Surface and interface effects in WSi2formation
作者:
J. P. W. B. Duchateau,
A. E. T. Kuiper,
E. G. C. Lathouwers,
A. H. Reader,
期刊:
Journal of Vacuum Science&Technology A: Vacuum, Surfaces, and Films
(AIP Available online 1993)
卷期:
Volume 11,
issue 1
页码: 6-10
ISSN:0734-2101
年代: 1993
DOI:10.1116/1.578722
出版商: American Vacuum Society
关键词: TUNGSTEN SILICIDES;INTERFACE PHENOMENA;IRON;X−RAY DIFFRACTION;RBS;AUGER ELECTRON SPECTROSCOPY;ANNEALING;SILICON;VACUUM COATING;DIFFUSION;WSi2
数据来源: AIP
摘要:
We studied the influence of a thin Fe interface layer between W and the substrate Si and of a surface W–oxide on the formation kinetics of WSi2. Auger depth profiling, Rutherford backscattering spectrometry and x‐ray diffraction have been used to investigate the reaction between the layers and the Si substrate. W layers with a thickness of 20 nm were deposited by electron beam evaporation on HF dipped Si(100) samples. If deposition and subsequent annealing are performed in ultrahigh vacuum, the complete conversion of a W layer into tetragonal WSi2occurs within 1 h at 800 °C. The intercalation of a 5 nm‐thick Fe layer between the W layer and the substrate reduces the conversion temperature to 650 °C. Ironsilicide is formed at a relatively low temperature. This silicide acts as a medium through which Si can easily diffuse towards the surface, thus maintaining a fast Si supply to the W layer. This experiment indicates that reactions at the metal/Si interface are rate determining in the formation of WSi2. Both with and without an Fe intermediate layer, the reaction proceeds via the migration of Si to the film surface followed by the formation of WSi2at the surface. Continuation of the reaction occurs from the surface to the substrate. Furthermore, we found that the presence of a native oxide layer at the W surface retards the reaction between W and Si. Oxygen migrates via the open structure of the W film to the interface where it probably forms a thin SiO2layer that hampers the transport of Si into the W film.
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