Room temperature damage, annealing and dislocation growth in silicon

The concentration of residual defects produced by self ion implantation of silicon has been shown to be a sensitive function of implantation temperature at temperatures near room temperature. In this study samples were heated to temperatures of 20°C and 60°C and implanted with 540 keV Si ions to a fluence of 2×10¹⁵Si.cm^-2 using a constant scanned ion flux of 0.2 μA.cm^-2. The resultant primary defect concentrations, measured by Rutherford backscattering spectrometry and channelling (RBS-C), were 2.3±0.1×10²² cm^-3 and 1.8±0.2×10²¹ cm^-3, respectively, i.e. a reduction by a factor of approx.13 for a temperature increase of 40°C. Such differences were not evident in the concentration of secondary defects formed by annealing these samples at 900°C for 15 minutes: the defect concentrations were equal within the experimental uncertainties of the RBS-C and transmission electron microscopy (TEM) measurements. This results appears to lead to the surprising conclusion that the number of displaced atoms that survive high temperature annealing to form extended defects is largely independent of the dynamic annealing processes operating during implantation but depends instead on parameters which scale with the ion fluence.