Nitridation for HfO2 high-k films on Si by an NH3 annealing treatment

The characteristics of nitrided HfO2 films suggest that the diffusion of Si from the Si substrate to the film surface is induced by annealing in an NH3 ambient and that the incorporation of N is closely related to the diffusion of Si. Changes in the core-level energy state of the N 1s peaks of nitrided HfO2 films indicate that the quantity of N incorporated into the film drastically increases with increasing annealing temperature, especially at temperatures over 900°C. The incorporated N is mostly bonded to Si that diffused from the Si substrate into the film, while some N is incorporated to HfO2 at high annealing temperature. Some molecular N2 is generated in the film, which is easily diffused out after additional annealing. Moreover, the chemisorbed N in the film is not completely stable, compared to that at the interfacial region: i.e., the N in the film predominantly out diffuses from the film after additional annealing in a N2 ambient.