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The intrinsic states and fixed charges of the Si-SiO2 interface.

Intrinsische Zentren und fixe Ladungen in der SiSiO2-Grenzfläche
: Klausmann, E.; Fahrner, W.R.; Bräunig, D.

Barbottin, G.; Vapille, A.:
Instabilities in silicon devices. Silicon passivation and related instabilities. Vol.2. Chapter 11
Amsterdam, 1989
Book Article
Fraunhofer IAF ()
Fixe Oxidladungen; fixed oxide charges; generation-recombination centres; Generations- und Rekombinations-Zentren; Grenzflächenzustand; Halbleiter-Isolator-Grenzfläche; interface states; MOS capacitor; MOS-Kondensator; semiconductor-insulator-interface

The four types of charges currently encountered in the Si-SiO sub 2 structure are first re-defined and the presently recommanded terminology and symbolism given. The interface states can exchange carriers with both bands of silicon and we can derive the equations of the exchange kinetics in the general case. These equations simplify for given experimental conditions. Four cases are thus studied, of which one that lets us calculate the admittance of interface states (discrete or distributed). We calculate next the admittance of the total MOS capacitor in which we take into account the admittance of the interface states. By comparing the theoretical behaviour with the experimental one, we conclude that the proposed circuits cannot explain such phenomenon as frequency dispersion. We must introduce another variable: surface potential fluctuations. Three models taking this new parameter into account are thus presented (including the statistical model of Nicollian and Goetzberger and Brews' approach). Equivalent circuits are also proposed for those cases in which the action of minority carriers cannot be neglected. The action of interface states, of the fixed interface charge and of surface potential fluctuations on the C(V) curve is studied from a phenomenological point of view. We next review those manufacturing process steps which may enhance or reduce the magnitude of both types of interface charges. Finally we indicate briefly the many models proposed in literature to explain the origin of both types of chages. The reader will find in the following chapter (Chap.12) a detailed review of the electrical techniques used to characterize interface states.