Integrated Fan-Out Package Alignment Mark Segmentation
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Solution Overview
Problem
Integrated fan-out packages face challenges in achieving precise alignment and reliable manufacturing due to limitations in existing alignment mark designs and processes, which affect the accuracy and yield of 3D packaging and 3DIC devices.
Innovation Solution
The implementation of a redistribution structure with multi-directional grid pattern alignment marks and a layered redistribution structure, including conductive vias and alignment marks embedded in dielectric layers, enhances overlay accuracy and reduces alignment failure rates by providing precise detection and protection during subsequent processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alignment mark designs are used in integrated fan-out packages, then manufacturing simplicity is maintained, but overlay accuracy and alignment precision deteriorate
Solution Approach 1:
The alignment mark is divided into multiple segments including a first alignment mark portion embedded in the encapsulant and a second alignment mark portion formed on the encapsulant surface. This segmentation allows each portion to serve specific functions: the embedded portion provides stable positioning while the surface portion enables precise detection, thereby improving overlay accuracy without requiring complete redesign of the entire alignment system.
Solution Approach 2:
The alignment mark structure extends from a two-dimensional surface marking into the third dimension by embedding the first alignment mark portion within the encapsulant volume. This three-dimensional configuration provides additional degrees of freedom for alignment and detection, enabling improved overlay accuracy through depth-based positioning while maintaining manufacturing feasibility.
2Reliability
If alignment marks are not protected during subsequent processes, then manufacturing simplicity is maintained, but alignment reliability deteriorates due to damage or displacement
Solution Approach 1:
The first alignment mark portion is embedded within the encapsulant material before subsequent manufacturing processes are performed. This embedding provides protective cushioning that shields the alignment mark from damage, displacement, or contamination during later processing steps, thereby ensuring alignment reliability without requiring additional protective structures.
Solution Approach 2:
The alignment mark structure is merged with the encapsulant material by embedding the first alignment mark portion within the encapsulant volume. This merging integrates the alignment function into the encapsulant itself, providing both structural support and protection while eliminating the need for separate protective elements, thus maintaining manufacturing simplicity.
3Manufacturing precision
If precise alignment detection is implemented, then overlay accuracy improves, but signal noise increases affecting detection reliability
Solution Approach 1:
The encapsulant material serves as an intermediary medium between the embedded first alignment mark portion and the external detection system. This intermediary provides a controlled environment that enhances signal transmission while filtering out external noise and interference, thereby improving detection precision without introducing additional noise sources.
Solution Approach 2:
The alignment mark structure exhibits local quality differences: the embedded first portion provides stable, low-noise positioning within the homogeneous encapsulant, while the second surface portion enables high-precision detection. This local differentiation optimizes each region for its specific function, minimizing signal noise in the detection process while maintaining high alignment precision.
Data Source
AI summary
An integrated fan-out (InFO) package includes an encapsulant, a die, a plurality of conductive structures, and a redistribution structure. The die and the conductive structures are encapsulated by the encapsulant. The conductive structures surround the die. The redistribution structure is disposed on the encapsulant. The redistribution structure includes a plurality of routing patterns, a plurality of conductive vias, and a plurality of alignment marks. The conductive vias interconnects the routing patterns. At least one of the alignment mark is in physical contact with the encapsulant.