Alignment Structures for Wafer Level Chip Scale Packages
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Solution Overview
Problem
The semiconductor industry faces challenges in efficiently forming alignment structures during the manufacturing of wafer level chip scale packages, particularly in ensuring proper alignment and protection of conductive pillars and interconnects during the singulation process, where the molding compound can obscure marks and scribe lines, and existing methods are costly and less effective when applied post-singulation.
Innovation Solution
The method involves forming a conductive pillar and alignment structure over a post-passivation interconnect, with a molding compound applied to protect and insulate these structures before singulation, allowing for accurate alignment and enhanced protection by extending the alignment structures above the molding compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a molding compound is applied to protect and insulate conductive pillars and interconnects, then protection and insulation are improved, but alignment marks and scribe lines become obscured during singulation
Solution Approach 1:
The molding compound is applied selectively only in regions that do not cover alignment marks and scribe lines, segmenting the application area to preserve visibility of critical features while still providing protection to conductive structures in other areas
Solution Approach 2:
The alignment structure serves as an intermediary element that extends through the molding compound, providing both protection where needed and visibility where required for alignment during singulation
2Manufacturing precision
If alignment structures are formed before applying molding compound, then alignment accuracy is improved, but the molding compound obscures the alignment marks
Solution Approach 1:
Instead of forming the alignment structure and then having it obscured, the solution inverts the approach by forming the alignment structure with portions that intentionally extend above the molding compound surface, ensuring visibility is maintained despite the protective coating being applied
3Difficulty of detecting and measuring
If alignment structures extend above the molding compound surface, then visibility during singulation is improved, but the complexity of forming the structure increases
Solution Approach 1:
The alignment structure is merged with the conductive pillar structure, combining multiple functions into a single integrated element that provides both electrical connectivity and alignment functionality while extending through the molding compound
Data Source
AI summary
Embodiments of the present disclosure include interconnect structures and methods of forming interconnect structures. An embodiment is a method of forming an interconnect structure, the method including forming a first post-passivation interconnect (PPI) over a first substrate, forming a second PPI over the first substrate, and forming a first conductive connector on the first PPI. The method further includes forming a second conductive connector on the second PPI, and forming a molding compound on top surfaces of the first and second PPIs and surrounding portions of the first and second connectors, a first section of molding compound being laterally between the first and second connectors, the first section of molding compound having a curved top surface.