Process-Variation Effect, Metal-Gate Work-Function Fluctuation, and Random-Dopant Fluctuation in Emerging CMOS Technologies

Abstract

This paper, for the first time, estimates the influences of the intrinsic-parameter fluctuations consisting of metal-gate work-function fluctuation (WKF), process-variation effect (PVE), and random-dopant fluctuation (RDF) on 16-nm-gate planar metal-oxide-semiconductor field-effect transistors (MOSFETs) and circuits. The WKF and RDF dominate the threshold-voltage fluctuation (σV th ); however, the WKF brings less impact on the gate capacitance and the cutoff frequency due to the screening effect of the inversion layer. The fluctuation of timing characteristics depends on the σV th and is therefore proportional to the trend of σV th . The power fluctuation consisting of the dynamic, short-circuit, and static powers is further investigated. The total power fluctuation for the planar MOSFET circuits is 15.2%, which is substantial in the reliability of circuits and systems. The static power is a minor part of the total power; however, its fluctuation is significant because of the serious fluctuation of the leakage current. For an amplifier circuit, the high-frequency characteristics, the circuit gain, the 3-dB bandwidth, the unity-gain bandwidth power, and the power-added efficiency are explored consequently. Similar to the trend of the cutoff frequency, the PVE and RDF dominate both the device and circuit characteristic fluctuations due to the significant gate-capacitance fluctuations, and the WKF is less important at this simulation scenario. The extensive study assesses the fluctuations on circuit performance and reliability, which can, in turn, be used to optimize nanoscale MOSFETs and circuits.

A Survey on Low-Power Techniques with Emerging Technologies

“…Therefore, this removes the major source of variability in current deep-submicron technology, that is, the random dopant fluctuation [Li et al 2010], which positively impacts the variability records. Note that the back plane is doped but has no impact on variability since the back plane only plays a support role.…”

Variation-aware deterministic ATPG

“…Therefore, gate delays are random variables described by a probability distribution. While uncorrelated variations have been predicted to be dominant in the nanoscale technologies [16][17][18], our approach is based on Monte-Carlo experiments and therefore works independent of the distribution. We will report experimental results for both uncorrelated and uncorrelated variations.…”

Advancement in Nanoscale CMOS Device Design En Route to Ultra-Low-Power Applications

“…The use of metal as a gate material introduces a new source of random variation due to the dependence of work function on the orientation of metal grains. Influences of the intrinsic parameter fluctuations and the metal gate workfunction fluctuation (WKF), process-variation effect (PVE), and random dopant fluctuation (RDF) on 16-nm-gate bulk MOSFETs' dc/ac and circuits' timing/power/high frequency characteristics are reported in [24]. The vast study assesses the fluctuations on digital circuit performance and reliability, which may benefit CMOS design and technology in the sub-22-nm era.…”

“…However, the rate of leakage reduction with temperature is diminished with technology scaling. Punch-through leakage current is increased with technology scaling; however, it can be significantly reduced [24] by cooling and by anti-punch-through implantation. Leakage current due to DIBL effect is increased with scaling and is almost insensitive to the temperature.…”