Charge-Based Compact Model for Bias-Dependent Variability of 1/ $f$ Noise in MOSFETs

Variability of low frequency noise (LFN) in MOSFETs is bias-dependent. Moderate-to-large-sized transistors commonly used in analog/RF applications show 1/f-like noise spectra, resulting from the superposition of random telegraph noise. Carrier number and mobility fluctuations are considered as the main causes of LFN. While their effect on the bias-dependence of LFN has been well investigated, the way these noise mechanisms contribute to the bias-dependence of variability of LFN has been less well understood. LFN variability has been shown to be maximized in weak inversion (subthreshold), while increased drain bias also increases LFN variability. However, no compact model has been proposed to explain this bias-dependence in detail. In combination with the charge-based formulation of LFN, this paper proposes a new model for bias-dependence of LFN variability. Comparison with experimental data from moderately sized nMOS and pMOS transistors at all bias conditions provides insight into how carrier number and mobility fluctuation mechanisms impact the bias-dependence of LFN variability.