A technical trend for a-Si TFTs is their application to large-size, high-pixel density AMLCDs such as XGA, EWS, and HDTV. In order to realize these LCDs, the TFT device characteristics must be improved. Future technologies, which will be necessary to fabricate TFTs with improved characteristics are as follows,
(1) Fully self-aligned TFT technology: A SA-TFT structure reduces the feedthrough voltage caused by parasitic capacitance due to gate/source overlap. This results in an improved picture quality and a higher aperture ratio. Fabrication of such a structure would require ion doping technology.
(2) Ion doping technology: This non-mass-separated implantation technique has large area doping capability and much higher doping speed compared to conventional ion implantation technique. The major problems with the ion doping technique is the implantation of unwanted species which deteriorate the quality of source/drain and channel regions of TFTs.