Mandrel and Spacer Patterning for Mixed-Density Layouts
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Solution Overview
Problem
Conventional optical lithography technologies struggle to accurately print small device features in integrated circuits due to resolution limits, leading to issues like rounding, pinching, necking, bridging, dishing, and metal line thickness variations, especially in ICs with mixed layout blocks requiring different design rules, which increases space and manufacturing costs.
Innovation Solution
The method involves inserting dummy mandrel patterns between layout blocks to connect line patterns, reducing the space between them, and using spacer patterning techniques to improve pattern density and uniformity, thereby adhering to manufacturing rules without increasing the overall area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If space is provided between layout blocks to accommodate printing inaccuracy, then manufacturing reliability is improved, but IC area increases
Solution Approach 1:
The patent applies preliminary action by inserting dummy mandrel patterns into spaces between layout blocks before the actual patterning process. These dummy patterns pre-establish continuous mandrel structures that guide spacer formation, ensuring that spacers from different layout blocks connect properly without requiring excessive spacing. This preliminary structuring allows reduction of the space between layout blocks while maintaining manufacturing reliability through controlled spacer continuity.
Solution Approach 2:
The patent uses dummy mandrel patterns as intermediary elements between separate layout blocks. These intermediaries serve dual purposes: they fill the spaces between blocks and provide continuous mandrel structures for spacer formation. The dummy mandrels act as mediators that enable spacer connection across layout block boundaries, allowing reduced spacing while maintaining pattern accuracy and manufacturing reliability.
2Device complexity
If conventional optical lithography is used for small device features, then manufacturing process simplicity is maintained, but pattern accuracy deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the patterning process into two distinct stages: first forming mandrel patterns using conventional optical lithography, then forming spacer patterns through a separate deposition and etching process. This segmentation allows each stage to be optimized independently - the mandrel formation uses simple optical lithography while the spacer formation provides the enhanced precision needed for small device features, ultimately achieving high pattern accuracy without requiring advanced lithography throughout the entire process.
Solution Approach 2:
The mandrel patterns serve as intermediary structures that enable the transfer of patterns from conventional optical lithography to the final high-precision spacer structures. The mandrels act as templates or mediators that capture the lithographic pattern and guide the subsequent spacer formation, allowing conventional lithography to produce accurate small features through the intermediary mandrel-spacer mechanism rather than requiring direct high-resolution lithography.
3Manufacturing precision
If spacer patterning is used to improve pattern density, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The patent merges the dummy mandrel patterns with the functional mandrel patterns into a single continuous mandrel structure. Rather than treating dummy patterns as separate entities, they are integrated with the actual device patterns to form unified mandrels that simultaneously serve pattern definition and spacer connection functions. This merging simplifies the overall process by eliminating the need for separate dummy pattern removal steps and reducing process complexity while maintaining the precision benefits of spacer patterning.
Solution Approach 2:
The dummy mandrel patterns are designed to serve multiple functions: they fill spaces between layout blocks, provide continuous mandrel structures for spacer formation, and enable spacer connection across block boundaries. By making the dummy patterns multi-functional, the patent eliminates the need for separate structures for each function, thereby reducing overall process complexity while achieving high pattern density and precision through spacer patterning.
Data Source
AI summary
A method of fabricating a semiconductor device includes generating at least one photomask based on a layout and forming a plurality of active patterns on a substrate, using the at least one photomask. The layout includes a plurality of first patterns that extend parallel to each other in a first direction on a low-density region of the layout and a plurality of second patterns that extend parallel to each other in the first direction on a high-density region of the layout. The forming of the plurality of active patterns includes using the first patterns and the second patterns of the layout to respectively form a plurality of first active patterns and a plurality of second active patterns on the substrate.