Copper Bonding Pad Protection Structure Against Oxidation
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Solution Overview
Problem
Copper oxidation in semiconductor devices during elevated temperature environments leads to performance issues, such as noise in measurements and difficulties in wire-bonding due to the formation of copper oxide, which can cause wire detachment from the bonding pad.
Innovation Solution
A package structure is formed with a passivation layer, an electrically-conductive structure, a dielectric structure, and a protection structure, where the electrically-conductive structure is made of copper and the protection structure, comprising metals like aluminum, nickel, and gold, is applied over the copper to prevent oxidation and enhance adhesion for stable wire-bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as the bonding pad material, then electrical conductivity is improved, but oxidation resistance deteriorates at elevated temperatures
Solution Approach 1:
The bonding pad structure uses a composite material system consisting of a copper layer combined with a protective capping layer (such as palladium, platinum, or other oxidation-resistant materials). This composite structure maintains the high electrical conductivity of copper while the capping layer provides oxidation resistance at elevated temperatures, resolving the contradiction between conductivity and oxidation resistance.
2Strength
If copper oxide forms on the bonding pad, then adhesion for wire-bonding is improved initially, but wire bonding reliability deteriorates due to detachment
Solution Approach 1:
The protective capping layer is applied in advance to the copper bonding pad surface before wire-bonding operations. This preliminary protective layer prevents copper oxidation during storage and handling, ensuring that the bonding surface remains clean and free of oxide layers that would cause wire detachment, thus maintaining both adhesion strength and long-term bonding reliability.
3Ease of operation
If the bonding pad is exposed at elevated temperatures, then measurement access is improved, but measurement precision deteriorates due to noise from oxidation
Solution Approach 1:
The protective capping layer creates an inert protective environment over the copper bonding pad surface, preventing exposure to oxidizing conditions even at elevated temperatures. This allows the bonding pad to remain exposed for measurement access while the capping layer blocks oxygen and moisture, eliminating oxidation-induced noise and maintaining measurement precision and stability.
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 protection structure effectively prevents copper oxidation, improving measurement stability and ensuring successful wire-bonding by providing a reliable connection that withstands high temperatures during reliability testing.
Implementation Method 1
the electrically-conductive structure is made of copper and the protection structure, comprising metals like aluminum, nickel, and gold, is applied over the copper to prevent oxidation
Data Source
AI summary
A semiconductor structure and method of manufacturing a semiconductor structure are provided. The semiconductor structure includes a package structure. The package structure includes a passivation layer formed over an interconnect structure; an electrically-conductive structure formed on the passivation layer and extending through the passivation layer to electrically contact the interconnect structure; a dielectric structure formed over the passivation layer and surrounding the electrically-conductive structure to expose at least a portion of a top surface of the electrically-conductive structure; and a metallic protection structure formed on the top surface of the electrically-conductive structure exposed from the dielectric structure. The top surface of the metallic protection structure is aligned with or lower than a top surface of the dielectric structure.