EUV Mask Assist Features for Bright Field Defect Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
EUV lithography in semiconductor manufacturing faces challenges with bright field patterning due to defects in EUV masks, particularly in low density layouts, leading to yield and reliability issues.
Innovation Solution
Incorporating dummy or assist features on the EUV mask to increase feature density, which are subsequently removed during the manufacturing process, thereby reducing defect visibility and improving patterning quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bright field patterning is used in low density layouts, then manufacturing simplicity is maintained, but defect visibility increases leading to yield problems
Solution Approach 1:
Dummy features are added to the mask design before lithography to preemptively cover defects. This preliminary action ensures that defects are obscured before the patterning process, preventing yield issues while maintaining bright field patterning simplicity.
Solution Approach 2:
Dummy features act as intermediary elements between the mask defects and the actual pattern features. These intermediary features absorb or obscure the harmful effect of defects, preventing them from affecting the final pattern quality and yield.
2Reliability
If absorber material coverage is increased to cover defects, then defect visibility is reduced, but pattern density increases which is not desirable for bright field patterning
Solution Approach 1:
Instead of uniformly increasing absorber material coverage across the entire mask, dummy features are strategically placed only in specific locations where defects exist. This local approach provides defect coverage precisely where needed without unnecessarily increasing overall absorber material or altering pattern density.
Solution Approach 2:
The solution changes the spatial distribution parameter of absorber material rather than increasing its total quantity. By adding dummy features with absorber material only in defect-prone areas, the local coverage is enhanced while maintaining the overall low density characteristic of bright field patterning.
3Reliability
If dummy features are added to increase feature density, then defect visibility is reduced, but mask complexity increases
Solution Approach 1:
Dummy features are designed as temporary, disposable elements that serve their purpose of defect coverage during lithography and are then completely removed in subsequent processing steps. Their temporary nature means they don't need to be permanent or integrated into the final device, simplifying their design and reducing long-term mask complexity.
Solution Approach 2:
The dummy features are intentionally discarded after serving their defect-masking function. They are removed in later processing steps, leaving no trace in the final device. This approach allows complex mask designs with dummy features without permanently increasing device complexity, as the dummy elements are recovered (removed) after use.
Data Source
AI summary
Techniques for improved extreme ultraviolet (EUV) patterning using assist features, related transistor structures, integrated circuits, and systems, are disclosed. A number of semiconductor fins and assist features are patterned into a semiconductor substrate using EUV. The assist features increase coverage of absorber material in the EUV mask, thereby reducing bright field defects in the EUV patterning. The semiconductor fins and assist features are buried in fill material and a mask is patterned that exposes the assist features and covers the semiconductor fins. The exposed assist features are partially removed and the protected active fins are ultimately used in transistor devices.