Fully-Aligned Skip-Vias via Subtractive Patterning
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Solution Overview
Problem
Conventional methods for forming skip-vias in semiconductor ICs often result in non-uniform via profiles, air gaps, misalignment of via portions, and increased resistance due to undesirable current leakages and metal short-connections, which affect the reliability and performance of the interconnect structures.
Innovation Solution
A novel subtractive patterning process is employed to form a stack of fully-aligned (FA) skip-via pairs, where each pair of via portions is precisely aligned to increase the contact area and allow trimming of via portions, reducing the distance between via portions and neighboring metal lines or vias, thereby enhancing the interconnect resistance and reducing current leakages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form skip-vias, then the fabrication process is simpler, but the via profiles become non-uniform and misalignment occurs
Solution Approach 1:
The skip-via is divided into multiple via portions formed in separate fabrication steps. Each via portion is formed independently through its own opening, allowing precise control and alignment of each segment. This segmentation enables the via stack to achieve uniform profiles and precise alignment while maintaining a manageable fabrication process through modular construction.
2Manufacturing precision
If via portions are not fully aligned, then the fabrication process is easier, but contact area decreases and resistance increases
Solution Approach 1:
The method forms openings and via portions in a predetermined sequence, with each subsequent via portion aligned to the previous ones. This preliminary positioning and sequential formation ensures that all via portions are fully aligned before final metallization, maximizing contact area and minimizing resistance while maintaining fabrication ease through structured process planning.
3Ease of manufacture
If via portions are misaligned, then fabrication is simpler, but current leakages and metal short-connections increase
Solution Approach 1:
The method addresses potential misalignment issues by forming each via portion through its own dedicated opening with precise alignment features. This approach converts the potential harm of misalignment into a benefit by ensuring that each via portion is intentionally positioned, eliminating current leakages and metal short-connections while maintaining ease of manufacture through a systematic formation process.
Data Source
AI summary
An interconnect structure includes a first electrically conductive via portion on an upper surface of a substrate, the first electrically conductive via elongated along a first direction, and a first ILD material on the substrate and covering the first electrically conductive via portion. The first ILD material includes an ILD upper surface exposing a via surface of the first electrically conductive via portion. A second electrically conductive via portion is on the ILD upper surface and the via upper surface thereby defining a contact area between the first electrically conductive via portion and the second electrically conductive via portion. The second electrically conductive via portion elongated along a second direction orthogonal with respect to the first direction. A second ILD material is on the ILD upper surface to cover the second electrically conductive via portion. The first and second electrically conductive via portions are fully aligned at the contact area.