Formation of microcrystalline silicon films using rapid crystal aluminum induced crystallization under low-temperature rapid thermal annealing

The process of obtaining thin film solar cells using the method of aluminum-induced crystallization under rapid thermal annealing (RTA) was investigated. 200-nm-thick amorphous Si (a-Si) film was deposited on a glass substrate using an ultra-high vacuum ion beam sputtering system. A 50-nm-thick crystal aluminum layer was then evaporated and deposited onto the a-Si film. In contrast to conventional furnace annealing, RTA can supply rapid thermal energy so that a-Si can be induced into microcrystalline-Si (μc-Si) in a short time at low temperatures. The crystal Al may promote the crystallization reaction because its surface energy is higher than 0.89 N/m, which is the minimum energy required to produce the (111) orientation. Free Si atoms are induced at the interface of the Al and Si sub-layers by the diffusion of Al along the grain boundaries. The Raman spectrum shows that the sample could be induced to crystallize at 350 °C. After the aluminum was etched, the maximum grain size was 4 μm. The carrier mobility was between 6.2 cm2/Vs and 18.8 cm2/Vs. The proposed method can be used to obtain μc-Si with reduced energy and time during the thermal annealing.