RESISTLESS, AREA-SELECTIVE ULTRASHALLOW P+ N JUNCTION FABRICATION USING PROJECTION GAS IMMERSION LASER DOPING/

The selective fabrication of ultrashallow p(+)/n junctions in silicon using projection gas immersion laser doping is reported. The method of fers substantial improvement and simplification in junction formation to integrated circuit manufacturers, since several processing steps re quired for conventional doping techniques like ion implantation are el iminated. Spatially selective incorporation of boron into silicon with out the use of any masking layer on the wafer surface is achieved. A p ulsed excimer laser beam is patterned using a chromeless reticle and t he pattern is transferred through a projection system onto a wafer tha t is kept in a BF3 dopant gas ambient. The depth of the fabricated jun ctions is 60 nm with a surface concentration of 5x10(19) cm(-3). The v ertical and lateral distribution of boron in silicon after patterned l aser processing is investigated using secondary ion mass spectroscopy (SIMS) and time-of-flight SIMS (ToF-SIMS). Vertical and lateral dopant profiles are steep and clearly resolved. (C) 1996 American Institute of Physics.