Reticle Masking Blade Positioning for EUV Lithography
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Solution Overview
Problem
Extreme ultraviolet lithography systems face challenges in maintaining critical dimension uniformity due to diffraction effects and penumbral light exposure, which can lead to irregularities in pattern formation on semiconductor substrates, affecting the electrical properties of fabricated devices.
Innovation Solution
The implementation of a method to control the positioning of reticle masking blades in extreme ultraviolet lithography tools, using a position sensor and controller to adjust the blades to minimize offset and penumbral exposure, thereby ensuring uniform critical dimension across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reticle masking blades are used to define exposure areas, then pattern formation is enabled, but diffraction and penumbral light cause critical dimension non-uniformity
Solution Approach 1:
The patent converts the harmful diffraction effect into a beneficial tool by intentionally designing penumbral regions in the reticle pattern. These penumbral regions compensate for the natural diffraction that occurs at the boundaries of exposure areas, thereby maintaining critical dimension uniformity across the substrate. The masking blades' diffraction is harnessed rather than merely mitigated.
Solution Approach 2:
The patent applies different pattern characteristics to different regions of the reticle. Specifically, penumbral regions are introduced at boundaries between exposure areas where diffraction effects are most pronounced, while other regions maintain standard pattern density. This localized modification addresses the harmful effects precisely where they occur without affecting the entire reticle.
2Manufacturing precision
If optical proximity correction is applied to compensate for diffraction, then pattern accuracy improves, but device complexity increases
Solution Approach 1:
The patent incorporates penumbral regions directly into the reticle pattern design before fabrication. This preliminary incorporation of diffraction compensation features eliminates the need for complex post-fabrication optical proximity correction algorithms and calculations, thereby reducing device complexity while maintaining pattern accuracy.
3Manufacturing precision
If reticle masking blade position is not precisely controlled, then device operation is simpler, but critical dimension uniformity deteriorates
Solution Approach 1:
The patent implements a feedback control system that includes a sensor to detect the actual position of reticle masking blades and a controller that adjusts blade positions based on detected deviations from target positions. This feedback mechanism ensures precise critical dimension uniformity while automating the positioning control to maintain ease of operation.
4Manufacturing precision
If penumbral regions are introduced in reticle patterns, then diffraction effects are compensated, but reticle manufacturing complexity increases
Solution Approach 1:
The patent introduces penumbral regions only at specific locations in the reticle pattern where diffraction compensation is needed, rather than modifying the entire reticle. This localized approach minimizes the impact on reticle manufacturing complexity while achieving the desired critical dimension uniformity improvement.
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 critical dimension uniformity to within 1 nm by reducing the impact of diffraction and penumbral light, ensuring consistent pattern formation and device performance.
Implementation Method 1
Lithography resolution is negatively impacted by diffraction
Data Source
AI summary
A method of controlling reticle masking blade positioning to minimize the impact on critical dimension uniformity includes determining a target location of a reticle masking blade relative to a reflective reticle and positioning the reticle masking blade at the target location. A position of the reticle masking blade is monitored during an imaging operation. The position of the reticle masking blade is compared with the target location and the position of the reticle masking blade is adjusted if the position of the reticle masking blade is outside a tolerance of the target location.