The Effect of Impurity Content and Ion Mass on the Depth Profiles of Vacancy-Type Defects in MeV Implanted Si

Abstract

We used deep level transient spectroscopy to determine the concentration and depth profile of the defects introduced by MeV He and Si implants in n-type crystalline Si. We have found that only ∼ 16% of the Frenkel pairs generated by the ion escapes recombination and is stored into room temperature stable defects such as divacancies and oxygen vacancy complexes. For a light ion (He), the depth distribution of these defect complexes is strongly dependent on the O content of the substrate: it mirrors the initial distribution of I-V pairs, as calculated by TRIM (a Monte Carlo Code) when the O content is high (∼ 10¹⁸/cm³) while it can be much wider (up to 2 μm) in a highly pure (low O content) epitaxial substrate. This effect is due to a long range migration of vacancies before clustering or trapping at impurities. This migration is strongly inhibited for an ion of higher mass (such as Si) since in a denser collision cascade direct clustering is strongly favoured with respect to agglomeration of migrating defects.