Lithographic Projection Pupil Manipulation for Aberration Control
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Solution Overview
Problem
Lithographic systems face challenges in achieving high resolution and large image field coverage with low image aberrations, requiring sophisticated optical designs and correction mechanisms that often result in non-linear relationships between optical elements, leading to distortion and crosstalk in Zernike coefficients.
Innovation Solution
A process of operating and manufacturing lithographic systems involves manipulating the projection system pupil using a non-linear function to approximate the offence against the sine condition, allowing for controlled aperture adjustments and wavefront corrections that decouple Zernike coefficients, reducing crosstalk and improving aberration control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a great number of optical elements are used to provide high resolution imaging over a large object field, then resolution and image field coverage are improved, but device complexity increases and image aberrations worsen
Solution Approach 1:
The projection system is divided into multiple subsystems: illumination system, projection system with object and image fields, and correction mechanisms. Each subsystem is optimized independently to reduce overall complexity while maintaining high resolution imaging capabilities across the large object field.
Solution Approach 2:
Correction mechanisms are applied locally at specific positions within the optical path to address aberrations in specific regions of the image field, rather than requiring uniform correction across all elements. This allows targeted correction of astigmatism and other aberrations without increasing the total number of optical elements.
2Productivity
If the object field size is increased to provide large image field coverage, then throughput is improved, but image aberrations increase
Solution Approach 1:
Aberration correction is performed in advance through the optical design of the projection system and illumination system configuration before imaging occurs. The system is pre-configured with correction mechanisms that automatically compensate for aberrations across the entire large object field, enabling high throughput without sacrificing image quality.
Solution Approach 2:
The system incorporates correction mechanisms that provide feedback on image quality and aberration levels, automatically adjusting optical parameters to maintain low aberrations across the large image field while preserving high throughput capabilities.
3Manufacturing precision
If sophisticated correction mechanisms are added to reduce image aberrations, then image quality is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Correction mechanisms are merged with existing optical elements in the projection system rather than being added as separate components. This integration approach reduces manufacturing difficulty by utilizing the same fabrication processes and material selections already established for the primary optical elements.
Solution Approach 2:
Optical elements in the projection system are designed to serve multiple functions: primary imaging and aberration correction. This multi-functionality eliminates the need for separate correction components, simplifying manufacturing while achieving low image aberrations across the large image field.
Data Source
AI summary
A lithographic system includes a projection system for projecting an object field through a projection system's pupil onto an image field. The projection system includes an optical element located at the projection system's pupil. The projection system's pupil is manipulable with respect to normalized pupil heights by the optical element. Related processes are also disclosed.