Orientation dependence of interface-trap transformation

Immediately after radiation or hot-electron damage, an interface-trap peak above midgap (~E_v+0.75 eV) invariably appears in MOS capacitors. This peak (designated peak-1), along with its background, continuously changes with time after damage. Three different regimes have been identified: (1) latent generation, (2) interface-trap transformation, and (3) room-temperature annealing. In the present work, the orientation dependence of the interface-trap transformation process is discussed. For samples made on (100) substrates, peak-1 gradually converts into a second peak below midgap, resulting in a double-peak interface-trap distribution. For samples made on (111) substrates, the most salient feature is the gradual shift of the energy position of peak-1 toward the valence band, and eventually a single peak residing below midgap is observed. No discernible double-peak distribution has been found in (111) samples. Results on (110) samples are qualitatively similar to those on (111) samples, whereas (311) samples are similar to (100) samples. The (111) results are interpreted in terms of the atomic relaxation of the dangling-bond defect at the (111)Si/SiO₂ interface