Interaction of radiation defects with the surface of silicon

Abstract

The formation and annealing processes of radiation defects in bulk crystals and thin (≈︁ 1.2 μm) epitaxial layers of Si are studied. Czochralski grown (pulled) and vacuum float-zone n-type Si crystals with ϱ = 1 to 2 Ωcm as well as n-type Si epitaxial layers (∂ ≈︁ 1 Ωcm) grown on substrates of p-type Si, 400 pm thick (ϱ ≈︁ 10 Ωcm) are used. The samples are irradiated (T ⪷ 50 °C) by 640 MeV protons. Results are obtained from the analysis of the temperature dependences of the Hall coefficient at various steps of irradiation or 15 min isochronous annealing as well as from the spatial distributions (over the layer thickness) of the doping impurity and irradiation- and annealing-produced defect concentration. It is established that due to the interaction with the surface of irradiation-generated vacancies and interstitials as well as mobile defects and their components migrating at annealing, a number of peculiarities in radiation defect accumulating and annealing processes take place in epitaxial layers of Si as compared to bulk crystals: 1) Lower charge-carrier removal rates due to the low E-centre introduction efficiency whereby they are not the main compensating defects in thin layers whose thickness is comparable to the vacancy diffusion length; 2) sufficiently wide radiation defect annealing range; 3) effective production of multivacancy complexes under heat treatment near the surface. The results obtained are explained taking into account electric fields and long-range elastic stress fields near the surface. [Russian Text Ignored].