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.