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

High-performance polysilicon thin-film transistors (TFTs) 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 ~4-9×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 TFTs in these films. By combining the grain-engineered channel polysilicon regions with laser-doped source-drain regions, TFTs are fabricated with electron mobilities up to 260 cm²/Vs and on/off current ratios greater than 10⁷. To our knowledge, these devices represent the highest performance laser-processed TFTs reported to date fabricated without substrate heating or hydrogenation