Catadioptric Projection Optics for High-NA Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithographic projection optics systems are limited by numerical aperture (NA) and field size, leading to low optical throughput and resolution, especially when using high-rep-rate lasers with broader spectral bandwidths, and they often require beamsplitters which are inefficient and restrict the use of hyper-NA illumination.
Innovation Solution
The design incorporates a spatial light modulator (SLM) with non-telecentric off-axis illumination and a catadioptric projection lens system, utilizing a fluid like water between the substrate and the last optical element to achieve a numerical aperture of 1.0 or more, allowing for higher reduction ratios and improved resolution with a spectral bandwidth of 1 picometer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a beamsplitter is used in the illumination system, then the system can achieve high NA and field size, but the light transmission efficiency becomes highly inefficient and the use of azimuthally-polarized light is precluded
Solution Approach 1:
The patent removes the beamsplitter from the optical system entirely, extracting this problematic component that was causing light transmission inefficiency and polarization restrictions. The illumination system is redesigned to work directly with the projection optics without requiring a beamsplitter, thereby achieving high light transmission efficiency while maintaining high NA and field size capabilities.
Solution Approach 2:
Instead of using a beamsplitter to divide and redirect light paths, the patent inverts the approach by designing a direct optical path where illumination and projection work together without beam splitting. This inversion eliminates the need for beamsplitters and enables the use of azimuthally-polarized light for higher resolution.
2Adaptability or versatility
If prior-art catadioptric optical designs are used with lasers having spectral bandwidths of the order of 1 pm, then the system can operate with broader spectral bandwidths, but unacceptable loss of image contrast occurs
Solution Approach 1:
The patent modifies the optical design parameters of the catadioptric system to accommodate broader spectral bandwidths (order of 1 pm) while maintaining image contrast. This involves adjusting the curvature radii, aperture diameters, and spacing of optical elements to minimize chromatic aberrations across the broader spectrum, enabling versatile laser source selection without sacrificing manufacturing precision or image quality.
3Manufacturing precision
If projection optics with NA 1.35 and 26 mm field size are used, then high resolution is achieved, but the optical throughput is limited
Solution Approach 1:
The patent creates a projection optics system that serves multiple functions simultaneously: it achieves high NA (1.35) for resolution, maintains large field size (26 mm) for coverage, and optimizes light throughput by eliminating beamsplitters and using direct illumination paths. The catadioptric design integrates reflective and refractive elements to accomplish all these functions in a single unified system.
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 configuration enables high optical throughput and resolution with a NA of 1.0 or more, supporting 10×, 20×, or 50× reduction ratios and accommodating broader spectral bandwidths, while eliminating the need for beamsplitters and enhancing image contrast.
Implementation Method 1
a spatial light modulator (SLM) from which radiation is reflected and directed to a projection lens
Implementation Method 2
the projection lens comprises a catadioptric projection lens
Implementation Method 3
a catadioptric projection lens arrangement, and utilize the off axis, non tele-centric illumination of the SLM, to reflect illumination
Implementation Method 4
a fluid (e.g. water) is provided between the substrate and the last optical element of the projection lens
Data Source
AI summary
Projection optics for a lithographic projection system is provided that comprises a spatial light modulator (SLM) from which radiation is reflected and directed to a projection lens that projects the radiation to a substrate. The SLM is illuminated by non telecentric off axis illumination (e.g. from laser radiation that has a spectral bandwidth of the order of 1 picometer, and the projection optics is configured for significant reduction (e.g. at least 10× reduction, 20× reduction, or 50× reduction).