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Study of HfAlOx Films Deposited by Layer-by-Layer Growth for CMOS High-k Gate Dielectrics

Published online by Cambridge University Press:  01 February 2011

Akira Toriumi
Affiliation:
Department of Materials Science, The University of Tokyo, Tokyo 113–8656, Japan MIRAI, Advanced Semiconductor Research Center (ASRC), National Institute of Advanced, Industrial Science and Technologies (AIST), Tsukuba 305–8569, Japan
Toshihide Nabatame
Affiliation:
MIRAI, Association of Super-Advanced Electronics Technologies (ASET), Tsukuba 305–8569, Japan
Tsuyoshi Horikawa
Affiliation:
MIRAI, Advanced Semiconductor Research Center (ASRC), National Institute of Advanced, Industrial Science and Technologies (AIST), Tsukuba 305–8569, Japan
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Abstract

We have investigated ternary metal oxide films for high-k gate dielectrics by using a layer-by-layer deposition & annealing method so as to keep the dielectric constant of the film high with no crystallization. HfAlOx films have been prepared by alternating deposition of HfO2 and Al2O3 layers, where it is a key for the improvement of the film quality to understand the intermixing process between two layers by thermal treatments. So, we first discuss the atomic diffusion and structural change of the HfO2/Al2O3 “superlattice” film as a function of the annealing temperature by changing the Hf/Al ratio. In a typical case of the film with HfOx/AlOx=3Å/9Å cycle, a clear superlattice peak is observed below 750 °C by XRD. Above 850 °C, a different type of crystalline structure with no superlattice peaks is observed. These results indicate that the intermixing in HfO2/Al2O3 (3Å/9Å) films occurs between 750 and 850 °C. The intermixing onset temperature increases with increasing Al content in Hf/Al ratio.

To further increase the crystallization temperature, nitrogen incorporation into the film is considered, and effects of the nitrogen incorporation into HfAlOx films are studied from the structural and electrical viewpoints. The results indicate that there is a tradeoff between crystallization restriction and leakage current degradation for the nitrogen incorporation into HfAlOx films.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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References

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