The effect of laser annealing on the electrical activity of boron-doped sil
icon wafers has been investigated as a function of boron concentration, ann
ealing time, and annealing temperature (from 600 degreesC to 1050 degreesC)
. Metastable supersaturated alloys were produced by the laser annealing of
ion-implanted Si < 100 > wafers using an excimer laser with a pulse duratio
n of 30 ns. The extent of dopant activation, deactivation, and tendency tow
ards precipitation were subsequently studied following rapid thermal anneal
ing in an argon ambient using a four-point probe of the sample resistance.
Sheet resistances as low as 15 Omega/square were achieved in 200 nm layers.
Following laser anneals, boron atoms remained active at concentrations of
7.5x10(20)/cm(3) up to 800 degreesC for 210 s. A two-mode relaxation model
including defect association and precipitation was proposed to describe the
annealing behavior. These results show that laser processing can produce m
etastable B-doping levels, stable to moderate thermal processing, at concen
trations adequate for all anticipated device structures. (C) 2001 American
Institute of Physics.