The kinetics of the C49-C54 polymorphic transformation in titanium disilicides thin films grown on amorphous Si substrate has been followed by sheet resistance and Infrared Spectroscopy measurements on both blanket samples and submicron lines. The transformation of a fine grained C49 films (davg=30 nm) into the C54 phase was complete after annealing for ∼300 s at a temperature of 700 °C in blanket samples and of 730 °C in submicron lines. The Avrami exponent decreases from n=3 in blanket films to n=l in stripes. The transformation time at a given temperature increases with decreasing linewidth in agreement with the nucleation density model. Infrared Spectroscopy shows no shift of the peaks of the C49 phonons going from blanket to patterned films, suggesting the lack of strain on TiSi2 patterned films. The different behavior between blanket and laterally limited samples has been explained in terms of the different surface energies.