Concentration Dependence of Arsenic on Solid Phase Epitaxial Regrowth of Amorphous Silicon

Abstract

ABSTRACTIn this work we measured the functional dependence of the solid phase epitaxial (SPE) regrowth rate, V, of amorphous silicon on the concentration of implanted arsenic (n-type) impurity, NAs. The SPE regrowth rates of self-ion amorphized layers in silicon wafers with (100) substrate orientation were measured by in situ, high precision, cw laser interferometry during isothermal annealing for temperatures from 470 °C to 580 °C, and concentrations in the range 1.5×1018cm−3 ≤NAs≤3.5×1020 cm−3.In the concentration range 7×1018 cm−3≤NAs≤2.2×1019 cm3, selected from the medium dose sample, the SPE regrowth data satisfied a linear equation; V/Vi=1+NAS/Ni, where Ni(T) was fit to an Arrhenius form obtained from the temperature dependent intersections of the SPE regrowth rate data with the concentration axis and Vi(T) was the temperature dependent apparent intrinsic SPE regrowth rate at zero impurity concentration. A similar linear dependence was obtained earlier for boron (B) and phosphorus (P).However, unlike B and P, an enhancement of SPE regrowth was observed for samples implanted with As in the concentration range 3×1018 cm−3 ≤NAS≤ 1.3×1019 cm−3, selected from the low dose sample. This result indicates that arsenic implanted at low dose levels has a higher fractional ionization in amorphous silicon than either boron or phosphorus implanted at the same dose.In the high dose samples with arsenic concentrations ≤NAs 2.2×1019 cm−3, the SPE regrowth rate varied nonlinearly with NAS. The nonlinear function had a negative curvature similar to that observed previously for P.