Polarization-Sensitive Detector for Mask Characterization
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Solution Overview
Problem
Current mask inspection systems are time-consuming and inaccurate due to the need for multiple imaging steps with different polarizer settings, which are affected by mechanical vibrations and manufacturing defects, leading to inefficient throughput and measurement inaccuracies.
Innovation Solution
A device with a polarization-sensitive detector unit that records intensity and polarization state in a single exposure step, emulating polarization-dependent effects, thereby reducing measurement complexity and time while avoiding mechanical inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple individual imagings with different polarizer settings are carried out to account for polarization-dependent effects, then measurement accuracy is improved, but measurement time and device complexity increase significantly
Solution Approach 1:
The detector unit is segmented into multiple pixel groups, where each pixel group is assigned a different polarization transmission direction. This allows simultaneous measurement of polarization-dependent effects across different orientations within a single exposure step, eliminating the need for multiple sequential imagings while maintaining measurement accuracy.
Solution Approach 2:
Multiple polarization measurements that would traditionally require separate exposure steps are merged into a single imaging operation. The detector unit with multiple pixel groups captures all polarization states simultaneously, combining what would have been multiple measurements into one unified process.
2Measurement precision
If multiple individual imagings are performed to capture polarization-dependent effects, then comprehensive data is obtained, but mechanical vibrations and thermal deformations cause measurement inaccuracies
Solution Approach 1:
The detector unit is segmented into multiple pixel groups, where each pixel group is assigned a different polarization transmission direction. This allows simultaneous measurement of polarization-dependent effects across different orientations within a single exposure step, eliminating the need for multiple sequential imagings while maintaining measurement accuracy.
3Measurement precision
If a greatly magnified imaging is used in the mask inspection apparatus, then detector resolution is improved, but the numerical aperture becomes almost zero causing significant difference from lithography conditions
Solution Approach 1:
Different regions (pixel groups) of the detector unit are assigned different polarization transmission directions tailored to specific measurement needs. This local differentiation allows the system to maintain high resolution while capturing polarization-dependent effects that are relevant to lithography conditions, bridging the gap between magnified imaging and actual lithography parameters.
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 increases the speed and accuracy of mask characterization, improving throughput and reducing measurement errors by averaging over multiple recordings and minimizing the impact of mechanical and thermal variations.
Implementation Method 1
the detector unit is configured for the spatially resolved determination of both the intensity and the polarization state of the respectively impinging light emanating from the mask
Implementation Method 2
the structures to be measured on the mask are illuminated by an illumination optical unit
Data Source
AI summary
The invention relates to a device and a method for characterizing a microlithographic mask. A device according to the invention has an illumination optical unit for illuminating structures of a mask intended for use in a lithography process in a microlithographic projection exposure apparatus, a detector unit, and an evaluation unit for evaluating the data recorded by the detector unit, wherein the detector unit is configured for the spatially resolved determination of both the intensity and the polarization state of the respectively impinging light emanating from the mask.