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.