Crystallization of Si Thin Film on Flexible Plastic Substrate by Blue Multi-Laser Diode Annealing

Si thin film coated on a flexible polyimide (PI) substrate was successfully crystallized by blue multi-laser diode annealing (BLDA) in the CW mode. The precursor Si film of 50 nm thickness was stably deposited at room temperature using a radio-frequency (RF) sputtering machine. Subsequently, a blue (445 nm) laser beam of 1.1 W was irradiated onto the Si film at a scan speed of 500 mm/s. After irradiation, neither damage to the substrate nor degradation of the Si film surface was observed, and the Si surface was kept smooth within 4.2 nm (RMS). By Raman peak shift at 520 cm -1 and transmission electron microscope (TEM) observation, the crystalline fraction of 100% was estimated in spite of the presence of micro-grains of ${\sim}50$ nm in diameter. The BLDA allows the realization of ultra-low temperature polycrystalline silicon (poly-Si) and is suitable for the next-generation system on panel (SoP).