AVS 61st International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS2+TF-ThM

Paper PS2+TF-ThM4
Precise Theoretical Calculation of Neutral Beam Generation Efficiency by Collision of Chlorine Against Graphite Surface

Thursday, November 13, 2014, 9:00 am, Room 308

Session: Atomic Layer Etching (ALE) and Low-Damage Processing
Presenter: Tomohiro Kubota, Tohoku University, Japan
Authors: T. Kubota, Tohoku University, Japan
N. Watanabe, Mizuho Information & Research Institute, Japan
S. Ohtsuka, Mizuho Information & Research Institute, Japan
T. Iwasaki, Mizuho Information & Research Institute, Japan
K. Ono, Mizuho Information & Research Institute, Japan
Y. Iriye, Mizuho Information & Research Institute, Japan
S. Samukawa, Tohoku University, Japan
Correspondent: Click to Email

We investigated the generation mechanism of neutral particles in high efficiency neutral beam source developed by Samukawa et al [1], by collision of positive and negative chlorine ions against graphite surface. It is already known experimentally that neutralization efficiency of negative ion (Cl-) is much higher than that of positive ion (Cl2+) [2]. However, the mechanism has not been clarified. Recently we investigated the neutralization mechanism by using numerical simulations based on quantum mechanics [3] and succeeded in explaining higher neutralization efficiency of negative ions than positive ions.

In this study, collision process of a chlorine particle (Cl, Cl-, Cl2, or Cl2+) against graphite surface was simulated by calculation based on time-dependent density functional theory (TD-DFT). Neutralization efficiency was calculated from the number of the valence electrons on the particle after the collision. By using a unit cell with enough size, dispersion of electron density into vacuum was suppressed and quantitative interpretation became possible.

Also, dependence on incident angle and energy of the particle was investigated. It was found that experimental result of energy dependence of the neutralization efficiency was quantitatively reproduced by the calculation. It suggests we have achieved a precise simulation of the neutralization process.

A part of this work was supported by the New Energy and Industrial Technology Development Organization (NEDO).

[1] S. Samukawa et al., Jpn. J. Appl. Phys. 40, L779 (2001).

[2] S. Samukawa, Jpn. J. Appl. Phys. 45, 2395 (2006).

[3] N. Watanabe et al., Phys. Rev. E 65, 036705 (2002).

[4] http://www.mizuho-ir.co.jp/solution/research/semiconductor/nano

[5] T. Kubota et al., J. Phys. D: Appl. Phys. 45, 095202 (2012).