David Esseni

On interface and oxide degradation in VLSI MOSFETs. II. Fowler-Nordheim stress regime

For pt. I see ibid., vol. 49, pp. 247-53 (2002).The assessment of the physical mechanisms governing the degradation of thin oxides is a very important and, unfortunately, elusive issue that has raised significant debate in recent literature. In this paper, we first use some of the results reported in Pt. I to estimate a reasonable boundary for the efficiency of a possible hydrogen release (HR) mechanism and argue that the HR appears too weak to explain our measurements of stress-induced leakage current (SILC) produced by Fowler-Nordheim (FN) tunneling stress measurements. Then, we present an in-depth investigation of the anode hole injection (AHI) mechanism at low stress gate voltages (V/sub G/). To this purpose, we used both previously discussed and ad hoc devised characterization techniques. Our results indicate that AHI is still operative at V/sub G/ lower than previously experimentally demonstrated. Furthermore, the correlation between the energy of holes at the anode, their injection into the oxide, and the eventual generation of SILC strongly indicate that AHI is the mechanism governing oxide degradation in the considered stress conditions.

On interface and oxide degradation in VLSI MOSFETs. I. Deuterium effect in CHE stress regime

This paper analyzes in detail the generation of interface states (N/sub it/) and stress-induced leakage current (SILC) during channel hot electron (CHE) stress experiments in the context of a possible hydrogen/deuterium (H/D) isotope effect. Our results show that N/sub it/ generation is related to the hydrogen release (HR) at the Si-SiO/sub 2/ interface at relatively high V/sub G/ where a large isotope effect is found. Instead, for gate voltages (V/sub G/) favorable for hot hole injection (HHI) the N/sub it/ creation becomes a unique function of hole fluence and the isotope effect disappears. In the studied stress conditions, we found no experimental evidence supporting a causal relation between SILC generation and HR because no isotope effect is observed even when the corresponding N/sub it/ measurements reveal a very different D/H release rate. Similar to N/sub it/ generation, we found that SILC becomes a unique function of hole fluence at low stress V/sub G/. Relevant implications and extensions of these results to the Fowler-Nordheim (FN) tunneling stress conditions are discussed in Pt. II.