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The growth, composition, electrical characteristics, and reliability performance of high-k HfO2 dielectric films that were deposited by an atomic layer deposition technique are studied. The films were grown using tetrakis(ethylmethylamino)hafnium precursor and either H2O or ozone (O3) as the oxidant. When H2O was the oxidant, the resulting HfO2 film had a thinner interfacial layer than that obtained using the O3 oxidant, but the bulk HfO2 layer was of a poorer quality. Of the annealed HfO2 films with a comparable equivalent oxide thickness, the O3 oxidant-based HfO2 films had better electrical properties and reliability. The oxide charge density, the hysteresis, the leakage current, the breakdown electrical field, and the time to dielectric breakdown of the HfO2 film that was deposited with O3 oxidant were all better those of the film that was deposited with H2O oxidant. Additionally, the dynamic stress, including unipolar and bipolar stresses, increases the times to dielectric breakdown for both HfO2 films. However, the increase under bipolar stress was greater for the HfO2 films that were grown using the H2O oxidant because more detrapping occurred.

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.

This study compares the physical, electrical, and reliability characteristics of the high-k HfO2 film that was fabricated by a single-step and a multiple-step deposition-annealed method. After annealing at 750oC, the single-step annealed HfO2 has transformed into the polycrystalline phase, whereas the multi-step annealed HfO2 is found to remain in a nanocrystalline phase, revealing that a multi-step deposition-annealing method could greatly improve the thermal stability of the HfO2 film with respect to the grain formation process. Additionally, the density and composition of the HfO2 film are enhanced by multi-step deposition-annealing process. These changes lead to 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 stacks.

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