A fully self-aligned thin-film transistor for display and imaging applications

Summary form only given. Fabrication of TFT-arrays for large-area display and imaging application requires low temperature processes which are compatible with glass substrates. This requirement often presents a problem for making self-aligned TFT source/drain contacts. The traditional self-aligned doping process is ion implantation, which needs a post thermal process to anneal-out the ion damage and to activate the carriers. The anneal must not cause any detrimental effects to the substrate. Recently, it has been realized that laser doping has the potential of simplifying this process and avoiding any high temperature steps. The dopant diffusion is very fast in molten Si. With a short-pulse excimer laser, a thin layer of Si can be melted quickly and remains molten for a few tens of nanoseconds, which is a sufficient time for the dopant to get into the Si film and to form a shallow junction. Since the melt time is very short, the substrate temperature remains low. Several doping sources for the laser process have been reported, such as gas molecules, spin-on doping sources, or doped films. In this work, we report on the performance of a-Si:H TFTs in which the source/drain contacts are formed by laser doping.