an electron cyclotron resonance (ecr) ion beam has been utilized for a developing surface cleaning process of high-t/sub c/ superconducting thin films. by means of silver-contact resistivity measurements, and ex situ surface analysis using x-ray photoelectron spectroscopy (xps) and reflection high-energy electron diffraction (rheed), the effects of ecr treatment on an air-exposed surface of a-axis euba/sub 2/cu/sub 3/o/sub 7-y/ (ebco) films are examined ag/ebco contacts are made with exposure of the ebco surface to an ecr oxygen ion beam with ion current densities of 100 mu a/cm/sup 2/ at room temperature for about 30 min and the in situ deposition of silver. the contacts, which are not annealed in oxygen, exhibit low contact resistivity in the 10/sup -8/-10/sup -7/ omega cm/sup 2/ range. these values are about five orders of magnitude lower than those of samples fabricated without ecr treatment. based on xps and rheed data, change in the ebco surface caused by ecr treatment is surmised