Papers Published

1. Hsia, S.L. and Tan, T.Y. and Smith, P.L. and McGuire, G.E., CoSi and CoSi₂ phase formation in bulk and SOI Si substrates, Silicides, Germanides, and Their Interfaces. Symposium (1994), pp. 373 - 8 .
   (last updated on 2007/04/10)

   Abstract:
   We have studied the CoSi and CoSi₂ phase formation sequence in (001) bulk and SOI Si wafers, using Co/Ti bimetallic layers as source materials which are suitable for growing epitaxial CoSi₂ films on (001) Si. In bulk Si, co-formation of polycrystalline CoSi and epitaxial CoSi₂ phases at T>500°C have been observed. These phases form respectively at the metal and Si sides of the film. For very long times and/or at high temperatures, only epitaxial CoSi₂ is observed, e.g., for samples annealed at 560°C for 30 min or at 900°C for 10 s. When using (001) SOI Si with inexhaustible Co supply, only polycrystalline CoSi has been formed for a 900°C 10 s annealing, which is in contrast to the bulk Si results. This phenomenon is understood on the basis of Gibbs free energy reduction in forming the two phases. In the CoSi₂ formation temperature range, Gibbs free energy release in forming CoSi₂ is only ~10% more than that of forming CoSi. Consequently, after all Si atoms have been consumed, the formation of CoSi becomes energetically more favorable, since the free energy reduction due to formation of 2x mole of CoSi is much larger than that due to formation of 1x mole of CoSi₂, where x is the SOI Si mole number

   Keywords:
   annealing;cobalt compounds;free energy;metallic epitaxial layers;MOSFET;semiconductor device metallisation;silicon-on-insulator;