Abstract
This paper discusses the ionization ratio and the ionization mechanism of atomic titanium in high-pressure (10–150 mTorr) magnetron sputtering plasmas employing a titanium target. The spatial distributions of Ti and Ti+ densities in a magnetron sputtering plasma source were visualized by laser-induced fluorescence imaging spectroscopy. It was observed that the ionization ratio of Ti was enhanced significantly in the downstream region by increasing the discharge pressure. The correlation between the ionization ratio and the deposition profile of Ti film inside a trench was examined, and it was confirmed that a deposition condition with a high ionization ratio resulted in a deposition profile with a high bottom coverage. Several experiments were carried out to investigate production processes of Ti+ in high-pressure magnetron sputtering plasmas. We examined the contributions of electron impact ionization, Penning ionization, charge exchange collision with Ar+, and three-body recombination. However, the experimental results revealed that none of the four processes was the dominant production process of Ti+.
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