Correlation between Reliability and Oxidation Temperature for Ultra-Dry Ultrathin Silicon Oxide Films

摘要

The correlation between time-dependent dielectric breakdown lifetime and oxidation temperature of 800--950O C for 3.5 and 5.0 nm thick silicon oxide films as gate insulators was investigated. To obtain ideal gate oxide films with few hydrogen-related defects and precise thickness distribution that extremely influence the lifetime, metal-oxide semiconductor diodes with the films used in the evaluation were produced by our continuous ultra-dry process. The films oxidized at 850 deg. C showed the largest lifetimes irrespective of thickness. The enhancement, however, was confirmed only in the diodes selecting the oxide- silicon substrate interfaces as the anode-side where the lifetime is mainly dominated. Interestingly, a similar relationship was observed in their density characteristics. This suggests that the condition near the oxide-silicon substrate interfaces is probably improved by the 850 deg C oxidation due to microscopic structural changes.