A Molecular Dynamics Study of Low-Energy Argon and Boron Implants on Silicon (100) Vicinal Surfaces Stepped Surface
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A MOLECULAR DYNAMICS STUDY OF LOW-ENERGY ARGON AND BORON IMPLANTS ON SILICON (100) VICINAL SURFACES STEPPED SURFACE. A.M.MAZZONE
C.N.R. LAMEL-via Gobetti 101 - [email protected].
ABSTRACT
The purpose of this study is to illustrate the e ects of the structure of the silicon surface on low-energy implants commonly used in current silicon technology. T o this aim Molecular Dynamics simulations with classical forces are used to study implantation of argon and boron with a kinetic energy in the range from 5eV to 30 eV into a silicon stepped surface. In addition to these calculations, the binding energy of boron atoms embedded in small clusters with a step shape hav e been studied with a quantum mechanical method of a semiempirical type. The purpose of these calculations is to compare the stable sites generated by theimplan ts with the ones attained during thermal treatments under nearequilibrium conditions. INTRODUCTION
Ion implantation and radiation damage of the silicon surface, bombarded with lo wenergy argon and silicon ions, hav e been the object of many Molecular Dynamics(MD) simulations (a detailed list of references can be found in [1,2]). In these studies the silicon surface has a realistic dimerized termination and the simulations show that strong re ection of the incident atoms and displacements with a lo wer energy than the one required to displace bulk atoms are characteristic e ects of the dimer rows. F urthermore MD simulations of lms growth b y MBE [3] show that the v arious step-edges present on the silicon surface are not equivalent and, depending on their geometry, they act as eÆcient, or poor, sinks for the deposited silicon adatoms. A natural question is if a similar step-dependence appears under ion bombardment and the purpose of this study is to gain insight into this problem. Therefore we examine a realistic (100) vicinal surface with one step and we study the motions of boron and argon ions implanted into the steps with a kinetic energy Ek 30eV b y using molecular dynamics with classical forces. In addition to these simulations, the total energy of small clusters with a step shape, containing a boron impurity, hav e been ev aluatedquantum mechanically. The purpose of these calculationsto is inv estigate if there is a coincidence between the stable sites of boron observed in ion implantation and the minima of the stationary energy obtained from cluster calculations. This represents an useful, and new, suggestion on the relationship between ion implantation and thermal treatments carried out under nearly equilibrium conditions. MOLECULAR DYNAMICS AND CLUSTER CALCULATIONS.
The simulation method is the one already presented in [1,2]. As in the previous studies, the simulation cell reproduces in a simpli ed formed a stepped (001) silicon surface. It has
B6.1.1
a terraced form with one step. The step edge is either SA or SB non-rebonded. A lattice view, which describes the di erence between the two steps, is shown in Fig.1. An Ar or B ion, directed along the surface n
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