Electrical Characterization of Deep-Lying Donor Layers Created by Proton Implantation and Subsequent Annealing in N-Type Float Zone and Czochralski Silicon

Abstract

The deep-lying donor layers created by proton implantation and subsequent isochronal annealing were investigated in silicon substrates with oxygen concentration changing from 2x10^16 cm-3 to 1.4x10^18 cm-3. Implantation was performed with 700 keV and 1.8 MeV protons to fluence ranging from 1x10^10 to 1x10^15 cm-2. Results of C-V measurement showed that proton implantation introduces a Gaussian like distribution of shallow hydrogen donors that corresponds to the profile of implanted hydrogen obtained from the secondary ion mass spectroscopy measurement. Subsequent isochronal annealing leads to annealing out of hydrogen donors (~250{degree sign}C) and formation of a series of hydrogen thermal donors (250-350{degree sign}C). In substrates with enhanced concentration of oxygen, the radiation enhanced thermal donors and ordinary thermal donors (>400{degree sign}C) were registered. It was shown that the introduction rate of hydrogen and thermal hydrogen donor layers is enhanced in materials with higher oxygen concentration. However, low oxygen concentration is preferred when better control over spatial distribution of the excess donor profiles is required.