Microelectromechanical Oscillator-Based Digital Logic Anthony Yeh EE C235, Spring 2009

Introduction Today’s Digital Computing ▫Transistor-based (switches that are on or off) The Parametron (1950s) ▫Dr. Eiichi Goto (University of Tokyo) ▫Digital computing element (analogous to transistor) ▫Based on interference of parametric oscillators (instead of switches) ▫Simpler, cheaper, more reliable than transistors of the time “The History of Computing Project,”

Parametric Oscillation Parametric oscillator versus driven oscillator Parametron used parametric oscillation of LC resonators (by periodically varying capacitance) Eiichi Goto, "The Parametron, a Digital Computing Element which Utilizes Parametric Oscillation,” Proceedings of the IRE, 1959

Parametron Binary Logic Parametric oscillation has two stable states of oscillation  Separated by 180 degree phase shift  Very stable  No drift (only two allowed stable states, energy concentrated in resonant frequency)  Strong force (voltage) required to switch between bistable states (unless oscillation is quenched and then restarted)  Selection of state determined by initial small oscillation  Outputs from multiple Parametrons can be combined to form the input to another Parametron to create logic gates Eiichi Goto, "The Parametron, a Digital Computing Element which Utilizes Parametric Oscillation,” Proceedings of the IRE, 1959

Microelectromechanical Parametron I. Mahboob, H. Yamaguchi ▫NTT Basic Research Laboratories, Japan ▫Demonstrated binary bit storage and bit flip GaAs beam (260 x 84 x 1.35 um) ▫Oscillates in out-of-plane direction Parametric oscillation ▫Vary spring constant of GaAs beam through piezoelectric effect ▫Quantum wells at beam ends concentrate electric fields to achieve efficient actuation I. Mahboob, H. Yamaguchi, “Bit storage and bit flip operations in an electromechanical oscillator,” Nature Nanotechnology, May 2008

Bit Storage and Bit Flip Parametric actuation (piezoelectric) Trigger switch (small initial oscillation) I. Mahboob, H. Yamaguchi, “Bit storage and bit flip operations in an electromechanical oscillator,” Nature Nanotechnology, May 2008

Technological Potential Detailed architecture for Parametron logic already exists ▫As opposed to other recent mechanical logic devices Electromechanical oscillators can be scaled to NEMS ▫Projection: 1um x 100nm oscillator beam ▫Operation frequencies up to 1GHz ▫10 8 bits/cm 2 density ▫Power for bit flip: 10pW (comparable to CMOS) ▫Power for stable oscillation: ~0.01pW Nanoelectromechanical logic-based computers I. Mahboob, H. Yamaguchi, “Bit storage and bit flip operations in an electromechanical oscillator,” Nature Nanotechnology, May 2008