Electrical activation processes of p+ions channeled along the [110] axis of silicon: Effect of annealing on carriers profiles shape

Abstract

Phosphorus ions at energies of 100, 200 and 300 keV and doses : etween 5 × 10¹⁴ and 5 × 10¹⁵ at/cm² have been implanted into silicon crystals along the [110] axis. Electrical carriers distributions have been determined by means of : ifferential sheet resistivity and Hall-effect together with the anodic oxidation stripping technique. Isochronal recovery of the number of carriers/cm² has also been performed, in the temperature range 25–900° C. Rutherford backscattering analysis has been used to determine the : adiation damage distributions produced by the implanted atoms; 300 keV proton back-scattering spectra as a function of annealing temperature has also given information on the damage recovery processes. The shape of carriers profiles, as a function of annealing temperature : etween 100 and 900° C, has been compared with the damage distribution due to the implantation itself and correlation between phosphorus electrical activation and damage has been shown. It seems possible to single out three different regions in the carriers depth distributions with different mechanisms of phosphorus electrical activation. In the region beneath the surface, where the damage distribution is peaked, the larger fraction of phosphorus atoms becomes electrically active, going into substitutional sites during the amorphous zones recrystallization at temperatures below 550–600° C. In the region 0.3–0.4 μm thick near the maximum range reached only by well channeled ions, P⁺ becomes electrically active approximately between 125°C and 175°C. This process is tentatively attributed to the migration of E-centers already formed at room temperature. In the intermediate region phosphorus becomes active in the temperature range 375–575°C.