Utilization of process TEG for fabrication of HTS circuits

Abstract

We improved the fabrication process of high-temperature superconducting (HTS) sampler circuits with multilayer structures by utilizing a test elements group (TEG). Among a lot of difficulties in the HTS circuit fabrication process, loss of oxygen is one of the most significant problems. Since the film transition temperature (Tc) has a strong relationship with the resistance at room temperature, we fabricated a test pattern on the same wafer of the circuits and measured the resistance at room temperature by using a prober to estimate the Tc of each layer. By introducing the measurement of the normal resistance after each process, we found better process conditions without a Tc drop. Moreover, we constructed a low-temperature probing system, in which we can measure the junction TEG. The system enabled feedback of the fabrication condition soon after the junction process. The utilization of the process TEG contributed to reproducible fabrication of HTS circuits and that is a promising advance of the HTS circuit technology.