Microlithography Exit Pupil Wavefront Correction
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Solution Overview
Problem
Existing methods for improving the imaging properties of microlithographic projection exposure apparatuses are insufficient for accurately imaging small structures, as they often result in intolerable deviations in the exit pupil, affecting the imaging quality.
Innovation Solution
A method that determines and corrects imaging quantities only in the regions of the exit pupil actually illuminated by the projection light, using wavefront detectors and manipulators to adjust optical elements and illumination angle distributions, ensuring accurate imaging by optimizing the wavefront profile and polarization state within these regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If corrective measures are applied across the entire exit pupil, then imaging properties are improved in theory, but intolerable deviations occur in regions not illuminated by projection light
Solution Approach 1:
The patent applies local quality by determining actual imaging quantities only in regions of the exit pupil that are actually illuminated by projection light during mask projection. The method calculates corrective measures based on imaging quantities at illuminated locations, applying corrections locally rather than uniformly across the entire exit pupil, thereby avoiding intolerable deviations in non-illuminated regions while maintaining imaging accuracy in illuminated regions.
2Manufacturing precision
If conventional illumination settings are used, then the system is simple to operate, but imaging accuracy for small structures is insufficient
Solution Approach 1:
The patent employs dynamics by allowing the illumination angle distribution to be variable and adaptable. Instead of using a fixed conventional illumination setting, the system can switch between different illumination settings (conventional, annular, dipole, quadrupole) and adjust illumination angle distributions dynamically based on the specific imaging requirements, enabling high imaging accuracy for small structures while maintaining operational flexibility.
3Manufacturing precision
If the illumination angle distribution is not adapted to the mask pattern, then the illumination system is simple, but the imaging accuracy of small structures deteriorates
Solution Approach 1:
The patent applies parameter changes by adapting the illumination angle distribution parameters to match the specific mask pattern being projected. The system determines the actual imaging quantities based on the specific mask structures and adjusts illumination parameters (such as illumination angle distribution, numerical aperture, and illumination shape) accordingly, thereby achieving high imaging accuracy for different small structure patterns through parameter optimization.
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 significantly improves the imaging accuracy and contrast, enabling the production of smaller structures with reduced deviations and enhanced integration density, by focusing corrective measures on the specific regions illuminated by the mask and illumination angle distribution.
Implementation Method 1
The actual value of an imaging quantity is determined for at least one image point of the projection objective
Implementation Method 2
manipulators to adjust optical elements and illumination angle distributions
Data Source
AI summary
In a method for improving the imaging properties of a projection objective of a microlithographic projection exposure apparatus, an appropriate illumination angle distribution adapted to a mask (24; 224) to be projected is selected. Then locations (40a, 40b; 60a, 60b; 80a, 80b, 80c) in an exit pupil of the projection objective (20), which are illuminated under these conditions by projection light during a projection of the mask, are determined. For at least one image point, an actual value of an imaging quantity, e.g. a wavefront profile or a polarization state, is determined that influences the imaging properties of the projection objective. Finally, corrective measures are calculated such that the actual value of the imaging quantity approximates a desired value at these locations. In this last step, however, deviations of the actual value from the desired value are taken into account exclusively at said locations illuminated in the exit pupil.