Chemical stability of lanthanum germanate passivating layer on Ge upon high-k deposition: A photoemission study on the role of La in the interface chemistry

The chemical stability of La-containing passivating layers /high-k gate stacks on Ge substrates is investigated by x-ray photoelectron spectroscopy. It is found that upon exposure to oxygen, a La-covered Ge surface spontaneously converts to a stable LaGeO x passivating layer. However, in the presenc...

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Published in:Journal of applied physics 2010-09, Vol.108 (6), p.064115-064115-7
Main Authors: Tsoutsou, D., Panayiotatos, Y., Sotiropoulos, A., Mavrou, G., Golias, E., Galata, S. F., Dimoulas, A.
Format: Article
Language:English
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Summary:The chemical stability of La-containing passivating layers /high-k gate stacks on Ge substrates is investigated by x-ray photoelectron spectroscopy. It is found that upon exposure to oxygen, a La-covered Ge surface spontaneously converts to a stable LaGeO x passivating layer. However, in the presence of overlying metal layers such as Al and Hf or upon deposition of high-k metal oxide cap layers such as Al 2 O 3 and HfO 2 , the LaGeO x layer strongly reacts with the overlayers forming LaAlO z and LaHfO z compounds. In the case of Al or Al 2 O 3 , the LaGeO x is completely dissociated, while in the case of Hf or HfO 2 , LaGeO x remains although with a change in composition. The results are interpreted in terms of oxygen densification according to which the strongly electropositive La drives the reaction toward the formation of oxides with the highest oxygen density. The results suggest that HfO 2 has a better chemical compatibility with LaGeO x making it more suitable for the gate stack.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3478751