Short-channel MOSFETs with superior gate dielectrics fabricated using multiple rapid thermal processing

Short-channel (0.8 μm channel-length) MOSFETs have been fabricated for the first time using ultrathin (~86 Å) rapid-thermal-reoxidized/rapid-thermal-nitrided oxides (RTO/RTN oxides) as the gate dielectrics. After LOCOS (local oxidation of silicon) isolation and active area definition steps, gate oxides of 86 Å were thermally grown in a dry O₂ at 875°C. The RTN processes were performed in a pure NH₃ ambient, followed by an in situ RTO in a dry O₂ ambient. The parameters were chosen so that the increase in the oxide thickness was within 10 Å. The RTN is used to incorporate small amount of nitrogen at the SiO₂-Si interface with a minimum number of defects induced in the bulk oxide region. The subsequent RTO is applied to remove the RTN-induced defects, to initiate rapid interfacial reoxidation, and to prevent any significant increases of film thickness. Devices with superior electrical characteristics have been produced. The small amount of nitrogen incorporated at the interface through RTN enhances the interface endurance property. Both the gate dielectric breakdown voltage and the threshold voltage distributions measured on 4-in wafers were improved by RTO/RTN. In addition, transistors with maximum G _m even higher than that of pure oxide devices have been obtained