Superconducting Under-Bump Metallization for Low-Loss RF Coupling
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Solution Overview
Problem
Conventional semiconductor fabrication methods face challenges in achieving both strong mechanical adhesion and superconducting electrical coupling between bump metallization structures, leading to signal loss and reliability issues in microwave/RF applications.
Innovation Solution
A two-component under-bump metallization (UBM) structure is developed, comprising a bonding region formed from a noble metal with low oxidation resistance and a conductive region made of superconducting materials, allowing for superior mechanical and electrical coupling through a selectively allocated interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bump junctions are used in SiGe HBTs, then manufacturing is simpler, but frequency response deteriorates above 50 GHz due to parasitic inductance
Solution Approach 1:
The patent changes the physical state and material parameters of the bump metallization by introducing a superconducting material layer that transforms the electrical properties at operating temperatures below the superconducting transition temperature, thereby reducing parasitic inductance and improving frequency response
Solution Approach 2:
The patent employs a composite metallization structure combining superconducting material with conventional metallurgical layers, creating a multi-layer composite that leverages the low-resistance properties of superconductors while maintaining the structural and bonding capabilities of traditional bump junctions
2Reliability
If superconducting material is used in bump metallization, then frequency response improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the superconducting material layer during the semiconductor fabrication process before final bump formation, ensuring proper material deposition and pattern alignment while simplifying subsequent manufacturing steps
Solution Approach 2:
The superconducting material layer serves multiple functions: it reduces parasitic inductance for improved frequency response, provides a conductive pathway for electrical connections, and integrates with standard semiconductor fabrication processes, thereby achieving multiple goals with a single structural element
3Loss of energy
If conventional metallization is used, then manufacturing is easier, but power loss increases at high frequencies
Solution Approach 1:
The patent exploits the dramatic change in electrical resistance parameters that occurs when materials transition to a superconducting state, achieving near-zero resistance and minimal power loss at operating temperatures below the superconducting transition temperature
Solution Approach 2:
The patent replaces the conventional resistive metallization system with a superconducting system that operates on different physical principles, eliminating ohmic losses that plague traditional metallization at high frequencies
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
The UBM structure provides enhanced mechanical bonding and low resistance electrical coupling, minimizing signal loss and improving reliability in semiconductor devices.
Implementation Method 1
the bump metallization comprises a superconducting material
Data Source
Figure 1
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Figure 3A
AI summary
An under-bump-metallization (UBM) structure includes a first region and a second region. The first and second regions are laterally positioned inthe UBM structure. The first region includes a superconducting material. A substrate opposes the UBM structure. A superconducting solder material joins the first region to the substrate and the second region to the substrate.