patterning of thin films and multilevel structures of high-temperature superconductors is a key technology for microelectronic applications. the authors performed a comparative study of ion beam etching (ibe) and reactive ion etching (rie) processes for yba/sub 2/cu/sub 3/o/sub 7- delta / 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 mu m regime could be fabricated without reducing the critical temperature t/sub c/ and the critical current density j/sub 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 /sub c/ was investigated by imaging the spatial distribution of the critical current along the patterned microstructures using low-temperature scanning electron microscopy (ltsem)