Abstract
We investigated the plasma nitridation mechanisms for an ultra-thin gate oxynitride (SiON) formation to extend the downscaling limit of equivalent oxide thickness (EOT). Using the slot plane antenna (SPA) plasma nitridation system, excellent gate SiON properties were obtained with low gate leakage and good carrier mobility down to less than 12 Å. From electrical and physical analysis results, the nitridation mechanism was discussed, which suggested that a control of oxygen partial pressure is important to achieve EOT reduction. A low electron temperature (Te) process under high-pressure condition leads to improved Gm and NBTI performance, which indicates that the reduction of a plasma damage under nitridation processes improve the performance and reliability of ultra thin SiON film. With optimized nitridation processes, the mobility degradation of nMOSFET is only 8% at EOT=11 Å. The NBTI reliability of pMOSFET is improved by more than 1 order compared with a low-pressure, high Te condition.