Wafers of (100) material were implanted with 120keV Ge ions at substrate temperatures of up to 600C. The Ge profile was monitored, together with the crystalline fraction of implanted Si, by means of Rutherford back-scattering spectroscopic channelling in the (100) direction. Extensive profile broadening was observed, with high-temperature implantation being accompanied by a peak shift of 50nm away from the surface for the highest-temperature implantation (600C). A Ge tail was also observed which extended deeper than 300nm for this implant, together with a more-than-60% reduction in the peak Ge concentration as compared with similar implantation at room temperature. Radiation-enhanced diffusion and enhanced sputtering were ruled out as being causes of the profile broadening. It was instead demonstrated that channelling along the (100) direction was the cause of the observed broadening and of the increase in peak depth. This was confirmed by eliminating profile broadening, from a sample implanted at 600C, by tilting the implantation direction away from major axial and planar channels. Positron annihilation spectroscopy was used to monitor the profile of open volume defects in the implanted material. The results showed that a defect concentration of more than 1016/cm3 extended to a depth of about 1.2μ for the implantation of 1014/cm2 of Ge at room temperature. A higher concentration of such defects appeared deeper in the sample for similar implantation at 450C. These deep open-volume defects could be eliminated by using tilted implantation through an amorphous 0.5μ SiO2 mask. Their formation was consistent with Ge ion channelling during the initial stages of room-temperature implantation and with extensive channelling during high-temperature implantation.

A.Nejim, A.P.Knights, C.Jeynes, P.G.Coleman, C.J.Patel: Journal of Applied Physics, 1998, 83[7], 3565-73