Growth of ultrathin silicon dioxide films during rapid-thermal oxidation

Growth of thin silicon oxide is the basis for modern IC technologies. The Deal-Grove model explains and predicts well the growth of oxide for thick films. Yet it fails for thin films. Other models based on the Deal-Grove mechanisms cannot be extended out of their fitting ranges to thinner films either. Recently, advanced experimentation such as isotopic labeling and medium-energy ion-scattering spectroscopy has found a hybrid or transitional layer between pure silicon dioxide and pure silicon during silicon oxidation. This paper established a physically consistent model for growth of oxide by considering a volumetric reaction in the transitional layer, in addition to the reaction at the interface of SiO₂/Si. The volumetric reaction plays a more important role for thin films, while the model approaches the Deal-Grove limits for thick films. The paper also studied the hybrid layer or transitional layer for the oxide grown in Axcelis´ hot-wall based rapid thermal furnace by using an advanced SIMS (secondary ion mass spectroscopy). The thickness of the transitional layer is between 20 to 40 angstroms for different growth temperatures. The model established in the study correctly predicts the growth rate of oxide for both ultrathin films and thick films, and the thickness of the transitional layer.