Semiconductor Seal Ring Structure with Dummy Gates
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Solution Overview
Problem
In semiconductor integrated circuits, moisture and ionic contaminants cause degradation, corrosion, and reliability issues, while the scaling-down of feature sizes leads to challenges in forming effective seal rings, particularly with high-k metal gate processes that result in chemical mechanical polishing (CMP) dishing.
Innovation Solution
The implementation of a semiconductor device with a substrate having a seal ring region and a circuit region, where a plurality of dummy gates, either polysilicon or dielectric, are formed over the seal ring region, and an interlayer dielectric is deposited between them, followed by a seal ring structure to prevent CMP dishing and enhance protection against moisture and contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate oxide and polysilicon gate electrode are replaced with high-k gate dielectric and metal gate electrode to improve device performance, then device performance is improved, but CMP dishing occurs in open areas such as seal ring regions
Solution Approach 1:
The seal ring region is segmented by forming dummy gates within it, dividing the open area into smaller sections. This segmentation prevents CMP dishing by providing distributed support structures across the seal ring region, while the actual seal ring structure remains intact for moisture protection.
Solution Approach 2:
Dummy gates are introduced as intermediary structures in the seal ring region. These dummy gates act as mediators during the CMP process, preventing dishing by providing uniform support across the open area, while being distinct from and not interfering with the functional seal ring structure.
2Productivity
If feature sizes are scaled down to increase functional density, then functional density is improved, but the ability to form effective seal rings deteriorates
Solution Approach 1:
The seal ring region is divided into multiple segments by forming dummy gates within it. This segmentation allows the seal ring structure to maintain its protective function while accommodating scaled-down feature sizes, as the dummy gates provide distributed support without compromising the overall seal integrity.
Solution Approach 2:
Different regions of the seal ring structure are given different qualities: the seal ring structure itself maintains its moisture-blocking properties, while the dummy gates within the seal ring region provide localized CMP protection. This local differentiation allows both high-k metal gate performance and effective sealing at scaled dimensions.
3Manufacturing precision
If dummy gates are formed over the seal ring region to prevent CMP dishing, then CMP dishing is prevented, but device complexity increases
Solution Approach 1:
The dummy gates serve multiple functions: they prevent CMP dishing in the seal ring region, maintain planarity during processing, and do not interfere with the seal ring's moisture protection function. By making these auxiliary structures multi-functional, the overall device complexity is minimized while achieving CMP dishing prevention.
Solution Approach 2:
Dummy gates are simple copies or replicas of gate structures that can be formed using the same fabrication processes as functional gates. This copying approach prevents CMP dishing without requiring new, complex manufacturing steps, thereby minimizing the increase in device complexity.
Data Source
AI summary
The present disclosure provides a semiconductor device that includes a substrate having a seal ring region and a circuit region, a plurality of dummy gates disposed over the seal ring region of the substrate, and a seal ring structure disposed over the plurality of dummy gates in the seal ring region. A method of fabricating a semiconductor device is also provided, the method including providing a substrate having a seal ring region and a circuit region, forming a plurality of dummy gates over the seal ring region of the substrate, and forming a seal ring structure over the plurality of dummy gates over the seal ring region.