Anamorphic Projection Demagnification for EUV Lithography
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Solution Overview
Problem
Conventional lithographic methods face challenges in reducing the critical dimension of features due to limitations in wavelength, numerical aperture, and demagnification, particularly in the y-direction, which affects the achievable resolution and throughput in manufacturing miniature ICs and other devices.
Innovation Solution
A lithographic apparatus with an anamorphic projection system that provides greater demagnification in the y-direction than in the x-direction, using EUV radiation and a support structure for a mask with a patterned area that allows scanning and projection with specific demagnification values, enabling the formation of smaller features on a substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the demagnification in the y-direction is increased to reduce the critical dimension, then the resolution is improved, but the throughput is reduced
Solution Approach 1:
The patent applies asymmetric demagnification by configuring the projection system to have different demagnification factors in the x-direction and y-direction. Specifically, the demagnification in the y-direction is set greater than 4× (e.g., 5×, 6×, or higher) while the demagnification in the x-direction remains at the conventional 4×. This asymmetric configuration allows the critical dimension to be reduced in the y-direction without proportionally reducing the exposure field size, thereby maintaining throughput while improving resolution.
2Manufacturing precision
If the numerical aperture on the substrate side is increased to improve resolution, then the critical dimension is reduced, but the complexity of the projection system increases
Solution Approach 1:
The patent changes the demagnification parameter of the projection system from a conventional uniform value (4× in both directions) to an asymmetric value (greater than 4× in the y-direction). This parameter change allows the numerical aperture on the substrate side to be effectively increased in the y-direction, improving resolution and reducing the critical dimension, while the overall system complexity is managed by building upon the conventional lithographic apparatus architecture.
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 reduces the critical dimension of features in the y-direction while maintaining or improving throughput by increasing the numerical aperture on the substrate side without increasing it on the mask side, thus enhancing the resolution and efficiency of the lithographic process.
Implementation Method 1
the projection system has a demagnification in the scanning direction which is greater than a demagnification in a second direction which is perpendicular to the scanning direction and wherein the demagnification in the second direction is greater than 4×
Implementation Method 2
an extreme ultraviolet (EUV) radiation source may be used. EUV radiation may be considered to be radiation having a wavelength within the range 4-20 nm
Data Source
AI summary
A lithographic apparatus including a support structure constructed to support a mask having a patterned area which is capable of imparting an EUV radiation beam with a pattern in its cross-section to form a patterned radiation beam, wherein the support structure is movable in a scanning direction, a substrate table constructed to hold a substrate, wherein the substrate table is movable in the scanning direction, and a projection system configured to project the patterned radiation beam onto an exposure region of the substrate, wherein the projection system has a demagnification in the scanning direction which is greater than a demagnification in a second direction which is perpendicular to the scanning direction and wherein the demagnification in the second direction is greater than 4×.