Electronic Design

Nanoscale Printed-Circuit Board Targets Interconnects

Hewlett-Packard may have the key to wiring nano-scale circuits without using high-resolution lithography. U.S. patent 6,314,019, which covers molecular wire crossbar interconnects, is one of a group of patents recently awarded to Philip Keukes, R. Stanley Williams, and James Heath.

The technology starts with a set of parallel wires on a silicon substrate. A molecular layer chosen for its electrochemical properties is deposited next, followed by another set of wires that are usually perpendicular to the first set. This regular array can then be configured electrochemically. Circuits can be created after the wiring is configured.

Configuration is done by applying voltages to one horizontal and one vertical wire. Three distinct voltages are used with the system. One will form a switch junction between the two wires. Another will oxidize the wire, essentially cutting it in two. The third and lowest voltage is used to connect circuits using the new wiring (see the figure). The latter is used once the system is configured.

The result is an architecture similar to a two-layer pc board with plated through-holes. This approach does not require the accuracy of lithography or lasers, and wire positioning isn't critical. Wires simply mustn't touch their neighbors. Creation of junctions and cuts is faster as wires get smaller. Some operations can be performed in parallel if wiring is symmetrical, which is the case for structures like memories.

Work in the lab hasn't reached the nanometer level, but the process has been demonstrated using larger wires. It may just be ready when nanoscale circuits are available for interconnections. HP has received related nanoscale circuit patents, too.

For more details, go to www.hp.com.

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