A comprehensive study for advanced in situ contact dry cleaning

An advanced in situ pre-contact dry cleaning process with fluorine species has been comprehensively investigated to effectively remove the native oxide on the top surface of Ni-salicide layer for ensuring lower contact resistance (Rc) without the drawbacks, including the clipping of contact top opening, the formation of by-product re-deposition and severe Ni-salicide loss, of the conventional argon ion bombardment process. In this study, two kinds of in situ dry cleaning approaches, called saturation and low etch rate (LER) modes, have been evaluated to further reduce Rc and prevent the contact to poly short issue as keeping contact size scaling down to 28 nm node. The Rc reduction of ∼40% at 45 nm and no contact to poly short issue at 28 nm contact design rules can be simultaneously demonstrated by implementing optimized in situ saturation and LER dry cleaning conditions.

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