Inductances of striplines and stacked vias in planarized multi-layer Nb circuits

We have evaluated the inductances of the striplines and the stacked vias which are realized in the planarized 6-Nb-layer device fabricated by our advanced Nb fabrication process. The inductances of centered and off-center striplines were compared with inductances of the microstrip lines which had insulators with the same thicknesses as an insulator or a thinner insulator between the signal line and the ground plane in the stripline. The centered striplines showed the sheet inductances about 0.65 times as much as those of the microstrip lines. The factor would be useful for designing passive transmission lines (PTLs) based on the stripline, and would provide the estimate of the line width of the PTLs. The stacked vias showed a small increase of similar to 0.1 pH in inductance every additional a via stacked on top of a via. A comparison between the inductance of the stacked via and that of conventional vias revealed that the stacked vias are effective in reduction of layout areas and parasitic inductances. (c) 2006 Elsevier B.V. All rights reserved.