High-resolution laser flash photography for probing the solidification of the new double laser recrystallization process

Abstract

A new double laser recrystallization technique that can produce lateral grains of tens of micrometers is presented. A nanosecond laser (excimer or Nd:YLF laser) and a pulse modulated Ar laser are used in the experiment. 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. This process has wide process window and is insensitive to both the excimer laser fluence and the Ar laser power fluctuations. Preheating and melting of the a-Si film with the laser before firing the excimer laser is found to be necessary for inducting lateral grain growth. The transient excimer laser irradiation is believed to generate nucleation sites for initiating the subsequent lateral grain growth. The solidification dynamics of the process is probed by high spatial and temporal resolution laser flash photography. A lateral solidification velocity of about 10 rn/s is observed.