Daniel Grogg

Curved in-plane electromechanical relay for low power logic applications

A curved design for in-plane micro- and nano-electromechanical switches based on a single clamped cantilever is proposed, optimized with finite-element simulations and demonstrated experimentally. The design enables precise control of the switch motion and of the closed-state air gap, resulting in a uniform electrostatic field and increased robustness. The switch size and curvature are optimized for actuation voltage, actuation energy and the electrostatic field strength. These optimizations and the proposed fabrication process are amenable to micro- and nano-electromechanical switches. The scalability of the concept is demonstrated with simulations of nanoscale relays in terms of force and energy, showing that the concept is suitable for sub-100 aJ switching energy. Experimental results on microscale devices demonstrate the advantages of the curved MEM switches, namely a fabrication process with a single sacrificial layer for a switch with a low actuation voltage and excellent robustness. The designed as well as the experimentally observed breakdown voltage is four times higher than the contact voltage, thus enabling a large operating window for electromechanical switches. (Some figures may appear in colour only in the online journal)

Modelling NEM relays for digital circuit applications

A reduced-order model for NEM relays is presented that combines electro-mechanical beam actuation and landing of beam tip on the surface electrode. This model shows a deviation of less than 2%, for the DC as well as the transient response for beam actuation in a circuit simulation, when compared to a finite-element simulation. It also shows an excellent match for the energy. The model allows accurate circuit simulation to aid in NEM-relay based logic design, and facilitates the quantification of key gate-level metrics.

Amorphous carbon active contact layer for reliable nanoelectromechanical switches

This paper reports an amorphous carbon (a-C) contact coating for ultra-low-power curved nanoelectromechanical (NEM) switches. a-C addresses important problems in miniaturization and low-power operation of mechanical relays: i) the surface energy is lower than that of metals, ii) active formation of highly localized a-C conducting filaments offers a way to form nanoscale contacts, and iii) high reliability is achieved through the excellent wear properties of a-C, demonstrated in this paper with more than 100 million hot switching cycles. Finally, a full inverter using a-C contacts is fabricated to demonstrate the viability of the concept.

Analytical Compact Model in Verilog-A for Electrostatically Actuated Ohmic Switches

Nowadays, electronics face a challenge regarding the power consumption of integrated circuits (ICs). There is a need for new devices that can provide improved switching capabilities. The downscaled electrostatically actuated ohmic switch, as a (re)emerging device, is a promising candidate to meet this need. To bring such a device seamlessly into IC design, it must be accompanied by an accurate, fast and robust analytical compact model. The development and the main characteristics of such a model are described within this paper. Extensive numerical simulations and measurements have been used to validate the model.

Energy and Latency Optimization in NEM Relay-Based Digital Circuits

Digital circuits based on nanoelectromechanical (NEM) relays hold out the potential of providing an energy efficiency unachievable by conventional CMOS technology. This paper presents a detailed analysis of the operating characteristics of fabricated curved cantilever NEM relays using a comprehensive physical model. The mode of energy distribution within the electrical and mechanical operational domains of the relay is described in detail and the energy saving achievable by the technique of body-biasing is quantified. The analysis further reveals that the latency in a relay can be much larger or much smaller than the nominal mechanical delay depending on the point of actuation in the oscillation of the beam that takes place after pull-out. The methods that can utilize this phenomenon to reduce the latency of relay-based circuits are discussed, thus addressing one of the biggest challenges in NEM relay-based design.

A 6.7 MHz nanoelectromechanical ring oscillator using curved cantilever switches coated with amorphous carbon

Nanoelectromechanical (NEM) switches have the potential to complement or replace traditional CMOS transistors in the area of ultra-low power digital electronics. This paper reports the demonstration of the first ring oscillator built using cell-level digital logic elements based on curved NEM switches. The NEM switch has a size of 5×3 μm2, an air gap of 60 nm and is coated with amorphous carbon (a-C) for reliable operation. The ring oscillator operates at a frequency of 6.7 MHz and confirms the simulated inverter propagation delay of 25 ns. The successful fabrication and measurement of this demonstrator is a key milestone on the way towards an optimized, scaled technology with sub-nanosecond switching times, lower operating voltages and VLSI implementation.

Wafer-level heterogeneous 3D integration for MEMS and NEMS

In this paper the state-of-the-art in wafer-level heterogeneous 3D integration technologies for micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS) is reviewed. Various examples of commercial and experimental heterogeneous 3D integration processes for MEMS and NEMS devices are presented and discussed.

Ultra-low-energy adiabatic dynamic logic circuits using nanoelectromechanical switches

Nanoelectromechanical (NEM) switches have the unique property of virtually zero leakage current, making it an appealing candidate for implementing dynamic logic circuits. However, NEM switches have relatively slow switching times (tens of nanoseconds) due to their mechanical nature. Adiabatic Dynamic Logic (ADL) is an approach that can achieve ultra-low-energy dissipation when operating at electrically slow speeds. We show through simulation that NEM switches can be used to implement ADL circuits that exploit its zero leakage property while operating at mechanically fast switching speeds. At least an order of magnitude reduction in energy consumption compared to conventional circuit design is shown in simulation using analytical compact modeling.

NEM switch technologies for low-power logic applications

The abrupt switching characteristic of nano-electromechanical (NEM) switch devices is an attractive characteristic to design energy-efficient circuits. In this paper we report the optimization of an in-plane curved cantilever switch geometry for high robustness and low switching energy. The scaling potential has been evaluated, showing that sub-100 aj switching energy is possible. The curved cantilever design has been validated experimentally with good electrical characteristics and high mechanical robustness.

Impact of the gas environment on the electric arc

The influence of the oxygen concentration on the break arc is observed in a range of 0 to 50 % oxygen in an oxygen-nitrogen mixture under a resistive DC load of 55.5 V and 10 Ω. The arc characteristics are observed by means of oscilloscope traces and high speed camera images showing a clear correlation of the arc motion and the speed of the motion with the oxygen concentration. In contrast, the electrical characteristics change only little over all gases containing oxygen and show a large difference for pure nitrogen. The motion of the arc on AgSnO2 and AgNi 0.15 is influenced in different ways by the higher oxygen concentration. The average distance between cathode spots (arc step) from frame to frame (observed at 483000 images/s) is lowest for pure nitrogen for both materials. For AgSnO2, the arc step increases with increasing oxygen concentration at low oxygen levels and reaches a maximum step size at 15 to 20 % oxygen. For AgNi 0.15 larger arc steps are observed at 5 % oxygen, decreasing with increasing oxygen concentration over the whole range. These experiments show the importance of oxygen on the arc behavior and, therefore, on the relay behavior.