[Legacy Report] Noise in Deep-submicron CMOS Transistors

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Abstract — During the early decades of their existence, MOS transistors were considered unsuitable for RF and low-noise applications due to their lower cutoff frequencies and higher noise, as compared to bipolar devices. With shrinking gate lengths, and cutoff frequencies in the upper millimeter wave frequency range, that perception began to change in the 1990s, with CMOS devices now becoming the workhorse for all but the most demanding of low-noise applications. A critical element in their widespread use in low-noise RF designs is the availability of CMOS device noise models. While the widespread use of CAD tools, some of them including noise models, gives the impression that things are well understood and under control, numerous difficulties exist. So-called “noise models” of CMOS devices often tend to be little more than empirical curve-fitting exercises; lack of robust parameter extraction methods prevents parametric studies based on experimental data; predictions of noise for devices with new (not merely scaled) designs is fraught with problems; and the impact of deep-submicron geometries on the high-frequency noise is still a subject of debate. This talk will trace the development of understanding in this area, and report the progress made on several fronts in CMOS noise investigation, including 1/f noise in the devices.

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