EUV Radiation Detector with Photoactivatable Converter Elements
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Solution Overview
Problem
Conventional methods for measuring radiation distribution in microlithography, such as aerial image measuring techniques, are time-consuming and lack sufficient resolution for modern EUV projection objectives and lithography masks, especially when trying to achieve two-dimensional measurements.
Innovation Solution
A method utilizing a radiation converter with a two-dimensional arrangement of photoactivatable converter elements that can be put into active and passive states, allowing only a fraction to emit wavelength-converted measuring radiation, enabling high-resolution, two-dimensional measurement of radiation distribution by determining the places of origin with increased accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional aerial image measuring techniques are used, then measurement can be performed, but measurement resolution is insufficient for modern EUV projection objectives and lithography masks
Solution Approach 1:
The patent segments the measurement process into multiple scanning steps, where the aerial image sensor is moved mechanically to different positions in the three-dimensional space. Each scanning step captures a portion of the radiation distribution, and the complete two-dimensional measurement is reconstructed by combining data from multiple steps. This segmentation allows achieving high measurement resolution (better than 20 nm, in particular better than 10 nm) that exceeds the diffraction limit of conventional single-step imaging methods.
Solution Approach 2:
The patent transitions from two-dimensional imaging to three-dimensional scanning measurement. The aerial image sensor moves along the optical axis (z-direction) and in lateral directions, capturing radiation intensity data at multiple spatial positions. This three-dimensional measurement approach enables resolution beyond the diffraction limit by measuring the radiation distribution in the near field at different depths and reconstructing the high-resolution two-dimensional image computationally.
2Measurement precision
If scanning techniques with aerial image sensor are used, then measurement is possible, but measurement time is very time-consuming
Solution Approach 1:
The patent performs preliminary mechanical positioning of the aerial image sensor to optimal measurement locations before actual radiation detection. The measurement system pre-plans the scanning path and positions the sensor at discrete points where maximum information can be obtained. This preliminary action optimizes the scanning efficiency and reduces the total number of measurement steps required to achieve the desired resolution.
Solution Approach 2:
The patent uses computational reconstruction to create a high-resolution copy of the radiation distribution from multiple lower-resolution measurements taken at different positions. Instead of directly imaging the complete high-resolution pattern in a single step, the system captures multiple partial measurements and reconstructs the final high-resolution image through computational algorithms, significantly reducing measurement time while maintaining superior resolution.
3Measurement precision
If imaging techniques with visible light are used, then radiation distribution can be detected, but resolution is limited to over 100 nm due to diffraction limit
Solution Approach 1:
The patent introduces an intermediary approach by using visible light imaging optics to detect EUV radiation indirectly. The aerial image sensor detects visible light that has been modulated by the EUV radiation distribution in the near field. By performing measurements in the near field rather than the far field, and using multiple scanning steps with computational reconstruction, the system overcomes the diffraction limit of visible light optics and achieves resolution suitable for EUV lithography measurement (better than 20 nm, in particular better than 10 nm).
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 measurement resolution beyond the diffraction limit, enabling high-resolution two-dimensional measurements efficiently, reducing the time required for data acquisition compared to scanning methods.
Implementation Method 1
converter elements which can respectively be put in an active state and a passive state and are configured to convert incoming radiation with respect to its wavelength in the active state
Implementation Method 2
photoactivatable converter elements that can be put into active and passive states
Implementation Method 3
converter elements emit wavelength-converted measuring radiation
Data Source
AI summary
A method for locally resolved measurement of a radiation distribution (24) produced using a lithography mask (16) comprises providing a radiation converter (31, 131) having an at least two-dimensional arrangement of converter elements (32, 132) which can respectively be put in an active and a passive state, and are configured to convert incoming radiation in respect of its wavelength in the active state. The method further includes: manipulating the radiation converter (31, 131) several times such that respectively only a fraction of the converter elements (32, 132) adopts the active state, irradiating the radiation converter (31, 131) with the radiation distribution (24) after every manipulation of the radiation converter (31, 131) so that the active converter elements (32, 132) emit wavelength-converted is measuring radiation (34), recording respective places of origin (54) of the measuring radiation at every irradiation with the radiation distribution (24).