Ultra-large lateral grain growth by double laser recrystallization of a-Si films

Abstract

A new double laser recrystallization technique that can produce ultra-large direction- and location-controlled lateral grains is presented. An excimer laser is combined with a pulse-modulated Ar+ laser to yield grains of tens of micrometers in size. The effect of different parameters on lateral grain growth is investigated. These parameters include the time delay between the two lasers, the excimer-laser fluence, the Ar+-laser power and the pulse duration. The process has a wide process window and is insensitive to both the excimer-laser fluence and the Ar+-laser power fluctuations. Preheating of the a-Si film with the Ar+ laser before firing the excimer laser is necessary for inducing lateral grain growth. The transient excimer-laser irradiation is believed to generate nucleation sites for initiating the subsequent lateral grain growth. The surface roughness of the recrystallized poly-Si is measured by atomic force microscopy.