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

Abstract

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.

Integrations and challenges of novel high-k gate stacks in advanced CMOS technology

“…By using isotope tracing, the structures of such ultra-thin films and the diffusion processes responsible for their formation or degradation can be determined. Therefore, one can determine the electronic structure of nitride films and understand the behavior of N as a function of thermal treatment at the interfacial region between Si and high-k gate dielectrics [105]. Cho et al investigated the characteristics of N incorporated HfO 2 films grown by atomic layer deposition (ALD) on Si and studied the change in chemical state related to N incorporation for a postannealing treatment in an NH 3 atmosphere by using MEIS.…”

“…Fig. 11 demonstrates MEIS spectra of HfO 2 films, prepared using different nitridation temperatures [105]. The ion backscattering energy is a direct measure of the atomic mass of the atom responsible for scattering the incident proton.…”

Characterization of HfO N thin film formation by in-situ plasma enhanced atomic layer deposition using NH3 and N2 plasmas

“…The degradation of electrical characteristics can be induced by incorporating nitrogen at the interface between dielectric thin films and the Si substrate [14,15]. Generally, there are several nitridation methods including chemical vapor deposition (CVD) [16], re-oxidation of HfN films formed by physical vapor deposition (PVD) [17], and thermal annealing with NH 3 [18] for HfO x N y thin films that have a high dielectric constant and thermal stability [9][10][11].…”

Change in band alignment of HfO2 films with annealing treatments

“…[4][5][6] Although N incorporation is a very promising process for control of interfacial reactions and enhancement of thermal stability of the film, the amount of nitrogen incorporated in HfO 2 is not stably maintained, which critically affects electrical device features. 4,7 Among the electrical device features, the most important characteristics in leakage and reliability of the gate dielectric are basically dependent on the band gap of the film and on band alignment with the Si substrate. This indicates that the incorporation of nitrogen can critically influence characteristics because the incorporated nitrogen affects the electronic structure, which changes both the band gap ͑E g ͒ and the band alignment.…”