Exploiting the Third Dimension: Stackable Quantum-dot Cellular Automata

The exponential growth of transistor density in integrated circuits is doomed to fail at the limits of physics in the foreseeable future. Quantum-dot Cellular Automata (QCA) is a post-CMOS contestant from the emerging Field-coupled Nanocomputing (FCN) paradigm which offers computations with tremendously low power dissipation. Recent physical accomplishments in this area also motivated the developments of corresponding design automation methods. However, although the higher integration density of QCA makes this technology a promising candidate for stacked, i.e. cuboid-like, chip architectures, all design automation solutions proposed thus far are limited to 2-dimensional architectures only. This work showcases the potential when the third dimension is additionally utilized. To this end, we must overcome certain obstacles for which corresponding solutions are proposed. Case studies on important regular structures such as bitwise AND/OR, binary adders, or multiplexers—for which we provide automatic generation scripts—confirm that exploiting the third dimension in this fashion yields a prodigious reduction in area occupation and cell count, differing by several orders of magnitude compared to the state of the art.

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