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How do I etch Ta without much effect on my underlying silica layer?
I am using a silica patterned wafer which contains a 10 nm layer of Ta over which is Cu. Using a Cu etchant (APS Cu etchant) I am easily able to remove the Cu but have no clue how to remove the Ta without effecting silica (or by causing least damage to it). Kindly let me know if there exists an etchant which can help me etch out Cu and Ta or what composition of Ta etchant will effect silica the least.
University of Florida - Gainesville, Florida, US
2006 "Thin Film Processes" [affil. link to book on Amazon] by Vossen and Kern, has a sort of A to Z of what chemicals etch what materials. For tantalum they list an etch containing 9 parts sodium hydroxide or potassium hydroxide to 1 part hydrogen peroxide - heat the alkali to 90 °C and then add the hydrogen peroxide. It lists an etch rate of 1000 to 2000 Angstroms per minute so I guess would etch your tantalum layer very quickly. I know that these alkalis will etch silicon if the concentration is high enough but I don't think they etch silica and you should be etching for a very quick time. The other etches the book lists for tantalum all contain HF which would attack silica.
Dr. Gary Callon
University of Dundee