HYSTERESIS-LIKE FLATBAND VOLTAGE INSTABILITIES IN Al/Ta2O5-SiO2/Si STRUCTURES AND THEIR CONNECTION WITH J-V CHARACTERISTICS

Abstract

Flatband and current-voltage instabilities in unstressed Al/Ta 2 O 5 -SiO 2 /Si structures were studied in details. It has been found that, after an initial run left on fresh samples, both C-V and J-V characteristics exhibit repeatable patterns. Precisely repeatable counterclockwise hysteresis-like loop in C-V characteristics occurs, while no significant hysteretic behaviour is observed in static J-V characteristics. The reduced instability in J-V characteristics is explained by mutual compensation of two opposite effects owing to the presence of trapped positive charges on slow traps in the interfacial SiO 2 -like layer: (i) flatband voltage shift and (ii) lowering of Fowler-Nordheim tunnelling barrier for holes injected from the Si substrate. Correct determination of equivalent oxide thickness and fast interface state densities requires using the C-V curves obtained during the runs right, because progressive trapping on slow states occurs during the runs left. Value of the oxide charge is to be determined using the value of the flatband voltage obtained from the run left (after an initial run right), since it corresponds to the state of empty slow traps.

Analysis of Conduction and Charging Mechanisms in Atomic Layer Deposited Multilayered HfO2/Al2O3 Stacks for Use in Charge Trapping Flash Memories

“…After this initial irreversible change, repeatable patterns of the − curves are obtained depending generally on the starting voltage. This is a common behavior of the metal/high-/SiO 2 /Si structures, as we have shown in [24].…”

“…Namely, as we have shown in the work [22], voltage stress causes an increase of the capacitance in accumulation ( 0 ) by effective thinning of the SiO 2 layer by creation of conductive paths in this layer during the stress, as it was previously found from stress induced leakage current characteristics in the work [23]. Detailed study of the variations of − characteristics with consecutive runs has been reported in [24].…”