| AVS 57th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS2-WeA |
| Session: | Neutral Beam Processing |
| Presenter: | N. Watanabe, Mizuho Information & Research Institute, Inc., Japan |
| Authors: | N. Watanabe, Mizuho Information & Research Institute, Inc., Japan S. Ohtsuka, Mizuho Information & Research Institute, Inc., Japan T. Iwasaki, Mizuho Information & Research Institute, Inc., Japan K. Ono, Mizuho Information & Research Institute, Inc., Japan Y. Iriye, BEANS Project 3D BEANS Center and University of Tokyo, Japan O. Nukaga, BEANS Project 3D BEANS Center and University of Tokyo, Japan S. Ueki, BEANS Project 3D BEANS Center and University of Tokyo, Japan T. Kubota, BEANS Project 3D BEANS Center and University of Tokyo, Japan M. Sugiyama, BEANS Project 3D BEANS Center and University of Tokyo, Japan S. Samukawa, BEANS Project 3D BEANS Center and Tohoku University, Japan |
| Correspondent: | Click to Email |
We have developed numerical simulation method which analyses neutral beam generated by collisions with aperture sidewalls.
The neutral-beam etching system developed by Samukawa, et al [1] has a carbon plate which has numerous apertures, where positive or negative ions pass through. In this system, we had found experimentally that most of those ions passing through the apertures are efficiently converted into neutral atoms with maintaining the motion energy. We consider ions are neutralized by the collision with aperture sidewall, namely, a negative ion transfers some of their valence electrons to the aperture sidewall by the collision, on the other hand, a positive ion receives some valence electrons from the aperture sidewall.
To realize more efficient neutral-beam etching system, we have to understand the dynamical process of electron transfer by the collision. The process of electron transfers can be described by the Quantum Mechanics as a time-evolution of wavefunction during the collision. For this purpose, we have developed computational simulation software named QuickQD[2,3] which can calculate the time-evolution of wavefunction of electrons around both an ion and the carbon plate during the whole process of collision. QuickQD is based on the density functional theory, and it can calculate the time-evolution of wavefunctions stably and efficiently.
Our numerical model consists of an ion and several carbon atoms forming a graphite sheet. We have taken the following ions and neutral atoms as the colliding ion respectively; Cl-, Cl, Cl+, Cl2-, Cl2, and Cl2+.
We have performed the numerical simulation of the collision of each ion and the carbon sheet. QuickQD has calculated the time-evolution of several ten wavefunctions of both the ion and carbon atoms. During the time-evolution, the ion has been moved to collide with the graphite sheet and then bounce back to its original position. At the end of time-evolution, we have counted the electron distribution left around the ion, and have estimated the valence number of the ion after the collision. In this way, we have determined the probability of neutralization of each ion. We have obtained results which show a Cl- is converted into Cl with a high probability, meanwhile a Cl2+ is converted into a Cl2 with a low probability. These numerical results agree well with the experimental results. We have established a numerical method that analyzes the neutralization process based on the Quantum Electrons Dynamics.
[1] S. Samukawa et al., Jpn. J. Appl. Phys., 40, L779 (2001).
[2] N. Watanabe and M. Tsukada, Phys. Rev. E. 65 036705 (2002).
[3] http://www.mizuho-ir.co.jp/science/meso/index.html