VBPR Contact Spacer Replacement to Prevent Gate-End Shorts
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Solution Overview
Problem
Conventional semiconductor structures face issues with via-to-buried power rail contact structures (VBPR) leading to gate-end shorts due to lithographic mis-alignment during etching, which damages the dielectric spacer and increases the risk of electrical shorts.
Innovation Solution
A semiconductor structure is designed with a dielectric spacer structure comprising a base dielectric spacer and a replacement dielectric spacer to mitigate gate-end shorts, where the damaged region of the dielectric spacer is replaced by a gate cut trench dielectric material, forming a VBPR contact structure with reduced shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional VBPR contact structure formation is used, then power rail connections are established, but gate-end shorts occur due to lithographic mis-alignment during etching
Solution Approach 1:
The patent performs preliminary actions by forming the VBPR contact structure before complete gate patterning, and uses a gate cut trench to protect the dielectric spacer during subsequent processing. This preliminary structuring prevents mis-alignment issues from causing gate-end shorts in later stages.
Solution Approach 2:
The gate cut trench acts as an intermediary protective structure between the VBPR contact etching process and the gate structure. It physically separates and protects the dielectric spacer region, preventing direct exposure to etching that would cause gate-end shorts.
2Ease of manufacture
If dielectric spacer is etched twice during VBPR formation, then contact openings are created, but dielectric spacer integrity is damaged
Solution Approach 1:
The patent segments the dielectric spacer protection into two distinct regions: the VBPR contact region where etching is performed, and the gate region protected by the gate cut trench. This segmentation allows selective etching without compromising overall dielectric spacer integrity.
Solution Approach 2:
The patent converts the potentially harmful repeated etching process into a beneficial selective process by using the gate cut trench as a mask. The etching that would normally damage the dielectric spacer is redirected to only affect intended contact regions, while the trench-protected regions remain intact.
3Productivity
If lithographic mis-alignment occurs during etching, then contact structure is formed, but gate-end shorts increase
Solution Approach 1:
The gate cut trench provides beforehand cushioning protection for the dielectric spacer and gate structure. Even when lithographic mis-alignment occurs during VBPR contact formation, the trench acts as a buffer zone that prevents etching from reaching and shorting the gate ends.
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
A semiconductor structure is provided in which a via to buried power rail (VBPR) contact structure is present that has a via portion contacting a buried power rail and a non-via portion contacting a source/drain region of a first functional gate structure present in a first device region. A dielectric spacer structure including a base dielectric spacer and a replacement dielectric spacer is located between the VPBR contact structure and the first functional gate structure. The replacement dielectric spacer is composed of a gate cut trench dielectric material that is also present in a gate cut trench that is located between the first functional gate structure present in the first device region, and a second functional gate structure that is present in a second device region. The replacement dielectric spacer replaces a damaged region of a dielectric spacer that is originally present during VBPR formation.