Straight-Line-Shaped Grooves Induced by Agglomeration in Thin Si Films Obtained by the Continuous-wave Laser Crystallization of A-Si on Insulator

We have obtained straight-line-shaped agglomeration grooves of 2~3.5 μm width in the ~60-nm-thick Si thin films by the continuous-wave laser crystallization (CLC) when the laser power is increased above the optimum power to obtain grain boundary-free (GB-free) films. The GB-free CLC is suitable for fabricating monolithic three-dimensional integrations. The grooves are formed in the Si film vertically from the Si surface to the underlying insulating substrate, and a hump of the Si film is generated along the edge of the groove at the retarded side of the scan. In situ observation of the crystal growth shows that the grooves originate from voids, which happen to be generated by agglomeration in the melt zone. The voids move at a constant velocity, V_void , within the melt zone. The melt zone moves at the scan velocity, V, to the scan direction. The void velocity, V_void , is obtained from the angle of the groove line to the scan direction, and is found to be proportional to V^−0.5.