Aluminum-induced crystallization of amorphous silicon (α-Si:H) at 150°C

Thin amorphous silicon (alpha -Si:H) films (50 nm) were grown by plasma-enhanced chemical vapor deposition (PECVD) on carbon-coated nickel transmission electron microscope (TEM) grids. A thin layer (50 nm or less) of aluminum (Al) was then deposited on the alpha -Si:H films by vacuum evaporation. These structures were then annealed at temperatures between 140 and 200 degreesC in vacuum using a lamp furnace to investigate the aluminum-induced crystallization (AIC) of PECVD grown alpha -Si:H. The process of crystallization was studied by TEM and electron diffraction (ED) and X-ray diffraction (XRD). For glancing angle XRD studies, 500 nm thick alpha -Si:H and 400 nm thick Al films were used, and in situ annealing was performed at temperatures between 100 and 250 degreesC using a model TTK low temperature camera mounted on the omega shaft of the goniometer of a Philips X'Pert XRD system. The TEM results revealed complete crystallization of the alpha -Si:H film in 30 min at an annealing temperature of 150 degreesC. The in situ XRD data also indicate conversion of the alpha -Si:H into a crystalline silicon phase at temperatures between 150 and 160 degreesC. These results show for the first time that polycrystalline silicon with grain sizes as large as 0.2 to 0.5 mm can be obtained by AIC of PECVD alpha -Si:H at a temperature as low as 150 degreesC. (C) 2001 The Electrochemical Society.