Ultrathin Gate Dielectrics grown in Mixtures of N2O and O2 Using Rapid Thermal Oxidation

Abstract

ABSTRACTA study comparing the oxide growth and electrical properties of 60Å oxides grown in different mixtures of O2 and N2O was performed. The oxide growth for all mixtures examined, as well as that of the pure O2 and N2O cases, fit a Deal-Grove oxidation model modified for Rapid Thermal Oxidation (RTO). Linear growth rate constants found for both a simple linear model and the modified Deal-Grove model are significantly greater for mixtures containing only 35% O2 than for pure N2O oxidation. The uniformity of the oxide growth across the wafer for the gas mixtures resembles that seen in pure N2O oxidation rather than pure O2 oxidation. The electrical properties were measured using Surface Photo-Voltage (SPV) techniques along with conventional Capacitance-Voltage (C-V) and Current-Voltage (I-V) techniques. Oxides grown in 100% N2O showed significantly higher oxide charge when compared to oxides grown in 100% O2. An in-situ anneal in an Ar ambient reduces the oxide charge for all gas mixtures examined. The higher oxide charge accompanies an increase in the interface trap density for the oxides grown in 100% N2O. The in-situ anneal reduces the interface trap density for oxide grown in 100% O2 but has little effect for oxides grown in 100% N2O. The interface trap density is reduced by the in-situ annealing for oxides grown in mixtures of O2 and N2O.