Nb/AlOx/Nb junctions fabricated using ECR plasma etching

We fabricated Nb/AlOx/Nb junctions using electron cyclotron resonance (ECR) plasma etching. When junctions were fabricated using ECR plasma etching for the junction definition process, they exhibited leaky current–voltage (<f>I</f>–<f>V</f>) characteristics and poor critical current <f>(Ic)</f> uniformity. This indicated that ECR plasma etching damaged the junction barrier. Excellent junction characteristics, on the other hand, were obtained by anodizing the junction periphery at 15 V after ECR plasma etching. This meant that the damaged region was within 14 nm from the junction periphery and that the leakage paths in the damaged region induced by ECR plasma were completely passivated by anodization. The uniformity of <f>Ic</f> in junctions fabricated using ECR plasma etching and anodization was quite good. The standard deviation, 1<f>σ</f>, in <f>Ic</f> was estimated to be 1.4% for a series array of 1000, 0.93-μm2 junctions with a critical current density of 9.8 kA/cm2. [Copyright &y& Elsevier]