5650-01, Session 1
Microshutter arrays for James Webb space telescope
M. J. Li, N. Acuna, M. Beamesderfer, S. Babu, S. Bajikar, A. Ewin,
R. Fettig, D. Franz, L. Hess, M. Jhabvala, D. Kelly, T. King, G.
Kletetschka, C. Kotecki, A. Kutyrev, B. Lynch, H. Moseley, B. Mott,
L. Oh, D. Rapchun, C. Ray, C. Sappington, W. Smith, S. Snodgrass,
R. Steptoe-Jackson, L. Wang, Y. Zheng, C. Zincke, NASA Goddard
Space Flight Ctr. (USA)
Two-dimensional MEMS microshutter arrays are being developed at NASA
Goddard Space Flight Center for use in the near-infrared region on the
James
Webb Space Telescope (JWST). The microshutter arrays are designed for
the
selective transmission of light with high efficiency and high contrast.
The
JWST environment requires cryogenic operation at 35K. Microshutter
arrays
are fabricated out of silicon-oxide-insulated (SOI) silicon wafers.
Arrays are
close-packed silicon nitride membranes with a pixel size of 100x200 mm.
Individual shutters are patterned with a torsion flexure permitting
shutters
to open 90 degrees with a minimized mechanical stress concentration. The
mechanical shutter arrays are fabricated using MEMS technologies. The
processing
includes a multi-layer metal deposition and patterning of shutter
electrodes and magnetic pads, reactive ion etching (RIE) of the front
side to
form shutters out of the nitride membrane, an anisotropic back-etch for
wafer
thinning, followed by a deep RIE (DRIE) back-etch down to the nitride
shutter
membrane to form frames and relieve shutters from the silicon substrate.
An additional metal deposition and patterning is used to form back
electrodes.
Shutters are actuated using a magnetic force and latched using an
electrostatic force.