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       Session TF-WeM

Paper TF-WeM3
On the Relative Motion of Thermal Gas Atoms In the Monte Carlo Simulation of Sputtering

Wednesday, October 31, 2001, 9:00 am, Room 123

Session: Fundamentals of Deposition
Presenter: T. Nakano, Seikei University, Japan
Authors: T. Nakano, Seikei University, Japan
S. Baba, Seikei University, Japan
Correspondent: Click to Email
In this study, we have developed the treatment of gas motion in the Monte Carlo (MC) simulation of sputter deposition process. It has been known well that the mean free path of the sputtered particle depends on the speed of the particle, but the distribution function of colliding gas has been assumed to be the Maxwellian, which is independent of the particle speed.@footnote 1@ We show here that the distribution also depends on it. The collision frequency of the sputtered particle with those gases which belong to some volume in the velocity space is proportional to the product of the density of the gas, the cross section and the relative speed between the sputtered particle and the gas atoms. Therefore, the colliding gas velocity does not obey the stock Maxwellian but the one weighed by the relative speed. This distribution function can be integrated by using the relative speed and the gas speed (in laboratory system) as integrating parameters, hence it is applicable to the MC simulation. Using this method, time evolutions of velocity and positional distributions of sputtered particles are calculated and demonstrated. It is shown that the speed distribution of the sputtered particles after some period of time is described well by the Maxwellian of the same temperature with the gas. It is also shown that this method has enabled the accurate calculation of the resident time of sputtered particles in the chamber, which leads the spatial density of the particle. @FootnoteText@ @footnote 1@G. M. Turner, et al., J. Appl. Phys. 65 (1989) 3671.