Lithography Flare Map Correction via Density and PSF Simulation
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Solution Overview
Problem
Current lithographic systems face challenges in accurately modeling and efficiently reducing flare effects, particularly in EUV and DUV lithography, which impact image contrast and critical dimension control due to system-induced flare effects.
Innovation Solution
A method is introduced to simulate a flare map by combining a density map of the design layout with a point spread function (PSF), incorporating system-specific effects such as reflections from the mask border, reticle-masking blades, and gas-lock sub-aperture, and applying location-dependent flare corrections to reduce flare effects in two stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional flare correction methods are used, then computational simplicity is maintained, but flare effect reduction accuracy is insufficient
Solution Approach 1:
The flare correction process is divided into two distinct stages: first applying optical enhancement features (OEF) to the design layout, then generating the flare map from the OEF-modified layout. This segmentation allows each stage to be optimized independently, improving overall accuracy without proportionally increasing computational complexity.
Solution Approach 2:
Optical enhancement features are applied to the design layout before generating the flare map. This preliminary action modifies the layout to account for optical effects, which then serves as the basis for more accurate flare map generation, thereby improving the overall correction accuracy.
2Manufacturing precision
If location-dependent flare corrections are applied, then critical dimension control is improved, but processing time increases
Solution Approach 1:
Location-dependent flare corrections are applied based on the spatial distribution of features in the design layout. Different regions of the exposure field receive customized corrections tailored to their specific flare conditions, improving critical dimension control where it is most needed while avoiding unnecessary processing in regions with minimal flare effects.
Solution Approach 2:
The flare map generation incorporates system-specific parameters such as numerical aperture, illumination conditions, and wavelength to accurately model flare effects. By adjusting these parameters based on the specific lithography system and exposure conditions, the correction process achieves high precision without requiring excessive computational resources.
3Measurement precision
If system-specific flare effects are incorporated in simulation, then flare reduction accuracy is improved, but model complexity increases
Solution Approach 1:
System-specific flare effects are incorporated by adjusting key simulation parameters including numerical aperture (NA), illumination wavelength, and illumination angular distribution. These parameter changes allow the simulation model to accurately reflect the specific lithography system being used, improving flare map accuracy without requiring a complete overhaul of the simulation framework.
Solution Approach 2:
The flare map generation process creates a computational representation (copy) of the actual lithography system's flare characteristics. By simulating the system-specific effects in a virtual model and applying the resulting corrections to the design layout, the method achieves high accuracy without modifying the physical lithography system itself.
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 improves the accuracy of flare map modeling, reduces flare effects, and enhances process latitude and critical dimension control, while maintaining computational efficiency and mask manufacturability.
Implementation Method 1
incorporating system-specific effects such as reflections from the mask border, reticle-masking blades, and gas-lock sub-aperture
Implementation Method 2
flare effects which impact image contrast and critical dimension control due to system-induced flare effects
Data Source
AI summary
A method for reducing an effect of flare produced by a lithographic apparatus for imaging a design layout onto a substrate is described. A flare map in an exposure field of the lithographic apparatus is simulated by mathematically combining a density map of the design layout at the exposure field with a point spread function (PSF), wherein system-specific effects on the flare map may be incorporated in the simulation. Location-dependent flare corrections for the design layout are calculated by using the determined flare map, thereby reducing the effect of flare.