Effects of Preoxidation Ambient in Very Thin Thermal Oxide on Silicon

The impact of the gas ambient used during the preoxidation warm-up of silicon wafers on the very thin oxide growth process and oxide dielectric strength is studied. It is shown that a 10 min warm-up in N₂ results in higher initial growth rate and decreased oxide dielectric strength as compared to the warm-up carried in Ar. These effects depend on temperature of oxidation and are more significant at 1100° than 900°C. Also, it is shown that the addition of 1% H₂to the Ar used as a warm-up ambient results in an increased oxidation rate and higher dielectric strength of very thin oxides due to water vapor formation inside the oxidation chamber during the replacement of Ar + 1% H₂ Fmixture with 0₂.