SiON Gate Dielectric Optimization for NBTI Improvement

Plasma nitride SiON films have been widely used as gate dielectric in advanced CMOS device fabrication since 90nm technology node. As a replacement material for conventional silicon dioxide, it can provide increased dielectric constant and serve as an effective boron barrier. Post nitridation anneal (PNA), a critical step for plasma nitride SiON formation, is used to stabilize plasma incorporated nitrogen radicals and ions through form thermal stable Si-N banding. Furthermore, PNA can repair the damaged Si/SiO2 interface by interface substrate re-oxidation under oxygen contained ambient. In this work, several PNA conditions were studied. Their effect on transistor performance and PMOS NBTI (Negative Bias Temperature Instability) lifetime were evaluated. It demonstrates that NBTI performance can be improved 20% by PNA process optimizing, while keeping the same Tinv thickness and Ioff/Ion performance.