Fin End Isolation Structure for Uniform FinFET Epitaxy
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Solution Overview
Problem
The challenge in semiconductor manufacturing is to reduce the layout-dependent effect (LDE) on semiconductor fins caused by isolation structures, which affects the uniformity of fin profiles and epitaxial growth in ICs, particularly in FinFET and GAA devices, leading to non-uniform source/drain trench etching and epitaxial growth across different areas.
Innovation Solution
A new fabrication process is introduced that involves forming isolation features between the ends of semiconductor fins, using a combination of gate spacer layers and inter-layer dielectric layers to reduce stress and enhance uniformity, while self-aligned fin-cutting techniques ensure vertical alignment with gate stacks, thereby improving the uniformity of gate structures and epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures are formed between semiconductor fins, then electrical isolation between fins is improved, but layout-dependent effects increase causing non-uniform fin profiles and epitaxial growth
Solution Approach 1:
The isolation structure is segmented into multiple portions: a first isolation portion extending between adjacent fins and a second isolation portion extending between the fin and the substrate. This segmentation allows different regions of the isolation structure to serve different functions, reducing layout-dependent effects while maintaining electrical isolation.
Solution Approach 2:
Different portions of the isolation structure have different depths and properties. The first isolation portion has a different depth than the second isolation portion, creating local variations that compensate for stress-induced variations and reduce layout-dependent effects on fin profile uniformity.
2Reliability
If isolation structures are formed between semiconductor fins, then electrical isolation between fins is improved, but epitaxial growth uniformity deteriorates across different areas
Solution Approach 1:
The isolation structure is divided into multiple portions at different depths, allowing selective stress compensation in different regions. This segmentation enables the isolation structure to uniformly support epitaxial growth across the substrate while maintaining electrical isolation.
Solution Approach 2:
The first isolation portion and second isolation portion have different depths and are positioned at different locations. This creates local quality variations that compensate for stress-induced variations, ensuring uniform epitaxial growth across different areas of the substrate.
3Reliability
If deeper isolation structures are used to improve electrical isolation, then isolation effectiveness increases, but stress-induced variations in fin profiles increase
Solution Approach 1:
The isolation structure is segmented into a first isolation portion and a second isolation portion at different depths. This segmentation distributes the isolation function across multiple levels, reducing the stress concentration that would occur with a single deep isolation structure.
Solution Approach 2:
Different portions of the isolation structure have different depths tailored to local requirements. The first isolation portion extends to a first depth while the second isolation portion extends to a second depth, creating local quality variations that reduce stress-induced variations in fin profiles.
Data Source
AI summary
A semiconductor structure includes a substrate, and first and second semiconductor fins extending from the substrate and lengthwise aligned along a first direction. The semiconductor structure further includes an isolation structure over the substrate and adjacent to sidewalls of the semiconductor fins, and first and second gate structures oriented lengthwise along a second direction generally perpendicular to the first direction. The first and the second gate structures are disposed over the isolation structure. The first gate structure is disposed over the first semiconductor fin. The second gate structure is disposed over the second semiconductor fin. The semiconductor structure further includes a spacer layer that is disposed on a sidewall of the first gate structure and on a sidewall of the second gate structure and extends continuously through a trench between an end of the first semiconductor fin and an end of the second semiconductor fin.