Superconducting multilayer structures with a thick SiO2 dielectric interlayer for multichip modules

One of the most promising applications for high temperature superconductors (HTSCs) is for use as signal interconnects between bare integrated circuits (ICs) in multichip modules (MCMs). For HTSC MCM and other related electronic applications, it is necessary to fabricate several YBa₂Cu₃O_7-x (YBCO) layers separated by thick low dielectric layers. In this work, YBCO/yttrium stabilized zirconia (YSZ)/SiO₂/YSZ/YBCO multilayer structures have been successfully deposited with patterned YBCO layers on single-crystal YSZ substrates. A reactive sputtering technique was used to grow the SiO₂ layer and the ion beam assisted deposition (IBAD) method was used to form biaxially aligned YSZ layers. In contrast to previously reported work, the top YBCO layer did not show any cracking. Using this process, a novel two-layer test vehicle was fabricated. A clock distribution circuit was mounted on the superconducting test vehicle to form a ring oscillator. The functionality of the test vehicle was found to be about 100 MHz