Processing and yield of Y1Ba2Cu3O 7-x thin films and devices produced with a BaF2 process

High-quality films were produced by coevaporation and cosputtering of Y, Cu, and BaF₂ followed by an ex-situ anneal. The Y₁ Ba₂Cu₃O_7-x films produced had microwave surface resistances as low as 1/10 that of Cu at 77 K and 10 GHz. This process is especially useful for producing uniform films over areas larger than 1 in² and is compatible with lift-off or traditional etch patterning processes for fabrication of microwave devices. More than 100 films have been deposited on (100) LaAlO₃ with various compositions and anneal conditions. Films were characterized by a wide variety of techniques aimed at optimization of film quality through process control. Emphasis was placed on determining the relationship between material properties and film microwave performance. Run-to-run reproducibility for a sample set of over 20 films was determined. In addition, C-band 5-GHz microstrip resonators were fabricated from these microwave-characterized films. Unloaded Q´s of these devices have exceeded 7500 at 77 K, compared to normal metal resonator Q´s of 300 for this structure. These Q´s correlate well with predicted performance based upon the previously measured microwave surface resistance of the unpatterned films