Effect of post-oxidation anneal on ultrathin SiO2 gate oxides

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Abstract
Ultrathin silicon oxide films 5–6 nm thick have been grown in a double‐walled furnace and annealed in N2 and Ar at temperatures varying between 850 and 1100 °C. The breakdown field distribution obtained is very tight and centered above 11 MV/cm for as‐grown oxides at 850 °C. The oxides that received a post‐oxidation anneal (POA) at 1000 °C show a consistent improvement in breakdown field distribution and breakdown charge density as compared to the oxides annealed at lower temperatures. Furthermore, under high field current stress, oxides with a POA at 1000 °C show a positive voltage flatband Vfb shift, while oxides with POA at a temperature TVfb shift. These results point out the efficacy of a high‐temperature POA of 5–6 nm oxides on breakdown strength and on the reduction of some defects responsible for the positive charge trapping.