Orthogonal Josephson Junction Electrodes for Stable Critical Current
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Solution Overview
Problem
The mass production of superconducting devices, such as Josephson junctions, is hindered by process variations and aging effects, leading to inconsistent critical current values, which affect the performance and reliability of superconducting circuits.
Innovation Solution
A Josephson junction device is fabricated using orthogonal superconductor electrodes with a dielectric material layer, formed through a process that includes perpendicular and angular superconductor deposition, reducing variations and stabilizing the critical current by maintaining a high-quality tunnel barrier and native oxide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional Dolan bridge JJ fabrication process is used, then JJ can be manufactured, but significant process variations and aging effects occur leading to inconsistent critical current
Solution Approach 1:
The patent transitions from the conventional planar Dolan bridge geometry to a three-dimensional orthogonal electrode configuration. The first superconductor structure extends in a first direction while the second superconductor structure extends in a second direction substantially orthogonal to the first direction, creating a vertical stacking arrangement that adds a dimensional aspect to the JJ geometry. This dimensional change provides greater design flexibility and reduces sensitivity to planar process variations.
Solution Approach 2:
The JJ structure is divided into distinct segmented components: a first superconductor structure with a first arm portion, a second superconductor structure with a second arm portion, and a dielectric material layer separating them. This segmentation allows each component to be optimized independently for its specific function, with the arm portions designed to minimize parasitic inductance and the dielectric layer engineered for optimal barrier properties, thereby improving overall critical current consistency.
2Productivity
If conventional JJ fabrication is used, then devices can be produced, but yield loss occurs due to process variations
Solution Approach 1:
The orthogonal electrode geometry inherently compensates for certain process variations through its own structural properties. The vertical stacking arrangement and orthogonal orientations create geometric constraints that automatically reduce the impact of deposition angle variations and photoresist thickness variations, allowing the structure to self-correct some fabrication imperfections without requiring extremely tight process controls.
Solution Approach 2:
The patent employs perpendicular and angular superconductor deposition processes to form the orthogonal electrode structures. By controlling the deposition parameters (angles, rates, and sequences) during fabrication, the process optimizes the geometric precision of the orthogonal arrangement, ensuring consistent critical current while maintaining high production throughput.
3Reliability
If orthogonal electrode structure is implemented, then IC stability improves, but fabrication process complexity increases
Solution Approach 1:
The orthogonal electrode structure serves multiple functions simultaneously: it creates the JJ tunneling barrier, defines the critical current path, minimizes parasitic inductance, and provides geometric constraints for process variation reduction. The dielectric material layer performs multiple roles as well, serving as both the tunneling barrier and an etch stop layer during fabrication. This multi-functionality reduces the need for additional separate structures and processes.
Solution Approach 2:
The dielectric material layer acts as an intermediary element between the two superconductor structures. It provides a controlled interface that defines the JJ operation region, prevents direct contact between the superconductors, and serves as a mask during deposition processes. This intermediary layer simplifies the overall fabrication by enabling sequential deposition steps with well-defined boundaries.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the consistency and stability of the critical current, reducing yield loss and improving the performance of superconducting microchips by minimizing process variations and aging effects, while being compatible with existing fabrication equipment and techniques.
Implementation Method 1
A JJ is a device that consists of two superconductors weakly coupled by a region which may be either non-superconducting or a weaker superconductor. For example, one type of JJ consists of two superconductors separated by a thin insulating barrier.
Implementation Method 2
performing one of a perpendicular superconductor deposition process and an angular superconductor deposition process on the JJ structure to form a plurality of superconductor bottom superconductor electrodes on the substrate
Data Source
AI summary
A Josephson junction (JJ) device is disclosed that includes a first superconductor structure having a bottom superconductor arm portion and a second superconductor structure having a top superconductor arm portion disposed substantially orthogonal to the bottom superconductor arm portion and overlapping the bottom superconductor arm portion in a JJ operation region. The JJ device further includes a dielectric material layer acting as a tunnel barrier disposed between the bottom superconductor arm portion and the top superconductor arm portion in the JJ operation region to form an operating JJ.