Excimer Laser Processing of IGZO Thin Films for Transparent TFTs
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The effects of post deposition annealing treatments on indium gallium zinc oxide IGZO thin films deposited by radio frequency RF magnetron sputtering at ambient temperature have been studied for application to thin film transistor TFT devices fabrication. Krypton Fluoride KrF (λ= 248 nm) excimer laser annealing ELA and low-temperature thermal annealing (150°C) has been applied to IGZO films of 30 nm and 50 nm thickness as part of the fabrication process for TFT devices. The effect of annealing pre and post patterning of the IGZO channel layers was investigated. The results indicate that single pulse ultra rapid ELA is a viable technique for processing of the channel layers to provide TFT characteristics equivalent to or even better than that produced by a 150°C annealing for one hour. ELA treatment pre-patterning resulted in TFTs demonstrating a higher ON current and on/off current ratio relative to ELA treatment post-pattering. This could be attributed to surface defects introduced by the photolithographic patterning of the IGZO channel. In comparison, the thermally treated films exhibited better performance with the post-patterning thermal treatment.