CHARACTERIZATION OF VACANCY-RELATED DEFECTS INTRODUCED INTO SILICON DURING HEAT-TREATMENT BY DEEP-LEVEL TRANSIENT SPECTROSCOPY AND GAMMA-RAY DIFFRACTION TECHNIQUES

Vacancy-related defects introduced into n-Si during annealing or alumi nium diffusion at high temperatures (1000-1250 degrees C) have been st udied. Different ambients (argon, nitrogen, vacuum and chlorine-contai ning 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 character ized by the following temperature dependences of the thermal emission rate: e(3) = 7.92 x 10(7)T(2) x exp(-0.455/kT), e(5) = 2.64 x 10(6) T- 2 x exp(-0.266/kT), e(7) = 7.26 x 10(6) T-2 x exp (-0.192/kT). The inf luence of different factors, such as heat-treatment conditions, concen tration of oxygen and doping level in initial crystals, on center form ation was studied. An asymmetric diffuse gamma-ray scattering was obse rved near the surface of a crystal irradiated by thermal neutrons and annealed in a chlorine-containing atmosphere. This scattering is relat ed 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. Comp arison of the gamma-ray diffraction and deep-level transient spectrosc opy (DLTS) data suggests that the formation of the center occurs under the conditions of Si supersaturation with vacancies.