Interfacial reactions of Co/Si0.76Ge0.24 and Co(Si0.76Ge0.24)/Si0.76Ge0.24 by pulsed KrF laser annealing

Abstract

Interfacial reactions of Co/Si0.76Ge0.24 and Co(Si0.76Ge0.24)/Si0.76Ge0.24 by pulsed KrF laser annealing as a function of energy density and pulse number were studied. For the Co/Si0.76Ge0.24 samples annealed at an energy density of 0.2-0.6 J/cm(2), three germanosilicide layers, i.e., amorphous structure and/or nanocrystal, Co(Si1-xGex), and Co(Si1-xGex)(2), were successively formed along the film-depth direction. At 0.3 J/cm(2) Ge segregated to the underlying Si0.76Ge0.24 film, inducing strain relaxation in the residual Si0.76Ge0.24 film. At 0.8 J/cm(2) the reacted region was mostly transformed to a single layer of Co(Si1-xGex)(2), whereas Ge further diffused to the Si substrate. At 1.0 J/cm2, constitutional supercooling appeared. Even the Co(Si0.76Ge0.24) film used as the starting material for laser annealing could not prevent the occurrence of constitutional supercooling at energy densities >1.6 J/cm2. The energy densities at which Co(Si1-xGex) transformation to Co(Si1-xGex)(2), Ge segregation to the underlying Si, and constitutional supercooling occurred were higher for the Co(Si0.76Ge0.24)/Si0.76Ge0.24 system than for the Co/Si0.76Ge0.24 system. Higher energy density and/or pulse number enhanced the growth of Co(Si,,Ge,), film. In the present study, the Co/Si0.76Ge0.24 samples subjected to annealing at 0.2 J/cm(2) for 20 pulses produced a smooth Co(Si,,,Ge,,,), film without inducing Ge segregation out of the germanosilicide and strain relaxation in the unreacted Si0.76Ge0.24 film.