Effect of stress on silicide formation kinetics in thin film titanium–selicon system

As the CMOS device feature size scales below sub 0.5 μm, formation of low resistive C54 phase TiSi2 becomes increasingly difficult. With the decreasing silicide thickness and shrinking line widths, unrealistic thermal budgets are required to transform the high resistive C49 phase to the low resistive C54 phase [Kittl J.A., Prinslow D.A., Apte P.P., Das M.F. Appl Phys Lett 1995;67:2308; Saenger K.L., Cabral Jr. C., Clevenger L.A., Roy R.A., Wind S. J Appl Phys 1995;78:7040; Clevenger L.A., Cabral Jr. C., Roy R.A., Lavoie C., Viswanathan R., Saenger K.L., Jordon-Sweet J., Morales G., Ludwig Jr. K.L., Stephenson G.B. Mater Res Soc Symp Proc 1996;402:257]. This phenomenon of sluggish C49 to C54 phase transformation, according to various researchers, has been attributed to the reduced nucleation density. i.e. relatively larger grained C49 phase formed as compared to the vertical and the lateral dimensions of the silicide. Motivated by this technologically important C49 to C54 phase transformation, we have studied the ways in which a nonthermal parameter such as the `stress state', of the Ti–Si diffusion couple, could affect the silicide formation and the C49 to C54 phase transformation. The stress state of the Ti–Si diffusion couple was varied in two different ways: (i) stress state of the Ti film and (ii) stress state of the silicon surface.