A graded lightly-doped region was fabricated in a polycrystalline Si film by the lateral diffusion of dopants introduced by excimer laser annealing. The lateral diffusion of P induced by excimer laser irradiation was confirmed, and the lateral diffusion length was measured by means of electrostatic force microscopy. The graded lateral diffusion profile was also observed by electrostatic force microscopy. The lateral diffusion length from a heavily doped Si region to the intrinsic Si region varied from 1.35 to 4.28µm; depending upon the excimer laser energy density and irradiation number. The experimental results indicated that a lightly doped drain structure could be fabricated in poly-Si thin film transistors by the lateral diffusion of dopants, without the need for any additional mask.

Lateral Diffusion of Phosphorous Induced by Excimer Laser Irradiation of Silicon Thin Film for Formation of Gradual Lightly Doped Region in Polycrystalline Silicon Thin Film Transistors. S.M.Han, S.G.Park, S.Y.Seong, C.J.Kang, M.K.Han: Japanese Journal of Applied Physics, 2007, 46[10A], 6525-9