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 μ s , 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 ) ∕ Si Ox ( 100 nm ) deposited on a glass substrate by plasma-enhanced chemical vapor deposition using Si H 4 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 ∕ cm 2 . The grain size is less than 50 nm at 1.55 – 1.78 J ∕ cm 2 , and a significant grain growth occurs at 1.82 J ∕ cm 2 . 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.