Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences


UC Berkeley


2008 Research Summary

Aluminum and Nickel Nano-Electro-Mechanical Relays for Low Power Electronics

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Joanna Lai, Hei Kam, Borivoje Nikolic and Tsu-Jae King Liu

Power consumption in current CMOS technology has emerged as a major challenge as transistor gate lengths continue to scale. The static leakage power has emerged as a major concern due to the exponential increase with gate length and gate dielectric reductions. Scaling power supply voltages in current technology has proven difficult due to fundamental limits for subthreshold swing (S ≥ 60 mV/dec).

We propose a novel nano-electromechanical (NEM) relay to achieve ideal switching behavior and subthreshold swings below the 60 mV/dec limit. The relay consists of a mechanically-actuated metal-insulator-metal (MIM) stack, positioned so that it can short the source and drain electrodes located in a separate plane. The lower metal layer is the gate electrode, which is a cantilever beam. An insulator electrically isolates the gate from the top metal layer, the metallic channel. The mechanical gate is actuated by a voltage difference applied between the gate and a separate body electrode. In the off-state, no conduction path exists to connect the source and drain electrodes, thus allowing zero leakage current. In the on-state, the metallic channel shorts the source and drain, providing low on-state resistance.

Prototype NEM relays and simple logic gates such as inverters, NAND and NOR logic gates, and ring oscillators are being fabricated. The mechanical properties of aluminum and nickel are being optimized. As well, silicon or molybdenum sacrificial layers for nanogap formation are being investigated to achieve this device. Due to the low-thermal budget in the fabrication, the NEM relays can be fabricated directly over CMOS electronics.

Figure 1
Figure 1: Cross-section schematic of NEM relay