Incorporation of oxygen in SiC implanted with hydrogen

Abstract

Oxygen accumulation at buried implantation-damage layers was studied after post-implantation annealing of hydrogen- or deuterium-implanted 4H–SiC. In this study H+ or 2H+ implantation was carried out at energies E, from 200keV to 1MeV, to fluences D, ranging from 2×1016/cm2 to 1×1017/cm2. For comparison, the implantation was also done into float-zone (FZ) and Czochralski (CZ) silicon wafers. Post-implantation annealing at temperatures from 400°C to 1150°C was performed either in pure argon or in a water vapor. Characterization methods included SIMS, RBS and TEM. At sufficiently high doses, hydrogen implantation into semiconductors leads to the irreversible formation of a planar zone of microcavities, bubbles and other extended defects located at the maximum of deposited energy. This kind of highly perturbed layer, containing large amounts of agglomerated hydrogen is known to efficiently getter a number of impurities. Oxygen was detected in both CZ and FZ silicon subjected to Smart-Cut™ processing. We have identified, by SIMS profiling, a considerable oxygen peak situated at the interface between the SiC substrate and a layer implanted with 1×1017H ions/cm2 and heated to 1150°C in either H2O vapor or in a nominally pure Ar. In view of a lack of convincing evidence that a hexagonal SiC might contain substantial amounts of oxygen, the objective of the present study was to identify the source and possible transport mechanism of oxygen species to the cavity band. Through the analysis of several implants annealed at various conditions, we conclude that, besides diffusion from the bulk or from surface oxides, an alternative path for oxygen agglomeration is migration of gaseous O2 or H2O from the edge of the sample through the porous layer.