PPI Structure Bump Reinforcement via Segmented Protective Layers
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Solution Overview
Problem
Wafer level chip scale packaging (WLCSP) experiences polymer film peeling issues during post-passivation interconnect (PPI) formation, leading to weak interfaces and device failures due to the limitations of existing PPI structures.
Innovation Solution
The formation of a bump structure on a PPI structure involves creating a first and second protective layer with specific openings to reinforce the package, using a solder bump and a barrier layer to enhance the strength and reliability of the PPI structure, and prevent copper diffusion, thereby improving the bonding and reducing peeling and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a typical WLCSP process forms PPI lines on passivation layers followed by polymer films and bumps, then the packaging can be achieved with low cost and relatively simple processes, but polymer film peeling issues occur which induce weak interfaces and cause device failures
Solution Approach 1:
The patent divides the protective layer into multiple segments: a first protective layer formed directly on the PPI structure, and a second protective layer formed on the first protective layer. This segmentation allows each layer to serve specific functions - the first layer provides immediate protection and bonding, while the second layer provides additional protection and prevents peeling, thereby resolving the contradiction between simple manufacturing and interface strength.
Solution Approach 2:
The patent implements a nested structure where the first opening is surrounded by the second opening, creating a concentric configuration. The bump structure fills both openings and is electrically connected through this nested arrangement. This nested design reinforces the interface between the bump and PPI structure, preventing polymer film peeling while maintaining the straightforward WLCSP manufacturing process.
2Device complexity
If existing PPI structures are used without additional protective layers, then the manufacturing process remains simple, but the interfaces are weak and prone to peeling and cracking
Solution Approach 1:
The patent applies preliminary action by forming the first protective layer on the PPI structure before forming the bump structure. This preliminary protective layer prepares the surface for subsequent bump formation and provides initial bonding strength, preventing peeling and cracking issues that would otherwise occur with simple PPI structures.
Solution Approach 2:
The patent uses composite material structures by combining multiple protective layers with different properties. The first protective layer and second protective layer are formed as composite structures with the PPI structure, creating a multi-layer composite system that enhances bonding strength and prevents interface failure while maintaining reasonable structural complexity.
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 proposed method strengthens the PPI structure, enhances joint reliability, and reduces bump fatigue, improving the overall performance and reliability of the packaging assembly process.
Implementation Method 1
a bump structure formed overlying the protective layer... the bump structure is electrically connected to the interconnect structure through the first opening and the second opening
Implementation Method 2
a bump structure formed overlying the protective layer... the bump structure is electrically connected to the interconnect structure through the first opening and the second opening
Data Source
AI summary
A semiconductor device includes a post-passivation interconnect (PPI) structure having a landing pad region. A polymer layer is formed on the PPI structure and patterned with a first opening and a second opening to expose portions of the landing pad region. The second opening is a ring-shaped opening surrounding the first opening. A bump structure is formed on the polymer layer to electrically connect the landing pad region through the first opening and the second opening.