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

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 the companion paper [80] 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-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-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.