High-performance thin-film transistors fabricated using excimer laser processing and grain engineering

High-performance polysilicon thin-film transistors (TFT's) are fabricated using an excimer laser to recrystallize the undoped channel and dope the source-drain regions, Using a technique we call "grain engineering" we are able to control grain microstructure using laser parameters, Resulting polysilicon films are obtained with average grain sizes of similar to 4-9 mu m in sub-100 nm thick polysilicon films without substrate heating during the laser recrystallization process; Using a simple four-mask self-aligned aluminum top-gate structure, we fabricate TFT's in these films, By combining the grain-engineered channel polysilicon regions with laser-doped source-drain regions, TFT's are fabricated with electron mobilities up to 260 cm(2)/Vs and on/off current ratios greater than 10(7). To our knowledge, these devices represent the highest performance laser-processed TFT's reported to date fabricated without substrate heating or hydrogenation.