The production and stability of implantation-induced vacancy excesses in silicon

Abstract

The spatial separation of implantation-induced Frenkel pairs can yield vacancy and interstitial excesses at depths, respectively, less than and greater than the projected range ( R p). For the present study, the production and stability of such excesses have been characterised with Rutherford backscattering spectrometry (RBS), double-crystal X-ray diffraction (DCXRD) and transmission electron microscopy (TEM) following high-energy, high-temperature implantation of Si substrates. Vacancy and interstitial excesses were manifested as tensile and compressive strains, respectively. At a given temperature, the compressive strain at depths greater than R p increased with dose until the onset of amorphisation. Similarly, the tensile strain at depths less than R p increased with dose until the yield strength of Si was exceeded. Thereafter, strain relaxation through dislocation formation was observed. At a given dose, the tensile strain decreased as the implant temperature increased due to increased dynamic annealing. Similarly, the maximum strain attainable prior to the onset of dislocation formation decreased as the implant temperature increased consistent with increased defect mobility and decreased yield strength.