Semiconductor Bridge Vias for Vacancy Migration Control
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Solution Overview
Problem
Semiconductor devices face a high likelihood of via failures due to vacancy accumulation and stress migration, especially as geometries shrink, despite the use of redundant vias, which are not entirely effective in preventing failures.
Innovation Solution
Placing at least three vias on bridges connecting buses, with the center via positioned at a distance greater than the critical distance from both buses to absorb vacancy migration and reduce the risk of failure, while additional vias can be added based on bridge length and bus width to enhance robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the width of buses is increased to reduce resistance, then electrical resistance decreases, but the area occupied increases and the risk of via voiding increases
Solution Approach 1:
The bus is segmented into multiple narrower parallel lines instead of using a single wide bus. This segmentation reduces the area occupied while maintaining low resistance through multiple current paths. The bridge connecting these segmented buses is also divided into multiple vias to distribute stress and prevent voiding.
2Reliability
If redundant vias are added to reduce via failure risk, then reliability improves, but device complexity increases
Solution Approach 1:
Instead of uniformly adding redundant vias throughout the device, the invention applies local quality by placing multiple vias specifically at the bridge locations connecting wide buses. This targeted approach addresses the highest-risk areas (where vacancy accumulation occurs) without unnecessarily increasing complexity in low-risk areas.
3Reliability
If the number of vias on a bridge is increased to absorb vacancy migration, then via failure resistance improves, but manufacturing complexity increases
Solution Approach 1:
The invention applies preliminary action by pre-positioning multiple vias on bridges during the design and manufacturing planning stage. This allows the vacancy migration to be absorbed by predetermined via locations rather than requiring complex real-time adjustments during manufacturing. The via placement follows systematic patterns based on bridge geometry and bus width.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the risk of via failures by distributing vacancy migration among the vias, thereby improving the reliability and integrity of the connections between buses.
Implementation Method 1
there are vacancies that are formed which later tend to accumulate at features, such as corners and vias, that are formed along sides of the buses... vacancies approach from both buses and thus potentially attack the via from both sides... the center via or vias are not attacked by the vacancies because the vacancies are absorbed by the vias closest to the buses
Data Source
AI summary
A semiconductor device comprises conductive buses and conductive bridges. A respective conductive bridge is conductively coupled to at least two portions of at least one of the conductive buses. At least N plus one (N+1) vias are coupled between every one of the conductive bridges and a respective feature in an integrated circuit when: (1) a width of the respective conductive bridge is less than a width of each of the at least two portions of the at least one of the conductive buses to which the respective conductive bridge is coupled, and (2) a distance along the respective conductive bridge and at least one of the vias is less than a critical distance. N is a number of conductive couplings between the respective one of the conductive bridges and the at least one of the conductive buses.