3D Ground Grid Layout for Low-Inductance Superconducting Circuits
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Solution Overview
Problem
As superconductor integrated circuits scale to many metal layers at sub-micrometer feature size, the inductance of ground return paths becomes too large, leading to increased cross-coupling between lines and inefficiencies in wireup, as traditional dedicated ground planes are inefficient and reduce the number of metal layers available for signal routing.
Innovation Solution
A three-dimensional ground grid is implemented, comprising parallel ground lines in multiple conductor layers and vias that extend vertically, creating a cage-like structure to provide a local current return path in all dimensions, reducing inductance and crosstalk while maintaining signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If superconductor ICs scale to many metal layers at sub-micrometer feature size, then the circuit integration density is improved, but the inductance of ground return paths becomes too large
Solution Approach 1:
The patent transitions from traditional two-dimensional ground planes to a three-dimensional ground grid structure. The ground grid extends vertically through multiple metal layers using vias and horizontally within layers using ground lines, creating a volumetric ground return path that reduces inductance while accommodating high-density circuit scaling
2Object-affected harmful factors
If intermediate ground planes are used to alleviate large inductance, then the inductance problem is reduced, but the number of metal layers available for wireup is reduced
Solution Approach 1:
The ground grid is segmented into multiple components: vertical vias connecting different metal layers, horizontal ground lines within each layer, and connection points to signal traces. This segmentation allows the ground function to be distributed across available metal layers without requiring dedicated intermediate ground planes, thus preserving wireup layers while reducing inductance
3Reliability
If ground return paths are provided above and below signal traces in dedicated ground layers, then the ground return path is established, but cross-coupling between adjacent lines increases
Solution Approach 1:
The ground grid provides locally optimized ground return paths for each signal trace by positioning ground lines and vias in close proximity to signal elements. This local ground provision minimizes the loop area for each signal return path, reducing electromagnetic coupling between adjacent lines while maintaining effective ground return
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 configuration controls inductance and reduces crosstalk, enabling more uniform signal response timing and improved performance in superconducting circuits by providing a consistent ground return path across all dimensions, enhancing the scalability and efficiency of superconductor ICs.
Implementation Method 1
a three-dimensional ground grid that provides a local current return path to wireup in all three dimensions
Implementation Method 2
superconducting circuits, and more particularly to a ground grid for superconducting circuits
Data Source
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AI summary
One example includes a superconducting circuit. The circuit includes a plurality of layers comprising a first conductor layer and a second conductor layer overlying the first conductor layer, each of the first and second conductor layers comprising at least one signal element. The circuit also includes a ground grid that is conductively coupled to ground and comprises a first plurality of parallel ground lines that occupy the first conductor layer and extend in a first direction and a second plurality of parallel ground lines that occupy the second conductor layer and extend in a second direction that is orthogonal with respect to the first direction.