Single-crystal silicon transistors in laser-crystallized thin films on bulk glass

High-performance thin-film transistors (TFT) have been fabricated in single-crystal silicon thin films on bulk fused silica. Deposited films of polycrystalline silicon were patterned to control nucleation and growth of single-crystal material in pre-selected areas and encapsulated with a dielectric layer (e.g., SiO2) in preparation for laser crystallization. Patterning also minimized microcracking during crystallization. The patterned silicon layer was crystallized with a scanning CO2laser, which produced islands with preferred crystal orientation. The single crystallinity of the islands was established with transmission electron microscopy after transistor evaluation. The silicon islands were processed with conventional microelectronic techniques to form metal-oxide-semiconductor-field-effect transistors operating in the n-channel enhancement mode. The devices display exceptional electrical characteristics with "low-field" channel mobilities > 1000 cm²/V sec and leakage currents < 10 pA, for a Channel length of 12 µm and width of 20 µm. Achievement of high-performance TFT\´s with the combined features of microcrack suppression, preferred orientation, and selected-area crystallization render CO2- laser processing of silicon films a viable and versatile basis for a silicon-on-insulator technology.