A spectroscopic ellipsometry study of the interfacial stresses and their correlation with microvoids in very thin thermally grown SiO2 films

Abstract

The intrinsic stress in the interfacial region of the SiO₂/Si interface was estimated, with in situ spectroscopic ellipsometry (SE) during a dry etching process of thermally grown oxides, to be 3.8 kbar. Furthermore, the microvoids distribution, in very thin thermally grown SiO₂ films studied with ex situ SE, was found to be correlated with the stress distribution in the direction of the oxide growth. The voids volume fraction exhibits an exponential decay behavior versus the oxidation time with a relaxation time similar to the strain relaxation time reported in the literature. The SE‐calculated voids relaxation time, 60 min (12 min) for oxides grown at 900 °C (1000 °C), is also predicted from IR results obtained through the dependence of the Si–O stretching frequency on the oxidation time.