Strain-driven defect evolution in Sn+ implanted Si/SiGe multilayer structure

We report on secondary defect evolution in a multilayered Si/SiGe structure after 1 MeV Sn+-ion implantation to a fluence of 2 × 1014 cm−2 followed by thermal annealing in a dry nitrogen atmosphere. Formation of a buried amorphous layer is registered after ion implantation. Thermal treatment leads to formation of dislocation loops in an EOR-defect band, and a mixture of tangle dislocations and “clamshell” defects at the depth of 200-500 nm. In addition, self-assembling of voids in a near-surface SiGe layer structure is observed. The voids are of nanometer size and are preferably located in thin SiGe layers. The results are discussed in terms of the separation of the vacancy and interstitial depth profiles attributed to the preferential forward momentum of recoiling Si atoms. The compressively strained SiGe layers play the role of vacancy accumulator, prevent in-surface diffusion of vacancies and, in this way, result in self-assembling of voids inside compressively strained SiGe layers.