8:40 am, Room 207

Session: Processing & Characterization of Materials for MEMS & NEMS
Presenter: A.V. Sumant, University of Wisconsin at Madison
Authors: A.V. Sumant, University of Wisconsin at Madison
D.S. Grierson, University of Wisconsin at Madison
G. Wabiszewski, University of Wisconsin at Madison
R.W. Carpick, University of Wisconsin at Madison
A. Corwin, Sandia National Laboratories
M. De Boer, Sandia National Laboratories
Correspondent: Click to Email
We present studies aimed at elucidating mechanisms of nanoscale wear in polysilicon-based microelectromechanical systems (MEMS) devices. Current silicon-based MEMS devices that involve frictional sliding fail due to wear. Coating MEMS parts with self-assembled monolayers (SAMs), which act as lubricating and passivating layers, can improve the performance of these devices to some extent. However, devices coated with SAMs have finite lifetimes and can fail after unsuitably short periods of time. We seek to determine the precise causes of failure to ultimately improve the performance of MEMS devices. We use a atomic force microscopy (AFM) and PEEM-NEXAFS (Photoelectron Emission Microscopy combined with Near-Edge X-ray Absorption Fine Structure) spectromicroscopy to obtain quantitative information on structural damage and chemical changes inside the wear track of a MEMS device specifically designed to conduct friction and wear tests under controlled conditions. The ability of the PEEM-NEXAFS technique to spatially resolve and chemically characterize regions of interest is unparalleled and therefore ideally suited for this work. The results show for the first time that it is possible to detect chemical changes occurring within the micro-scale wear track. Furthermore, we are able to correlate the spectroscopically-observed features from the PEEM-NEXAFS measurements with AFM measurements of the modified surface topography in the wear track. One critical challenge is to minimize radiation damage of the SAMs due to synchrotron X-rays exposure during characterization. We show that by using radiation-blocking shutters and adjusting photon exposure and flux, damage can be reduced and reliable data can be obtained.