Excimer-laser doping into Si thin films

Abstract

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/⧠ for n+ and 9 kΩ/⧠ 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.

Poly-Si TFT fabricated by laser-induced in-situ fluorine passivation and laser doping

“…In the PSG/a-Si region (Region A in Fig. 1), the dopants enter the molten a-Si so that the phosphorus-doped poly-Si film is formed [7]. On the other hand, the dopants cannot penetrate the SiO F barrier, but the fluorine atoms diffuse from the SiO F film into the molten a-Si in the PSG/SiO F /a-Si region (Region B in Fig.…”