| AVS 58th Annual International Symposium and Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS-ThM |
| Session: | Neutral Beam and Low Damage Processing |
| Presenter: | Shingo Ohtsuka, Mizuho Information & Research Institute, Inc., Japan |
| Authors: | S. Ohtsuka, Mizuho Information & Research Institute, Inc., Japan N. Watanabe, 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, Japan O. Nukaga, BEANS Project 3D BEANS Center, Japan S. Ueki, BEANS Project 3D BEANS Center, Japan T. Kubota, Tohoku University, Japan M. Sugiyama, University of Tokyo, Japan S. Samukawa, Tohoku University, Japan |
| Correspondent: | Click to Email |
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, most of those ions passing through the apertures are efficiently converted into neutral atoms. We consider ions are neutralized by the collision with aperture sidewall. A negative ion transfers some of their valence electrons to the aperture sidewall by the collision, and a positive ion receives some valence electrons from the aperture sidewall. The dynamical process of electron transfer by the collision can be described by the Quantum Mechanics as a time-evolution of wave-function during the collision, and we have developed computational simulation software named QuickQD [2].
To realize more practical neutral-beam etching system, we also have to analyze the energy and angular distribution passing through the aperture. Those distributions characterize the ability of etching system. In other words, to achieve efficient etching system, we have to develop optimized aperture configurations (i.e. arrangement and aspect ratio of apertures) and get conditions for suitable energy and angular distribution of neutral beam.
In this study, we calculate the trajectory of particles generated by Monte-Carlo method, and analyze the energy and angular distribution of neutral beam at aperture outlet. To analyze energy and angular distribution at outlet, we have to determine the initial conditions of incident beam at aperture inlet, and have to describe the scattering process for collision between incident particles and side wall of aperture. We determine initial beam condition at inlet using the experimental data fitting. And we use the inelastic surface scattering model known as Hard-Cube model [3] for treating collision between particles and side wall of aperture. Particles injecting into aperture which have broad angular distribution are collimated by this inelastic scattering process.
Using above simulation scheme, we analyze the energy and angular distribution for specific aperture configuration (i.e. aperture aspect ratio) and compare with experimental data. We also analyze the particle distribution of neutral beam at silicon wafer injecting from aperture outlet and discuss the uniformity of neutral beam etching. Using above angular distribution of neutral beam and etching simulator, we predict etching shape by neutral beam generated by various aperture configurations (i.e. aperture aspect ratios).
[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] R. M. Logan and R. E. Stickney, J. Chem. Phys., 44, 195 (1966).