Package Via Structure for Thermal Stress Crack Prevention
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Solution Overview
Problem
Existing package structures and fabrication methods for semiconductor devices, particularly in package on package (PoP) configurations, are inadequate in managing stress and preventing cracks and voids due to mismatched thermal expansion coefficients between conductive and passivation layers, leading to reliability issues.
Innovation Solution
The introduction of a conductive structure with a first via portion directly connected to a through via structure and a second via portion with one end connected to the substrate, which balances stress and prevents cracking by acting as a support, combined with a specific design of via portions and metal portions to manage thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive structure with multiple via portions is used to connect layers, then electrical connectivity is improved, but stress concentration and cracking risk increase due to thermal expansion mismatch
Solution Approach 1:
The conductive structure is divided into multiple separate via portions (first via portion, second via portion, third via portion) instead of a single continuous conductor. Each via portion is independently formed and connected to different layers, which segments the stress path and prevents crack propagation through the entire structure while maintaining electrical connectivity.
Solution Approach 2:
The conductive structure acts as an intermediary element between the substrate and the cap structure, providing both electrical connection and mechanical stress relief. The via portions are strategically positioned to connect different layers while the insulating material surrounding them serves as a mediator that accommodates thermal expansion differences between layers.
2Reliability
If conductive material is deposited to connect through via structures, then electrical connection is achieved, but thermal expansion mismatch causes stress and potential delamination
Solution Approach 1:
The patent applies different materials with different properties to different locations: conductive material (e.g., copper, aluminum) is used specifically in the via portions where electrical connection is needed, while insulating material (e.g., dielectric material, polymer) is used in the surrounding areas to provide mechanical support and accommodate thermal expansion. This local differentiation allows electrical connectivity without uniform stress distribution.
Solution Approach 2:
The package structure uses a composite construction combining conductive materials (for electrical connection) with insulating materials (for mechanical support and stress relief). The conductive structure includes both conductive via portions and surrounding insulating material, creating a composite element that simultaneously provides electrical connectivity and thermal stress management.
3Ease of manufacture
If a simple conductive layer is used, then fabrication is easier, but stress management and crack prevention are insufficient
Solution Approach 1:
Instead of forming a single continuous conductive layer, the patent segments the conductive material into discrete via portions that are formed through the insulating material. This segmentation is achieved through standard lithography and deposition processes, maintaining ease of manufacture while significantly improving stress management by preventing stress concentration in continuous conductors.
Solution Approach 2:
The conductive structure transitions from a two-dimensional planar conductive layer to a three-dimensional structure with via portions extending vertically through the insulating material. This dimensional change allows electrical connection between multiple layers while the vertical via portions distribute stress more effectively than a flat conductive layer would.
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 design effectively reduces stress, preventing cracks and voids, thereby enhancing the reliability and quality of the package structure.
Implementation Method 1
mismatched thermal expansion coefficients between conductive and passivation layers
Data Source
AI summary
A package structure and method for forming the same are provided. The package structure includes a substrate having a front surface and a back surface, and a die formed on the back surface of the substrate. The package structure includes a first through via structure formed in the substrate, a conductive structure formed in a passivation layer) over the front surface of the substrate. The conductive structure includes a via portion in direct contact with the substrate. The package structure includes a connector (formed over the via portion, wherein the connector includes an extending portion directly on a recessed top surface of the via portion.