Poly-crystallized SiGe thin films in a low-temperature process

Precise control of the threshold voltage is required for complementary metal oxide semiconductor transistors, including fully-depleted silicon-on-insulator thin film transistors. We have produced amorphous SiGe films by sputtering without using flammable gas, and have characterized the films annealed subsequently in a furnace, or by an excimer laser aiming to lower the processing temperature. Using excimer laser annealing, we confirmed crystallization and dopant activation with low energy density without modifying the dopant profile. In a single gate of p-type SiGe for silicon-on-insulator thin film transistors with 1 mum channel length, the threshold voltage could be adjusted to the optimum point corresponding to the flat-band voltage of metal oxide semiconductor capacitors. By using a low-temperature process, poly-SiGe films prepared by excimer laser annealing after sputtered deposition are expected to provide a single-gate as well as a channel of undoped films for silicon-on-insulator thin film transistors driven at low voltage.