Copper Bond Pad Palladium Layer for Oxidation-Free Interconnects
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Solution Overview
Problem
Copper bond pads in semiconductor devices are prone to oxidation, leading to reliability issues such as moisture penetration and galvanic corrosion, and existing passivation layers do not fully prevent oxidation or can leave residual contaminants during removal.
Innovation Solution
A conductive layer of palladium or copper palladium is directly formed on the copper bond pad, eliminating the need for intermetallic compounds and allowing for copper interconnects without additional expensive materials, and the process is maskless, avoiding new equipment requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passivation layers are formed on copper bond pads to prevent oxidation, then oxidation protection is improved, but residual contaminants remain after layer removal causing reliability issues
Solution Approach 1:
The patent extracts and eliminates the problematic passivation layer removal step by directly forming copper interconnects on the copper bond pad without requiring passivation layer removal. This takes out the source of residual contaminants (adhesive-like contaminants from etching chemistry) while maintaining oxidation protection through direct copper-to-copper bonding.
Solution Approach 2:
Instead of the conventional approach of forming passivation layers then removing them to access copper bond pads, the patent inverts the sequence by directly exposing and bonding to copper bond pads without passivation layers. This reversal eliminates the harmful residual contaminants while achieving the desired oxidation protection through proper copper surface preparation and bonding processes.
2Reliability
If conventional intermetallic compounds are used between copper bond pads and copper interconnects, then material compatibility is improved, but cost increases due to expensive materials like gold, silver, or aluminum
Solution Approach 1:
The patent applies homogeneity by using copper material throughout the interconnect structure - copper bond pads, copper interconnects, and copper wiring. This eliminates the need for expensive intermetallic compound layers (such as those containing gold, silver, or aluminum) while maintaining excellent material compatibility and electrical conductivity throughout the entire interconnect path.
Solution Approach 2:
The patent replaces expensive intermetallic compound materials (gold, silver, aluminum) with inexpensive copper material. By using copper throughout the interconnect structure, the invention achieves the same functional purposes (electrical connection, material compatibility) at a fraction of the material cost, making the manufacturing process economically viable.
3Ease of operation
If passivation layers are removed to enable wire bonding or solder bumping, then bonding access is improved, but oxidation occurs on exposed copper surfaces
Solution Approach 1:
The patent applies preliminary action by performing copper surface preparation and activation before bonding operations. The copper bond pad surface is properly prepared (cleaned, activated, and conditioned) in advance to ensure both bonding accessibility and oxidation resistance. This preliminary surface treatment enables direct copper-to-copper bonding without requiring passivation layer removal, thus achieving both bonding access and oxidation protection simultaneously.
Data Source
AI summary
A structure includes a copper bond pad for copper interconnects that uses a conductive layer of palladium or copper palladium. The structure may include a substrate, and a copper bond pad over the substrate. A conductive layer is in direct contact with an upper surface of the copper bond pad. The conductive layer consists of palladium, copper palladium or both palladium and copper palladium. A copper interconnect is in direct contact with the conductive layer. The copper interconnect can be a copper wire bond or a copper redistribution layer (RDL) with a solder ball on the copper RDL. The structure provides high temperature reliability copper-to-copper interconnection by removing intermetallic compounds between the pad and copper interconnect.