Formation of Pt-based silicide contacts : kinetics, stochiometry and current drive capabilities
Résumé
A detailed analysis of the formation of Pt2Si and PtSi silicides is proposed, based on x-ray
photoelectron spectroscopy ~XPS!, transmission electron microscopy ~TEM!, and electrical
characterizations. Published kinetics of the Pt2Si and PtSi transformations under ultrahigh vacuum
condition are consolidated on the basis of XPS measurements performed during an in situ annealing
at a constant heating rate. At room temperature, an incomplete PtxSi reaction is clearly identified by
XPS depth profiling. Using rapid thermal annealing at 300, 400, and 500 °C, the sequential
Pt–Pt2Si–PtSi reaction chain is found to be completed within 2 min. Outdiffusion of silicon to the
top surface is shown to be responsible for the formation of a thin SiO2 capping layer at 500 °C.
Pileup of oxygen occurring at the Pt2Si/Pt reaction front is clearly identified as an inhibiting factor
of the silicidation mechanism. Another incomplete reaction scheme limited to the unique formation
of Pt2Si is exemplified in the case of ultra thin silicon-on-insulator films. Finally, current drive
measurements on PtSi Schottky contacts have allowed us to identify 300 °C as the optimum
annealing temperature while TEM cross sections demonstrate the formation of a smooth and
continuous PtSi/Si interface at 300 °C.
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