Characterization of vacancy-related defects introduced into silicon during heat treatment by deep-level transient spectroscopy and gamma-ray diffraction techniques

Abstract

Vacancy-related defects introduced into n-Si during annealing or aluminium diffusion at high temperature (1000–1250°C) have been studied. Different ambients (argon, nitrogen, vacuum and chlorine-containing atmosphere) were used to create a vacancy supersaturation during heat treatments. Three deep-level centers whose formation is governed by the presence of vacancies have been identified. They were characterized by the following temperature dependences of the thermal emission rate:e3 = 7.92 × 10⁷ T ² × exp(− 0.455/kT),e ₅ = 2.64 × 10⁶ T ² × exp( − 0.266/kT),e ₇ = 7.26 × 10⁶ T ² × exp (− 0.192/kT). The influence of different factors, such as heat-treatment conditions, concentration of oxygen and doping level in initial crystals, on center formation was studied. An asymmetric diffuseγ-ray scattering was observed near the surface of a crystal irradiated by thermal neutrons and annealed in a chlorine-containing atmosphere. This scattering is related to the formation of structural defects of the vacancy type. In the same region of the crystal, the concentration of the E7 center was one order of magnitude higher than that of other deep-level centers. Comparison of theγ-ray diffraction and deeplevel transient spectroscopy (DLTS) data suggests that the formation of the center occurs under the conditions of Si supersaturation with vacancies.