Spatially Varying Polarization for Low k1 Lithography
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Solution Overview
Problem
Current lithographic techniques face challenges in optimizing polarization conditions for complex two-dimensional patterns in device manufacturing, particularly at low k1 values, where standard polarization methods may not provide the best imaging results.
Innovation Solution
The method involves determining an optimized or beneficial illumination polarization condition by selecting predefined spatially varying or custom polarization conditions, incorporating non-traditional polarization types such as TM/TE, diagonal, and Y+X polarization, and varying polarization directionality in the source pupil plane, enhancing conventional Source Mask Optimization (SMO) through Source Mask Polarization Optimization (SMPO).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard polarization conditions (X, Y, X+Y, TM, TE) are used, then the imaging process is simple and well-defined, but image contrast and lithographic response are insufficient for complex two-dimensional patterns at low k1 values
Solution Approach 1:
The patent applies parameter changes by transitioning from standard discrete polarization conditions to continuous spatially varying polarization states. The polarization direction and magnitude are varied continuously across the source pupil plane according to a spatial distribution function, enabling optimization of image contrast for complex two-dimensional patterns at low k1 values while maintaining controllable process parameters.
Solution Approach 2:
The patent implements dynamics by introducing spatially varying polarization conditions that can be dynamically adjusted across different regions of the source pupil plane. The polarization state becomes a dynamic parameter that varies with position, allowing adaptive optimization of lithographic response for different pattern features within the same exposure field.
2Manufacturing precision
If conventional Source Mask Optimization (SMO) is used, then the optimization process is straightforward, but it cannot achieve optimal imaging results for complex two-dimensional patterns at low k1 values
Solution Approach 1:
The patent extends conventional SMO by adding the polarization dimension to the optimization space. Instead of optimizing only source shape and mask features, the method incorporates spatially varying polarization states as an additional degree of freedom. This dimensional extension enables optimization of lithographic response for complex two-dimensional patterns that cannot be achieved with conventional SMO alone.
Solution Approach 2:
The optimization process changes parameters by incorporating spatially varying polarization magnitudes and directions as adjustable parameters. The method optimizes a polarization distribution function across the source pupil plane, transforming the optimization from geometric parameters only to include electromagnetic field parameters, thereby achieving superior lithographic response.
3Manufacturing precision
If uniform polarization is applied across the source, then the polarization system is simple, but it cannot provide optimal imaging for all regions of complex two-dimensional patterns
Solution Approach 1:
The patent applies local quality by implementing spatially varying polarization conditions across different regions of the source pupil plane. Each region can have customized polarization magnitude and direction optimized for local pattern features. This localized optimization enables faithful reproduction of complex two-dimensional patterns by addressing the specific imaging requirements of different pattern regions rather than applying a uniform polarization state.
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 image contrast and reduces line edge roughness, enabling successful imaging at lower k1 values by customizing polarization conditions based on specific lithographic responses, thereby enhancing the effectiveness of lithographic processes.
Implementation Method 1
Polarized illumination is a tool to achieve better imaging, especially for a lithographic process having a low k1 value
Data Source
AI summary
Improved low k1 lithographic imaging is disclosed by optimizing or improving an illumination polarization condition. The polarization condition may be a pre-defined spatially varying polarization, or a spatially customized local polarization of bright illumination points based on tracking a value of a desired lithographic response. Several non-traditional polarization conditions, e.g., TM/TE polarization (with or without a central TM region), diagonal polarization, and Y+X polarization (typically for dark field illumination) are disclosed, that offer substantial imaging advantages for specific lithographic problems, especially at low k1 values. The initial polarization definition may be limited to specific fixed polarization angles.