Computer Simulation of Annealing after Cluster Ion Implantation
- PDF / 1,639,787 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 0 Downloads / 282 Views
promising new technique for future small scale PMOS devices. Very shallow junctions have been obtained with low-energy decaborane implantation into a Si surface [3]. Equilibrium diffusion of dopants in a slightly doped Si is a well studied area of semiconductor physics [4,5]. Dopant diffusion in silicon under equilibrium and nonequilibrium concentrations of point defects has recently been studied by combination of Molecular Dynamics (MD) and (kinetic) Monte-Carlo (MC) methods in [6,7], and by using kinetic equations for defect and dopant concentrations [8]. Tight-binding MD simulations were used to study Si self-diffusion due to the vacancy/interstitial mechanisms [9]. The authors have shown that at a lower temperature self-diffusion is dominated by vacancies, and by interstitials at higher temperature. Defect diffusion and surface effect were studied in [10] by a combination of MD and STM technique. Modeling of low energy decaborane implantation has attracted much less attention so far compared with that of single B+ ion implantation. To the authors' knowledge, there has been simulation of 1.5 and 4 keV decaborane implantation into a Si substrate with Molecular Dynamics [11]. The aim of this paper is to simulate decaborane implantation into Si at room temperature and the following RTA process at a much higher temperature, by a combination of Molecular Dynamics and Monte-Carlo methods, in a low ion energy implantation region. For comparison, simulation has also been performed for the monomer B' ion implantation with the same dose and same energy per atom. 147
Mat. Res. Soc. Symp. Proc. Vol. 532 © 1998 Materials Research Society
MODEL As the B atomic mass makes up only 1/3 of the Si atomic mass, the implanted B atoms undergo rare but violent collisions with neighboring Si atoms. Therefore, the motion of B atoms could not be considered as a Brownian one. This makes finding the B diffusion constant a challenging problem for theory. Molecular Dynamics can in principle find the diffusion coefficient, but it is incapable of treating a realistic system for a long computation time. This is usually limited to tens of ps which is not long enough to simulate diffusion of B during RTA processing. On the other hand, the kinetic models using rate equations for defect concentrations, are rather insufficient for the real three-dimensional modeling of decaborane implantation. This follows because the space scale of averaging in this technique is much larger than that in the case of decaborane, due to a higher non-uniformity of dopant distribution. As RTA is usually applied for 10s, a time scale which too long for a MD method, a method combining MD with MMC is developed in this paper. As we discuss further, the proposed method could easily extend simulation time up to - 0.01 - 0.1 s., which is long enough for finding parameters of dopant diffusion. To the authors' knowledge, the MMC has not been used before for obtaining diffusion characteristics of dopants in Si for the ion implantation process of interest. MOLECULAR DYNAMICS Th
Data Loading...
