3D Chip Stack Pad Layout for Warpage-Controlled Packaging
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Solution Overview
Problem
Current semiconductor packages face challenges in achieving compact, multifunctional designs with increased capacity, particularly in efficiently stacking semiconductor chips in a 3D structure while maintaining reliable electrical connections and minimizing warpage during manufacturing.
Innovation Solution
The proposed solution involves a chip stack structure with vertically stacked semiconductor chips, where each chip includes a semiconductor substrate, device layers, pad layers, and redistribution layers, with specific pad arrangements and bonding methods to ensure electrical connectivity and reduced warpage, allowing for miniaturization and increased chip density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple semiconductor chips are stacked vertically in a 3D structure to increase capacity and reduce size, then the device density and functionality are improved, but manufacturing warpage and alignment precision deteriorate
Solution Approach 1:
The chip stack is divided into multiple discrete chip units (first chip, second chip, third chip) that can be independently manufactured and then assembled. Each chip maintains its own pad layout independently, allowing for modular stacking with controlled alignment requirements at each interface rather than requiring perfect alignment across the entire stack.
Solution Approach 2:
Pad layers serve as intermediary elements between chips, with redistribution layers acting as mediators to reconfigure pad arrangements. The pad layers with reversed ordering (first pad layer vs. second pad layer) enable alignment compensation, where the redistribution layer maps pads from one chip to corresponding pads on the next chip despite orientation differences.
2Reliability
If pad layers are arranged in reverse order between stacked chips to enable electrical connection, then electrical connectivity is improved, but structural complexity increases
Solution Approach 1:
The second pad layer is arranged in reverse order relative to the first pad layer, and the third pad layer is arranged in reverse order relative to the second pad layer. This inversion strategy enables direct electrical connection between stacked chips by reversing the pad sequence to match corresponding pads on adjacent chips, eliminating the need for complex routing while maintaining connectivity.
Solution Approach 2:
The pad layer reversal operates in the planar dimension (arrangement order across the pad layer), enabling vertical stacking connectivity without adding complexity in the vertical dimension. The redistribution layer handles the dimensional transformation by mapping reversed pad orders to correct electrical connections.
3Reliability
If redistribution layers are added to connect pads between chips with different pad arrangements, then electrical connectivity is improved, but manufacturing complexity and process steps increase
Solution Approach 1:
The pad layers are designed with universal functionality to serve multiple purposes: they provide electrical connection points, enable alignment reference, and through redistribution, accommodate different pad arrangements between chips. The same pad layer structure is used across all chip interfaces, simplifying manufacturing by standardizing the connection interface despite varying internal chip designs.
Data Source
AI summary
The inventive concept provides a chip stack structure including a first semiconductor chip and a second semiconductor chip bonded to each other, and a semiconductor package including a plurality of chip stack structures stacked in a vertical direction.