Spectroscopic ellipsometry model for optical constant of NiSi formed on silicon-on-insulator substrates

Abstract

Nickel silicide is considered the best candidate material to achieve the lowest contact resistance in sub 45 nm CMOS devices. NiSi films with thickness 20-60 nm were prepared by rapid thermal annealing of Ni (temperature 230 C-780 C) on top of thin 230 nm silicon-on-insulator substrates, with a constant formation ratio. Based on film independent characterizations, a novel model for the interpretation of spectroscopic ellipsometry data, featuring a combination of two Lorentzian oscillators and one Drude dispersion model, is proposed, and its goodness is checked in comparison to other known models. This new approach is proved to deliver more accurate estimation of the film thickness and resistivity. V C 2012 American Institute of Physics.

Optical conductivity of Ni1−xPtxSi monosilicides (0 < x < 0.3) from spectroscopic ellipsometry

“…5 with type (2) and peak c with type (1). 12 The same two peaks were observed in the imaginary part of the dielectric function for PtSi 13 as well as another peak at 3 eV (not observed in our results for Ni 1Àx Pt x Si). 13 Previous optical studies measured the real and the imaginary parts of the dielectric function for NiSi using spectroscopic ellipsometry 12,15,33 and reflectance followed by Kramers-Kronig transform.…”

“…The complex dielectric function ¼ 1 þ i 2 versus photon energy E for Ni 1Àx Pt x Si alloys can thus be written in the following functional form known as the Drude-Lorentz model: 12,15,17,[24][25][26] …”

“…31 We therefore expect two types of interband transitions in Ni 1Àx Pt x Si monosilicides: (1) Transitions from Ni (3d) or Pt (5d) ground states to Si (3p) excited states, and (2) transitions from Si (3p) ground states to Si (3p) excited states. 13 Previous optical studies measured the real and the imaginary parts of the dielectric function for NiSi using spectroscopic ellipsometry 12,15,33 and reflectance followed by Kramers-Kronig transform. 5 with type (2) and peak c with type (1).…”

“…2-6 Both need to be avoided, since they lead to high silicide resistivity. 12 We also explain our optical constants using the electronic structure by studying the possible interband transitions in Ni 1Àx Pt x Si monosilicides in comparison with ab initio theory and measurements on PtSi and NiSi. The disilicide NiSi 2 tends to form inverted pyramid defects into the Si (100) substrates used for complementary metal-oxide-semiconductor (CMOS) transistors.…”