EUV Reticle Multilayer Absorption Stack for Image-Error Compensation
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Solution Overview
Problem
Conventional EUV lithography systems suffer from the penumbra effect, leading to issues with device pattern uniformity and lithographic performance due to heavy absorption of EUV radiation by certain substances.
Innovation Solution
The use of a reticle with a reflective multilayer, capping, and absorption stack designed to minimize EUV absorption and maximize constructive interference, combined with a method for image-error compensation using a light shading member to control exposure fields and record images of specific patterns, which allows for accurate compensation of image distortion caused by the penumbra effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If EUV radiation is used for lithography, then smaller geometric sizes can be achieved, but heavy absorption by certain substances degrades lithographic performance
Solution Approach 1:
The patent employs a composite reticle structure consisting of multiple functional layers: a reflective multilayer (alternating high and low refractive index materials), a capping layer, and an absorption stack with patterned absorber layers. This composite structure minimizes EUV radiation absorption while maintaining pattern fidelity, resolving the contradiction between achieving small geometric sizes and avoiding harmful absorption effects.
Solution Approach 2:
The patent converts the harmful absorption effect into a beneficial measurement tool by using the absorption stack to deliberately absorb EUV radiation and create measurable image errors. These controlled absorption effects are used to characterize penumbra and other optical imperfections, which are then compensated through OPC to improve overall lithographic performance.
2Productivity
If conventional EUV lithography systems are used, then lithography processes can be performed, but the penumbra effect leads to non-uniform device patterns
Solution Approach 1:
The patent implements a feedback-based compensation methodology where image errors are measured using the absorption stack and reflective multilayer structure, then fed back into OPC algorithms to calculate compensation patterns. These compensation patterns are applied to subsequent lithography processes, creating a closed-loop system that continuously improves pattern uniformity and compensates for penumbra effects.
Solution Approach 2:
The patent performs preliminary characterization of optical imperfections (penumbra, defocus, astigmatism) using the specialized reticle structure before actual device manufacturing. This preliminary measurement enables pre-calculation of compensation patterns that are applied in advance to counteract expected imaging errors, ensuring uniform device patterns from the start.
3Measurement precision
If multiple reticles are used to gather information for different field sizes, then comprehensive optical characterization is achieved, but device complexity and cost increase
Solution Approach 1:
The patent designs a universal reticle structure that can characterize optical imperfections across multiple field sizes using a single device. The reticle includes a reflective multilayer, capping layer, and absorption stack with features that can be measured across different exposure fields, eliminating the need for multiple specialized reticles and reducing overall system complexity.
Solution Approach 2:
The patent merges multiple characterization functions into a single integrated reticle structure. The reflective multilayer serves both as a pattern definition layer and as an optical reference, while the absorption stack simultaneously measures penumbra, defocus, and astigmatism across different field sizes, consolidating what would traditionally require multiple separate reticles into one unified device.
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 solution enhances lithographic performance by reducing non-uniformity and improving pattern fidelity across different exposure fields, increasing manufacturing efficiency and reducing costs by allowing for the use of a single reticle to gather information across various field sizes.
Implementation Method 1
a reticle with a reflective multilayer, capping, and absorption stack designed to minimize EUV absorption and maximize constructive interference
Implementation Method 2
Due to the heavy absorption of EUV radiation by certain substances, an EUV lithography system typically uses a reflective optics apparatus
Data Source
AI summary
A method for collecting information in image-error compensation is provided. The method includes providing a reticle having a first image structure and a second image structure; moving a light shading member to control a first exposure field; projecting a light over the first exposure field; recording an image of the first image structure after the light is projected; moving the light shading member to control a second exposure field; projecting the light over the second exposure field; and recording an image of the second image structure after the light is projected.