The accumulation of O and H at buried implantation-damage layers was studied after the post-implantation annealing of H- and He-implanted Czochralski-type samples. The H implantation was carried out using an energy of 180keV and a dose of 2.7 x 1016/cm2. The He implantation was carried out using an energy of 300keV and a dose of 1016/cm2. Implantation of H was also carried out using float-zone wafers. Post-implantation annealing at 1000C was performed under H or N. The H and O concentration profiles were measured by means of secondary ion mass spectroscopy. It was shown that the type of ambient, during annealing, played an appreciable role in the gettering of O at buried implantation-damage layers in Czochralski material. In the case of both H and He implantation, the buried defect layers acted as effective gettering centres for O and H under suitable conditions. The more efficient gettering of O during post-implantation annealing in a H ambient was attributed to the H-enhanced diffusion of O towards the buried implantation-damage layers; where fast O-accumulation occurred (concentrations of above 1019/cm3 were detected). On the basis of a comparison of measurements on H-implanted Czochralski and float-zone samples, it was concluded that - at the buried defect layers - H was probably trapped by voids and/or was stable as immobile molecular-H species. The H therefore accumulated at the defect layers and was remained there even after annealing at 1000C.

Oxygen and Hydrogen Accumulation at Buried Implantation-Damage Layers in Hydrogen- and Helium-Implanted Czochralski Silicon. R.Job, A.G.Ulyashin, W.R.Fahrner, A.I.Ivanov, L.Palmetshofer: Applied Physics A, 2001, 72[3], 325-32

Table 31

Out-Diffusion Coefficients for O in Si