MRS 1999 Fall Meeting

Ion Implantation and Misfit Dislocation Formation in P/P+Silicon

P. Feichtinger, H. Fukuto, R. Sandhu, B. Poust, and M.S. Goorsky,
Dept of Materials Science and Engineering, University of California, Los Angeles.


 





We determined that Si ion implantation (1 x 1014 cm-2 at 100 keV) of pseudomorphically strained silicon epitaxial layers greatly attenuates strain relaxation.  We employed highly boron doped 150 mm diameter silicon with a nominally un-doped, 2 mm thick epitaxial layer (p/p+).  The compressively strained layer showed inhomogeneous relaxation after epitaxial growth, with misfits forming only near the wafer periphery.  This non-uniform dislocation distribution was utilized during subsequent implantation steps to study the role of the implant on both the nucleation and growth of the misfit segments.  The silicon self implantation was performed at room temperature.  The dose and energy were kept below the amorphization threshold, as confirmed by triple axis x-ray diffraction.  High temperature rapid thermal annealing was employed to study misfit dislocation nucleation and glide.  Double axis x-ray topography was used to measure the evolution of the misfit segments after annealing.  The implanted regions exhibited neither growth nor nucleation of misfit dislocation segments, in marked contrast to the growth and nucleation of misfits observed in the non-implanted regions.  SIMS measurements confirmed that transient enhanced diffusion of boron was not appreciably different in the two regions, ruling out the reduction of bi-axial stress as the origin for the differences observed.  This comparison and subsequent modeling - indicated that the excess point defects and crystallographic damage act to impede both dislocation motion and dislocation nucleation.  Our results suggest that low dose ion implantation has a potential to reduce misfit dislocation propagation and nucleation in multi-layer thin films.