AVS 52nd International Symposium
    Manufacturing Science and Technology Wednesday Sessions
       Session MS-WeA

Paper MS-WeA1
Optical Interferometric Microscope for Real-Time Monitoring and Control of Focused Ion Beam Processes

Wednesday, November 2, 2005, 2:00 pm, Room 207

Session: Metrology & Process Control for Advanced Manufacturing
Presenter: M.J. Vasile, Sandia National Laboratories
Authors: D.P. Adams, Sandia National Laboratories
M.B. Sinclair, Sandia National Laboratories
T.M. Mayer, Sandia National Laboratories
M.J. Vasile, Sandia National Laboratories
W.C. Sweatt, Sandia National Laboratories
Correspondent: Click to Email
Focused ion beam (FIB) techniques have a wide range of applications including lithographic mask repair, specimen preparation, semiconductor analysis and nanodevice prototyping. Although FIB systems offer excellent in-plane spatial resolution, these do not include instrumentation that actively monitors milled feature depth. In order to enhance the control of FIB systems, we have designed, fabricated and tested a custom optical interferometer microscope suitable for operation during processing. This Michelson interferometer is intended for real-time monitoring and feedback control of focused ion beam processes including sputtering. The apparatus is designed for minimal outgassing / UHV operation, and the optics are retractable (within the vacuum system) providing ample space when removed for other commonly-used diagnostic tools and gasjet assemblies. The optical path and ion beam vector are co-incident at the sample. This is made possible through use of a pinhole mirror that is positioned between the exit aperture of the ion gun and the specimen. Long working distance (39 mm), high numerical aperture (NA = 0.39) objectives have been custom designed and fabricated for the interferometer. Tests with FIB-milled Si samples demonstrate 1.0 micron optical in-plane resolution. Out-of-plane resolution is approximately 1-2 nm.