QCA Circuits for Robust Coplanar Crossing

Quantum-dot cellular automata (QCA) [16] may overcome some of the limitations of current technologies, while meeting the density foreseen by Moore's Law and the International Technology Roadmap for Semiconductors (ITRS). For manufacturing, molecular QCA implementations have been proposed to allow for room temperature operation; the feature of wire crossing on the same plane (coplanar crossing) provides a significant advantage over CMOS. Coplanar crossing is very important for designing QCA circuits; multi-layer QCA has been proposed [4] as an alternative technique to route signals, however it still lacks a physical implementation. At design level, algorithms have been proposed to reduce the number of coplanar wire crossings [9]. In QCA circuits, a reliable operation of coplanar crossing is dependent on the temperature of operation. Resilience to temperature variations due to thermal effects is also an important feature to consider for practical applications. A reduction in the probability of generating an erroneous signal is also of concern, hence, robustness must be addressed.