以非晶硅为硬掩膜的TaN金属栅的选择性湿法腐蚀

提出了一种在HfSiON介质上，采用非晶硅为硬掩膜的选择性去除TaN的湿法腐蚀工艺。由于SC1(NH4OH:H2O2:H2O)对金属栅具有合适的腐蚀速率且对硬掩膜和高K材料的选择比很高，所以选择它作为TaN的腐蚀溶液。与光刻胶掩膜和TEOS硬掩膜相比，因非晶硅硬掩膜不受SC1溶液的影响且很容易用NH4OH溶液去除（NH4OH溶液对TaN和HfSiON薄膜无损伤），所以对于在HfSiON介质上实现TaN的选择性去除来说非晶硅硬掩膜是更好的选择。另外，在TaN金属栅湿法腐蚀和硬掩膜去除后, 高K介质的表面是光滑的，这可防止器件性能退化。因此，采用非晶硅为硬掩膜的TaN湿法腐蚀工艺可以应用于双金属栅集成，实现先淀积的TaN金属栅的选择性去除。

Selective wet etch of a TaN metal gate with an amorphous-silicon hard mask

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.