Nitrogen profile in high-k dielectrics using ultrathin disposable capping layers

Abstract

Metal Oxide Semiconductor (MOS) transistors fabricated using current art may utilize a nitridation process on the gate dielectric to improve transistor reliability. Nitridation by the current art, which involves exposing the gate dielectric to a nitridation source, produces a significant concentration of nitrogen at the interface of the gate dielectric and the transistor substrate, which adversely affects transistor performance. This invention comprises the process of depositing a sacrificial layer on the gate dielectric prior to nitridation, exposing the sacrificial layer to a nitridation source, during which time nitrogen atoms diffuse through the sacrificial layer into the gate dielectric, then removing the sacrificial layer without degrading the gate dielectric. Work associated with this invention on high-k gate dielectrics has demonstrated a 20 percent reduction in nitrogen concentration at the gate dielectric—transistor substrate interface.