CW laser crystallization of amorphous silicon; dependence of amorphous silicon thickness and pattern width on the grain size

We report the preliminary results of the micro-structural change, especially crystalline grain size, on the effect of process parameters, such as amorphous silicon (a-Si) thickness and the width of Si island, via CW laser crystallization (CLC) of island-patterned a-Si thin films. We have found that the average grain boundary spacing, representing grain size, strongly depends on both the thickness and the width of the Si island. The grain size increases with increasing the film thickness in proportion until it reaches a certain value, and then saturates even though the thickness is further increased when the laser energy intensity is enough for inducing complete melting of the region. The grain size of the wider width of Si island is proved to be larger than that of the smaller width of Si island under given CLC conditions. This is thought to be due to the efficient energy absorption of the wider width of Si island. By optimization of process parameters, very high quality thick poly-Si film is demonstrated.