Calculation of Surface Charge Noise at the Si-SiO2 Interface

Abstract

A theoretial analysis of the surface charge noise a t t.he Si-SiO, interface is presented. The interface state charge spectral density is evaluated as a function of the interface state conductance associated with the energy dissipation due t o the electronic exchanges into the interface state reservoir. The interface charge noise spectrum is investigated using different electrical models of the Si-SiO, interfwx. Moreover, a compact formulation of the drain current spectral density both for enhanced and depletion mode MOSFETs is establislicd. It allows a complete anihlysis of the frequency, gate bias, and temperature dependence of the noise spectrum characteristics of an MOS transistor.Une analyse thkorique du bruit de la charge de surface Q l'intcrface Si-SiO, est, prksentee. La dsnsitk spectrale de la charge d'interface est Bvaluke en fonction de la conductance des &tits d'interface associbe A la dissipation d'bnergie dans le rhservoir des ktsts d'interface. 1,e spectre de bruit dc la charge d'interface est investiguk en utilisant diffkrents modkles Blectriqnes de I'interface Si-SiO,. Do plus, une formulation compacte de la donsite spectrale de courant pour drs MOSFETs A enrichissement et Q dBplktion est ktablie. Elle permet une analyse completc de la dkpendance en frBquence, en tension de grille et en tcinpbrature des caracthistiques spectralcs de bruit d'un transistor MOS.

Analytical modelling of the MOS transistor

“…As is well known for MOS capacitors, G, is proportional to the interface state density XbS. Moreorer, if on a certain range of frequency G,/w is constant with frequency, then XQas and finally X1,,lclrarge exhibit a l/f behariour [24].…”

“…One source of fluctuations for the di-aiii current comes froin the fluctuations of the electrical charge a t the semiconductor-oxide interface. I n this process which is nothing but a generalized McWhorter model [ 2 3 I, the current fluctuations evolve from the transfer via the transconductance, of the inversion charge fluctuations induced by those of the total interface charge [24]. A s a result, the drain current spectral density induced by the charge fluctuations, Xldlcharge, is linked to the equivalent pate roltage spectral density Xc, by [24,…”

“…For that, we proceed as for the calculation of noise induced by interface charge fluctuations [24,251. So, let 8Qqq be the charge fluctuation a t the Si-SiO, interface.…”

“…Srditilarge = gnJrg . The gate voltage spectral density Xc, is simply related to the interface charge spectral density SQ,, by the capacitive relationship [34, 251If only fast interface states are inrolred, the interface charge spectral density SQ,, can be shown to be connected, in a general \Tray, to the resistive part of the interface state admittance G, as[24] …”

MOSFET Degradation Studied by Low Frequency Noise, Charge Pumping, and StaticI(U) Measurements

“…7 shows typical noise characteristics representing the variations of the normalized drain current spectral density s,,/I," as a function of drain current I d from weak to strong inversion regimes. This kind of plots is well suited for the diagnosis of the noise mechanism responsible for the drain current fluctuations [18,19]. Indeed, in this case, one can easily see that the normalized drain current noise dependence on gate voltage or drain current is well correlated to that of the corresponding transconductance to drain current ratio squared for virgin and stressed devices.…”