Improvement of Laser-Crystallized Silicon Film Quality via Intermediate Dielectric Layers on a Glass Substrate.

Abstract

The laser crystallization (LC) of amorphous silicon thin films into polycrystalline silicon (pc-Si) thin films on glass substrates is an active field of research in the fabrication of Si-based thin film transistors and thin film solar cells. Efforts have been, in particular, focused on the improvement of LC technique. Adhesion promoters of the crystallized Si thin films at the glass interface play a crucial role in the stability and device performance of fabricated structures. The crystalline Si thin films are required to be produced free of contamination risks arising from impurity diffusion from the glass substrate. Moreover, it is preferable to fabricate pc-Si thin films at temperatures as close as possible to the ambient temperature for an effective cost reduction. In this work, we demonstrate the successful use of a commercially available nanosecond pulsed laser marker at 1064 nm wavelength for Si crystallization at ambient conditions compared to the common method of pre-elevated substrate temperatures used in continuous wave laser irradiation technique. As a result, our technique results in a better energy balance than that in previous works. The second main purpose of this study is to enhance the crystallinity of Si thin films and to determine the best choice of an intermediate dielectric layer (IDL) comparatively among four thin buffer layers, namely, SiNx, SiO2, ZnO, and TiO2, for the sake of obtaining improved adhesion and larger crystalline domains as compared to that on a direct Si–glass interface. The crystalline qualities of samples containing IDLs of SiNx, SiO2, ZnO, and TiO2 were compared via Raman spectroscopy analysis and electron backscatter diffraction method against the direct Si–glass interface reference. The analyses quantitatively showed that both the crystallinity and the domain sizes can be increased via IDLs.