Dielectric and interface properties of pyrolytic aluminum oxide films on silicon substrates

Abstract

Aluminum oxide films have been deposited on silicon substrates by thermal decomposition of aluminum-isopropoxide. MOS capacitance and conductance measurements have been made on Al2O3-Si structures,and the influence of deposition parameters and silicon surface preparation on interface properties has been examined. The density of interface states varies from 1010 to 1011 cm−2(ev)−1, and the flatband voltage (for ∼1000A oxide) can vary between zero and several volts positive depending upon the deposition parameters and silicon surface preparation. Postdeposition annealing in moist or dry-O2 at 800°C decreases the flatband voltage. Infrared measurements indicate that this effect is accompanied by the growth of a thin interface SiO2 film. Only a very thin interface SiO2 film (∼50A) is required to produce zero flatband voltage. Biastemperature stress increases the flatband voltage value under negative gate bias. Excessive localized conduction and breakdown can be correlated with the occurrence of silicon surface defects. The radiation resistance of Al2O3-Si structures is strongly dependent upon the presence of a thin interface SiO2 film.