Laser annealing for solid‐phase thin‐film reactions

We investigated the possibility of using laser annealing for solid‐phase thin‐film reactions. Under ideal conditions, simple analytical solutions are obtained for reaction temperature T (t), if the absorbed laser power is a step, linear or polynomial function of time t. The thickness of the reacted film is equivalent to that of a furnace annealing at an effective temperature Teff, for an effective time Δteff, i.e. (reacted thickness) γ=A Δteff e−Ea/KTeff, with γ=1 for reaction‐controlled process and γ=2 for diffusion‐controlled process. Teff is the peak value of T (t) and Δteff? (kTeff/Ea)mΔt, where m=1 or 1/2(determined by the function form of T (t) near Teff), Ea is the activation energy of the process, and Δt is the duration of the laser irradiation. Calculations show that irradiation times longer than 1 μsec are required for appreciable amount (≳100 A) of metal‐silicide formation at temperatures below the melting point. For shorter pulse irradiations (Δt≲10−7 sec), measurable silicide formation thickn...