Copper Contact Layer Solder Bump Formation Without Terminal Metal
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Solution Overview
Problem
The existing process for forming solder bumps on copper-based contact areas in integrated circuits is complex and prone to issues like aluminum pitting and polyimide delamination, leading to moderate electrical performance and high manufacturing costs.
Innovation Solution
A simplified process flow that eliminates the need for a terminal aluminum layer and underbump metallization, directly forming a solder bump on a copper-based contact region with an underbump metallization layer, enhancing thermal and electrical conductivity and reducing process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a terminal aluminum layer and underbump metallization are used on copper-based contact areas, then mechanical adhesion and diffusion barrier are provided, but process complexity increases and aluminum pitting occurs
Solution Approach 1:
The patent removes the terminal aluminum layer from the conventional structure, extracting only the essential copper-based contact area that provides both electrical connection and serves as the foundation for solder bump formation, thereby simplifying the process while maintaining reliability
Solution Approach 2:
The copper-based contact area serves multiple functions simultaneously: it provides electrical conductivity, acts as a diffusion barrier foundation, and serves as the direct substrate for solder bump adhesion, eliminating the need for separate terminal metal layers
2Strength
If a terminal aluminum layer is deposited on copper contact areas, then adhesion is improved, but aluminum pitting and polyimide delamination occur
Solution Approach 1:
The patent converts the potential harm of direct copper-solder interaction into a benefit by using the copper surface itself as the adhesion substrate, where the copper oxide layer that would normally be considered a defect actually provides excellent solder wetting and adhesion properties
Solution Approach 2:
The patent eliminates the terminal aluminum layer that is prone to pitting and reliability issues, using instead a simpler copper-based structure that avoids these harmful effects while maintaining the necessary adhesion function
3Strength
If multiple metallization layers are used for solder bumps, then mechanical fastening is improved, but thermal and electrical conductivity decrease
Solution Approach 1:
The patent extracts and eliminates the intermediate terminal metal layers that impede thermal and electrical conduction, creating a direct copper-to-solder bump pathway that maximizes conductivity while maintaining mechanical integrity through optimized copper contact area design
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 improves the current drive capability and thermal dissipation of the bump structure, reduces manufacturing costs, and minimizes yield loss due to aluminum pitting and delamination, while allowing for smaller bump dimensions and more efficient heat dissipation.
Implementation Method 1
The copper-based metallization layer is formed, for instance, by means of a sputtering process
Implementation Method 2
Electroplating is presently the preferred deposition technique, since physical vapor deposition of solder bump material
Implementation Method 3
wherein the contact layer is configured to provide copper-based contact areas connected to a lower-lying metallization layer for directly attaching an appropriately formed package or carrier substrate to a die carrying one or more integrated circuits
Data Source
AI summary
By directly forming an underbump metallization layer on a copper-based contact region, the formation of any other terminal metals, such as aluminum and corresponding adhesion/barrier layers may be avoided. Consequently, the thermal and electrical behavior of the resulting bump structure may be improved, while process complexity may significantly be reduced.