The technology and application of laser crystallised poly-Si TFTs

摘要

High performance FTFs, in the emerging generation of poly-Si AMLCDs, are based upon the use of excimer laser crystallisation for the formation of the poly-Si films. SOme of the fundamental aspects of the laser crystallisation process are eviewed, including the rrole of the energy density and the number of laser shots, and the way in which these basic effects impact device unformity are discussed. In addition to the laser process itself, another important issues relates to device design and the implementation of drain field relifef. A comparison is made between self aligned and non-self alighed TFTs, in terms of process complexity and performance, with the self-aligned device being more technologically demanding, particularly with regard to controlling the effects of lattice damage caused by the phosphorus implants. Various field relief options are reviewed and a structure containing a gate overlapped LDD region is shown to be the best compromise for self aligned devices.