AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA3
Numerical Simulation of Oxidation Process in Silicon by O2 Gas Cluster Beam

Thursday, October 31, 2013, 2:40 pm, Room 104 C

Session: Low Damage Processing
Presenter: K. Mizotani, Osaka University, Japan
Authors: K. Mizotani, Osaka University, Japan
M. Isobe, Osaka University, Japan
S. Hamaguchi, Osaka University, Japan
Correspondent: Click to Email
A surface modification process based on a gas cluster ion beam (GCIB) is known to be less damaging to the surface than that based on an ordinary atomic or molecular ion beam. In a GCIB process, several thousands of atoms or molecules aggregated by Van der Waals interactions form a gas cluster and such gas clusters are ionized and accelerated up to a high kinetic energy (typically in the range of several keV) toward a surface that is to be processed. Although the total acceleration energy for each cluster can be very high, each atom or molecule has relatively low kinetic energy. Therefore a GCIB process is essentially a low energy beam process. In this study, we use molecular dynamics (MD) computer simulations to examine surface oxidation processes for silicon (Si) by oxygen-molecule GCIBs at various incident energies and compare the results with those of earlier experimental studies. Especially in this study, we focus on extremely low energy processes, where incident oxygen molecules in gas clusters have kinetic energies close to thermal energy at room temperature. It has been found in MD simulations that only the top surface layer of the substrate can be oxidized with little damage to the surface in GICB processes. This is in contrast with oxygen molecular-ion beam processes, where oxygen hardly sticks to the Si surface when the beam kinetic energy is sufficiently low (so that the chemical bond of O2 cannot be broken). If the kinetic energy is high, then the surface can be oxidized but the beam impact causes surface damage. It has been observed that, in the case of low-energy gas cluster beam incidence, each gas cluster sticks to the Si surface for dozens of picoseconds until the gas cluster is sublimed by heat transport from the substrate. While a cluster remains on the substrate surface, a large number of oxygen molecules with a solid density are directly exposed to the substrate surface, which increases the probability for the formation of Si-O bonds only on the top surface.