Effect of O2 Gas during Inductively Coupled O2/Cl2 Plasma Etching of Mo and HfO2 for Gate Stack Patterning

In this study, we investigated the etching characteristics of Mo and HfO2 single layers and Mo/HfO2 stacked structure for metal electrode/high-k gate stack patterning in O-2-/Cl-2 inductively coupled plasmas and the effects of O-2 addition on the etch rates and etch selectivity of the Mo to the HfO2 layer. By controlling the process parameters such as the O-2/Cl-2 flow ratio, the top electrode power and the do self-bias voltage (V-dc), the Mo/HfO2 etch selectivity as high as congruent to 67 could be obtained. Addition of O-2 gas to the O-2/Cl-2 chemistry improved the Mo/HfO2 etch selectivity because the O-2 gas in a certain flow ratio range reduced the HfO, etching reactions due to less chlorination of Hf but enhanced the Mo etch rate presumably due to effective formation of highly volatile Mo-O-Cl etch by-products.