EXCIMER-LASER DOPING INTO SI THIN-FILMS

The fabrication of n+ and p+ silicon thin film by using a combination of "spin-on-glass" and XeCl excimer-laser doping is described. The doping can be achieved by rapid dopant atom diffusion into molten silicon from a spin-coated film containing the dopant. This technology offers the advantages of process simplicity, low processing temperature, and ultrashallow high-concentration doping. The obtained sheet resistances (2 kΩ/D'Alembertian sign for n+ and 9 kΩ/D'Alembertian sign for p+) are acceptable for thin-film transistors (TFTs). The energy required for doping into a thin film was less than half of that for a silicon wafer. This is mainly due to the absorption rate difference between noncrystalline and crystalline silicon. This process appears extremely promising for TFT fabrication.