AVS2016 Session MN+MS-FrM: Radiation Effect in Emerging Micro/Nano Structures, Devices, and Systems

Gamma rays, x-rays, as well electrons and ions are expected to deposit charge in dielectrics and may also charge the sealed gas environment in which the devices operates. Neutrons, protons, and ions may change the underlying mechanical properties, optical properties, and ferroelectric or piezoelectric properties of MEMS materials. All types of radiation may alter the surface chemistry and morphology causing changes in the performance of physical and electrical contacts. It is expected that MEMS devices will be resistant to upsets or changes in state due to individual strikes by high energy particles. However, nanoscale devices may be susceptible to either the physical impact or the associated charge deposition. It is important to understand these fundamental effects of radiation on MEMS/NEMS devices and materials before they are incorporated in critical DoD systems.

This talk introduces the DTRA basic research radiation effects program and the radiation effects in MEMS/NEMS topic.

Radiation survivability of MEMS microelectronic circuits with carbon nanotube field emitters

Jason J. Amsden,^†* Erich J. Radauscher,^† Tasso von Windheim, ^† Kristin H. Gilchrist,^§ Shane T. Di Dona,^† Zach E. Russell,^† Leif Z. Scheick,^{^} Jeffrey R. Piascik, ^§ Charles B. Parker,^† Brian R. Stoner, ^§,† Jeffrey T. Glass ^†

† Department of Electrical & Computer Engineering, Duke University, 130 Hudson Hall, Box 90291, Durham, NC 27708, USA

§ Engineering and Applied Physics Division, RTI International, Research Triangle Park, NC 27709, USA

^ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91108

*e-mail: jason.amsden@duke.edu [mailto:jason.amsden@duke.edu]

INVITED ABSTRACT

Solid-state technology dominates the consumer electronics market because of the low cost associated with large-scale integration. However, there are numerous applications in which solid-state devices are unreliable or do not provide adequate performance, particularly applications with military systems operating in high radiation environments. In these applications, vacuum microelectronic devices present an attractive alternative. Despite the performance advantages, the use of vacuum electronics has been limited because there is no versatile and reliable microscale platform that enables integration of large numbers of vacuum circuit elements on a single substrate. To address this need, RTI International in collaboration with Duke University has been developing a Microelectromechanical systems (MEMS) platform that enables integration of high-performance microelectronic vacuum components into functional circuits on a single silicon substrate.¹ We have demonstrated a wide variety of vacuum electronic devices including vacuum triodes and ion sources using a freestanding panel approach fabricated with the Polysilicon Multi-User MEMS Process (PolyMUMPS) with integrated carbon nanotube field emission cathodes. While these devices avoid the radiation-induced charge carrier problems in solid-state devices, other effects of radiation on this MEMS platform have not been studied. The presentation will present our preliminary findings on the radiation effects on this vacuum microelectronics platform.

1. Stoner, B. R.; Piascik, J. R.; Gilchrist, K. H.; Parker, C. B.; Glass, J. T., A Bipolar Vacuum Microelectronic Device. Electron Devices, IEEE Transactions on 2011, 58, 3189-3194.

Acknowledgements: This work was supported by the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-15-1-0071, to Duke University. The contents does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred

and accurate platforms for quantifying radiation effects in optical materials and MEMS/NEMS systems.

Our approach benefits from the high precision of optical interrogation techniques. Further, compared to

traditional capacitive or piezoelectric actuated devices, NOMS are immune to extrinsic

degradation associated with driving circuit and metal contact failure or charge-trapping in dielectrics, and

are thus ideal test vehicles to measure radiation-induced, intrinsic optical and mechanical material

property modifications. In this talk, we will discuss design, fabrication and characterization of optical and

NOMS devices based on Si, SiN and SiC materials as well as gamma-ray radiation effects in these

devices. Defect identities responsible for the observed optical and mechanical property shifts are clarified

through spectroscopy and microscopy characterization techniques to unravel the radiation damage

mechanisms in these devices.

The dramatic reduction in size and power consumption offered by micro- and nano-scale electromechanical systems (M&NEMS) offer compelling advantages for adoption in many areas, including space and military systems. Mission reliability and survivability of next-generation space-borne systems depends critically upon a detailed understanding of the radiation response and reliability of the constituent devices when exposed to the relevant radiation environment. M&NEMS may be employed for a variety of sensor and actuation applications, oscillators, and have potential to be incorporated as high-reliability solid-state (logic) switches.

While there has been considerable study of radiation effects on some of the common materials (single and poly crystalline silicon, and silicon-dioxide), the study in the context of MEMS has been more limited, and mainly experimental. The general indication is that depending on the operating principal, MEMS can be sensitive to radiation-induced charging of insulators, and to displacement damage at very high exposure doses of energetic particles.

More recently, fabrication process, namely the ability to create nano-scale structures, and the introduction of new materials (esp. 2D and CNTs), have expanded the opportunities for M&NEMS. The Defense Threat Reduction Agency (DTRA) has recently initiated multiple projects in the study of various aspects and configurations of M&NEMS. This talk will discuss a specific project which seeks to advance the understanding of the effect of radiation on the relevant electro-mechanical properties of the constituent materials and structures, focusing on 2D materials and CNTS, and the implications for space and military applications.

The key question for this work is: How does radiation damage to constituent materials impact the mechanical and electrical basis of operation of M&NEM structures? In particular, cumulative damage by non-ionizing energy loss can, in principle, alter the mechanical properties of structures such as cantilever’s and 2D membranes, and surface effects and trapped charge in insulators can impact electrical operating conditions. Presently, the extent to which such effects impact the operation of advanced M&NEM devices is unclear. This particular project combines expertise and experience in materials science, M&NEMS, and radiation effects of the University of California at Berkeley, Sandia National Laboratories, and Vanderbilt University to conduct a systematic study of the impact of relevant radiation types on the key operating properties of novel M&NEM structures, and to capture observed effects in finite element models.

We report on exploratory research effort on investigating fundamental radiation effects in resonant-mode and contact-mode microelectromechanical systems (MEMS/NEMS) enabled by silicon carbide (SiC) micro/nanostructrues. We calibrate and compare the radiation effects in a few selected MEMS/NEMS resonators – namely, SiC microdisk resonators, SiC membrane resonators, SiC-on-insulator (SiCOI) cantilever beam resonators, and resonant switches.

We focus on discovering fundamental effects of SiC MEMS/NEMS devices due to exposure to radiation sources representative of space and nuclear environments, and attaining comprehensive, in-depth understandings of how these radiations affect the key attributes and performance of the devices. The main properties and metrics include resonance frequency, quality (Q) factor, multimode responses, off-state leakage, on-current, on-voltage, switching speed, surface and nanocontact properties, reliability and lifetime, etc.

In this work, we have carefully performed experiments on extensive testing of multimode SiC MEMS/NEMS resonators and resonant switches, before and after controlled radiation exposure with designed dosage and energetic parameters of the radiation sources. Furthermore, we have done extensive computer simulation studies on the effects of implanting protons (hydrogen ions, H+) into SiC thin layers on silicon (Si) substrate and on SiO2, and explore the ion implantation conditions that are relevant to experimental radiation of SiC device layers.