Via Structure With Sacrificial Stress Barrier Ring Against Void Formation
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Solution Overview
Problem
As semiconductor devices shrink in size, stress migration (SM) becomes a significant reliability issue in integrated circuits, leading to void formation and reduced electrical contact between metal layers, which can cause device failure.
Innovation Solution
The implementation of a VIA structure with a sacrificial stress barrier ring around the primary interconnect structure to attract and prevent the formation of large voids by accumulating plastic deformation vacancies, thereby protecting the interconnect from stress migration effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency increases and costs decrease, but stress migration becomes a significant reliability issue leading to void formation and device failure
Solution Approach 1:
A sacrificial stress barrier ring is introduced as an intermediary structure between the upper and lower metal interconnect layers. This ring acts as a mediator that attracts and accumulates plastic deformation vacancies, preventing them from forming large voids in the primary interconnect structure. The barrier ring is positioned at a specific distance from the primary interconnect structure, creating a protective zone that mitigates stress migration effects while maintaining electrical connectivity.
Solution Approach 2:
The sacrificial stress barrier ring is formed in advance during the fabrication process, before stress migration issues can affect the primary interconnect structure. By pre-positioning this barrier structure, the patent proactively prevents void formation rather than addressing it after the fact. The ring is created as part of the via structure formation process, ensuring protection is in place before operational stresses occur.
2Area of moving object
If geometric size decreases to increase functional density, then more devices fit per chip area, but fabrication process complexity increases especially with decreasing lithographic feature sizes
Solution Approach 1:
The via structure is segmented into multiple functional components: a primary interconnect structure for electrical connectivity and a separate sacrificial stress barrier ring for protection. This segmentation allows each component to be optimized independently - the primary structure for conductivity and the barrier ring for stress management. The segmented approach simplifies the overall fabrication process by allowing standard via formation techniques to be used for both components through a unified patterning process.
Solution Approach 2:
The sacrificial stress barrier ring serves multiple functions: it acts as a stress barrier to prevent void formation, serves as a structural support element, and can be formed using the same lithographic and deposition processes as the primary interconnect structure. This multi-functionality reduces fabrication complexity by eliminating the need for separate specialized processes while providing enhanced reliability protection.
Data Source
AI summary
An interconnect structure on a semiconductor die includes: a lower conductive layer; an upper conductive layer disposed above the lower conductive layer; and a VIA disposed between the lower conductive layer and the upper conductive layer. The VIA includes: a primary interconnect structure and a sacrificial stress barrier ring disposed around the primary interconnect structure and separated a distance from the primary interconnect structure. A fabrication method for the interconnect structure includes: forming a dielectric layer over a lower conductive layer; patterning photoresist (PR) layer over the dielectric layer to define a location for a plurality of VIA trenches, wherein the patterning includes patterning the PR layer to provide a center opening for the VIA trenches that is surrounded by a ring opening for the VIA trenches, wherein the center opening and the ring opening are spaced apart.