Mirror-Image Contact Pad Layouts for Stacked IC Die Alignment
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Solution Overview
Problem
Existing techniques for face-to-face stacking of integrated circuit (IC) dies face challenges due to non-symmetrical geometrical patterns of contact pads, which can lead to misalignment and increased complexity and cost.
Innovation Solution
The solution involves using IC dies with contact pads arranged in mirror-image geometrical patterns, allowing for precise alignment and coupling without the need for symmetrical designs, thereby simplifying the stacking process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If non-symmetrical geometrical patterns are used for contact pads in face-to-face stacking, then design flexibility and circuit functionality are improved, but alignment accuracy deteriorates due to misalignment between stacked dies
Solution Approach 1:
The patent applies asymmetry by intentionally creating mirror-image asymmetric patterns on opposing surfaces of stacked IC dies. Each die has a non-symmetrical contact pad arrangement, but the pattern on the opposing surface is its mirror image, allowing the asymmetric designs to align perfectly when stacked. This resolves the contradiction by enabling design flexibility through non-symmetrical layouts while maintaining alignment accuracy through the mirror-image relationship.
Solution Approach 2:
The patent uses inversion by creating mirror-image patterns where one surface's contact pad arrangement is the geometric mirror reflection of the other surface's arrangement. This inversion technique allows non-symmetrical designs to align perfectly when the dies are stacked face-to-face, as the mirror-image relationship ensures that corresponding contact pads align despite the asymmetric geometry. This resolves the alignment issue while preserving design flexibility.
2Manufacturing precision
If symmetrical geometrical patterns are used for contact pads to ensure alignment, then alignment accuracy is improved, but design complexity increases due to constraints on circuit layout
Solution Approach 1:
The patent eliminates the need for symmetrical patterns by using mirror-image asymmetric patterns instead. Each die can have its own optimized asymmetric layout without being constrained by symmetry requirements, thereby reducing design complexity while maintaining alignment accuracy through the mirror-image relationship between stacked dies.
Solution Approach 2:
By using mirror-image inversion, the patent allows each die to be designed independently with optimized asymmetric layouts. The inversion relationship ensures alignment without requiring the dies to have identical symmetrical patterns, thus reducing design complexity while maintaining manufacturing precision.
3Manufacturing precision
If mirror-image geometrical patterns are used on opposing surfaces, then alignment accuracy is improved, but manufacturing complexity increases due to additional pattern definition steps
Solution Approach 1:
The patent merges the pattern definition process by using a single reticle containing both the direct and mirror-image patterns. This allows both patterns to be defined and transferred in one lithography step, eliminating the need for separate manufacturing steps and reducing overall manufacturing complexity while maintaining the alignment benefits of mirror-image patterns.
Solution Approach 2:
The reticle is designed with multi-functionality, serving as a single tool that defines both the direct and mirror-image contact pad patterns. This universal reticle approach simplifies manufacturing by consolidating what would otherwise require multiple specialized tools or steps, thereby reducing manufacturing complexity while achieving precise alignment.
4Adaptability or versatility
If separate reticles are used for direct and mirror-image patterns, then manufacturing flexibility is improved, but production cost increases due to additional reticle fabrication and handling
Solution Approach 1:
The patent combines both the direct and mirror-image patterns into a single reticle, eliminating the need for separate reticles. This consolidation reduces reticle fabrication costs, handling complexity, and inventory requirements, thereby reducing production cost while maintaining manufacturing flexibility through the integrated design.
Solution Approach 2:
The single reticle is designed with multi-functionality, capable of defining both direct and mirror-image patterns. This universal approach eliminates the need for multiple specialized reticles, reducing production costs associated with fabricating, storing, and handling multiple reticle types while maintaining the flexibility to produce different pattern configurations.
Data Source
AI summary
An electronic device includes first and second integrated circuit (IC) dies. The first IC die includes a first set of contact pads arranged, on a first surface of the first IC die, in a first geometrical pattern which is non-symmetrical under reflection about a given axis in a plain of the first IC die. The second IC die includes a second set of the contact pads that are arranged, on a second surface of the second IC die, in a second geometrical pattern that is a mirror image of the first geometrical pattern with respect to the given axis, the second surface of the second IC die is flipped about the given axis and facing the first surface of the first IC die, and the contact pads of the first and second sets are aligned with one another and mounted on one another.