A study of oxide traps and interface states of the silicon-silicon dioxide interface

Abstract

Vacuum-ultraviolet light (10.2 eV) generated electrons or holes are injected into the oxide by dc biasing metal-oxide-semiconductor Al-SiO2 capacitors with 2800-Å (1000 and 1100 °C) dry oxides annealed in dry oxygen at 600 or 800 °C. The injected charges are trapped in the oxide. The trapped charge density is determined by the capacitance-voltage method and its location by the photocurrent-voltage method. The trapped-hole charge injected under positive dc bias was found to be within 100 Å of the oxide-silicon interface. Trapping kinetic data revealed two donorlike neutral hole traps with hole capture cross sections of 6×10−14 and 1×10−15 cm2. Both of these traps, after being positively charged by hole capture, were efficient electron traps with an electron-capture cross section of 3×10−13 cm2. An acceptorlike electron trap with an electron-capture cross section of 1×10−15 cm2 was also detected which anneals out during 800 °C anneal in dry oxygen. Little increase in the interface-state density was observed during the charge-injection and trapping experiments. Analyses of the annealing kinetics of these oxide traps suggest that the larger hole trap is an excess silicon center (trivalent silicon) and the smaller hole trap is an excess oxygen center (nonbridging oxygen).