Sub-resolution Assistant Patterns and Dipole Illumination for Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor photolithography techniques face challenges in minimizing mask fabrication loading effects and optical proximity issues, particularly when dealing with dense and isolated patterns, despite advancements like off-axis illumination and double dipole lithography.
Innovation Solution
Incorporating sub-resolution assistant patterns on masks with orientations perpendicular to main patterns, and using dipole illumination that is parallel to the orientation of assistant patterns but perpendicular to the main patterns, to reduce mask fabrication loading and enhance optical proximity, while ensuring the assistant patterns are not printed onto the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If off-axis illumination and double dipole lithography are used to print smaller features, then resolution is improved, but mask fabrication loading effects and optical proximity issues worsen
Solution Approach 1:
The patent applies preliminary action by adding assistant patterns to the mask design before the actual patterning process. These assistant patterns are pre-configured to have the same orientation as the main patterns but with adjusted dimensions (smaller width/space) to compensate for loading effects during fabrication. This preliminary modification to the mask design ensures that the main patterns print with correct dimensions despite the presence of dense and isolated pattern variations.
Solution Approach 2:
The patent employs parameter changes by systematically varying the dimensions of assistant patterns relative to main patterns. Specifically, the assistant patterns are designed with reduced width and spacing parameters compared to their corresponding main patterns. This parameter adjustment allows the assistant patterns to mitigate loading effects without being printed themselves, thereby improving the dimensional accuracy of the main patterns while maintaining process compatibility.
2Manufacturing precision
If assistant patterns are added to reduce loading effects, then pattern fidelity is improved, but mask complexity increases
Solution Approach 1:
The patent applies local quality by making the assistant patterns locally optimized for specific functions rather than uniformly designing the entire mask. Each assistant pattern is strategically placed and dimensioned according to its local context - having the same orientation as adjacent main patterns but with locally adjusted dimensions to address specific loading effects in that region. This localized approach improves pattern fidelity without requiring a complete redesign of the entire mask.
Solution Approach 2:
The patent uses segmentation by dividing the mask design into distinct functional components: main patterns that define the final circuit geometry and assistant patterns that serve as optical proximity correction elements. This segmentation allows independent optimization of each component's dimensions and placement, enabling the assistant patterns to be tuned for loading effect compensation while keeping the main patterns intact for their primary patterning function.
3Manufacturing precision
If dipole illumination is used perpendicular to main patterns, then optical proximity is enhanced, but assistant patterns may be printed onto substrate
Solution Approach 1:
The patent employs parameter changes by carefully controlling the dimensions of assistant patterns, specifically setting their width and spacing parameters below the printing threshold of the dipole illumination system. The assistant patterns are designed with reduced dimensions compared to main patterns, ensuring they fall into the sub-resolution regime for the given illumination conditions. This parameter optimization allows the dipole illumination to enhance optical proximity for main patterns while automatically suppressing the printing of assistant patterns.
Solution Approach 2:
The assistant patterns serve as an intermediary element between the illumination system and the main patterns. By placing these intermediate structures on the mask with specific orientations and dimensions, they mediate the optical interaction to improve proximity effects for the main patterns while their sub-resolution characteristics prevent them from being printed, thus acting as a beneficial intermediary that enhances overall patterning quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively alleviates mask fabrication loading effects and enhances pattern fidelity by enlarging the design window for photolithography, ensuring high contrast and minimal imaging errors for main patterns while preventing unwanted printing of assistant patterns.
Implementation Method 1
a diffractive optical element (DOE) for directing a radiation having an aerial image of the main patterns onto the workpiece
Data Source
AI summary
A photolithography system includes a substrate stage for holding a workpiece, and a mask having main patterns and sub-resolution assistant patterns. The system further includes a diffractive optical element (DOE) for directing a radiation having an aerial image of the main patterns onto the workpiece. The DOE includes a first pair of poles that is positioned symmetrically about a center of the DOE along a first direction. The main patterns are oriented lengthwise along a second direction that is perpendicular to the first direction. The sub-resolution assistant patterns are oriented lengthwise along the first direction.