Physical, Electrical, and Reliability Characteristics of Multi-Step Deposition-Annealed HfO₂Film

The physical, electrical, and reliability characteristics of the HfO2 gate dielectrics that were fabricated by a single-step and a multi-step deposition-annealing method are compared in this study. After annealing at 750°C, the single-step annealed HfO2 film has transformed into the polycrystalline phase, whereas the multi-step annealed HfO2 film is found to remain in a nanocrystalline phase. Additionally, the density and composition of the HfO2 dielectric films are enhanced by multi-step deposition-annealing process. These changes result in an improvement in the electrical characteristics, breakdown voltage, and reliability for the multi-step deposition-annealed HfO2 film, revealing that the multi-step deposition-annealing method is a promising means for improving the thermal stability and reliability of HfO2 gate dielectrics. In addition to static stress (DC) evaluation, the reliability characteristics of multi-step deposition-annealed HfO2 dielectrics under unipolar and bipolar stresses were also examined. The dielectric breakdown failure time under bipolar stress is longer than those under the other two stress methods. Moreover, as the number of deposition-annealing steps increases, the lifetime enhancement is reduced. However, the failure time is still longer than that of the single-step annealed HfO2 film.