Ultra-shallow junction semiconductor device fabrication

Abstract

A practical, low-cost and low hazard method and apparatus for the fabrication of ultra large scale integrated circuits is provided. Plasma source ion implantation (PSII) is employed for realizing required ultra-shallow doping junctions, while avoiding previous difficulties and costs associated with PSII of dopant containing plasmas generated from hazardous gases. The invention makes use of solid boron sources, such as boron carbide (B.sub.4 C), for p-type doping, and solid phosphorus sources, such as red phosphorus, for n-type doping. The solid dopant sources are both stable and relatively inexpensive. Thin layers of p-type or n-type material are deposited on the surface of a semiconductor substrate, such as of Si, by sputtering or vaporization of the solid dopant source material. PSII using a plasma generated from a non-reactive gas, such as argon, is then used to drive the deposited dopant atoms into the surface of the substrate. Deposition and implantation steps may be followed by sputter cleaning of the substrate, such as by use of an argon plasma, to remove any remaining film of dopant material from the substrate. A subsequent annealing step is used to heal the crystalline lattice of the substrate, and to diffuse any incidentally implanted argon ions from the substrate. To prevent deposition of impurities into the substrate as a result of argon sputtering of the PSII chamber walls, the walls may be coated with a thin film of B.sub.4 C prior to PSII processing.