The combination of different X-ray topography techniques and reciprocal space mapping is used to monitor the early stages of relaxation in silicon-based heterostructures. For lightly doped silicon layers grown on heavily boron-doped 150 mm substrates, Lang transmission topography demonstrates that an orthogonal array of 60 • misfits nucleates only at the wafer periphery. The length of the individual misfit segment depends on the epitaxial layer thickness and on the presence of the orthogonal blocking misfit segments. Double-crystal X-ray topography, with better strain and tilt resolution, allows one to distinguish between the different tilt components of parallel misfit dislocations. Relaxation is quantified using triple-axis X-ray diffraction. Reciprocal space maps around both the ( 004) and ( 224) reflections show that the misfits relieve about 38% of the strain. The combination of these X-ray techniques offers insight into the means to reduce dislocation formation and into the fundamental nature of the dislocations themselves.

We determined that self implantation of pseudomorphically strained silicon epitaxial layers greatly attenuates strain relaxation. We employed highly boron doped 150 mm diameter silicon with a nominally un-doped, 2.5 μm thick epitaxial layer (p/p+). The compressively strained layer (mismatch ≈ 1.5 × 10−4) showed inhomogeneous relaxation after epitaxial growth, with misfits forming only near the wafer periphery. High temperature rapid thermal annealing was employed after ion implantation to study misfit dislocation nucleation and glide. Our results suggest that low dose ion implantation has a potential to reduce misfit dislocation propagation and nucleation in epitaxial thin films.

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We studied damage evolution and the influence on defect interactions as a function of Si self implantation dose in p/p+ silicon wafers. Highly boron doped 150 mm diameter silicon substrate wafers with a 2.5 μm thick nominally un-doped epitaxial layer (p/p+) were employed. Due to the misfit strain, misfit dislocations formed during the epitaxial growth process around the wafer edges. This localized dislocation distribution was utilized to study the role of the implant on both the nucleation and growth of the misfit dislocation segments. Triple axis x-ray diffraction was used to determine changes to the strain in the layer due to both the implant and to subsequent annealing. Double axis x-ray topography combined with rapid thermal annealing was used to measure the nucleation and extension of the misfit dislocation segments after annealing. For the lower implantation dose (1012 cm−2) samples, the velocity of dislocations was reduced measurably and the density of newly formed misfit dislocations also decreased significantly relative to regions that received no ion implantation. A higher implantation dose reduced the nucleation and glide velocity further such that neither glide nor nucleation of new segments was detected. SIMS measurements confirmed that the interfacial lattice parameter grading was not appreciably different after an anneal step for the lower implant dose sample, but was measurable for the higher dose sample. In the latter case, transient point defect enhanced diffusion of boron was responsible for the grading. However, the lack of grading in the low dose sample indicates that interfacial grading did not significantly impede dislocation kinetics. This comparison indicates that it is the excess point defects that are produced during implantation that retard both the nucleation and extension of misfit dislocation segments.