A cryogenic measurement setup for microelectromechanical systems used in space applications

Abstract

We present a cryogenic measurement setup installed inside a focused-ion-beam ͑FIB͒ system to characterize and microrepair microelectromechanical systems ͑MEMS͒ for space applications. The setup allows testing of MEMS devices under vacuum condition of 10 −6 Torr at variable temperatures ranging from 298 to 20 K. In the experiment, a lead-zirconate-titanate translator powered by a function generator and a dc voltage is utilized as an actuator, and a thin-film thermo-resistor fabricated with test devices is used as an integrated temperature sensor. Additionally, a motorized x-y-z stage is installed to achieve highly accurate positioning function. Resonant techniques and bending tests based on the designed setup are developed to measure the mechanical properties of silicon nitride thin films at cryogenic temperatures. Combined with the functions of the FIB system, this setup also demonstrates the capability to microrepair microshutter arrays, programmable field selectors in the NASA James Webb Space Telescopes. The presented test setup exhibits its feasibility to test MEMS devices needed for the space applications and can be extended to other cryogenic applications.

Nano-scale fatigue study of LPCVD silicon nitride thin films using a mechanical-amplifier actuator

“…In our previous work, a measurement setup was designed and installed inside a FIB system to characterize Young's modulus and fracture strength of LPCVD silicon nitride thin films at room and cryogenic temperatures [11,17]. The FEI 620 FIB used in our experiment is a dual beam system, with ion and electron columns, permitting ion milling and in situ scanning electron microscopy (SEM).…”

“…Mechanical amplification of the test device is achieved based on a resonant technique to obtain different stress levels without high applied voltages. All experiments are performed inside a focused-ionbeam (FIB) system with a previously developed measurement setup [11]. The presented device design, fabrication processes and experimental techniques are suitable for characterizing fatigue properties of a number of NEMS materials and can be extended for different NEMS/MEMS applications.…”