The structural aspects of non-crystalline SiO2 films on silicon: a review

Abstract Thermal oxidation of silicon results in vitreous (v) SiO 2 films that are non-crystalline (nc) but have a high degree of short-range-order and bond ordering that is usually not the case with amorphous solids. This combination results from the small variation of the Si–O bond energy as the Si–O–Si bond angles ( φ ) vary from less than 120° to ∼180°. The flexibility of the nc structure is responsible for the crucially important low density of interface states resulting from the quasi-epitaxial accommodation of the growing oxide to the Si substrate. The grown oxide is in a non-elastically compressed (densified) state which profoundly affects various properties. The bond energy increases rapidly as φ becomes less than ∼120°. These ‘strained’ bonds are responsible for several electrical effects as, for instance, hole trapping. SiO 2 films prepared by deposition or O + implantation techniques are similar to thermally grown oxides, as they are also non-crystalline, but some of their properties are significantly different.