697GG Nano Computering Fall 2005

CMOL: Device, Circuits, and Architectures

Konstantin K.Likharev and Dmitri B. Strukov Stony Brook University

Prepared by Sheng Xu

The Device

• There is a tradeoff between molecule simplicity and functionality --Simple ones with nonlinear but monotonic I-V curves are insufficient for highly functional intergrated circuits --Complex molecule have many configurations are “soft” to thermal fluctuations --Short and ridig molecules have just few metastable internal states is best choice --Example of a possible circuit: --The challenges : 1. no process is available of acceptable yield yet due to the difficulty to ensure a unique position of the molecule relative to the electrodes possible solutions: chemical synthesis of molecules including large “floating electrodes”; Self-assembled monolayer (SAM) on the surface 2.Fabrication of wires with nanometer-scale cross-section is difficult possible solutions: Nanoimprint, interference lithography

The circuit

• The only plausible way toward high-performance nanoelectronic circuits: hybrid of integrate molecular device, nanowires and CMOS • Fabrication brings the circuit design two requirements: no precise alignment with each other and with CMOS subsystem – The resistivit of semiconductor nanowire would be too high for hybrid circuits – Chemical synthesized semi- nanowires into highly ordered parallel arrays is not available yet.

• An approach and CMOL circuit implementation -form a small angle between nanowire and CMOS wires need precise aligned with former nanowire CMOL modified the form “In-Bar” networks by providing contact pins distributed all over the circuit area.

CMOL Memories

• CMOL architecture need to be defect-tolerant -Chemically-dricted self assemlby of molecular deviecs can not achieve 100% yield – Two major techniques: memory matrix reconfiguration, error correction – Several analysis results: chip area VS linear n size of blocks optimized area per bit VS the molecular device yield

CMOL FPGA: Boolean Logic Circuits

• • • • Why FPGA style circuits -The location of a defective gate from outside is hardly possible -The error detection and correction method is inefficient Two FPGA varieties: LUT & PLA existing problem: – LUT: memory array can not provide address decding and output signal sensing. Must be implemented in CMOS subsystem leading to a large overhead – PLA: the fraction of open device is of the order of on half comparing to LUT’s one devie which leads to a high power consumption. Meanwhile dynamic logic is not realistic in nanodevices.

CMOL cell-based FPGA – Mol FPGA configuration approach to reduce original exponential circuit size.

NOR input

CMOL CrossNets: Neuromorphic Networks

• From Neural network and more… – Neural cell bodies: nanowires – Axon and dendrites: mutually perpendicular nanowires of the CMOL crossbar – Synapses: molecular latching switches – Remark property of CMOL CrossNet: the connectivity could be very large – No external software code needed, can be trained to perform certain tasks.

• Challenges: --swicth between continuous signal and discrete --difficult to control synapse --processes of control single-electron latches are statistical FlossBar CMOL CrossNet