3DIC Core Ball Interconnect Structure for Simpler Die Stacking
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Solution Overview
Problem
The semiconductor industry faces challenges in increasing integration density and reducing turnaround time and yield due to the complexity of forming high-aspect-ratio metal posts in 3D integrated circuits (3DICs) with stacked structures, where the upper semiconductor chip die has a larger area than the lower chip die.
Innovation Solution
The use of core balls instead of metal posts to couple the upper semiconductor chip die and the front side redistribution layer (FRDL) structure in 3DICs, with each core ball comprising an inner core and conductive layers, simplifies the manufacturing process and improves yield by reducing the need for repetitive processes like exposure and etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal posts are used to couple the upper semiconductor chip die and the front side redistribution layer (FRDL) structure, then the structural strength and electrical connection are improved, but the manufacturing complexity and turnaround time increase due to repeated exposure, development, etching, and deposition processes
Solution Approach 1:
The patent extracts the complex multi-step metal post formation process (exposure, development, etching, deposition) and replaces it with a simplified core ball attachment process. The core ball structure eliminates the need for forming high-aspect-ratio metal posts through repetitive semiconductor fabrication processes, thereby reducing manufacturing complexity while maintaining structural integrity and electrical connection functionality.
Solution Approach 2:
The core ball structure serves as a disposable or sacrificial element that simplifies the overall manufacturing process. Instead of creating permanent, complex metal post structures requiring multiple processing steps, the core ball provides the necessary mechanical support and electrical connection during assembly, allowing for a more straightforward and less complex manufacturing workflow.
2Reliability
If metal posts are used to couple the upper semiconductor chip die and the front side redistribution layer (FRDL) structure, then the electrical connection is improved, but the turnaround time increases due to repeated processing steps
Solution Approach 1:
The core balls are pre-formed and pre-positioned on the FRDL structure before the upper semiconductor chip die is attached. This preliminary action eliminates the need for time-consuming in-situ metal post formation processes during the assembly stage, thereby reducing turnaround time while ensuring reliable electrical connections are established from the outset.
Solution Approach 2:
Instead of creating complex metal post structures through multiple fabrication steps, the patent uses core balls that replicate the essential function of metal posts (mechanical support and electrical connection) in a simpler, more time-efficient manner. The core ball design copies the functional requirements of metal posts without duplicating the complex manufacturing process.
3Strength
If metal posts are used to couple the upper semiconductor chip die and the front side redistribution layer (FRDL) structure, then the structural support is improved, but the yield decreases due to process variability and defects
Solution Approach 1:
The core ball structure serves as a simplified, robust mechanical support element that is less susceptible to process variability and defects compared to metal posts. By using core balls instead of complex metal post structures, the manufacturing process becomes more forgiving and less prone to yield-reducing defects, thereby improving overall manufacturing yield while maintaining adequate structural support.
4Productivity
If the area of the lower surface of the upper semiconductor chip die is larger than the area of the upper surface of the lower semiconductor chip die, then the integration density is improved, but the manufacturing complexity increases due to the need for additional coupling structures
Solution Approach 1:
The patent extracts the complex coupling structure requirements that arise from the area mismatch between stacked chip dies and replaces them with a simplified core ball-based solution. The core balls provide the necessary mechanical and electrical coupling without requiring complex redistribution layer extensions or additional interconnection structures, thereby reducing manufacturing complexity while supporting high integration density configurations.
Data Source
AI summary
A 3D integrated circuit structure includes a redistribution layer structure; a first semiconductor chip die on the redistribution layer structure; a plurality of core balls on the redistribution layer structure and adjacent the first semiconductor chip die; a molding material encapsulating the first semiconductor chip die and the plurality of core balls on the redistribution layer structure; an interconnection structure on the molding material; and a second semiconductor chip die on the interconnection structure. A footprint of the first semiconductor chip die and footprints of the plurality of core balls are within a footprint of the second semiconductor chip die.