Laser crystallization of amorphous SiC thin films on glass

Abstract

Usually, crystalline SiC films are produced by high-temperature processes such as chemical vapor deposition combined with the conventional thermal annealing. These processing technologies have the disadvantage that large area low-cost materials such as glass cannot be used as substrates. Long-term high-temperature annealing, however, can be avoided by laser irradiation of amorphous SiC films. Amorphous SiC films 50–500 nm thick deposited by laser ablation were crystallized by a single shot of a KrF excimer laser (248 nm wavelength, 25 ns pulse duration). As observed by transmission electron microscopy (TEM), polycrystalline SiC with a grain size of 10–20 nm resulted. During laser annealing, the crystallization process was studied by time resolved reflection (TRR) measurements by means of a cw-He–Ne laser (633 nm wavelength). The TRR results lead to the conclusion that above a threshold of 250 mJ/cm 2 amorphous SiC is melted during the laser irradiation. After approximately 50 ns, the melt solidifies to crystallites. This observation is in contradiction to the equilibrium-phase diagram of SiC in which no liquid phase occurs at ambient pressure. The observed melt may be a metastable phase with respect to the SiC crystal at any temperature under consideration.