Wafer-Level Package Passivation Steps for Polymer Layer Adhesion
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Solution Overview
Problem
Existing Wafer Level Package (WLP) technologies face challenges in ensuring reliable adhesion between polymer layers and underlying structures, leading to potential delamination issues that affect the overall reliability of the package.
Innovation Solution
The implementation of a polymer layer delamination prevention design, which involves forming a step structure on the top surface of the top passivation layer by increasing the number of openings in the bottom passivation layer and/or widening these openings, thereby enhancing the engagement and adhesion of the polymer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional WLP packaging processes are used, then manufacturing simplicity and low cost are maintained, but polymer layer delamination occurs reducing package reliability
Solution Approach 1:
The patent applies preliminary action by forming a step structure on the passivation layer before depositing the polymer layer. This pre-prepared structural feature (the step structure with its vertical walls and recessed regions) is created in advance to ensure proper polymer layer adhesion and prevent delamination, rather than attempting to fix adhesion issues after polymer deposition fails.
Solution Approach 2:
The patent applies segmentation by dividing the passivation layer into multiple regions with different heights (step structure). The passivation layer is segmented into a first region at a first height and a second region at a second height, creating distinct zones that provide different adhesion characteristics for the polymer layer, thereby improving overall bonding reliability.
2Strength
If the polymer layer is deposited directly on a flat passivation layer, then manufacturing simplicity is maintained, but adhesion is insufficient leading to delamination
Solution Approach 1:
The patent applies dimensionality change by transitioning from a two-dimensional flat passivation layer surface to a three-dimensional step structure. The vertical dimension is introduced with the step structure having a first region at a first height and a second region at a second height, creating vertical walls and recessed regions that provide enhanced mechanical interlocking and increased surface area for polymer layer adhesion.
Solution Approach 2:
The patent applies local quality by creating regions with different adhesion characteristics on the passivation layer. The step structure provides localized areas (vertical walls and recessed regions) with enhanced adhesion properties compared to flat surfaces, ensuring that the polymer layer bonds more strongly at critical interfaces where delamination is most likely to occur.
Data Source
AI summary
A package structure is provided, including a substrate, a first passivation layer, a metallization layer, a second passivation layer, and a polymer layer. The first passivation layer is formed over the substrate. The metallization layer is conformally formed on the first passivation layer. The second passivation layer is conformally formed on the first passivation layer and the metallization layer. A step structure is formed on the top surface of the second passivation layer, and includes at least one lower part that is lower than the other parts of the step structure. The polymer layer is formed over the second passivation layer. A portion of the polymer layer extends into the lower part of the step structure to engage with the step structure.