The fabrication of crossbar memories with sublithographic features is expected to be feasible within several emerging technologies; in all of them, the nanowire (NW) decoder is a critical part since it bridges the sublithographic wires to the outer circuitry that is defined on the lithography scale. In this paper, we evaluate the addressing scheme of the decoder circuit for NW crossbar arrays, based on the existing technological solutions for threshold voltage differentiation of NW devices. This is equivalent to using a multivalued logic addressing scheme. With this approach, it is possible to reduce the decoder size and keep it defect tolerant. We formally define two types of multivalued codes (i.e., hot and reflexive codes), and we estimate their yield under high variability conditions. Multivalued hot decoders yield better area saving thann-ary reflexive codes, and under severe conditions, reflexive codes enable a nonvanishing part of the code space to randomly recover. The choice of the optimal combination of decoder type and logic level saves area up to 24%. We also show that the precision of the addressing voltages when a high variability affects the threshold voltages is a crucial parameter for the decoder design and permits large savings in memory area. Moreover, a precise knowledge about the variability level improves the design of memory decoders by giving the right optimal code.

Several technologies with sub-lithographic features are targeting the fabrication of crossbar memories in which the nanowire decoder is playing a major role. In this paper, we suggest a way to reduce the decoder size and keep it defect tolerant by using multiple threshold voltages (VT), which is enabled by our underlying technology. We define two types of multi-valued decoders and model the defects they undergo due to the VT variation. Multi-valued hot decoders yield better area saving than n-ary reflexive codes (NRC), and under severe conditions, NRC enables a non-vanishing part of the code space to recover. There are many combinations of decoder type and number of VT’s yielding equal effective memory capacities. The optimal choice saves area up to 24%. We also show that the precision of the addressing voltages for decoders with unreliable VT’s is a crucial parameter for the decoder design and permits large savings in memory area.