Bonding Pad Structure With Selective Passivation for Wire-Bond Reliability
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Solution Overview
Problem
Delamination issues between materials in wire-bonding structures, such as between the passivation layer and the redistribution layer (RDL), can occur, leading to reliability concerns during the wire-bonding process due to stress on bonding pads.
Innovation Solution
A bonding pad structure incorporating a copper-containing layer and a gold-containing layer, where the gold-containing layer is not covered by a passivation layer, along with a method of manufacturing that includes forming these layers and a passivation layer with an opening to expose the gold-containing layer, enhancing electrical performance and minimizing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is disposed over the entire RDL to protect it, then protection is improved, but delamination occurs between the passivation layer and the RDL due to stress during wire-bonding
Solution Approach 1:
The passivation layer is selectively disposed only over portions of the RDL that do not require bonding pad exposure. This local coverage approach provides protection where needed while avoiding stress concentration and delamination at bonding pad interfaces, resolving the contradiction between comprehensive protection and structural stability.
Solution Approach 2:
The RDL is segmented into different functional zones: bonding pad regions where the passivation layer is removed to expose underlying layers, and non-bonding pad regions where the passivation layer remains for protection. This segmentation allows simultaneous achievement of protection and prevention of delamination by treating different areas differently.
2Reliability
If the gold-containing layer is covered by the passivation layer, then protection is improved, but electrical performance deteriorates due to increased resistance and potential delamination
Solution Approach 1:
The passivation layer is selectively absent over the gold-containing layer at bonding pad locations, providing local exposure that maintains low electrical resistance and prevents delamination. In non-bonding pad areas, the passivation layer provides protection. This local quality differentiation resolves the contradiction between protection and electrical performance.
3Manufacturing precision
If a multi-layer conductive structure is used to improve electrical performance, then electrical conductivity is improved, but manufacturing complexity increases
Solution Approach 1:
The copper-containing layer and gold-containing layer are merged into a single integrated conductive structure where the gold layer is disposed over the copper layer. This combination leverages the high conductivity of copper and the oxidation resistance and bondability of gold, achieving superior electrical performance and reliability without requiring separate processing steps for each layer's functional optimization.
Data Source
AI summary
A bonding pad structure and a method of manufacturing a bonding pad structure are provided. The bonding pad structure includes a carrier, a first conductive layer disposed over the carrier, a second conductive layer disposed on the first conductive layer and contacting the first conductive layer, and a third conductive layer disposed on the second conductive layer and contacting the second conductive layer. The bonding pad structure also includes a first passivation layer disposed on the first conductive layer and contacting at least one of the first conductive layer or the second conductive layer. An upper surface of the third conductive layer facing away from the carrier is exposed from the first passivation layer.