Series MIM Capacitor Vertical Stacking for Leakage Reduction
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Solution Overview
Problem
Series-connected MIM capacitors in integrated circuits face issues with asymmetrical leakage current and inefficient space usage due to forward and reverse biasing, as well as lateral extensions of plates, affecting reliability and space efficiency.
Innovation Solution
The implementation of series-connected MIM capacitors with first and second conducting plates on a first insulating layer, third and fourth conducting plates overlapping the first and second, a second insulating layer between them, and blind vias coupling the first and fourth plates, with connections to the second and third plates, optimizing placement within the back-end structure of a semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two identical capacitors are formed with lower plates extending laterally beyond upper plates to provide connection space, then connection space is provided, but space utilization becomes inefficient
Solution Approach 1:
The patent transitions from a planar lateral extension approach to a vertical three-dimensional stacking approach. Lower plates are positioned directly beneath upper plates in overlapping vertical relationships, with connections achieved through vertical vias rather than lateral extensions. This dimensional change eliminates the need for lateral plate extensions while maintaining connection functionality, thereby improving space utilization.
2Extent of automation
If MIM capacitors are connected in series with side-by-side plates, then series connection is achieved, but asymmetrical leakage current and forward/reverse biasing issues occur
Solution Approach 1:
The patent intentionally introduces asymmetry in the form of a blind via that connects only the first lower plate to the fourth upper plate, creating an asymmetrical series connection structure. This asymmetrical configuration balances the electrical biasing conditions across the series-connected capacitors, eliminating the forward/reverse biasing issues and asymmetrical leakage current problems associated with symmetrical side-by-side configurations.
3Ease of operation
If lower plates extend laterally beyond upper plates, then connection access is improved, but device complexity increases
Solution Approach 1:
The patent resolves the connection access problem by moving from lateral horizontal connections to vertical connections through the substrate. Blind vias provide vertical access to lower plates without requiring them to extend laterally beyond upper plates. This vertical approach simplifies the plate structure while maintaining ease of connection access through the third dimension.
Data Source
AI summary
Two series-connected metal-insulator-metal (MIM) capacitors are disclosed that are suitable for fabrication in the back-end structure of an integrated circuit. The MIM capacitors have first and second electrically conducting plates on a first insulating layer, third and fourth electrically conducting plates overlapping the first and second conducting plates, a second insulating layer between the first and third conducting plates and between the second and fourth conducting plates, a blind via coupling the first and fourth conducting plates, and connections to the second and third conducting plates. Methods of fabricating such series-connected MIM capacitors are also disclosed.