Xenon flash lamp annealing of poly-Si thin films

We have investigated xenon (Xe) flash lamp annealing for the crystallization of amorphous silicon (a-Si) films for polycrystalline silicon (poly-Si) thin film transistors on glass substrates. The Xe flash lamp emits white light with a wavelength range of 400-800 nm for 40 μs, thereby instantaneously supplying the energy necessary to crystallize a-Si films to poly-Si films. The distance between electrodes in the lamp is 1000 mm, the bore diameter is 10 mm, and the peak voltage is up to 20 kV. The sample structure is a-Si (50 nm) SiOx (100 nm) deposited on a glass substrate by plasma-enhanced chemical vapor deposition using Si H4 gas. An average grain size of 500 nm is obtained without substrate heating during Xe flash lamp annealing when the light energy density is 1.82 J cm2. The grain size is less than 50 nm at 1.55-1.78 J cm2, and a significant grain growth occurs at 1.82 J cm2. The light energy is absorbed by the whole a-Si film, because the Xe flash lamp emits light with a wide wavelength range of 400-800 nm. Therefore, when the light energy exceeds its threshold at which the a-Si film melting point is observed, a-Si films can be partially melted and subsequently crystallized at the top and bottom surfaces, thereby forming large-grain poly-Si.