Direct-write programming of nanoscale demultiplexer arrays

Abstract

We report a direct- write method to form vertical metal - metal connections between crossing metal wires at a 60 nm pitch. Patterned connections within crossed wire arrays enable construction of nanoscale- to- microscale demultiplexer circuits which are required elements in any integrated nanowire memory, logic or sensing system. However, fabricating dense nano - micro connections below a pitch of similar to 80 nm exceeds standard electron- beam ( e- beam) lithography capabilities, and usually requires more than 10 yield- reducing process steps including two critical pitch overlay alignments. We describe direct- write programming that requires only two high- yield process steps and micron- scale overlay accuracy, and appears to be extendable to sub- 30 nm pitch. Electron- beam irradiation was used to modify the electrical conductivity of a 23 nm insulating polymer film separating metal nanowires and microwires of a demultiplexer crossbar array. Junction conductivities were programmed over five orders of magnitude from G < 10(-11) to G > 10(-6) Omega(-1). Monte Carlo simulations of electron scattering assist optimization of structural design, electron energy and dose. The time, voltage and temperature dependences of programmed junctions indicate that the insulating polymer is graphitized into conductive fragments that show percolation- limited electronic transport.