Improvement in breakdown field strength of thin thermally grown SiO2 by selective anodic oxidation

Oxide reliability is a major concern for the thin gate oxides of future ULSI technology. For controlled growth of ultra-thin oxide, it is necessary to carry out the gate oxidation at comparatively lower temperature. However, due to the increase of the weak spots and pinholes in the low temperature grown oxides, they exhibit poor dielectric strength, high leakage current and high interface trap densities. This paper proposes a method, which identifies the weak spots and repairs them by selective anodisation. After the thermal gate oxidation, during the anodisation, current flows only through the weak spots in the oxide. Anodic oxide therefore grows over these weak spots, improving the stability of the oxide. An improvement in electrical characteristics was observed in the gate oxides treated by anodic oxidation under optimized conditions.