A low temperature doping technique to be applied in poly-Si TFTs on plastic substrates was investigated. Heavily-doped amorphous silicon layers were deposited on poly-Si and the dopant atoms were driven in by subsequent excimer laser annealing. The entire process was carried out under a substrate temperature of 120 $^{circ}C$, and a sheet resistance of as low as 300 ${Omega}$/sq. was obtained.