Optical Lithography Illumination Pupil Optimization
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Solution Overview
Problem
Current optical lithography techniques face challenges in effectively combining illumination and polarization to achieve optimal resolution for both X and Y orientations in integrated circuit design, leading to inadequate performance, especially for asymmetrical patterns and off-contact designs, due to complexity and cost issues in implementation.
Innovation Solution
The method involves bisecting the illumination pupil plane into elements, selecting preferred elements for IC design features, evaluating performance at different polarization states, and synthesizing optimal illumination and polarization conditions at various intensity ratios to meet design tolerance requirements, specifically addressing sub-resolution assisted features for improved imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dipole X and dipole Y are combined together (cross pole) to improve lithography capability for both directions, then lithography capability for both directions is compromised
Solution Approach 1:
The patent applies dynamics by making the illumination source configuration adjustable and reconfigurable. Instead of using a fixed cross-pole configuration, the system dynamically switches between different illumination modes (dipole X, dipole Y, annular, etc.) based on the specific pattern orientation being printed. This allows optimal illumination conditions to be applied for each orientation separately, resolving the contradiction between versatility and performance.
Solution Approach 2:
The patent changes illumination parameters (source shape, polarization state, numerical aperture) based on the specific design requirements. By adjusting these parameters dynamically according to whether X-orientation or Y-orientation features are being printed, the system achieves optimal performance for each orientation without the degradation caused by fixed composite configurations.
2Manufacturing precision
If SMO and SMPO techniques are used to address illumination and polarization optimization, then expected performance improvement is not realized due to implementation complication and cost
Solution Approach 1:
The patent segments the illumination optimization problem into separate, manageable components: source shape optimization and polarization optimization. Instead of simultaneously optimizing all parameters together (which creates complexity), the system addresses each aspect independently using simplified models, then combines the results. This segmentation reduces implementation complexity while maintaining imaging performance.
Solution Approach 2:
The patent uses simplified computational models that copy the essential physics of illumination and polarization effects without requiring full-blown SMO/SMPO simulations. These simplified models capture the key relationships between source parameters and imaging performance, enabling practical implementation without the prohibitive complexity of complete source-mask-polarization co-optimization.
3Measurement precision
If each point or pixel source has its own illumination profile and polarization characteristics for precise optimization, then implementation becomes almost impossible and very time consuming and costly
Solution Approach 1:
The patent applies local quality by assigning different illumination profiles and polarization characteristics to different regions of the pupil plane corresponding to specific source elements. Each source element (annular, dipole, quadrupole) has locally optimized parameters tailored to its function, rather than applying uniform parameters across the entire illumination system. This localized optimization achieves precision without requiring individual pixel-level customization.
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 optimizes illumination and polarization for advanced optical lithography, enhancing imaging performance and yield by identifying optimal conditions for entire IC designs, particularly improving NILS by 21-81% for asymmetrical and symmetrical patterns.
Implementation Method 1
an optical system (e.g. a scanner) is used to transfer a circuit design to a substrate through an optical radiation illumination system and projection system
Implementation Method 2
The mask selectively blocks, transmits, or otherwise modifies light from the light source to define a pattern on the object
Implementation Method 3
a projection system having a numerical aperture (NA) used to project the pattern onto a resist-coated substrate
Data Source
AI summary
Embodiments of the invention provide approaches for optimizing illumination and polarization for advanced optical lithography. Specifically, an illumination pupil plane of an illumination source is bisected into a plurality of elements. Preferred elements of the illumination pupil plane are selected for a set of integrated circuit (IC) design features. An imaging performance of the set of IC design features for the preferred elements is evaluated at different polarization states to determine an optimal illumination and polarization condition for each IC design feature. Imaging performance of the combined IC design features, evaluated at various optimal illumination and polarization outcomes synthesized at different intensity ratios, is reviewed against a set of design tolerance requirements to finalize optical illumination and polarization conditions for the entire IC design. An optimal illumination and polarization solution is identified for an off-contact pattern with a plurality of sub-resolution assisted features connecting line-line-end portions of main mask features.