Response of a MEMS Microshutter Operating at 60 K to Ionizing Radiation

2011

SPIE Proceedings

The sensitivity of MEMS devices to radiation is reviewed, with an emphasis on radiation levels representative of space missions. While silicon and metals generally do not show mechanical degradation at the radiation levels encountered in most missions, MEMS devices have been reported to fail at doses of as few krad, corresponding to less than one year in most orbits. Radiation sensitivity is linked primarily to the impact on device operation of radiation-induced trapped charge in dielectrics, and thus affects most strongly MEMS devices operating on electrostatic principles. A survey of all published reports of radiation effects on MEMS is presented. The different sensing and actuation physical principles and materials used in MEMS are compared, leading to suggested was to increase radiation tolerance by design, for instance by choice of actuation principle or by electrical shielding of dielectrics.

Section: Electrostatic Mems Sensors and Actuatorsmentioning

confidence: 99%

Effects of radiation on MEMS

2011

SPIE Proceedings

“…45 A microshutter array designed to be used on a spectrometer on the James Webb Space Telescope was tested up to 200 krad, 46 which is the expected lifetime dose expected for the instrument located outside the spacecraft in a second Lagrange point ͑L2͒ orbit with little shielding. The device uses an electromagnetic force to move each microshutter, consisting of a multilayer of two dielectrics and two metals, which is then held in place with an electrostatic force.…”

Section: Electrostatic Microelectromechanical System Sensors and Actumentioning

confidence: 99%

Radiation sensitivity of microelectromechanical system devices

J. Micro/Nanolith. MEMS MOEMS

2009

Abstract. The sensitivity of microelectromechanical system ͑MEMS͒ devices to radiation is reviewed, with an emphasis on radiation levels representative of space missions rather than of operation in nuclear reactors. As a purely structural material, silicon has shown no mechanical degradation after radiation doses in excess of 100 Mrad. MEMS devices, even when excluding control/readout electronics, have, however, failed at doses of only 20 krad, though some devices have been shown to operate correctly for doses greater than 10 Mrad. Radiation sensitivity depends strongly on the sensing or actuation principle, device design, and materials, and is linked primarily to the impact on device operation of radiation-induced trapped charge in dielectrics. MEMS devices operating on electrostatic principles can be highly sensitive to charge accumulation in dielectric layers, especially for designs with dielectrics located between moving parts. In contrast, thermally and electromagnetically actuated MEMS are much more radiation tolerant. MEMS operating on piezoresitive principles start to slowly degrade at low doses, but do not fail catastrophically until doses of several Mrad. A survey of all published reports of radiation effects on MEMS is presented, as well as a summary of techniques that can improve their radiation tolerance.

“…Optical instrumentation: the NIR-Spec (Near InfraRed Spectrometer) on the James Webb Space Telescope (JWST) will use MEMS-based micro-shutters manufactured by NASA/GSFC, whose radiation testing at 60 K is reported in [20]. The JWST is expected to be launched in 2013.…”

Section: Bio and Microfluidicsmentioning

confidence: 99%

MEMS for pico- to micro-satellites

2009

SPIE Proceedings

MEMS sensors, actuators, and sub-systems can enable an important reduction in the size and mass of spacecrafts, first by replacing larger and heavier components, then by replacing entire subsystems, and finally by enabling the microfabrication of highly integrated picosats. Very small satellites (1 to 100 kg) stand to benefit the most from MEMS technologies. These small satellites are typically used for science or technology demonstration missions, with higher risk tolerance than multi-ton telecommunication satellites. While MEMS are playing a growing role on Earth in safetycritical applications, in the harsh and remote environment of space, reliability is still the crucial issue, and the absence of an accepted qualification methodology is holding back MEMS from wider use. An overview is given of the range of MEMS applications in space. An effective way to prove that MEMS can operate reliably in space is to use them in space: we illustrate how Cubesats (1 kg, 1 liter, cubic satellites in a standardized format to reduce launch costs) can serve as low-cost vectors for MEMS technology demonstration in space. The Cubesat SwissCube developed in Switzerland is used as one example of a rapid way to fly new microtechnologies, and also as an example of a spacecraft whose performance is only possible thanks to MEMS.Keywords: MEMS, spacecraft, satellites, nanosatellites, cubesats, space OVERVIEW OF MEMS APPLICATIONS IN SPACEIn 2008 the market for MEMS (MicroElectroMechanical Systems) devices was nearly $8 Billion according to Yole Développement [1]. MEMS encompass an enormous range of applications, from RF switching to projection display to inertial sensors to implantable pumps. Combining low mass, low power consumption, small volume and possible integration with control and sense electronics, MEMS seem ideal for space applications, where it costs approximately 10'000 $ to place one kg in low Earth orbit (LEO).Reliability is a key concern for spacecraft, in view of the very larger development costs, near impossibility of repair (the service missions to the Hubble Space Telescope are the notable exception), and limited launch slots. One major difference between operation on Earth and in Space is the radiation level [2]. Other space-specific reliability concerns are thermal cycling and thermal shocks, vibration and mechanical shock at launch and stage/heat shield separation, and operation in very high vacuum. The typical service life of a telecommunication satellite is 15 years, during which time the spacecraft must operate continuously and flawlessly. For this reason, and because of the need for radiation tolerance, new technologies are generally accepted in space applications only many years later than in consumer electronics, except for cases where a new technology is required for a mission, or allows dramatic performance enhancement or mass reduction. This was the case for instance for FPGAs and is now the case for MEMS.The fraction of the $8 Billion MEMS market for space is very small, and MEMS for use in space ...