Sloped niobium etching using CF4 and O2

A sloped etching process for Nb is developed for pilot line operations. Reactive ion etching and plasma processes are compared for a CF4/O2 parallel plate etch system. The higher pressure etches were found to have better characteristics for the numerous combinations of independent variables examined. Process settings tested include rf power, chamber pressure, and etchant flow rates. Higher Nb etch rates, photoresist:niobium etch rate selectivity of 1:1, and adequate selectivity over SiO2 were obtained with the plasma etches. For both types of processes, control of plasma loading affects were determined to be crucial to accomplish successful patterning. Finally, mathematical models of the etch process were derived from the data and used to determine basic etch mechanisms occurring within the reactor