Superconducting Solder Bumps for Cryogenic Chip Interconnects
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Solution Overview
Problem
The semiconductor industry faces challenges in testing and packaging superconducting chips due to contamination issues and the need for continuous, uninterrupted superconducting electrical connections, which are not effectively addressed by existing techniques that use non-superconducting materials like gold and copper, leading to resistivity and heat generation at cryogenic temperatures.
Innovation Solution
A method involving the formation of superconducting solder bumps on both the chip and the testing or packaging module, using materials like osmium, rhenium, and tin, with Under Bump Metal (UBM) pillars to ensure uniform height and continuous superconducting signal paths, allowing for easy attachment and detachment while maintaining superconductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-superconducting materials like gold and copper are used for solder bumps and interconnects, then the bonding process is easier and materials are more readily available, but electrical resistance increases and heat is generated at cryogenic temperatures
Solution Approach 1:
The patent changes the material parameters of solder bumps and interconnects from non-superconducting materials (gold, copper) to superconducting materials (niobium, aluminum, lead, or their alloys). This parameter change ensures that all interconnect components maintain superconductivity at operating temperatures, eliminating resistance and heat generation while preserving bonding capability through established semiconductor fabrication processes.
Solution Approach 2:
The patent creates a homogeneous superconducting interconnect structure where all components (solder bumps, UBM layers, and trace connections) are made from superconducting materials. This homogeneity ensures continuous superconducting current paths without interruption from non-superconducting materials, maintaining both ease of manufacture through standard processes and superior electrical conductivity.
2Ease of manufacture
If non-superconducting materials are used in superconducting chip bonding, then conventional semiconductor processes can be used, but continuous superconducting current paths are interrupted
Solution Approach 1:
The patent changes the material composition parameters of all bonding components to be superconducting. Specifically, it uses superconducting UBM layers (niobium, aluminum, or their alloys) and superconducting solder bumps, ensuring that the entire interconnect path maintains superconducting properties. This allows conventional semiconductor bonding processes to be used while achieving continuous superconducting current paths.
Solution Approach 2:
The patent employs composite superconducting structures consisting of multiple superconducting material layers (UBM layers, solder bumps, and trace connections) that work together to form continuous superconducting pathways. These composite structures maintain compatibility with conventional fabrication processes while ensuring uninterrupted superconductivity throughout the interconnect.
3Ease of manufacture
If solder bumps of non-uniform height are used, then fabrication is simpler, but opens or shorts are formed affecting circuit performance
Solution Approach 1:
The patent applies preliminary action by forming UBM (Under Bump Metal) pillars or thick layers before depositing the solder bumps. These pre-formed UBM structures serve as elevation platforms that automatically ensure uniform solder bump heights across the chip surface. This preliminary structuring step simplifies the overall fabrication process while achieving the precision required for uniform interconnects, as the UBM layers compensate for variations in substrate topography.
4Reliability
If superconducting materials are used for all interconnect components, then continuous superconducting paths are achieved, but fabrication complexity increases
Solution Approach 1:
The patent applies universality by using the same superconducting material system (niobium, aluminum, or their alloys) for multiple functions: as UBM layers, as solder bump material, and as trace connection material. This multi-functional approach simplifies fabrication by eliminating the need to handle and process multiple different superconducting materials, reducing fabrication complexity while maintaining continuous superconducting pathways throughout the interconnect structure.
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 accurate testing and packaging of superconducting chips with minimal resistance and noise, ensuring the chip's electrical properties can be accurately characterized and integrated into computing systems without heat interference.
Implementation Method 1
forming a first set of superconducting solder bumps on the superconducting chip; superconductively electrically coupling the superconducting chip to a testing module via the first set of superconducting solder bumps; cooling the testing assembly to a first temperature below the critical temperature such that the superconducting chip superconducts
Data Source
AI summary
Superconductive interconnection structures providing continuous, uninterrupted superconducting signal paths between a superconducting chip and a superconducting chip carrier are described. The superconductive interconnection structures employ superconducting solder bumps and pillars of Under Bump Metal (“UBM”). The superconductive interconnection structures are employed in a two-stage solder bumping process in which the superconducting chip is first bonded to a testing module for screening and then bonded to a chip packaging module for operation. Either the testing module or the chip packaging module, or both, may include a multi-chip module for carrying multiple superconducting chips simultaneously.