3D Stacked Josephson Junctions for Critical Current Maintenance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As technology nodes shrink, the critical current of Josephson junctions (JJs) in superconducting devices falls below acceptable thresholds, posing a challenge for maintaining sufficient noise margins in Single Flux Quantum (SFQ) technology, which relies on JJ pulse widths and logic state transmission.
Innovation Solution
The JJ structure is extended vertically to maintain a larger cross-sectional area and critical current by incorporating a non-superconducting structure between superconducting layers, allowing for smaller feature sizes while ensuring the critical current remains above a desired threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the technology node is reduced to increase integration density, then the device size decreases, but the critical current of Josephson junctions falls below acceptable thresholds
Solution Approach 1:
The patent transitions from planar (2D) Josephson junction structures to three-dimensional (3D) vertically-stacked structures. By stacking multiple superconducting layers and non-superconducting barriers vertically, the junction volume increases in the vertical dimension while maintaining a small footprint on the wafer surface, thereby preserving critical current density despite reduced lateral dimensions
Solution Approach 2:
The patent employs composite structures consisting of alternating superconducting layers (e.g., niobium, aluminum) and non-superconducting barrier layers (e.g., aluminum oxide, silicon oxide). This composite approach allows optimization of each layer's properties independently, maintaining sufficient critical current through proper material selection and thickness control in the vertical stack
2Area of moving object
If the Josephson junction cross-sectional area is reduced to enable smaller feature sizes, then the technology node shrinks, but the noise margin becomes insufficient
Solution Approach 1:
The patent compensates for reduced lateral cross-sectional area by increasing the vertical dimension through multiple stacked layers. The total junction volume (and thus total critical current) is maintained by extending the structure vertically rather than laterally, preserving noise margins despite smaller feature sizes
Solution Approach 2:
The patent changes the geometric parameters of the Josephson junction from lateral dimensions to vertical dimensions. By controlling layer thicknesses and stacking configurations, the critical current density can be maintained at appropriate levels even as the lateral footprint shrinks to enable smaller technology nodes
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 enables SFQ technology to support future computing and storage demands by maintaining a sufficient noise margin and critical current even at smaller technology nodes, allowing for the continued advancement of JJ feature sizes in SFQ circuits.
Implementation Method 1
Single flux quantum (SFQ) technology, which relies on the quantum mechanical quantization of magnetic flux, is a technology that may help meet future computing and storage demands. SFQ technology is based on flux storage and transmission, and uses pulses emitted by JJs.
Data Source
AI summary
Josephson junction (JJ) structures are disclosed. In some embodiments, a JJ structure may include a first superconducting structure and a second superconducting structure disposed on a plane parallel to a silicon wafer surface. A non-superconducting structure may be disposed between the first superconducting structure and the second superconducting structure. A direction of current flow through the non-superconducting structure may be parallel to the silicon wafer surface.