Point defect–dislocation interactions in BEOL-compatible Ge-on-Si epitaxy
Author(s)
Postelnicu, Eveline; Wen, Rui-Tao; Ma, Danhao; Wang, Baoming; Wada, Kazumi; Michel, Jurgen; Kimerling, Lionel C; ... Show more Show less
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Reduced thermal budget is required for back-end-of-line (BEOL) integration of application specific functionality into the multilevel metal stack of a processor “substrate.” We report 400 °C BEOL-compatible Ge-on-Si growth (LT Ge) that is epitaxial and single crystalline with a defect density similar to high temperature growth and a small 0.05% tensile strain. Room temperature methanol–iodine passivation is employed pre-growth in lieu of the typical 800 °C oxide removal step. Undoped LT Ge exhibits p-type conductivity initially and n-type conductivity conversion upon annealing. Hall effect measurements following post growth heat treatment between 400 and 600 °C reveal an acceptor removal reaction that follows first-order kinetics with an activation energy of 1.7 ± 0.5 eV and a pre-exponential factor of 2.3×107 s−1 consistent with a point defect, diffusion limited process. We also observe that 90° sessile dislocations identified via transmission electron microscopy are annihilated in the same temperature regime, which is evidence for point defect-mediated climb. Ensuring high-quality epitaxy by characterizing defect reactions in a BEOL-compatible Ge-on-Si process flow is key to enabling vertical integration of optical interconnects.
Date issued
2023-07-17Department
Massachusetts Institute of Technology. Department of Materials Science and EngineeringJournal
Applied Physics Letters
Publisher
AIP Publishing
Citation
Eveline Postelnicu, Rui-Tao Wen, Danhao Ma, Baoming Wang, Kazumi Wada, Jurgen Michel, Lionel C. Kimerling; Point defect–dislocation interactions in BEOL-compatible Ge-on-Si epitaxy. Appl. Phys. Lett. 17 July 2023; 123 (3): 031103.
Version: Final published version