Study of the resputtering effect during rf-sputter deposition of YBCO films

We propose an angular redistribution model to understand the negative ions resputtering effect in sputter depositing YBa2Cu3O7-x (YBCO) films. On the basis of this model, the negative oxygen ions resputtering effect has been greatly minimized by introducing a Cu mask between the substrate and the target to block energetic oxygen particles from directly bombarding the growing film. Thus, YBCO films with almost exact stoichiometric composition and zero resistance critical temperatures as high as 90 K are obtained under oxygen partial pressure as low as 3 mTorr in a temperature regime well beyond that proposed by R. H. Hammond and R. Bormann. Preliminary results of a modified masking and shielding technique to eliminate the resputtering effect and fabricate large area (>1 in. X 1 in.) YBCO superconducting films with high uniformity are also presented.