Solid-phase epitaxial regrowth of phosphorus-doped silicon by nanosecond laser annealing.

In view of 3D sequential integration, it is proposed to perform solid-phase epitaxial regrowth (SPER) of amorphous silicon, based on nanosecond laser pulses at energy densities (ED) kept right below the melting threshold. Si substrates were amorphized down to 29 nm by Ge and P implantation. The application of up to 1000 laser pulses at constant energy density values did not enable full regrowth. To overcome such limitations, an adaptive energy density strategy was developed. In this new approach, the ED was progressively increased in steps, with N pulses being applied at each ED value, while always remaining below the increasing melting threshold. Sequences with N = 100 pulses enabled complete recrystallization and dopant activation rates beyond 90 %. Sheet resistance and time-resolved reflectivity measurements proved to be efficient techniques to both monitor the progressive regrowth up to the surface and detect undesirable melting if any. Phosphorus atomic concentration depth profiles evidenced some snow-plow towards the surface upon regrowth and a very limited in-depth diffusion. Finally, the adaptive ED SPER strategy was successfully transposed to P-doped source and drain regions of 28 nm FD-SOI transistors that were fully regrown without any degradation of the gate stack. [Display omitted] • Complete regrowth of pre-amorphized phosphorus doped Si by nanosecond laser annealing. • Original processing strategy optimizing regrowth and dopant activation. • In-situ monitoring using time-resolved reflectometry. • Phosphorus depth profiles: redistribution upon recrystallization. • Application to 28 nm FD-SOI transistors: source and drain regrowth. [ABSTRACT FROM AUTHOR]