A 5-/spl mu/m-wide 18-cm-long low-loss YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// coplanar line for future multichip module technology

Narrow and low-loss YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) coplanar lines, which can be used in multichip module technology for future high-density and high-speed digital circuits, have been developed. Etch-back planarization and a patterning process combining Ar-ion milling and wet-etching enabled us to form an 18-cm-long 5-/spl mu/m-wide YBCO coplanar line without electrical shorts, even for the narrow spacing of 2.5 /spl mu/m. The surface resistance of this line was kept at a level comparable to that of 10- or 25-/spl mu/m-wide YBCO coplanar lines and also comparable to that of unpatterned films. This indicates successful fabrication of the 5-/spl mu/m-wide YBCO coplanar line without notable loss increase resulting from process damage. The 5-/spl mu/m-wide line showed a low-transmission loss of 0.49 dB at 10 GHz and 55 K. This level of loss is similar to that in Cu coaxial cables. No significant increase in transmission loss was observed up to an input power level of 16 mW at 10 GHz and 55 K. This input power is comparable to the power-handling capability required for transmitting high-speed digital signals through the lines with characteristic impedance of 50 /spl Omega/. These results show that the narrow 5-/spl mu/m-wide YBCO coplanar line has great potential for high-density and high-speed digital circuits.