<title>Optimization of high-power excimer laser for TFT annealing</title>

Abstract

The flat panel display market is presently experiencing an annual growth rate of over 20%, and shows no signs of slowing down. Polycrystalline-silicon (poly-Si) thin film transistor (TFT) devices offer both improved quality and decreased cost over amorphous silicon displays, and will undoubtedly capture an ever increasing share of this market. However, producing poly-Si TFTs in high volume has presented a number of practical challenges. One of these challenges is transforming an amorphous silicon layer into poly-Si. For several years, researchers have investigated using excimer lasers for this purpose. In excimer laser annealing, a high-power excimer laser beam is scanned across the surface of a substrate coated with amorphous silicon. The intense UV light causes the silicon to melt, leading to subsequent recrystallization in polycrystalline form. This process is very non-linear, and places tight tolerances on laser beam parameters such as energy stability and beam uniformity. Furthermore, for this technique to be successfully integrated into a high volume production line, the laser must exhibit extremely high reliability, minimum downtime and low cost of ownership. In the past few years, excimer laser manufacturers have made significant technical improvements, leading to products that can successfully meet the rigorous demands of industrial TFT production. As a result, major display manufacturers in Japan, Korea and Europe have now adopted this technology for mass production.