Interface Properties of Si ‐ ( SiO2 ) ‐ Al2 O 3 Structures

Abstract

Aluminum oxide films have been deposited on silicon substrates at 420°C by thermal decomposition of aluminum‐isopropoxide. An electrical evaluation of the interface properties of and structures has been made. MOS capacitance measurements have shown the important role of a postdeposition heat treatment in O2 in eliminating room‐temperature hysteresis and reducing the scatter in flat‐band voltage values of structures. This treatment has an overriding effect on the influence of deposition conditions on interface properties. The density of interface states varies from 1010 to 1011 cm−2 (eV) −1, and the flat‐band voltage (for ∼1000Aå oxide) is about + 2V. The flat‐band voltage gradually shifts to more positive values under large negative bias (field ∼106 V/cm) at 250°C. There is a strong tendency toward localized conduction in these films and there are indications that conduction is controlled by the interface (s) rather than by the bulk material. This problem was alleviated by growing a thin film (∼200Aå) on Si prior to deposition. The interface properties of structures depend on the Si orientation. For (100) orientation, the density of interface states is about 1010 cm−2 (eV)−1 and the flat‐band voltage is zero. The radiation resistance of deposited is better than that of and comparable to that of films prepared by plasma anodization. Irradiation by 1 MeV electrons under +10V bias introduces a density of positive oxide charge of a few times 1012 e/cm2.