Wavefront Sensor Mask Layout for High-Frequency Radiation Sensing
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Solution Overview
Problem
Existing wavefront metrology sensors, particularly those used in combination with ptychography, are not optimal for wavefront sensing in terms of wavefront and spectral sensitivity, especially when used with high-frequency radiation such as hard X-ray, soft X-ray, and EUV radiation, which are necessary for measuring small structures in modern lithographic processes.
Innovation Solution
A wavefront sensor is designed with a mask pattern that interacts with radiation to form a detection pattern on a detector, where the mask pattern is optimized based on the requirement of the detection pattern, enhancing sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing wavefront metrology sensors are used with high-frequency radiation (hard X-ray, soft X-ray, EUV), then measurement capability for small structures is enabled, but sensitivity and accuracy of wavefront sensing deteriorate
Solution Approach 1:
The mask is divided into multiple zones with different transmission characteristics. Each zone is designed to interact with specific spatial frequencies of the wavefront, enabling segmented measurement of different wavefront components. This segmentation allows the sensor to maintain sensitivity across the full range of high-frequency radiation wavelengths.
Solution Approach 2:
The invention transitions from conventional 2D detector plane measurements to 3D spatial frequency space analysis. By designing the mask pattern to map wavefront deviations into specific spatial frequency components that can be detected and analyzed, the system achieves accurate wavefront sensing for high-frequency radiation through dimensional transformation of the measurement space.
2Reliability
If conventional mask patterns are used, then device simplicity is maintained, but wavefront and spectral sensitivity are insufficient
Solution Approach 1:
Different regions of the mask are assigned different local transmission properties and pattern densities optimized for specific measurement functions. The mask incorporates zones with varying spatial frequencies, orientations, and transmission coefficients, allowing each local region to contribute optimally to specific aspects of wavefront sensing while maintaining overall system sensitivity.
Solution Approach 2:
The mask employs composite structural design combining multiple pattern types (gratings, zones, apertures) with different geometries and materials properties within a single mask element. This composite approach enables the mask to simultaneously provide spectral filtering, spatial frequency modulation, and wavefront encoding functions that enhance sensitivity without requiring multiple separate components.
3Device complexity
If simple grating targets are used for scatterometry, then measurement setup is simplified, but measurement precision for small structures deteriorates
Solution Approach 1:
The mask pattern parameters (spatial frequency, orientation, transmission coefficient, zone size) are specifically optimized as functions of the radiation wavelength and the target feature dimensions. By adjusting these parameters according to the measurement requirements for small structures, the system achieves high measurement precision while maintaining relatively simple mask geometries that can be fabricated with current technology.
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
The solution improves the sensitivity and accuracy of wavefront sensing, allowing for precise measurement of small structures using high-frequency radiation, overcoming the limitations of existing sensors.
Implementation Method 1
a mask comprising a pattern located in path of the radiation to interact with the radiation. The radiation impinging on the mask forms a radiation detection pattern on a radiation detector subsequent to the mask
Data Source
AI summary
Disclosed is a wavefront sensor for measuring a wavefront of a radiation. The wavefront sensor comprises a mask comprising a pattern located in path of the radiation to interact with the radiation. The radiation impinging on the mask forms a radiation detection pattern on a radiation detector subsequent to the mask, and the pattern of the mask is designed at least partly based on a requirement of the radiation detection pattern.