Effective Dopant Activation in Silicon Film Using Excimer Laser Annealing for High-Performance Thin Film Transistors

Abstract

After ultraviolet (UV) pulsed excimer laser annealing (ELA) for highly phosphorus doped Si film at a dose of 2 ×1015 cm-2, the relationship between conductivity and crystallinity of the film was studied. As a result of spectroscopic ellipsometry (SE) analysis, the conductivity increased with improving the crystallinity of the annealed Si film. By optimizing laser annealing condition at 350 mJ/cm2, efficient solidified activation after melting occurs, the Si film showed extremely low sheet resistance down to 100 Ω/□, and was decreased furthermore to as low as 80 Ω/□ by increasing the shot number. The effectively activated result for the doped Si film is comparable to the result for bulk single-crystalline Si under thermal equilibrium condition. By observing the Raman shift for the effectively activated film, tensile stress was clearly confirmed similar to the case of excimer laser crystallization (ELC) for undoped Si film. ELA activation for phosphorus-doped Si film is considered to be effective for the formation of the source and drain in high-performance Si thin film transistors (TFTs) as well as for the formation of the junction of a diode sensor for system on panel (SoP).