Concentration-controlled phase selection of silicide formation during reactive deposition

Slow (low-rate) reactive deposition of a metal onto a Si substrate can resu lt in direct formation of a metal disilicide, thereby skipping the metal-ri ch phases in the formation sequence. These observations have been explained thermodynamically by using the effective heat of formation model. As a res ult of this concentration-controlled phase selection, it is possible to for m disilicides, such as CoSi2, NiSi2, or beta-FeSi2 at much lower growth tem peratures than possible in conventional solid-phase reaction of a metal lay er deposited onto Si at room temperature (i.e., lower than the nucleation t emperature). Moreover, epitaxial growth of CoSi2/Si(100), which is not poss ible by solid-phase reaction, becomes achievable when depositing Co atoms s ufficiently slowly onto a heated Si substrate. (C) 1999 American Institute of Physics. [S0003-6951(99)03521-4].