Gate Air Spacer Protection During Self-Aligned Source/Drain Via Etching
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Solution Overview
Problem
Conventional semiconductor fabrication methods fail to adequately protect gate air spacers during source/drain via hole etching, leading to potential electrical shorting between the source/drain via and the gate due to misalignment and the 'tiger-tooth' issue, which degrades device yield and performance.
Innovation Solution
A uniquely shaped etching-stop layer is formed to protect the gate air spacers during the etching process, ensuring they are not inadvertently punched through, and the source/drain via is self-aligned with the source/drain contact, optimizing the process window and preventing electrical shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used for source/drain via hole formation, then the etching process is simple and fast, but the gate air spacer is inadvertently punched through causing electrical shorting
Solution Approach 1:
The protective layer is segmented into two distinct portions: a first portion with greater thickness disposed over the gate air spacer, and a second portion with lesser thickness disposed over the source/drain contact. This segmentation allows differential protection where the thicker first portion prevents etching of the air spacer while the thinner second portion permits proper via formation, thereby resolving the contradiction between protection precision and structural simplicity.
Solution Approach 2:
The protective layer exhibits local quality variations with different thicknesses in different regions. The first portion has greater thickness specifically over the air spacer region to provide enhanced protection, while the second portion has lesser thickness over the source/drain contact to allow etching penetration. This local differentiation enables precise control of etching depth in different areas, achieving high alignment precision without excessive overall complexity.
2Reliability
If the source/drain via is formed with large process window for self-alignment, then misalignment tolerance is improved, but the risk of punching through air spacer increases
Solution Approach 1:
The protective layer is formed preliminarily before the etching process to pre-establish depth control boundaries. The varying thicknesses are predetermined such that the etching process naturally stops at different depths in different regions, preventing over-etching that would punch through the air spacer. This preliminary structuring enables self-aligned via formation with improved reliability while maintaining etching precision through the built-in thickness gradient.
Solution Approach 2:
The thicker first portion of the protective layer acts as a cushioning layer over the air spacer, providing a safety margin against etching penetration. This beforehand cushioning ensures that even with process variations or misalignment, the etching process will not punch through the air spacer, thereby enhancing device reliability without requiring extremely precise etching depth control.
3Reliability
If a thick protective layer is used to protect air spacer, then protection effectiveness is improved, but the etching process time increases
Solution Approach 1:
The protective layer is segmented into different thickness portions rather than using a uniformly thick layer. The first portion over the air spacer is sufficiently thick to provide effective protection, while the second portion over the source/drain contact is thinner to reduce etching time. This segmentation achieves both protection effectiveness and time efficiency by optimizing thickness locally rather than globally.
Solution Approach 2:
The protective layer exhibits local quality with varying thickness: thicker where protection is critical (over air spacer) and thinner where protection is less critical (over source/drain contact). This local optimization ensures adequate protection effectiveness in vulnerable areas while minimizing unnecessary material removal time in less vulnerable areas, thereby reducing overall etching process time.
Data Source
AI summary
A semiconductor device includes a gate disposed over a substrate. A source/drain is disposed in the substrate. A conductive contact is disposed over the source/drain. An air spacer is disposed between the gate and the conductive contact. A first component is disposed over the gate. A second component is disposed over the air spacer. The second component is different from the first component.