Dry Thermal Oxidation of Polycrystalline and Amorphous Silicon Films for Application to Thin Film Transistors

Abstract

Dry thermal oxidation of polycrystalline silicon (p-Si) and amorphous silicon (a-Si) has been studied. An oxidation temperature of 1070°C is a break point, at which the oxidation time of one atomic layer is nearly equal to the stress relaxation time. Below the break point temperature, oxidation stress is not relaxed at the silicon-oxide interface, because the stress relaxation time is longer than the oxidation time of one atomic layer. The high oxidation stress, together with the presence of grains and grain-boundaries, makes the interface rough, resulting in poor electrical properties in p-Si thin film transistors (TFTs). It is, therefore, important for fabricating good TFTs that p-Si or a-Si films are oxidized under conditions such that the oxidation time of one atomic layer is longer than the stress relaxation time to relax the oxidation stress at the interface.