Air Spacer Protection in Source/Drain Via Etching
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Solution Overview
Problem
Conventional semiconductor fabrication methods lead to electrical shorting between source/drain via and gate structures due to misalignment and the 'tiger-tooth' issue, where the source/drain via protrudes into air spacers, causing device yield and performance degradation.
Innovation Solution
A uniquely shaped etching-stop layer is formed to protect air spacers during source/drain via hole etching, allowing self-aligned source/drain via formation and preventing electrical shorting by ensuring the air spacers are preserved and the source/drain via is formed with a 'T'-shaped profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional source/drain via hole etching is performed without air spacer protection, then manufacturing process is simpler, but electrical shorting occurs between source/drain via and gate structures
Solution Approach 1:
A protective layer is formed over the air spacer before the source/drain via hole etching process begins. This preliminary protective action ensures that the air spacer is shielded from etching damage before the harmful etching process occurs, preventing the tiger-tooth issue and electrical shorting while maintaining a manageable fabrication process
Solution Approach 2:
The protective layer acts as an intermediary element between the etching process and the air spacer. It allows the etching process to proceed without directly damaging the air spacer, serving as a mediator that enables both the via formation and air spacer preservation to occur simultaneously
2Reliability
If source/drain via is formed with tight alignment to source/drain contact, then electrical shorting is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The protective layer is formed in advance to counteract the potential harmful effect of misalignment during via etching. By establishing this protective barrier before etching, the process tolerates alignment variations without causing electrical shorting, effectively preempting the problem before it can occur
Solution Approach 2:
The protective layer provides a cushioning effect that absorbs the impact of alignment misalignment. Even if the source/drain via is not perfectly aligned with the source/drain contact, the protective layer prevents the via from penetrating into the air spacer, cushioning against the harmful effects of imprecision
3Ease of manufacture
If air spacers are removed during via etching, then etching process is simpler, but parasitic capacitance increases
Solution Approach 1:
The protective layer serves as an intermediary that allows the etching process to proceed without directly contacting or removing the air spacer. This enables the via etching to be performed while preserving the air spacer structure, maintaining low parasitic capacitance without requiring complex selective etching processes
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.