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Proceedings Paper

Thermal-stress control of microshutter arrays in cryogenic applications for the James Webb Space Telescope
Author(s): Daniel P. Kelly; Wen-Hsien Chuang; Larry Hess; Ron Hu; Murzy Jhabvala; Todd King; Mary J. Li; James Loughlin; S. Harvey Moseley; Christopher Ray; Yun Zheng
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Paper Abstract

We report on methods to minimize thermally-induced deformation in a MEMS-based reconfigurable aperture. The device is an enabling component of the Near-Infrared Spectrometer, a principle instrument on NASA’s James Webb Space Telescope. The Microshutter Array consists of 384x175 individually addressable shutters which can be magnetically rotated 90° into the plane of the array and electrostatically latched open. Each shutter is a 100x200 μm rectangular membrane suspended by a small neck region and torsion flexure. The primary materials in the shutter are a 5000Å Si3N4 layer for mechanical rigidity, 2000Å Al for opacity and electrostatic latching, and 2200Å Co90Fe10 for magnetic actuation. This multi-layer stack presents a challenge due to the operating temperatures required for the device: both room temperature (300K) and cryogenic temperature (30K). Thermal expansion of the materials causes the shutters to bow out of plane excessively, which can prevent actuation of the shutters, cause damage to portions of the array, and allow light leakage around closed shutters. Here we present our investigation of several methods to prevent microshutter bowing including deposition of additional materials on the shutters to create a symmetrical layer stack and replacing the current stack with low-coefficient of thermal expansion materials. Using shutter-size suspended cantilever beams as a rapid-development test bed, we have reduced out-of-plane bowing between 300K and 30K to 10% or better. We are currently applying these results to microshutter arrays to develop shutters that remain flat from room temperature to cryogenic temperature while retaining the required mechanical, optical, and magnetic properties.

Paper Details

Date Published: 1 July 2005
PDF: 8 pages
Proc. SPIE 5836, Smart Sensors, Actuators, and MEMS II, (1 July 2005); doi: 10.1117/12.608754
Show Author Affiliations
Daniel P. Kelly, NASA Goddard Space Flight Ctr. (United States)
QSS Group, Inc. (United States)
Wen-Hsien Chuang, Univ. of Maryland College Park (United States)
Larry Hess, NASA Goddard Space Flight Ctr. (United States)
Raytheon Corp. ITSS (United States)
Ron Hu, NASA Goddard Space Flight Ctr. (United States)
Raytheon Corp. ITSS (United States)
Murzy Jhabvala, NASA Goddard Space Flight Ctr. (United States)
Todd King, NASA Goddard Space Flight Ctr. (United States)
Mary J. Li, NASA Goddard Space Flight Ctr. (United States)
James Loughlin, NASA Goddard Space Flight Ctr. (United States)
S. Harvey Moseley, NASA Goddard Space Flight Ctr. (United States)
Christopher Ray, NASA Goddard Space Flight Ctr. (United States)
Raytheon Corp. ITSS (United States)
Yun Zheng, NASA Goddard Space Flight Ctr. (United States)
QSS Group, Inc. (United States)


Published in SPIE Proceedings Vol. 5836:
Smart Sensors, Actuators, and MEMS II
Carles Cane; Jung-Chih Chiao; Fernando Vidal Verdu, Editor(s)

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