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001-es BibID:	BIBFORM042934
Első szerző:	Lakatos Ákos (fizikus, környezetmérnök, létesítménymérnök)
Cím:	Investigations of failure mechanisms at Ta and TaO diffusion barriers by SNMS / A. Lakatos , A. Csik, G. A. Langer, G. Erdélyi, G. L. Katona, L. Daróczi, K. Vad, J. Tóth, D. L. Beke
Dátum:	2008
ISSN:	0231-3596
Megjegyzések:	Copper is widely used interconnect mate-rial as a replacement of aluminum in semicon-ductor devices because of its high electricalconductivity and electromigration resistance.The most important life-time limiting processin devices is diffusion between semiconductorand interconnects layers. It was an early ob-servation that Cu can easily migrate to silicon,forming silicides with even at temperatures aslow as 473 K. In order to prevent mixing andsilicide formation, reliable diffusion barriers areneeded. As for barrier materials for coppermetallization, Ta and its alloys are expected tobe the best candidates due to their high melt-ing points, lack of reactivity with Cu, as wellas relatively good adhesion to SiO2.In this work we report on the thermal sta-bility and barrier performance of Ta, TaOxand TaOxTa films. Our research is focusedon the very early stage of the degradation ofthese systems. Structural and compositionalchanges in the thin films were investigated byan X-Ray Diffractometer (XRD, equipped witha Siemens-made Cu?anode x-ray tube), anX-ray Photoelectron Spectroscope (XPS) anda Transmission Electron Microscope (TEM).Secondary Neutral Mass Spectrometer (SNMS)was applied to map the depth profiles.Our investigations, based on depth profileanalysis, show, that early degradation of Tabarrier takes place by the diffusion of Ta troughthe Cu layer and simultaneously the diffusionof Si into the Ta layer. Around 773 K, Ta-silicide formation was observed. Furthermore,deterioration of the barrier layer is strongly af-fected by the coarsening of the Ta film.The failure mechanism in the TaOxbarrierseems to be a crystallization controlled process(823 K). At higher temperature (873 K) thedecomposition of the TaOxfilm also influencesthe degradation.The combined TaOx-Ta barrier proved tobe much more effective than the Ta or TaOxsingle film. The observed outstanding perfor-mance of the combined film can be explainedby the continuous oxidation of Ta film in TaOx-Ta bilayer. The reaction product of the ox-idation process, the freshly formed TaOxfilmbetween the as-deposited TaOxand Ta is prob-ably amorphous (metastable TaO). This oxidelayer in amorphous state is less permeable toSi and Cu than the layer in crystalline form,therefore it successfully prevents the degrada-tion of samples up to 1023 K
Tárgyszavak:	Természettudományok Fizikai tudományok kutatási jelentés
Megjelenés:	Atomki Annual Report. - 16 : 1 (2008), p. 50. -
További szerzők:	Csik Attila (1975-) (fizikus) Langer Gábor Antal (1950-) (fizikus) Erdélyi Gábor (1950-) (fizikus) Katona Gábor (1977-) (fizikus) Daróczi Lajos (1965-) (fizikus) Vad Kálmán Tóth J. Beke Dezső László (1945-) (fizikus)
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