Dry-etching processes for high-temperature superconductors

Patterning of thin films and multilevel structures of high-temperature superconductors is a key technology for microelectronic applications. We performed a comparative study of Ion Beam Etching (IBE) and Reactive Ion Etching (RIE) processes for YBa₂Cu₃O_7-δ thin films. The RIE process with a pure chlorine plasma yielded small etching rates, caused by chemical modifications of the sample surface which result in a passivation layer reducing the chemical etching rate. Using IBE, microstructures down to the 1 μm regime could be fabricated without reducing the critical temperature T_c and the critical current density J_c of the material. Etching rates up to 40 nm/min could be achieved without deteriorating the properties of the superconducting film by cooling the sample effectively during the etching process. The influence of the etching process on J_c was investigated by imaging the spatial distribution of the critical current along the patterned microstructures using Low-Temperature Scanning Electron Microscopy (LTSEM).