Comprehensive computer model for magnetron sputtering. I. Gas heating and rarefaction

The complex interaction between several variables in magnetron sputtering discharges is a challenge in developing engineering design tools for industrial applications. For instance, at high pressures, rarefaction and gas heating should no longer be neglected for determining several parameters of the process. In this article, we use a comprehensive 3D reactor-scale simulator that incorporates most phenomena of interest in a self-consistent manner to simulate the transport of sputtered particles over a wide range of pressures and powers. Calculations of aluminum deposition rates and metal vapor densities are in reasonable agreement with experiments over a wide range of pressures and powers. Of the elements investigated (Al, Ti, and Cu), copper showed the greatest rarefaction (30%) due to its higher sputtering yield. Titanium, despite a slightly lower sputtering yield than Al, shows a greater rarefaction than aluminum as more particles are reflected from the target as high energy neutrals. In this case, a more efficient energy transfer process is responsible for the higher rarefaction observed in Ti sputtering when compared to Al. The authors also observed that by sputtering at a higher pressure, the probability of electron impact ionization of sputtered particles is increased and speculate about the role of this process in contrast to penning ionization, which is believed to be the dominant ionization mechanism in magnetron sputtering.