EUV Illumination System Using 1D Patterned Mask
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Solution Overview
Problem
Current EUV lithographic systems are complex and costly due to their 2D pattern imaging requirements, leading to inefficient optical power usage, sensitivity to reticle defects, and tight optical aberration demands, making them economically unattractive for printing simplified geometries.
Innovation Solution
A catoptric system with a reflective pattern-source and a simplified optical train using only three optical components, including a primary and secondary reflector, to transfer EUV radiation and form a high spatial frequency image of a 1D pattern with reduced optical power and increased efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a general-purpose EUV system with 2D pattern imaging is used, then arbitrary 2D patterns can be transferred onto the substrate, but the system complexity and cost increase substantially
Solution Approach 1:
The patent segments the 2D pattern transfer problem into two separate 1D pattern transfers. By using two 1D reticles (first and second reticles with first and second 1D patterns respectively) and transferring them sequentially to form a composite 2D pattern on the substrate, the system avoids the complexity of imaging arbitrary 2D patterns directly while still achieving versatile pattern transfer capability
Solution Approach 2:
The system employs periodic action by performing sequential exposure steps: first exposing the substrate with the first 1D pattern, then exposing with the second 1D pattern. This periodic exposure process allows complex 2D patterns to be built up from simpler 1D patterns, reducing the instantaneous optical complexity while maintaining pattern transfer versatility
2Manufacturing precision
If a general-purpose EUV system with multiple moving stages is used, then complete pattern transfer is achieved, but productivity decreases due to reduced exposures per unit time
Solution Approach 1:
The patent divides the pattern transfer into segmented 1D exposures rather than requiring complete 2D pattern imaging in one step. Each 1D pattern can be transferred more quickly with simpler optics, and the segmented approach allows for faster cycle times between exposures, improving overall productivity while maintaining precision through the sequential building of the complete pattern
Solution Approach 2:
The system uses partial action by transferring only 1D patterns in each exposure step rather than complete 2D patterns. This partial transfer approach reduces the complexity and time required for each individual exposure, allowing more exposures to be performed per unit time, while the complete pattern emerges after multiple partial exposures
3Manufacturing precision
If a general-purpose EUV system with six polished mirrors is used, then high-resolution imaging is achieved, but operational cost increases substantially
Solution Approach 1:
The patent segments the optical imaging task into simpler 1D imaging operations rather than requiring complex 2D imaging with six mirrors. Each 1D pattern can be imaged with fewer optical components, reducing the mirror count and associated costs while maintaining the required imaging resolution for each exposure step
Solution Approach 2:
The system employs simpler, less expensive optical components for 1D pattern imaging rather than investing in six highly polished mirrors with sub-0.1 nm surface roughness. The reduced optical complexity lowers the cost of design and fabrication while still achieving sufficient resolution for 1D pattern transfer, making the system more economically attractive
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
The solution enables cost-effective high-resolution imaging of dense line patterns, reducing the number of reflective surfaces and operational complexity, thus lowering the cost and improving the efficiency of EUV lithography systems.
Implementation Method 1
a reflective pattern source configured to receive the EUV radiation from the IU and to diffract such EUV radiation to form first and second diffracted beams of the EUV radiation
Implementation Method 2
a combination of only three optical components disposed sequentially with respect to one another to transfer an EUV radiation (incident on a first optical component from the only three optical components) onto the pattern-source
Implementation Method 3
configured to form an optical image of the pattern-source (with a reduction factor N>1 on an image plane, which plane is optically-conjugate to the pattern-source)
Data Source
AI summary
A catoptric system having a reference axis and including a reflective pattern-source (carrying a substantially one-dimensional pattern) and a combination of only three optical components disposed sequentially to transfer EUV radiation incident the first optical component onto the pattern-source. The combination is disposed in a fixed spatial and optical relationship with respect to the pattern-source, and represents an illumination unit (IU) of a 1D EUV exposure tool that additionally includes a projection optic sub-system configured to form an optical image of the pattern-source on an image plane with the use of only two beams of radiation. These only two beams of radiation originate at the pattern-source from the EUV radiation transferred onto the pattern-source.