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Monte Carlo approach for the sputtering deposition process has been developed since midst of 1980's. Most of these studies, gas motion has been neglected. It is because that the initial energy of the sputtered particles is much higher.

The particles repeat collision and scattering with stationary gas atoms, and lose their energy. After the thermalization, random walk diffusion is generally used.

Recently, we have proposed a method to take the gas motion into account in the MC simulation. If the kinetic energy of the gases is ruled under the Maxwellian, it is possible to lead the speed and angular distributions of colliding gas atoms, as a function of the particle speed.

We have obtained better results with this, but at more high pressures, Mean Free Path becomes very short and we must calculate so many collisions. So, computation time becomes very large.

It's very wasteful. So in this study, we try to solve the problem with diffusive approach after the thermalization.