STUDY OF THE SPUTTERING OF ONE-COMPONENT, 2-COMPONENT AND 3-COMPONENT TARGETS FOR THE PREPARATION OF YBA2CU3O7 SUPERCONDUCTING FILM

Although single-cathode magnetron sputtering is widely used for the preparation of YBa2Cu3O7 superconducting films, the film composition often deviates widely from that of the target. Multiple-cathode magnetron sputtering is desirable to achieve precise control of the film composition. We studied targets made of several components to understand how the composition of sputtered films produced by single-cathode magnetron sputtering deviates, and to prepare stoichiometric film using four-cathode magnetron sputtering. With almost all the targets, a resputtering effect on the film due to negative oxygen ions was observed. In particular, the effect was very noticeable with targets containing barium, and special features of barium-containing targets were clarified. Using a carousel sputtering apparatus with four cathodes of YBa2CU3O7, BaCu0.2O(x), Y2O3, and CuOx, targets, we could control the film composition precisely through an appropriate combination of different r.f. input powers to the targets. We could prepare nearly stoichiometric films with a deviation of less than +/- 10% within a relatively large cylindrical substrate area 40 mm in height and 290 mm in diameter.