Transformation of defect layer and zinc implant profile in silicon during thermal annealing

Abstract

The transformation of the structure of a radiation-damaged silicon layer and profiles of implanted dopant Zn during thermal annealings has been investigated. The analysis was performed by Rutherford back-scattering spectroscopy, secondary-ion mass spectrometry, and high-resolution X-ray diffraction. It is established that the surface region of radiation-induced point defects (Frenkel pairs) 78 nm thick is formed in the implanted samples. A heat treatment at 400°C leads to the annealing of interstitial point defects and reduces the damaged-layer thickness to 56 nm. This layer may contain vacancy clusters or clusters of zinc-vacancy complexes. The segregation of implanted dopant Zn is observed near the maximum of its depth distribution. Annealing at 700°C leads to the almost complete recovery of the damaged layer. Two concentration peaks were formed in the sample, i.e., one near the substrate surface and the other near the peak of distribution of radiation-induced point defects. During the ion implantation of zinc and at subsequent stages of thermal annealing, zinc precipitated in the form of zinc silicide (of the ZnSiO₃ type).