INFLUENCES OF THERMAL ANNEALING, THE ELECTROLYTE PH, AND CURRENT-DENSITY ON THE INTERFACE STATE DENSITY DISTRIBUTION OF ANODIC MOS STRUCTURES

An investigation of the effect of thermal annealing and anodization pa rameters, such as the electrolyte pH and current density, on capacitan ce-voltage and interface state density distribution characteristics ha s been made. Al(anodic oxide) SiO2/p-Si MOS structures were prepared: in 0.1 M K2SO4 electrolyte with a pH of 7 (the 0.1 M KOH solution was buffered with H2SO4) at current densities of 3, 5, and 7 mA/cm(2) and with four different pH; values of the electrolyte at 3 mA/cm(2). It is found that thermal annealing a relatively low temperature can be used to improve the anodic MOS characteristics. Moreover, of the pH and cu rrent density it followed that the pH has a dominant role in the inter face electrical properties. The lowest interface state densities at th e maximum and the midgap positions are 7.1 x 10(11) and 2.7 x 10(10) e V(-1) cm(-2) for a sample made with pH = 7, J = 3 mA/cm(2). The charac teristics of this sample seem satisfactory for device applications of anodized p-Si.