Thin Solid Films, Vol.575, 21-24, 2015
The control of the film stress of Cat-CVD a-Si films and its impact on explosive crystallization induced by flash lamp annealing
Catalytic chemical vapor deposition (Cat-CVD) can produce amorphous silicon (a-Si) filmswith low film stress, in general, compared to plasma-enhanced CVD, and is thus suited for the preparation of precursor a-Si films for thick poly-Si films applied for solar cells. The stress of a-Si films is known to sometimes play an important role for the crystallization of a-Si films and resulting grain size of polycrystalline Si (poly-Si) films formed. I investigate the impact of the stress of Cat-CVD a-Si films on the mechanismof explosive crystallization (EC) induced by flash lamp annealing (FLA). The stress of Cat-CVD a-Si films can be controlled by changing the temperatures of substrates and/or a catalyzing wire during film deposition. Cat-CVD a-Si films with tensile stress (similar to 200 MPa) can be deposited as well as films with compressive stress. The enlargement of grain size is observed in a part of flash-lamp-crystallized (FLC) poly-Si films formed from Cat-CVD films with tensile stress compared to those with compressive stress, which might be an indication of a certain degree of impact of film stress on poly-Si formation. The grain size is, however, much smaller than that of FLC poly-Si films formed from electron-beam-(EB-) evaporated a-Si filmswith similar tensile stress. This fact may indicate the existence of other critical determinants of EC mechanism. (C) 2014 Elsevier B. V. All rights reserved.
Keywords:Flash lamp annealing;Amorphous silicon;Polycrystalline silicon;Crystallization;Film stress;Explosive crystallization