New excimer laser recrystallization of poly-Si for effective grain growth and grain boundary arrangement

A new excimer laser recrystallization of polycrystalline silicon thin film is proposed to increase the grain size and control the grain boundary locations. The proposed method utilizes the lateral grain growth employing a masking window during excimer laser irradiation. We designed a specific laser-masking window to maximize the lateral growth effect and arrange the location of grain boundaries. As a result of laser irradiation through the opened gap in the masking window, we obtained polycrystalline silicon film with the grain size exceeding 1 mu m and also observed well-arranged grain boundaries by transmission electron microscopy. To enhance the overall grain quality of the film, the second laser irradiation without masking window was carried out to recrystallize the residual amorphous silicon regions shaded by the masking patterns during the first laser irradiation. Thin film transistors fabricated by the proposed method showed considerably improved electrical characteristics which directly reflect the quality of polycrystalline silicon active layer.