Abstract
On-wafer evaluation of white thermal and shot noise in nanoscale MOSFETs is demonstrated by directly sensing the drain current under zero- and nonzero-drain-bias ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{d}$ </tex-math></inline-formula> ) conditions for the first time, without recourse to a hot noise source, commonly needed in noise figure measurement. The dependence of white noise intensity on the drain bias clearly shows thermal noise at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{d} \boldsymbol = {0}$ </tex-math></inline-formula> V and shot noise at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{d} > {0}$ </tex-math></inline-formula> V with its gate-bias-dependent suppression. An empirical expression for the Fano factor (shot-noise suppression factor) that is well-behaved even at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{d} \boldsymbol = {0}$ </tex-math></inline-formula> V exactly and suitable for measurement-based evaluation is proposed. The direct measurement approach could allow more accurate and predictive noise modeling of RF MOSFETs than has conventionally been possible.
Highlights
M OSFETs are known to exhibit flicker noise at low frequencies (LFs) and white noise at high frequencies (HFs)
OHMORI AND AMAKAWA: DIRECT WHITE NOISE CHARACTERIZATION OF SHORT-CHANNEL MOSFETs ac-component of dc drain current is amplified by the low-noise amplifier (LNA) in the noise probe and its output is read by a spectrum analyzer (N9030A, Agilent Technologies)
We have developed a methodology for conveniently characterizing white noise of dc-biased nanoscale MOSFETs through wafer probing without a hot noise source or complicated de-embedding procedures
Summary
M OSFETs are known to exhibit flicker (or 1/ f ) noise at low frequencies (LFs) and white noise at high frequencies (HFs). White noise in MOSFETs is typically characterized by noise figure (NF) measurement at RF, where flicker noise is negligible. There have, been some reports on “cold” direct noise measurement of discrete MOSFETs over frequencies ranging from flicker noise region to white noise region [17], [18]. A proofof-concept noise probe that extended the maximum measurable frequency to above 100 MHz was demonstrated in [19] and [20]. It has a broadband low-noise amplifier (LNA) built in the probe itself, thereby reducing the parasitic capacitance significantly.
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