Thermal stability study of NiSi and NiSi2 thin films

Abstract

The phase formation and thermal stability of NiSi and NiSi2 with 20, 16, 8, and 4 nm initial pure Ni thin films on p-type Si(100) substrates have been systematically investigated in this paper. Both the stoichiometric composition of NiSi determined by Rutherford backscattering and the molecular structure of it examined by micro-Raman spectroscopy are independent of the initial Ni thickness under 500 °C annealing. The sheet resistance as well as surface roughness of thinner films start to increase at a lower temperature, indicating that thinner films are thermally less stable. Agglomeration of NiSi film agrees with the grain boundary grooving model and occurs more easily within thinner films. The NiSi2 phase nucleates irregularly but epitaxially in certain areas at around 750 °C, resulting in the remarkable increase of both the sheet resistance and the surface roughness. The transformation from NiSi to NiSi2 of thinner films begins at a lower temperature than that of thicker ones. © 2003 Elsevier B.V. All rights reserved.