Laterally actuated nanoelectromechanical relays with compliant source-drain contacts are presented. The relay sidewalls are coated with a 30 nm-thick conductive layer of titanium nitride (TiN) deposited using atomic layer deposition (ALD). By hollowing the tip of the relay, a flexible sidewall is formed from the thin TiN that results in a larger contact area and therefore improves the contact properties of the relay. This modification improves the on-state resistance (R ON ) and also provides better stability over a larger number of switching cycles compared to a rigid contact. The results of life-time tests show that the contact resistance increases with the number of switching cycles possibly due to degradation of the contact material. However, flexible contacts show improved contact resistance stability under cyclic contact.
This paper describes the improvement of pull-in stability, contact properties, and reliability of laterally actuated nanoelectromechanical relays by partitioning the mechanical and electrostatic domains in the relay structure. Separation of the two physics allows us to individually optimize the structural stiffness and the actuation voltage to increase the contact pressure and reduce the ON-state resistance without applying excessive drain voltage. The devices can tolerate more than 200% overdrive gate voltage, resulting in near 100% increase in contact force, and reducing the contact resistance from ∼10 G to ∼23 K . For a given overall device dimension, tailoring the mechanical and electrostatic elements independently also enables us to control the pull-in and pull-out voltages, which have different design requirements for different applications. The measurement results show that the pull-in/pull-out hysteresis could vary between 30% and 60% of the actuation (pull-in) voltage. Increasing the mechanical force without affecting the device actuation voltage improves the relay reliability by reducing the possibility of failure due to source-drain stiction when the relay is switched ON. As a proof of concept, mechanical relays are fabricated using polycrystalline silicon coated by a titanium nitride layer deposited via plasma enhanced atomic layer deposition.[2014-0018] IndexTerms-Nanoelectromechanical systems, low power electronics, laterally actuated relay, partitioning electrostatic-structural domains, contact reliability.
applications, power consumption issues have hindered development. An example of such power issues involves the size of pill cameras for colon inspections, which could be smaller and safer if smaller batteries could be used while maintaining adequate battery life (Darrin and Barth 2012). Another example involves the use of Field Programmable Gate Arrays (FPGAs) in aerospace applications, which is hindered by the large size and poor efficiency of FPGAs compared to ASICs (Chen et al. 2010). As a potential solution to these power issues, Nanoelectromechanical (NEM) relays are being investigated as logic components, due to their zero leakage current and steep subthreshold slope (Peschot et al. 2015). In configurations which can effectively leverage NEM relay's near-zero leakage current, integrated CMOS-relay systems show particular promise for reducing power. For example, it has been shown that hybrid CMOS-relay FPGA systems can reduce power by 10× and footprint by 2× compared to CMOS-only FPGA designs (Chen et al. 2010). For these reasons, NEM relays are described as potential "beyond CMOS" devices by the International Technology Roadmap for Semiconductors (ITRS 2011). However, industry adoption of NEM relays has been hindered by poor lifetime, high on-resistance, and CMOS-incompatible fabrication processes. Thus, the development of CMOS-compatible NEM relays with sufficiently low resistance and reliable behavior over many cycles would greatly accelerate their adoption in integrated electronic systems.NEM relays can be fabricated on top of CMOS-based devices if the relay fabrication meets all the criteria for back-end-of-line (BEOL) processing: low temperature deposition (<450 °C), low-stress materials, inclusion of diffusion barrier layers between silicon structures and buried aluminum interconnects to prevent spiking, and release processes that preserve interlayer dielectric layers. Previous Abstract Nanoelectromechanical (NEM) relays show promise in a wide variety of low power applications. NEM relays have near-zero leakage current, in contrast to the relatively high leakage current of nanoscale CMOS transistors, thus enabling hybrid CMOS-NEM relay systems that are more energy efficient. If NEM relays can be fabricated in the back-end-of-line (BEOL) metallization process, they can be added to a CMOS integrated circuit without adding significantly to the die area. In this paper, we demonstrate a CMOS BEOL-compatible fabrication process of NEM relays with protected, buried interconnects. The NEM relay processing steps are at temperatures below 425 °C and all mechanical and chemical processing steps are designed to avoid damage to underlying CMOS transistors. We demonstrate a lateral relay with buried interconnect that switches for more than 1000 cycles with resistances below 300 kΩ in nitrogen at atmospheric pressure.
A novel design for a six-terminal nanoelectromechanical relay is presented. The design includes a secondary beam in the signal pathway of the device, which allows direct contact between the source and drain. The advantages of the new design include avoidance of fabrication-based contact degradation during the isolation etch, lower sensitivity to high gap variations and reduction in the number of contacts needed to close the signal pathway. Also, the new design introduces a novel anti-stiction mechanism. An analytical model is presented which compares the mechanical behavior of the new design to the older design. The devices are fabricated using a silicon nitride hard mask with an ammonium hydroxide based etchant. An inverter made using the new design is demonstrated.
Two 0.125 meter low resolution spectrographs have been built covering the wavelength ranges of 125 -231 nm and 180 -339 nm. Each spectrograph was designed to have high sensitivity, large dynamic range, and modest spectral resolution.There were hard design constraints on collecting area and pointing knowledge.These spectrographs measured the spectrum using a linear array. The wavelength conversion was done via an image intensifier, converting a UV spectrum to green light. The spectrographs had a 0.5° nearly circular field of view with resolutions of <2 nm.After electronics processing, the spectrograph output consisted of a 128 bin spectrum every 0.2 seconds (one scan).The minimum sensitivity was -10 photons /cm2-sec. in a single output scan.With the use of a neutral density filter and an image intensifier automatic range system, the spectrographs had a dynamic range of >l09.
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