Formation of Shallow P+ Junctions Using Two-Step Anneals

Abstract

ABSTRACTShallow (0.15-0.2 μm deep) p+ junctions have been formed using boron implanted into silicon which was pre-amorphized using a silicon implant. The implants were annealed using a two-step process; initially the wafers were furnace annealed at 600 °C for 100 min., followed by a rapid isothermal anneal (RIA) at 950-1100 °C for 10 sec. For comparison, some wafers were only given a single-step rapid isothermal anneal at 950-1100 °C for 10 sec. The shallowest junctions were formed when the amorphous silicon layer was deeper than the boron implant, because of the suppression of channelling. When the amorphous/crystalline interface was shallower than the tail of the boron implant, some channeling occurred. This channeling tail exhibited an enhanced diffusion during the single-step RIA which was reduced significantly by the two-step anneal. When the amorphous layer was deeper than the boron implant, the single-step and two-step anneals gave identical results.