Run-to-Run Yield Evaluation of Improved Nb 9-layer Advanced Process using Single Flux Quantum Shift Register Chip with 68,990 Josephson Junctions

29th International Symposium on Superconductivity

Nagasawa, Shuichi^1 ; Hidaka, Mutsuo^1

National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba

305-8568, Japan^1

关键词: Advanced process;    Circuit size;    Fabrication yield;    Ion milling;    Josephson-junction;    Plasma enhanced chemical vapor depositions (PE CVD);    Single flux quantum;    Surface profiles;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/871/1/012065/pdf
DOI  :  10.1088/1742-6596/871/1/012065

来源: IOP

【 摘 要 】

We have improved an Nb 9-layer advanced process (ADP2) using a plasma-enhanced chemical vapor deposition (PECVD) SiO2insulator. We could solve the problems due to the surface profile of the PECVD SiO2by adding an ion-milling process. The reliability of the ADP2 was evaluated by the operating yield of the SFQ shift registers (SRs). The SRs with six different bit sizes from 16 to 2560 were designed to evaluate the circuit size dependency of their yields. The total number of SRs is 16, and the total number of junctions per chip is 68,990. By introducing the PECVD SiO2insulator, we could obtain a high operating yield of more than 80% even for large-scale 2560-bit shift registers with more than 10,000 junctions. Moreover, we could obtain nine perfect chips (in which all the SRs in the chip functioned) out of 26 measured chips fabricated using the PECVD SiO2. From these results, we believe that the fabrication yield of the ADP2 is at a level of 100,000 Josephson junction circuits.