Observation of positively charged state generation near the Si/SiO2 interface during Fowler–Nordheim tunneling

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Abstract
In previous work, we have established that thin oxide (40–50 Å) MOSstructures exhibit, prior to large levels of Fowler–Nordheim injection, the ideal tunneling behavior of a uniform trapezoidal barrier with thick oxide properties. With increasing levels of electron injection towards the Si/SiO2interface (up to 6×1018 e/cm2), a build‐up of excess current results. This behavior is shown to be due to the generation of positive states in the SiO2 about 14 Å from the Si/SiO2interface, giving excellent agreement with our analysis of charge‐assistedtunneling. The approach is seen to offer a sensitive probe of the oxide interfacial region, capable of locating and detecting as few as 1010 cm−2 positive states. Comparisons are made among three oxidation processes, revealing wet oxides to be more susceptible than dry oxides to the state generation process. The results are consistent with the mechanism of breaking strained Si–O–Si bonds near the interface, observed in x‐ray photoelectron spectroscopy experiments.

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