Bonding Film Alignment Marks for Low-Dishing 3DIC Packaging
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Solution Overview
Problem
Three-dimensional integrated circuits (3DICs) face challenges related to alignment and bonding processes, particularly due to the dishing issue that occurs during planarization, which can lead to errors in identifying alignment marks and increase the process time and cost.
Innovation Solution
The formation of alignment marks with patterns having an area no larger than 30 μm2 on a horizontal plane, using a first and second bonding film with dielectric and conductive materials in trenches, and a planarization process to create coplanar surfaces, allowing for precise alignment and reduced error in bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If planarization process is used to create coplanar surfaces for alignment, then alignment accuracy is improved, but dishing issue occurs during planarization which leads to errors in identifying alignment marks
Solution Approach 1:
The patent changes the physical parameters of the alignment marks by forming them with a first material having a different etch selectivity than the surrounding bonding film material. This allows the alignment marks to be differentiated and identified accurately even when dishing occurs during planarization, as the selective etching preserves the marks' distinguishability despite surface non-uniformities.
Solution Approach 2:
The patent anticipates the dishing problem by designing alignment marks with contrasting material properties before the planarization process. By pre-establishing marks with different etch selectivity, the system compensates for the anticipated dishing effect, ensuring that alignment can still be performed accurately despite the known limitations of the planarization process.
2Ease of operation
If alignment marks with larger patterns are used, then easier identification during bonding process, but increased error in identifying alignment marks due to dishing
Solution Approach 1:
The patent changes the material composition parameter of alignment marks to have different etch selectivity compared to the bonding film. This allows even small-pattern marks to be clearly identified through selective etching contrast, eliminating the need for large patterns while maintaining high identification accuracy despite dishing effects.
3Device complexity
If conventional bonding process is used without selective etching, then simpler process flow, but increased process time and cost due to alignment errors
Solution Approach 1:
The patent replaces reliance on purely mechanical/geometric alignment mark features with a materials-based identification system. By using etch selectivity differences, the system substitutes physical dimension-based identification with chemical/compositional identification, enabling more accurate and efficient alignment without significantly complicating the overall process flow.
Data Source
AI summary
A package structure is provided, and includes a first bonding film formed on a first substrate, and a first alignment mark formed in the first bonding film. The first alignment mark includes a plurality of first patterns spaced apart from each other. The package structure includes a second bonding film formed on a second substrate and bonded to the first bonding film, and a second alignment mark formed in the second bonding film. The second alignment mark includes a plurality of second patterns spaced apart from each other. In a top view, the first alignment mark is spaced apart from the second alignment mark, and the distance between adjacent first patterns is less than the distance between the first alignment mark and the second alignment mark.