Fabrication Process Comparison and Dynamics Evaluation of Electrothermal Actuators for a Prototype MEMS Safe and Arming Devices

Electrothermal actuators fabricated using the Polysilicon Multi-User MEMS Process (PolyMUMPs) and the Sandia Ultra-Planar, Multi-Level MEMS Technology 5 (SUMMiT V) have been investigated for use in integrated microelectromechanical systems (MEMS) safe and arming devices. The fabricated electrothermal actuators have been dynamically tested to determine and compare the responses of devices from both processes. Furthermore, the integration of these devices into a safe and arming device were tested and investigated for each process. Initial results indicate that the SUMMiT devices provide the most optimum results based on consistency of operation and reliability.     

Stress Monitoring of Post-processed MEMS Silicon Microbridge Structures Using Raman Spectroscopy

Inherent residual stresses during material deposition can have profound effects on the functionality and reliability of fabricated Micro-Electro-Mechanical Systems (MEMS) devices. Residual stress often causes device failure due to curling, buckling, or fracture. Typically, the material properties of thin films used in surface micromachining are not well controlled during deposition. The residual stress; for example, tends to vary significantly for different deposition methods. Currently, few nondestructive techniques are available to measure residual stress in MEMS devices prior to the final release etch. In this research, micro-Raman spectroscopy is used to measure the residual stresses in polysilicon MEMS microbridge devices. This measurement technique was selected since it is nondestructive, fast, and provides the potential for in-situ stress monitoring. Raman spectroscopy residual stress profiles on unreleased and released MEMS microbridge beams are compared to analytical and FEM models to assess the viability of micro-Raman spectroscopy as an in-situ stress measurement technique. Raman spectroscopy was used during post-processing phosphorus ion implants on unreleased MEMS devices to investigate and monitor residual stress levels at key points during the post-processing sequences. As observed through Raman stress profiles and verified using on-chip test structures, the post-processing implants and accompanying anneals resulted in residual stress relaxation of over 90%.     

Pushing the Limits of Direct Spectra and Composition Measurements

Physics of Atomic Nuclei - The recent years saw the implementation and deployment of a new generation of instruments flown in space or on stratospheric balloons. They are targeted at the study of a...     

New measurement of the cosmic-ray positron fraction from 5 to 15 GeV

We present a new measurement of the cosmic-ray positron fraction at energies between 5 and 15 GeV with the balloon-borne HEAT-pbar instrument in the spring of 2000. The data presented here are compatible with our previous measurements, obtained with a different instrument. The combined data from the three HEAT flights indicate a small positron flux of nonstandard origin above 5 GeV. We compare the new measurement with earlier data obtained with the HEAT-e(+/-) instrument, during the opposite epoch of the solar cycle, and conclude that our measurements do not support predictions of charge sign dependent solar modulation of the positron abundance at 5 GeV.