Annealing effect on physical and electrical characteristics of thin HfO2, HfSixOy and HfOyNz films on Si

We report the effect of annealing on electrical and physical characteristics of HfO2, HfSixOy and HfOyNz gate oxide films on Si. Having the largest thickness change of 0.3 nm after post deposition annealing (PDA), HfOyNz shows the lowest leakage current. It was found for both as-grown and annealed structures that Poole–Frenkel conduction is dominant at low field while Fowler–Nordheim tunneling in high field. Spectroscopic ellipsometry measurement revealed that the PDA process decreases the bandgap of the dielectric layers. We found that a decreasing of peak intensity in the middle HfOyNz layer as measured by Tof-SIMS may suggest the movement of N toward the interface region between the HfOyNz layer and the Si substrate during the annealing process.