Starting with a brief review on 0.1-/spl mu/m (100 nm) CMOS status, this paper addresses the key challenges in further scaling of CMOS technology into the nanometer (sub-100 nm) regime in light of fundamental physical effects and practical considerations. Among the issues discussed are: lithography, power supply and threshold voltage, short-channel effect, gate oxide, high-field effects, dopant number fluctuations and interconnect delays. The last part of the paper discusses several alternative or unconventional device structures, including silicon-on-insulator (SOI), SiGe MOSFET's, low-temperature CMOS, and double-gate MOSFET's, which may lead to the outermost limits of silicon scaling.

Based on a first order cycle time model performance trends and limits are projected for both bipolar and CMOS processors. The key in identifying trends is the understanding of the pivotal factors at any given stage of technology progression. One such parameter is the physical area of the processor. In coming technologies there will be opposite demands placed on the system's area stemming from a need to reduce the proportion of interconnection capacitance and to send signals across the processor. Contrary to the usual perception, delays resulting from wiring capacitance decrease if processor area increases, while the minimization of signal travel times favors reducing area. The system size tradeoff in the case of bipolar processors is primarily determined by power density, while CMOS processor sizes are determined by wirability requirements. To achieve the full potential of CMOS, interconnections will have to be carefully planned. The performance limits of bipolar and room temperature CMOS uniprocessors are shown to be very similar. The highest performance technology on the horizon is liquid nitrogen temperature CMOS. Alternate technologies, based on III-V compound devices, or more exotic quantum structures, are not expected to play a role in future general-purpose high-end systems.>

Results based on a new cycle-time model are presented to demonstrate performance trends for complex bipolar ECL-CSEF and CMOS processors. It is shown that performance constraints are quite different for these two systems. For a given design the performance of a CMOS processor is tied to lithography, whereas future CSEF bipolar processors will be gated primarily by the power density capability of the package. Liquid nitrogen temperature (LN/sub 2/) CMOS is seen as having the potential to become the highest performance technology for mainframe uniprocessors.>