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The authors found that a BCl3/N2 plasma is very suitable for metal gate patterning and profile control as it produces a passivating film during the etching. On blanket wafers, a boron-nitride-like film is deposited from a boron trichloride/nitride plasma mixture in a standard etch chamber at temperatures as low as 60 °C. Deposition rate can be varied from 10 to more than 100 nm/min depending on the plasma conditions and BCl3/N2 ratio. The film contains hexagonal boron nitride but is very unlikely to be a stoichiometric BN. It decomposes at elevated temperatures and is water soluble. The latter property makes the postetch clean relatively straightforward. This film can be used for sidewall passivation during the patterning of advanced non-Si gates, e.g., metal gates. They are presenting the use of BCl3/N2 plasma for patterning of Ge and TaN gates as examples. The Ge gate profile is damaged by a pure BCl3 plasma during high-k dielectric (HfO2) etching after the gate patterning. Addition of 10% N2 to the BCl3 plasma preserves the gate profile while removing the high k. In the other example, a TaN gate is etched isotopically by pure BCl3 plasma. Addition of 5% N2 prevents the lateral attack providing straight TaN profile. [ABSTRACT FROM AUTHOR]