Characterization of laser patterned a-Si:H thin films by combined AFM/local current measurements

Laser interference crystallization of amorphous hydrogenated silicon (a-Si:H), followed by selective plasma-enhanced deposition and etching can be used for new large area microelectronic applications. In this letter we have studied a-Si:H layer of 200 nm thickness which has been prepared by rf PECVD (13.56 MHz, silane dilution in hydrogen 8%) on Corning 7059 glass coated by indium-tin oxide bottom electrode. Prior to the laser crystallization, hydrogen has been effused by heating up the sample to 450°C in vacuum for one hour. The sample has been crystallized in air by a single pulse of frequency doubled Nd:YAG laser with wavelength 532 nm and energy density 80 mJ/cm². Primary laser beam was split into two beams forming an interference pattern with 5.3 μm period. We have used the combined AFM giving the picture of surface morphology and simultaneously measured current through the layer influenced predominantly by material properties for characterization of the interference-laser patterned a-Si:H/μc-Si:H layer. These measurements provided clear identification of amorphous and microcrystalline parts of the layer and should lead to a better understanding of the laser patterning process.