Contoured Solder Bump Opening for Crack Propagation
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Solution Overview
Problem
Conventional flip-chip solder joints are prone to crack propagation and delamination due to mechanical stresses from thermal expansion mismatches and ductility differences, particularly at the intermetallic interface between the under bump metallization (UBM) structure and the solder bump, where the planar interior wall of the dielectric opening allows unimpeded crack propagation.
Innovation Solution
A method of forming a dielectric layer with contoured openings that include plural protrusions, which act as barriers to crack propagation, is used to couple a solder structure to a semiconductor chip's conductor structure, thereby enhancing the strength and strain resistance of the intermetallic interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar interior wall dielectric opening is used, then the manufacturing process is simple, but crack propagation occurs unimpeded leading to solder delamination and joint failure
Solution Approach 1:
The dielectric opening transitions from a planar symmetric interior wall to an asymmetric contoured interior wall with protrusions. These protrusions create an asymmetric geometry that interrupts crack propagation pathways while maintaining manufacturing feasibility through standard lithography and etching processes.
Solution Approach 2:
The interior wall of the dielectric opening incorporates curved contoured surfaces with protrusions rather than straight planar walls. This curvature creates a more complex three-dimensional geometry that effectively blocks crack propagation paths, improving solder joint reliability without significantly complicating the manufacturing process.
2Ease of manufacture
If the dielectric opening has a large open expanse between sidewalls, then the manufacturing process is straightforward, but cracks can propagate across the entire interface leading to solder delamination
Solution Approach 1:
The contoured interior wall with protrusions segments the continuous interior space into multiple smaller regions. This segmentation creates multiple barriers that cracks must navigate around, effectively dividing the failure path into smaller segments and preventing unimpeded crack propagation across the entire interface.
Solution Approach 2:
The protrusions create curved contoured surfaces that reduce the effective open expanse available for crack propagation. The curved geometry forces cracks to change direction and navigate around protrusions, thereby reducing the continuous path length and improving overall joint strength.
Data Source
AI summary
Methods and apparatus to inhibit cracks and delaminations in a semiconductor chip solder bump are disclosed. In one aspect, a method of manufacturing is provided that includes forming a first dielectric layer over a first conductor structure of a semiconductor chip and forming a first opening in the first dielectric layer to expose at least a portion of the conductor structure. The first opening defines an interior wall that includes plural protrusions. A solder structure is coupled to the first conductor structure such that a portion of the solder structure is positioned in the first opening.