| Summary: | 碩士 === 國立中興大學 === 材料工程學研究所 === 86 === Metal silicides have been widely used as ohmic contacts, gate
electrodes, and interconnects in high－speed deep submicron CMOS
devices. NiSi is a possible candidate as next generation
silicide material due to its low stresses, low resistivity, low
formation temperatures (>375oC), little silicon consumption,
extended thermal stability range (375-811oC), and no linewidth
dependence of the sheet resistance. In this thesis, the
evolution of stresses was studied using in situ curvature
measurements with scanning laser method during isochronal
annealing in a vacuum with pressure better than 3*10-6 Torr.
For Ni(100nm)/Si samples, the phase sequence of Ni->Ni2Si->
NiSi->NiSi2 occurs with increased annealing temperatures at a
constant ramping rate, 5oC/min. We observed three apparent
valleys in the curvature-to-temperature plot. In this case, the
first (328oC) and the second (375oC) valleys were identified to
be completely transformed phases of Ni2Si and NiSi,
respectively. According to Arrhenius plot of the duration for a
specific phase transformation at various annealing temperatures,
the activation energy was determined to be 1.53eV for NiSi
formation. The activation energies determined by Kissinger-like
analysis based on the various ramp rates ranging from 1oC/min to
30oC/min were 1.81, 1.55 and 3.42eV for Ni2Si, NiSi and NiSi2
formation, respectively. For Ni(100nm)/Si samples with
measurable oxygen impurity at Ni/Si interfaces, the formation
temperature for Ni2Si and NiSi were retarded. Therefore, there
was only one (470oC) broad valley in the curvature-to-
temperature plot. The effect of a thin Pd layer between Ni film
and Si substrate on the silicidation process includes changing
the formation sequence of the nickel silicide and retarding the
transformation of Ni2Si from NiSi. The curvature-to-temperature
plots for samples with thin Pd layers were different from those
without thin Pd layers. Two steep valleys (268oC and 420oC) and
one broad valley (562oC) were observed. The 420oC valley was
identified to be associated with formation of NiSi.
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