Abstract: The appropriate wet etch process for the selective removal of TaN on the HfSiON dielectric with an amorphous-silicon (a-Si) hardmask is presented. SC1 (NH₄OH : H₂O₂ : H₂O), which can achieve reasonable etch rates for metal gates and very high selectivity to high-k dielectrics and hardmask materials, is chosen as the TaN etchant. Compared with the photoresist mask and the tetraethyl orthosilicate (TEOS) hardmask, the a-Si hardmask is a better choice to achieve selective removal of TaN on the HfSiON dielectric because it is impervious to the SC1 etchant and can be readily etched with NH₄OH solution without attacking the TaN and the HfSiON film. In addition, the surface of the HfSiON dielectric is smooth after the wet etching of the TaN metal gate and a-Si hardmask removal, which could prevent device performance degradation. Therefore, the wet etching of TaN with the a-Si hardmask can be applied to dual metal gate integration for the selective removal of the first TaN metal gate deposition.

Key words: TaN,  Wet etching,  Metal gate,  High k dielectric,  hardmask,  Integration