Back-End-of-Line Via Bar Stacking for VNCAP Reliability
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Solution Overview
Problem
The increasing complexity of integrated circuits and stringent minimum pitch requirements for back-end-of-line (BEOL) vertical natural capacitors (VNCAP) structures lead to process difficulties and reliability issues such as via protrusions causing time-dependent dielectric breakdown (TDDB) failures, which are challenging to address with conventional capacitor designs.
Innovation Solution
The formation of viabars or via groups with a horizontal via length at least twice as long as the horizontal via width, which increases the interconnect area, reduces resistance, and enhances the effective capacitor plate area, thereby improving the reliability and capacitance density of VNCAP structures by staggering or overlapping these interconnects between metallization layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the finger pitch of the VNCAP structure is reduced to achieve higher capacitance density, then capacitance density is improved, but via protrusions occur causing TDDB failure
Solution Approach 1:
The via structure is segmented into multiple portions (first via portion and second via portion) with different dimensions. The first via portion has a larger diameter than the second via portion, creating a stepped configuration that prevents protrusion into the dielectric layer while maintaining adequate capacitance density through the stacked inter-digitated metal structures.
Solution Approach 2:
Different portions of the via structure are given different local qualities - the first via portion has a larger diameter to prevent protrusion, while the second via portion has a smaller diameter to maintain pitch requirements. This local differentiation allows the structure to satisfy both reliability and capacitance density requirements simultaneously.
2Quantity of substance
If conventional planar capacitors such as MIM capacitors are used, then capacitance density can be achieved, but extra process steps and masks are required
Solution Approach 1:
The via structure serves multiple functions: it provides electrical connection between metallization layers and simultaneously forms part of the capacitor structure through the stacked inter-digitated metal patterns. This multi-functionality eliminates the need for separate MIM capacitor fabrication processes and masks, achieving capacitance density without increased device complexity.
Solution Approach 2:
The via connection structure and capacitor structure are merged into a single integrated VNCAP structure. The stacked via and inter-digitated metal structures combine the functions of inter-layer connectivity and capacitance formation, eliminating the need for separate MIM capacitor process steps and masks.
3Length of moving object
If via dimensions are reduced to meet minimum pitch requirements, then pitch compliance is improved, but manufacturing precision and reliability deteriorate
Solution Approach 1:
The via is segmented into portions with different diameters along its length. The first via portion has a larger diameter that prevents protrusion into the dielectric layer, while the second via portion has a smaller diameter that meets pitch requirements. This segmentation allows compliance with minimum pitch specifications while maintaining manufacturing precision and reliability.
Data Source
AI summary
An integrated circuit system that includes: providing a substrate including front-end-of-line circuitry; forming a first metallization layer over the substrate and electrically connected to the substrate; forming a viabar or a via group over the first metallization layer; and forming a second metallization layer over the first metallization layer and electrically connected to the first metallization layer through either the viabar or the via group.