Phase-Balanced Scattering Bar Placement for Sub-Wavelength Lithography
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Solution Overview
Problem
Current methods struggle to achieve satisfactory printing performance for sub-wavelength pitch features in photolithography, particularly for two-dimensional features like contact or via holes, due to difficulties in optimizing the placement of scattering bars using rule-based approaches.
Innovation Solution
A model-based method is introduced for automatically applying phase-balanced scattering bars to mask designs, utilizing interference maps to determine the placement of 0-phase and π-phase assist features, ensuring non-printability and maintaining process latitude for main design features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rule-based approaches are used to place scattering bars, then the process is simple and automated, but satisfactory printing performance for sub-wavelength pitch features cannot be achieved
Solution Approach 1:
The patent changes the placement parameters of scattering bars from fixed rule-based values to variable parameters optimized through interference map analysis. By calculating constructive and destructive interference patterns, the system determines optimal scattering bar positions that enhance imaging performance for sub-wavelength features while maintaining manufacturability.
Solution Approach 2:
The patent implements a feedback mechanism where interference maps are generated based on the target pattern, used to determine scattering bar placements, and then re-evaluated to assess imaging performance. This iterative feedback loop allows the system to optimize scattering bar positions automatically without requiring complex manual intervention.
2Manufacturing precision
If assist features are added to enhance imaging of target features, then imaging performance improves, but assist features may be printed on the substrate which is undesirable
Solution Approach 1:
The patent applies local quality by placing scattering bars with specific properties (phase, size, orientation) at specific locations determined by interference map analysis. Each scattering bar is locally optimized to provide constructive interference for target features while maintaining sub-resolution characteristics to prevent unwanted printing. The scattering bar parameters vary by location to achieve the desired local effect.
Solution Approach 2:
The patent changes the parameters of assist features (scattering bars) by determining their phase, size, and position based on interference map analysis. By carefully controlling these parameters, the system enhances imaging of target features while keeping the assist features themselves below the printing threshold, thus preventing unwanted printing.
3Manufacturing precision
If scattering bars are placed to enhance imaging, then target feature imaging improves, but process latitude for main features may be reduced
Solution Approach 1:
The patent optimizes scattering bar parameters (phase, size, position) to achieve the right balance between enhancing target feature imaging and maintaining process latitude. By using interference map analysis, the system identifies placements that provide maximum imaging enhancement while staying within the process window, thus preserving reliability.
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 enhances imaging performance by preventing the printing of assist features while optimizing the imaging of target features, allowing for a full-pitch range of deep sub-wavelength mask patterns under various illumination conditions.
Implementation Method 1
a radiation system for providing a projection beam of radiation; a mask table for holding a mask, serving to pattern the projection beam; a projection system for projecting the patterned projection beam onto a target portion of the substrate
Implementation Method 2
determining a first interference map based on the target pattern, which defines areas of constructive interference between at least one of the features to be imaged and a field area adjacent the at least one feature to be imaged
Data Source
AI summary
A method of generating a mask design having optical proximity correction features disposed therein. The methods includes the steps of obtaining a desired target pattern having features to be imaged on a substrate; determining a first interference map based on the target pattern, which defines areas of constructive interference between at least one of the features to be imaged and a field area adjacent the at least one feature; placing a first set of assist features having a first phase in the mask design based on the areas of constructive interference defined by the first interference map; determining a second interference map based on the first set of assist features, which defines areas of constructive interference between assist features of the first set of assist features and a field area adjacent at least one of the assist features of the first set of assist features; and placing a second set of assist features having a second phase in the mask design based on the areas of constructive interference defined by the second interference map, wherein the first phase does not equal the second phase.