SELECTED 2-DIMENSIONAL EFFECTS IN GAS IMMERSION LASER DOPING OF UNPATTERNED SILICON

We have performed a theoretical investigation of two-dimensional effec ts in melting and arsenic gas immersion laser doping of unpatterned si licon under patterned excimer-laser exposure. For pattern sizes below a few microns, the melt depths depend on the pattern size, rendering p rocessing of narrow and wide features with the same laser fluence diff icult. For wide exposed areas, molten regions are significantly narrow er than tile exposed widths, particularly for lower fluences. For deep submicron unexposed spaces, tile melt may encroach into unexposed are as, potentially melting through them for higher fluences. Raising conc erns regarding the processing nf unpatterned wafers, these results ind icate that structures on patterned wafers should be exploited to contr ol thermal diffusion effects. (C) 1998 American Vacuum Society.