Local donor doping by proton implantation in p

Abstract

The effect of excess donor doping introduced by implantation with 700 kV and 1.8 MeV protons and subsequent annealing up to 550°C in silicon substrates with different oxygen content was investigated. Three different types of silicon material were chosen for this purpose: Czochralski, oxygen-lean and oxygen rich float-zone silicon. Deep and shallow levels resulted from implantation and subsequent annealing were studied by deep level transient spectroscopy and C-Vprofiling. Results show that hydrogen donors appear at the proton end-of-range after implantation in all materials. Their introduction rate depends linearly on proton fluence and is substantially higher in Czochralski and oxygen-rich float zone materials due to higher oxygen concentration. It is shown that during post-implantation annealing, the excess donor doping changes in several phases. Hydrogen donors anneal out above 250°C and then, hydrogen-related thermal donors and thermal donors are generated. When annealing temperature exceeds 400°C, the hydrogen thermal donors are still localized at the proton end-of-range in oxygen-lean float zone silicon while in Czochralski silicon and oxygen-rich float zone material, thermal donors arise in the whole bulk and radiation enhanced thermal donors decorate the profile of radiation damage. The level of local doping by hydrogen thermal donors is proportional to implantation fluence and layers are stable up to 550°C for implantation fluences above 1013 cm-2 . The detrimental effect of hydrogen donors and thermally activated donors on blocking characteristics of power p+nn+ diodes is also discussed.