Via-to-Buried Power Rail Spacer Structure for Gate Isolation
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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, which is formed in the gate cut trench to replace the damaged region, reducing the likelihood of gate-end shorts by maintaining electrical isolation between the VBPR contact and the functional gate structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a VBPR contact structure is formed using conventional etching processes, then power rail connections are established, but gate-end shorts occur due to lithographic mis-alignment damaging the dielectric spacer
Solution Approach 1:
The patent applies preliminary action by forming a replacement dielectric spacer in the gate cut trench before the VBPR contact structure etching process. This pre-positioned spacer serves as a protective measure that prevents gate-end shorts during the subsequent etching operation, eliminating the need for perfect lithographic alignment.
Solution Approach 2:
The replacement dielectric spacer acts as a cushioning element positioned beforehand in the gate cut trench. It provides a protective buffer that absorbs or prevents the harmful effect of etching mis-alignment, ensuring that the gate structure is not damaged even when lithographic alignment is not perfect.
2Ease of manufacture
If the dielectric spacer is damaged during VBPR formation, then contact openings can be etched, but electrical isolation is compromised leading to shorts
Solution Approach 1:
The patent applies local quality by providing different dielectric spacer configurations in different locations. The replacement dielectric spacer is specifically positioned in the gate cut trench region where it is needed for protection, while the original dielectric spacer remains in other areas. This localized approach maintains electrical isolation precisely where the VBPR contact structure formation requires it.
Data Source
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.