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 HfO 2 single layers and Mo/HfO 2 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 HfO 2 layer. By controlling the process parameters such as the O 2 /Cl 2 flow ratio, the top electrode power and the dc self-bias voltage ( V dc ), the Mo/HfO 2 etch selectivity as high as 67 could be obtained. Addition of O 2 gas to the O 2 /Cl 2 chemistry improved the Mo/HfO 2 etch selectivity because the O 2 gas in a certain flow ratio range reduced the HfO 2 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.