HRTEM observation on microstructures in the Ge-implanted silicon wafers re-processed by solid phase epitaxy

Solid-phase epitaxy combined with Ge implantation has been employed to process silicon wafer. The resulting microstructural details have been examined by high-resolution transmission electron microscopy. It is observed that a thin layer of SiGe alloy forms around the projected ion range. Some dislocations as half loops extend into the substrate itself instead of the top part above the alloy layer, so the completeness in the top silicon has less destruction. It is assumed that the gradient profile of Ge composition under the SiGe alloy layer may be the primary cause. Within the SiGe alloy layer, there appear special nanoclusters. The distribution and the number of these nanoclusters are closely correlated with the implant energy and dose. It is revealed by Fourier transform analysis that the lattice within the nanoclusters is modulated with a period of four times the (1 1 1) plane spacing in the regular Si lattice. It is argued that the lattice-modulated characteristics should result from Ge ordering instead of Moiré interference.