The use of dissolution curves to determine amorphization depths and damage ranges in silicon

Abstract

Amorphization depths in ion-bombarded Si can be readily measured with dissolution curves, i.e. curves giving the residual activity of the implanted ions versus the time of exposure to an HF-H₂O₂ mixture. The depth calibration is established by comparison with integral ion distributions. Amorphization depths have been determined in this way both for room-temperature Kr implants (where they range from 35–60 Å, at 2 keV, to 105–205 Å at 10 keV, to 395–570 Å, at 40 keV) and for Kr implants at 95 to 360°C (where they are consistently smaller). An important application of amorphizationdepth (R _α) measurements lies in deducing mean projected damage ranges (<x _d>). Thus it is argued that the following quantity must be independent of dose (Et)for a given energy: where the constant “1.28” is an approximation which is valid for intermediate mass ratios and for energies such that (⟨x _d ⟩) 1. Solution of this relation gave the result that ⟨x _d⟩was 25 ± 2.5 Å, at 2 keV, 70 ± 10 Å at 10 keV, and 190 ± 15 Å at 40 keV. The present experiments also yield estimates of the rate of dissolution of Si in HF-H₂O₂ or HF and of the threshold dose for amorphization.