Successive agglomeration of Cu atoms in Si: The early stages of TM precipitation.
Final Report Abstract
Electronic devices in crystallin silicon rely on the stability of the host material and its defect structure during operation. All processes which introduce fast-diffusing defects and/or defect reactions at room temperatures (RT) lead to undesirable device degradation. Despite the importance of these detrimental processes e.g. in high power devices or solar cells, there is still a lack of fundamental insight in the basic reactions. In our work we use copper as a model to understand the introduction and defect formation of transition-metal defects at RT. We find that Cu is introduced easily in Si at low temperatures by chemo mechanical polishing in a Cu contaminated slurry or by wet chemical etching in acids or alkaline solutions with dissolved Cu. In a combined theoretical/experimental study we identified the formation of Cu defect centers with low formation energies and detected the interactions of substitutional copper (Cus) with fast diffusing copper interstitials (Cui). Starting with substitutional Cus we generated larger complexes by successively adding Cui, Cus, CusCui, CusCui2, CusCui3. The defect structures, their formation energies, and the electronic level positions were calculated and compared to experimental results. The level position of the most stable defect CusCui3, which exhibits a strong characteristic photoluminescence signal, is not accurately described by our calculations, indicating another defect structure or additional participating defect. A possible path to Cu precipitation (Cu3Si silicide) has been proposed. In this scenario, the generation of a vacancy near the CusCuin (n=1-3) complexes with reduced formation energy leads to the formation of a second Cus, resulting in a large change in the gap levels and allowing the continued agglomeration of Cui’s. Studies on samples doped with Ag, Au, Pd and Pt reveal close similarities with the Cu-doped samples. Apparently, there is a general principle for a successive growth of TMCuin (n=0-4) complexes. Specific differences are found in the electronic level energies and stabilities of the complexes. During this study, we also identified Ni as another fast diffusing impurity in Si, which is also introduced at RT into the crystal, and forms new electrically- active defects. The analysis of these defects was however not part of the present work.
Publications
- Deep level centers in electron-irradiated silicon crystals doped with copper at different temperatures. Phys. Status Solidi C 14, 1600267 (2017)
N. Yarykin, J. Weber
(See online at https://doi.org/10.1002/pssc.201600267) - Nickel in silicon: Room-temperature in-diffusion and interaction with radiation defects. Phys. Status Solidi C 14, 1700005 (2017)
N. Yarykin, J. Weber
(See online at https://doi.org/10.1002/pssc.201700005) - Electrically Active Copper-Nickel Complexes in p-Type Silicon. Phys. Status Sol. A 1900304 (2019)
N. Yarykin, J. Weber
(See online at https://doi.org/10.1002/pssa.201900304) - Nickel Interaction with Vacancy-Type Radiation Defects in Silicon. Phys. Status Solidi RRL 13, 1800651 (2019)
N. Yarykin, S. Lastovskii, J. Weber
(See online at https://doi.org/10.1002/pssr.201800651) - Platinum–Copper Defects in Silicon. Phys. Status Solidi A, 1900311 (2019)
V. Kolkovsky, V. Kolkovsky, and J. Weber
(See online at https://doi.org/10.1002/pssa.201900311) - The Cu photoluminescence defect and the early stages of Cu precipitation in Si . J. Appl. Phys. 127, 085704 (2020)
T. M. Vincent, S. K. Estreicher, J. Weber, V. Kolkovsky, and N. Yarykin
(See online at https://doi.org/10.1063/1.5140456)
