Molecular Dynamics Study of Fast Diffusion of Cu in Silicon

Abstract

A distinguishing property of copper impurities in silicon is their very fast diffusivity, which is undesirable in silicon device processes. This paper is the first attempt to simulate the fast diffusion of Cu by first-principles calculations. It is shown that, even near room temperature, the amplitude of Cu vibrations is very large; this is a consequence of the fact that the local mode of Cu has very low frequencies. At T>1000 K, the simulations demonstrate clear migration between adjacent cells. The diffusion path is from an interstitial T site to the next T site through an H site. The Arrhenius plot of the calculated diffusion constants agrees with the experimental data on the intrinsic diffusion of Cu, which are currently most reliable data available.

Multi-walled carbon nanotube structural instability with/without metal nanoparticles under electron beam irradiation

“…For e-beam irradiation effects in Au NPs, phonon softening induced by positive curvature effects in the shell structure can facilitate the e-beam to activate Au atomic displacements via d 10 -to-d 9 type electronic excitations. The tetragonal d 9 systems (Cu(II) and Au(II)) with elongated bonds in z-axis direction are expected to undergo Jahn−Teller distortions [41][42][43][44]. As compared with Cu, d-orbital splitting is much more probable in Au.…”

“…The relaxation energy needed to undergo an intermediate interstitial site defines barrier height. By classical mechanics, it can be assumed that relaxation energy determines the barrier height reasonably [41]. Nevertheless, quantum mechanically, Au atom displacements can be easily associated with dynamic coupling of atom movements to the electronic excited states, i.e.…”

Gettering mechanism of transition metals in silicon calculated from first principles

“…[3,4]. The first-principles pseudo potential method based on the local-density approximation (LDA) were used for the calculation.…”

“…For the heavier 3d elements, it is known that E d becomes small, less than 0.5 eV. In this case, the dynamic effect becomes important, and validity of frozen-phonon calculation is restrictive [4]. For example, Ni can be named in this case.…”

“…In previous papers (Refs. [3,4]), we have developed a theoretical approach to predict the gettering efficiency among various combinations of electronic dopant atoms. In those papers, we concentrated ourselves to Cu for the target impurity, because of its practical importance.…”