Electric-field-enhanced aluminum-induced crystallization of amorphous silicon thin film using decreasing stepwise current method

Abstract

Electric-field-enhanced aluminum-induced crystallization (AIC) was applied to the crystallization of amorphous Si (a-Si) using a stepwise current method with two to four decreasing steps. In AIC, Si diffuses into an Al layer, which generates a layer exchange from an a-Si/Al layer to an Al/polycrystalline Si (p-Si) layer. This increases the electrical resistivity of the Al/p-Si layer. The stepwise decreasing current was an attempt to overcome the limitations of electric-field-enhanced AIC using a constant current. The samples were fabricated by depositing a 200 nm-thick a-Si layer and sputtering a 300 nm-thick Al layer onto an Eagle XG glass substrate. In-situ resistance and reflectivity were measured to monitor the AIC mechanism and layer exchange. The reflectivity measurements were compared with thin-film optics calculations on the a-Si/Al and Al/p-Si layers to indicate the growth of p-Si. The temperature variations during the heating process were supported by a numerical analysis. The crystallinity of produced polycrystalline silicon (p-Si) was verified by a Raman peak at around 519–520 cm−1. The stepwise current supply increased the crystallization time and improved the crystallinity of the produced p-Si compared to the constant current method.