35.1: Blue-Diode Laser Annealing of Amorphous Silicon Films for Low-Cost, Large-Scale Manufacturing of Advanced Displays

Abstract

Blue diode laser annealing (BLA) systems have been successfully developed for low-temperature crystallization from amorphous silicon film on glass substrates. It is demonstrated that it can achieve high quality poly-Si film with large grain sizes, as studied by optical microscopy, Raman spectroscopy and AFM measurements. The p-channel poly-Si TFT on glass using BLA exhibited the field-effect mobility of 168.05 cm2/Vs and subthreshold swing of 220 mV/dec. BLA is scalable to large-scale display manufacturing and significantly lowers the capital expense and operating cost, since diode lasers are highly reliable and rugged, remarkably efficient, and maintenance-free, allowing 24/7 operations without the need of consumables. The BLA system consists of an array of high-power blue diode lasers (λ ~ 450 nm) and beam-shaping optics to produce a line-shaped beam which can be scanned at high speed to anneal the Si film in a single scan, where the high scan speed minimizes thermal stress. The scan-to-scan is seamless to cover a large panel such as G6 or G8 without glass damage. The physical phenomena responsible for melting and recrystallization are explained by heat transfer simulations for process optimization.