Laser Processing of Amorphous Silicon for Polysilicon Devices, Circuits and Flat-Panel Imagers

ABSTRACTPulsed excimer-laser processing of amorphous silicon on non-crystalline substrates allows for the fabrication of high-quality polysilicon thin-film transistors (TFTs). It also provides procedures for doping self-aligned amorphous silicon TFTs. In addition, laser-crystallized polysilicon exhibits some interesting materials properties, such as, large lateral grain growth with a corresponding enhancement in the electron mobility. Under optimized processing conditions, excellent polysilicon TFTs with high mobilities, sharp turn on, low off-state leakage currents and good spatial uniformity have been achieved. These improved parameters, particularly the low off-state leakage currents and good uniformity, enable not only displays but also the moredemanding flat-panel imaging arrays to be fabricated in polysilicon. Results on both polysilicon CMOS circuits and a polysilicon flat-panel imager are presented.