In situ monitoring of excimer laser annealing of tin-doped indium oxide films for the development of a low-temperature fabrication process

摘要

In this paper, in situ monitoring of excimer laser irradiation processing is examined for application to the production of thin films of transparent conductive oxides (TCOs) such as tin-doped indium oxide (ITO). Numerical simulations reveal that differences in the thin film state, for example, in the dopant levels, could greatly affect the proper laser fluence, suggesting the importance of in situ monitoring of the excimer laser processing. The thermal emission signals of ITO thin films under irradiation by a pulsed ultraviolet laser were successfully detected in situ with a near-infrared sensor on a nanosecond timescale. Non-monotonic decay of the thermal radiation from the ITO thin films was observed under XeCl laser irradiation above a certain fluence. At this fluence, the surface morphology of the ITO thin films observed by atomic force microscopy changed to a microstructure reflecting melting and solidification. This correspondence between the thermal radiation and morphology suggests that the observed nonmonotonic decay was caused by recalescence upon solidification and that the in situ monitoring technique can be used to detect such phase changes.