Channeling of implanted phosphorus through polycrystalline silicon

Publisher Website
Google Scholar
Abstract
Implanted phosphorus was found to penetrate phosphorus‐diffused polycrystalline silicon (polysilicon or poly) gate masks during complimentary metal oxide semiconductor processing. The result is unwanted depletion mode (turned‐on) N‐channel metal oxide semiconductor transistors. The effect is interpreted as channeling of phosphorus through large‐grain polysilicon. The channeling effects were eliminated when (1) the upper polysilicon atomic layers were made amorphous prior to 31P+ implantation, (2) thermal oxides were grown to a thickness which prevents high‐energy 31P+ from entering the grains of the polysilicon, or (3) when the ion‐energy‐to‐poly thickness ratio is reduced below about 200 keV/μm.