Quantitative Depth Profiles of Vacancy Cluster Defects Produced by MeV Ion Implantation in Si: Species and dose Dependence

Abstract

AbstractMonte Carlo simulation codes such as TRIM or MARLOWE show a net displacement of interstitials with respect to vacancies from the Frenkel pairs produced in implant cascades. As a result, defect profiles after recombination have an excess of vacancies (Vex) in the shallow region of these implants, with excess interstitials near the projected range Rp. Typically, accurate estimates of the Vex distribution are computer intensive as the complete history of each damage cascade must be recorded. In this work we introduce a method for fast estimation of the Vex profile based on the derivative of the recoil distribution obtained from binary collision simulations using the Kinchen-Pease approximation for damage production. Also, Au labeling has been used to quantitatively analyze and compare the experimental depth profiles of Vex produced by implants of B, Si, and Ge into Si for a range of doses. Specific conditions like matching of the projected range of the implanted ions and matching of the number of Frenkel pairs created have been compared. This detailed study and comparison with simulation provides the first systematic, quantitative measurements of the Vex concentrations over such a range of species and doses. In analogy to the “+ number” for excess interstitials from ion implantation, we determine the range of “minus (-) numbers”, that is the number of excess vacancies per implanted ion for the different species. For Si it is constant in the dose range studied at -0.05, while for B it is -0.001 to -0.004 and for Ge, -0.1 to -0.2. The general shapes of the Vex profiles are similar to those obtained from simulation. Evidence is presented that one significant difference, namely an experimentally observed vacancy depletion near the surface, may be due to the diffusion and annihilation of vacancies at the surface. In addition, an increased nucleation probability of vacancy defects close to Rp may account for the growth of excess vacancies from close to Rp towards the surface with increasing implant dose.