Protective Layer for Wire Bonding on Reactive Copper Metallization
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Solution Overview
Problem
The challenge in wire bonding on copper-based metallization structures is the inhomogeneous self-oxidization and corrosion of copper surfaces, leading to unreliable bond connections due to the reactive nature of copper, which necessitates the use of aluminum-based terminal metal layers, increasing process complexity and costs.
Innovation Solution
A protective layer is formed over the copper-containing surface to passivate it during the wire bonding process, allowing for reliable intermetallic connections without the need for aluminum-based techniques, thereby simplifying the process and reducing costs by using established materials and equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is performed on copper surfaces without protection, then the process is simple and direct, but the bond connections become unreliable due to inhomogeneous self-oxidization and corrosion
Solution Approach 1:
A protective layer is formed on the copper surface before wire bonding to prevent oxidation and corrosion during the bonding process and subsequent storage, ensuring reliable bond connections without requiring complex aluminum-based terminal metal layers
Solution Approach 2:
The protective layer acts as an intermediary between the copper surface and the bonding environment, isolating the reactive copper from harmful factors like oxygen and moisture while allowing the bonding process to proceed effectively
2Reliability
If aluminum-based terminal metal layers are used to protect copper surfaces, then wire bonding reliability improves, but manufacturing complexity and costs increase due to additional deposition and patterning sequences
Solution Approach 1:
The patent extracts the essential protective function from the complex aluminum-based terminal metal layer system and implements it through a simpler protective layer formed directly on the copper surface, eliminating the need for additional aluminum deposition and patterning sequences
Solution Approach 2:
The protective layer serves as a temporary protection mechanism that fulfills its purpose during the bonding process and can be removed or degraded without affecting the underlying copper metallization, avoiding the need for permanent complex aluminum structures
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 provides uniform and reliable wire bonding on copper surfaces, reducing the complexity and cost of the manufacturing process by avoiding the use of aluminum-based deposition and patterning sequences, while maintaining the integrity of the copper metallization system.
Implementation Method 1
A protective layer is formed over the copper-containing surface to passivate it during the wire bonding process
Implementation Method 2
allowing for reliable intermetallic connections without the need for aluminum-based techniques
Data Source
AI summary
In semiconductor devices having a copper-based metallization system, bond pads for wire bonding may be formed directly on copper surfaces, which may be covered by an appropriately designed protection layer to avoid unpredictable copper corrosion during the wire bond process. A thickness of the protection layer may be selected such that bonding through the layer may be accomplished, while also ensuring a desired high degree of integrity of the copper surface.