Multiple Seal Ring Structure for Semiconductor Moisture Protection
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Solution Overview
Problem
Semiconductor integrated circuits face issues with moisture ingress and ionic contamination, leading to degradation, threshold voltage instability, and die saw peeling during dicing processes, particularly in backside illuminated devices with low-k inter-metal dielectric films.
Innovation Solution
A multiple seal ring structure is formed around the integrated circuit die, comprising concentric seal ring structures with stacked conductive layers and via layers through dielectric layers, and a passivation layer to prevent die saw peeling and protect the internal circuit from moisture and ionic contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single seal ring structure is used to protect the IC, then moisture and ionic contamination are blocked, but die saw peeling occurs during dicing processes
Solution Approach 1:
The single seal ring is divided into multiple concentric seal rings (first seal ring, second seal ring, etc.) with different structural characteristics. The outer seal ring provides mechanical strength to resist die saw cutting forces, while the inner seal ring focuses on blocking moisture and ionic contamination. This segmentation allows each seal ring to be optimized for its specific function, resolving the contradiction between protection and mechanical strength.
2Reliability
If low-k inter-metal dielectric films are used in backside illuminated devices, then device performance is improved, but die saw peeling susceptibility increases
Solution Approach 1:
Multiple concentric seal rings are implemented with the inner seal ring positioned to provide enhanced mechanical support specifically for devices with low-k inter-metal dielectric films. This segmentation allows the low-k materials to maintain their performance benefits while the additional seal ring structure compensates for the reduced mechanical strength, preventing die saw peeling during dicing processes.
3Strength
If a thicker single seal ring is used to prevent die saw peeling, then mechanical strength is improved, but moisture and ionic contamination blocking capability may be compromised
Solution Approach 1:
The seal ring function is segmented into multiple concentric rings with different thicknesses and material compositions. The outer seal ring is designed with greater thickness to provide mechanical strength against die saw forces, while the inner seal ring is optimized with appropriate thickness and material properties to effectively block moisture and ionic contamination. This segmentation resolves the contradiction by distributing the functional requirements across multiple specialized structures.
Solution Approach 2:
Different regions of the seal ring structure are given different local qualities - the outer seal ring has greater thickness for mechanical strength, while the inner seal ring has optimized thickness and material composition for contamination blocking. This local quality differentiation allows each region to excel at its specific function without compromising the other.
Data Source
AI summary
The present disclosure provides a method of fabricating a semiconductor device, the method including providing a substrate having a seal ring region and a circuit region, forming a first seal ring structure over the seal ring region, forming a second seal ring structure over the seal ring region and adjacent to the first seal ring structure, and forming a first passivation layer disposed over the first and second seal ring structures. A semiconductor device fabricated by such a method is also provided.