Titanium Nitride Hard Mask Removal with Selectivity to Tungsten in FEOL

This paper describes etching of titanium nitride (TiN) highly selective to tungsten (W), where the TiN etch rate (E/R) was about 100 Å/min and W E/R was less than 1 Å/min at 60°C. The formulation concept was adapted from the Entegris TK-10 series, but it was modified to fit the criteria for front-end application. No damage to tantalum nitride (TaN) was required during the etching process but silicon oxide compatibility requirement was relaxed. By replacing W inhibitors with more suitable ones, W loss was well controlled, while the particle issue previously found in the scale up lots was also solved.