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Investigation of Si1-XGeX epilayers behavior upon ultraviolet nanosecond laser annealing

Abstract : Nanosecond Laser Annealing is a promising method for dopant activation in thin junctions, enabling activation levels above the solid solubility limits in Si and Ge. Due to its short pulse duration, only the surface of the irradiated material is heated, which is particularly appropriate for 3D sequential integration. Materials such as Si and Ge can reach their melting point near the surface, causing the formation of a molten layer that solidifies at high velocities. This annealing technique can be applied to Si1-xGex junctions, but strain behavior and dopant activation are not fully understood yet. This work focuses on the detection of the various annealing regimes encountered when submitting Si1-XGeX (x0.4) layers to nanosecond laser annealing , the evolution of the strain and on the dopant activation as a function of the laser energy density. A first part is dedicated to the detection of the annealing regimes, and the corresponding SiGe layer characteristics. A particular focus is given to the surface melt regime, in which we observed the appearance of isolated molten islands on the surface, leading to increased surface roughness. In a second time, we focused on Ge redistribution and the evolution of the strain in these regimes, and showed how relaxation is related to both the liquid/solid interface roughness and to the stored elastic energy. The rough l/s interface observed in partial or surface melt regimes facilitated the formation of strain relieving defects, leading partial relaxation in most layers. A smooth liquid/solid interface however enabled perfect regrowth unless the elastic energy stored in the layer exceeded 750 mJ/m². A last section is dedicated to the study of boron activation in Si0.7Ge0.3 layers. The best results are obtained with laser annealing conditions leading to the exact melt and recrystallization of the whole 30 nm-thin SiGe layer. In this case, pseudomorphic layers with active dopant concentrations up to ~2.4×1020 B/cm3 and a strong Ge segregation toward the surface were obtained. These layers were observed to be stable up to 600°C for 20 minutes additional furnace anneals.
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Submitted on : Tuesday, September 28, 2021 - 10:29:18 AM
Last modification on : Monday, April 11, 2022 - 4:09:46 PM
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  • HAL Id : tel-03637329, version 1

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Léa Dagault. Investigation of Si1-XGeX epilayers behavior upon ultraviolet nanosecond laser annealing. Micro and nanotechnologies/Microelectronics. Université Toulouse 3 Paul Sabatier, 2021. English. ⟨tel-03637329v1⟩

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