Si/SiO2 interface studies by spectroscopic immersion ellipsometry and atomic force microscopy

Abstract

The dependence of the Si/SiO2 interface characteristics on the thickness and oxidation temperature for SiO2 films grown on different Si orientations was studied by spectroscopic immersion ellipsometry (SIE) and atomic force microscopy (AFM). Essentially, SIE uses liquids that match the refractive index of the films, thereby optically removing the films and consequently increasing the sensitivity to the interface. We show that as the thickness of the thermally grown SiO2 overlayer increases, the thickness of the suboxide layer at the interface also increases, and the average radius of the crystalline silicon protrusions (roughness) at the interface decreases for the three different Si orientations (100), (110), and (111), and two different oxidation temperatures (800 and 1000 °C) studied. The dependence of the interface roughness on the thickness of the SiO2 overlayer was confirmed by AFM. The results include unintentionally and intentionally roughened Si samples and are shown to be consistent with the commonly accepted Si oxidation model.

Structural characterization of radiofrequency magnetron sputter deposited SiO2thin films

“…If an abrupt transition from the a-SiO 2 thin film to c-Si occurs, a one-layer model should work and if there is a transition layer between the main SiO 2 layer and the Si substrate, a two-layer model should be used. Both cases have been reported by other researchers via various characterization techniques [12][13][14][15][16][17][18][19][20]. We checked the one-layer model, two-layer model, surface and interface roughness, layer density and layer thickness.…”

“…Via a high-resolution core-level photoemission spectroscopy measurement, Grunthaner et al [13] and Himpsel et al [14] suggested a substoichiometric interfacial layer of compressed SiO 2 or approximately 1 nm and perhaps extending to 3 nm in thickness. Spectroscopic immersion ellipsometry [15,16], which is an interface sensitive technique, detected a thin layer of higher refractive index, which was interpreted as a region of suboxide formation and compressed SiO 2 . By using x-ray reflectivity, Woronick et al [17] observed the presence of a higher-density interface layer of about 4.5 nm at the SiO 2 /Si interface.…”