ION SHOWER DOPING IN POLYCRYSTALLINE SILICON

To fabricate polycrystalline silicon thin-film transistors, a low temp erature doping technique is needed. ion shower doping using P2HX (x = 1, 2,...) as the main ion source was investigated, because this tequni que implants molecules and hydrogen atoms in the surface of the polycr ystalline silicon with a low acceleration voltage. The sheet resistanc e was significantly reduced by raising the implantation temperature; a sheet resistance of 5 x 10(2) Omega/rectangle was obtained by implant ation at 200 degrees C without annealing. This improved sheet resistan ce is not due solely to thermal annealing by ion beam heating, rather the impurity profile is averaged by radiation enhanced diffusion, and collisions between atoms produce low-temperature recrystallization in the implanted region.