Positron annihilation study of defects in boron implanted silicon

Defects and their annealing behavior in boron implanted silicon have been s tudied using positron annihilation spectroscopy (PAS), ion channeling, nucl ear reaction analysis, and transmission electron microscopy. Silicon wafers were implanted with 80 keV boron ions to fluences from 10(12) to 10(15) cm (-2). Furnace annealing or rapid thermal annealing (RTA) of the implanted S i samples was conducted to temperatures in the range 750-950 degrees C in a N-2 ambient. For as-implanted samples, the defect profiles extracted from PAS spectra were found to extend beyond the implanted boron distribution gi ven by TRIM calculations. The S-defect/S-bulk values increased monotonicall y with increasing boron fluences. For boron fluences greater than or equal to 10(13) cm(-2),S-defect/S-bulk was found to be > 1.04 (the characteristic value for divacancy), while S-defect/S-bulk was found to be < 1.04 for a b oron fluence of 10(12) cm(-2). After annealing at 750 degrees C, all B-impl anted samples had similar S-parameter values in the near-surface region, wh ile in the deep region the S values for high B fluences (phi greater than o r equal to 10(14) cm(-2)) were found to be lower than those for low B fluen ces (phi less than or equal to 10(13) cm(-2)). Annealing at 950 degrees C d id not change the S-parameter data for the lowest boron fluence (10(12) cm( -2)), but caused a slight increase of the S parameters in the deep region f or other boron fluences. RTA at 750 degrees C shows that major defects in B -implanted Si are annealed out within the first 3 s. An interesting transie nt annealing behavior is observed in which the S value decreases in the ini tial annealing stage, and then increases to a saturating value after prolon ged annealing. Possible effects of electric fields resulting from the elect rical activation of implanted boron on the behavior of positron annihilatio n line shapes after annealing are discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)07110-3].