Enabled by advances in our basic scientific understanding at the molecular and atomic scales, we can now engineer designed nanostructures without using lithography. Key features can be a few nanometers wide---a few silicon atoms wide, perhaps the ultimate scale for devices. This allow us to design computing components without the costs or limits of ultra-fine lithography. Design at this scale, however, will not simply be an extension of our familiar VLSI design. We may not be able to directly pattern complex features, but rather must exploit basic physical properties to define feature sizes, self-assembly to create ordered devices, and post-fabrication reconfigurability to define functionality and mask defects. This creates new challenges for design and exposes a different cost structure which motivates different computing architectures than we found efficient in conventional, lithographically patterned silicon. I will review the emerging nanoscale fabrication building blocks, sketch a hybrid fabrication scheme which uses these building blocks along with lithography, and present a plausible architecture for nanoscale electronics based on silicon nanowires. I demonstrate that these nanoscale constructs are sufficient to provide universal logic functionality with all logic and signal restoration operating at the nanoscale.
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