A critical review on atomistic simulations of solid-phase epitaxial regrowth of amorphous Si and Ge layers


A critical review on atomistic simulations of solid-phase epitaxial regrowth of amorphous Si and Ge layers

Posselt, M.; Gabriel, A.-A.

In semiconductor technology ultra-shallow junctions are produced by ion implantation and subsequent annealing. The relatively high fluence applied in dopant implantation and the use of pre-amorphization implantation may lead to the formation of an amorphous (a-)layer. In the first stage of annealing the solid phase epitaxial regrowth (SPER) of the a-layer takes place. SPER leads to redistribution of dopants, and they are incorporated into the crystal either substitutionally or within clusters containing self-interstitials (Is) or vacancies. In Si the SPER process leaves beyond the original a/c interface the end-of-range (EOR) damage which contains an excess of Is. During further annealing, free Is are emitted from the EOR damage and may cause an enhanced diffusion of the dopants. It is highly desirable to understand the processes occurring during SPER on the atomic level. This work presents results of classical molecular dynamics simulations of SPER in pure Si and Ge. While in the last decade several authors investigated SPER in Si, the regrowth of a-Ge layers has not been considered yet. The critical review of SPER simulations using different interatomic potentials shows that the experimental regrowth rates cannot be reproduced reasonably well. Moreover, it is found that the results obtained by different groups under virtually equal conditions do not agree. Possible reasons for these differences are outlined. The main cause for the disagreement with experimental data is the inaccuracy of the interatomic potentials used. Proposals for physically-based improvements are discussed. They are based on a better description of the amorphous phase using a modified potential, without changing the established potential for the single-crystalline material. It is shown that a-Si and a-Ge with realistic structural and thermodynamic propertied can be obtained by various modifications of known interatomic potentials, whereas it is very difficult to find a modification which also yields the correct SPER rate.

Keywords: computer simulation; Si; Ge; solid-phase epitaxial regrowth

  • Lecture (Conference)
    The 9th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES2008), 12.-17.10.2008, Beijing, China

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Publ.-Id: 11839