Polarized Illumination Optics for 1D Lithography Resolution
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Solution Overview
Problem
Existing optical systems for lithographic projection exposure apparatuses face challenges in achieving high structure resolution and manageable optical design properties, particularly when imaging one-dimensional object structures.
Innovation Solution
The optical system is designed with an illumination optical unit that polarizes illumination light parallel to the shorter field extent, using polarization deflection mirrors to achieve a pupil aspect ratio greater than 3, allowing for efficient imaging of one-dimensional structures with reduced production costs and installation space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the optical system uses conventional illumination without polarization control, then the optical design is simpler, but the structure resolution and image contrast are insufficient
Solution Approach 1:
The patent applies parameter changes by controlling the polarization state of illumination light as a key physical parameter. By setting the polarization direction parallel to the shorter field extent and using polarization-defining optical components, the system achieves enhanced image contrast and structure resolution for one-dimensional patterns without requiring fundamentally new optical architectures
Solution Approach 2:
The patent employs asymmetry in the pupil design with a pupil aspect ratio greater than 3, creating an asymmetric illumination distribution that matches the one-dimensional structure geometry. This asymmetric pupil configuration, combined with polarized light, optimizes the imaging of line-like structures while maintaining manageable optical design
2Productivity
If the optical system uses a circular pupil with aspect ratio close to 1, then the illumination is uniform in all directions, but the imaging of one-dimensional structures is less efficient and requires larger optical components
Solution Approach 1:
The patent transforms the conventional circular pupil into an asymmetric pupil with aspect ratio greater than 3, elongating the pupil extent in the direction perpendicular to the one-dimensional structures. This asymmetric configuration concentrates the illumination angles where they are most useful for imaging line structures, improving throughput while allowing smaller optical components
Solution Approach 2:
The patent applies local quality by tailoring the illumination characteristics specifically for one-dimensional structures. The asymmetric pupil and polarized light provide locally optimized illumination in the direction perpendicular to the structures, while reducing illumination in directions where it would not contribute to imaging the one-dimensional patterns
3Manufacturing precision
If the illumination light is polarized parallel to the shorter field extent, then the image contrast and structure resolution are improved, but the optical components must maintain precise polarization control
Solution Approach 1:
The patent applies preliminary action by defining the polarization state of illumination light before it reaches the object plane. Optical components in the illumination path are configured in advance to establish the required polarization direction parallel to the shorter field extent, ensuring that the main imaging optics receive pre-conditioned light that enhances contrast without requiring precise polarization control during operation
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 design facilitates high throughput and resolution in imaging one-dimensional structures by controlling the polarization state, reducing optical component size and installation space, and optimizing object illumination.
Implementation Method 1
The illumination optical unit is embodied such that the illumination light which impinges on the object field is polarized in a polarization direction that extends parallel to the shorter field extent along the second field coordinate
Implementation Method 2
using polarization deflection mirrors to achieve a pupil aspect ratio greater than 3
Data Source
AI summary
An illumination optical unit serves for use in a lithographic projection exposure apparatus. The illumination optical unit serves to guide illumination light from a light source toward an object field. A structured object is arranged in the object field. The illumination optical unit is embodied such that the object field illuminated by the illumination optical unit has a field extent along a first field coordinate and a field extent, shorter in comparison, along a second field coordinate perpendicular thereto. The illumination optical unit is embodied such that the illumination light which impinges on the object field is polarized in a polarization direction that extends parallel to the shorter field extent along the second field coordinate. This yields an illumination optical unit which, firstly, can offer a high structure resolution and, secondly, can impose manageable properties on the optical design.