Effect of ramp rate on the C49 to C54 titanium disilicide phase transformation from Ti and Ti(Ta)

The C49 to C54 TiSi2 transformation temperature is shown to be reduced by increasing the ramp rate during rapid thermal processing and this effect is more pronounced for thinner initial Ti and Ti(Ta) films. Experiments were performed on blanket wafers and on wafers that had patterned polycrystalline Si lines with Si3N4 sidewall spacers. Changing the ramp rate caused no change in the transformation temperature for 60 nm blanket Ti films. For blanket Ti films of 25 or 40 nm, however, increasing the ramp rate from 7 to 180 degrees C/s decreased the transformation temperature by 15 degrees C. Studies of patterned lines indicate that sheet resistance of narrow lines is reduced by increased ramp rates for both Ti and Ti(Ta) films, especially as the linewidths decrease below 0.4 mu m. This improvement is particularly pronounced for the thinnest Ti(Ta) films, which exhibited almost no linewidth effect after being annealed with a ramp rate of 75 degrees C/s. (C) 2000 American Vacuum Society. [S0734-211X(00)05104-0].