A 64-Bit Arm CPU at Cryogenic temperatures: Design Technology Co-Optimization for Power and Performance

Compute demand has grown over 100X within the last decade and has well surpassed the growth in classical Moore's Law transistor density (Fig. 1 (a) [1]). Plateaued dimension scaling even with fin depopulation, short channel effects and shrinking wire dimensions (leading to exponential rise in resistance) have made matters worse. Modern microprocessor designs are now equally limited by transistor and wire performance (e.g., Fig. 1 (b)). Thus, advancements in both transistors and interconnects are needed alongside new architectures to meet the datacenter and High-Performance Computing (HPC) demands. Low-temperature CMOS has emerged as a potential way to provide the needed process technology advancement [2], [3]. Operating CMOS at low temperatures (down to -77K) improves transistor carrier mobility (μ), subthreshold swing (SS) and source/drain resistances, but also increases transistor threshold voltage, V_th, (due to Fermi potential shift and bandgap widening [4]). Despite the increased Vth, overall performance improvements with low temperature CMOS have been demonstrated with appropriate process changes [5]. Additionally, bulk resistivity of wires also improves with temperature reduction [10].