Investigation of inductance for high-Tcsuperconducting single-flux-quantum circuits

To achieve stable operations of high-Tc superconducting (HTS) single-flux-quantum circuits, we have studied the reproducibility and uniformity of inductances for HTS striplines. Optimizing a fabrication process of the striplines, the sheet inductances of the striplines for four samples were ranged from 0.77 to 0.93 pH per square at 4.2 K. The differences between these values and a designed value (Ld) of the sheet inductance were less than 10% of Ld. A 4 h oxygen annealing at 450 °C in 1 atm oxygen decreased the 1σ-spread of the stripline inductances from 12 to 4.9% at 4.2 K. It was found that taking into account the reproducibility and spread of inductances, the designed value of the sheet inductance should be less than 0.8 pH/ in order to obtain low inductance (less than 1 pH/) in a circuit area.