Study on Microwave ECR Directional Etching of HfO₂Films in AAO Template

Nano-structuring of HfO₂ films deposited on AAO(Anodic Aluminum Oxide) template by home-made microwave electron cyclotron resonance(ECR) plasma equipment is described.The remove of HfO₂ films was carried out by the reaction ion beam etching using CF₄, Ar and O₂ plasmas.A combination of high-resolution scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray spectroscopy microanalysis was used to characterize the before and after samples pattern morphology, structure, and chemical composition.We found that the etch of HfO₂ in our experiments is directional which is favorable to the process of high aspect ratio micro mechanical structures.The etch rate of HfO2 in the high aspect ratio construction that is up to 10:1 in our operations was measured as a function of microwave power supply, negative pulsed bias power supply, CF₄/Ar/O₂ mixing ratio in the range of 0 to 100% Ar and working pressure at a fixed the others parameters.The experiments indicate that the optimum etch rate is 0.36nm/min in our device at gas pressure(0.3 Pa), microwave power(600 W), bias power(100 V).The etched HfO₂ at the bottoms of the AAO template was found to be residue-free and automically smooth with a root mean square line roughness of 0.17 nm after CF₄/Ar/O₂ plasma etching.