Tina He

Dual-gate silicon carbide (SiC) lateral nanoelectromechanical switches

We present demonstration and experimental results of four-terminal nanoscale electromechanical switches with a novel dual-gate design in a lateral configuration based on polycrystalline silicon carbide (poly-SiC) nanocantilevers. The switches operate at both room temperature and high temperature up to T 500oC in ambient air with enhanced control over the distributed electrostatic actuation force, and also enable recovery from stiction at contact. We have experimentally demonstrated multiple switching cycles of these nanomechanical switches with different actuation control schemes, and active release from stiction by exploiting a repulsive mechanism. In combination with modeling of cantilever deflection, the experiments help reveal the coupled electromechanical behavior of the device when making contact during switching operations, and suggest possible correlation between the switch degradation observed over cycles and the elastic deformation of nanocantilevers.

Nanomechanical non-volatile memory for computing at extreme

A computing platform that works under extreme conditions (> 250 °C and at radiation > 1 Mrad) can be attractive in a number of important application areas, including automotive, space and avionics. Nanoelectromechanical systems (NEMS) switches have emerged as promising candidates for computing in harsh environment. Designing reliable memory specifically non-volatile memory is a major challenge for these computing systems. In this paper, we propose a novel non-volatile memory (NVM) design for reliable operation in extreme environment using NEMS structure. It exploits a common failure mode in these devices, namely stiction. Unlike traditional charge-based memories, it relies on the mechanical state of a NEMS switch as information carrier. We analyze device and circuit-level design issues to enable robust NVM array implementation with NEMS devices.

Probing contact-mode characteristics of silicon nanowire electromechanical systems with embedded piezoresistive transducers

This article reports on a new method of monitoring nanoscale contacts in switches based on nanoelectromechanical systems, where the contact-mode switching characteristics can be recorded with the sensitive embedded piezoresistive (PZR) strain transducers. The devices are manufactured using state-of-the-art wafer-scale silicon-on-insulator technology featuring suspended silicon cantilevers and beams as switching elements and sub-100 nm thin silicon nanowires (SiNWs) as PZR transducers. Several different device configurations are studied, including mechanically ‘cross’-shaped (‘+’), coupled cantilever-SiNW structures, with and without local drain electrodes, and doubly clamped SiNW beams. Through detailed measurement and analysis, we demonstrate that the PZR transducers can enable detection of both mechanical and tunneling switching with multiple repeatable cycles. With the strong PZR effects in thin SiNWs, this type of device could be valuable especially for monitoring cold switching events, and when conventional direct readout of the switching events from the local gate or drain electrodes would not be efficient or sensitive, as nanoscale contacts may not be highly conductive, or may be degrading over time.

Silicon Carbide (SiC) Nanoelectromechanical Antifuse for Ultralow-Power One-Time-Programmable (OTP) FPGA Interconnects

We report a new nanoscale antifuse featuring low-power and high-programming speed, by employing silicon carbide (SiC) nanoelectromechanical systems (NEMS). We show that the SiC NEMS antifuses can enable ultralow-power one-time-programmable (OTP) field-programmable gate arrays (FPGAs) with characteristics promising for security-sensitive and harsh-environment applications. The SiC NEMS antifuses offer minimal leakage, low-programming voltage (down to ~1.5 V), ideally abrupt transient, high on/off ratios (>107) and high-current carrying ability (>106 A/cm2), and very small footprints (~1 μm2 to ~0.1 μm2 per device). We further describe new designs of antifuses, simulate FPGA benchmarking circuits based on experimentally demonstrated practical NEMS antifuses, and compare their advantageous performance with state-of-the-art conventional antifuse FPGAs. We also demonstrate a SiC NEMS antifuse-based OTP memory cell with a read margin of >106.

Toward ultralow-power computing at exteme with silicon carbide (SiC) nanoelectromechanical logic

Growing number of important application areas, including automotive and industrial applications as well as space, avionics, combustion engine, intelligent propulsion systems, and geo-thermal exploration require electronics that can work reliable at extreme conditions - in particular at a temperature > 250°C and at high radiation (1-30 Mrad), where conventional electronics fail to work reliably. Traditionally, existing wideband-gap semiconductors, e.g., silicon carbide (SiC) transistor-based electronics have been considered most viable for high temperature and high radiation applications. However, the large-size, high threshold voltage, low switching speed and high leakage current make logic design with these devices unattractive. Additionally, the leakage current markedly increases at high temperature (in the range of 10 μA for a 2-input NAND gate), which induces self-heating effect and makes power delivery at high temperature very challenging. To address these issues, in this paper we present a computing platform for low-power reliable operation at extreme environment using SiC electromechanical switches. We show that a device-circuit-architecture co-design approach can provide reliable long-term operation with virtually zero leakage power.