Metrology Sensor Segmentation for Dynamic Range
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Solution Overview
Problem
Current metrology sensors in lithographic apparatuses face limitations in dynamic range due to zeroth-order scattered light, which can be mitigated by increasing the size of the zeroth-order stop, but this is undesirable due to volume and thermal constraints, and they struggle with low signal strength when measuring through opaque layers.
Innovation Solution
A metrology sensor system that separates parameter-sensitive signals from noise signals using an obscuration located outside the housing, allowing for adjustable and tunable blocking of noise signals, and includes an optical system to demagnify radiation prior to detection, enabling improved signal detection and reduced dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the zeroth order stop size is increased to block more scattered light, then the dynamic range is improved, but the volume and thermal constraints are violated
Solution Approach 1:
The patent segments the radiation collection and detection process into multiple diffraction orders. By using a diffraction grating to separate radiation into different orders and selectively detecting only specific orders (e.g., first order) while blocking others (e.g., zeroth order), the system achieves high dynamic range without requiring a large physical stop. This segmentation allows precise control of noise signals while maintaining compact sensor module dimensions.
2Measurement precision
If the zeroth order stop size is increased to block more scattered light, then the dynamic range is improved, but thermal constraints are violated
Solution Approach 1:
The patent segments the radiation collection and detection process into multiple diffraction orders. By using a diffraction grating to separate radiation into different orders and selectively detecting only specific orders (e.g., first order) while blocking others (e.g., zeroth order), the system achieves high dynamic range without requiring a large physical stop. This segmentation allows precise control of noise signals while maintaining compact sensor module dimensions.
3Adaptability or versatility
If radiation is collected through opaque layers, then measurement capability is improved, but signal strength decreases
Solution Approach 1:
The patent changes the wavelength parameter of the radiation used for measurement. By utilizing longer wavelength radiation (e.g., infrared) that can penetrate opaque layers more effectively, the system maintains signal strength while achieving measurement capability through opaque structures. This parameter change allows the sensor to measure positions of marks on substrates even when covered by opaque layers that would block shorter wavelengths.
4Measurement precision
If detector size is increased to improve signal detection, then signal detection capability is improved, but dark current increases
Solution Approach 1:
The patent extracts only the useful signal components by selectively detecting specific diffraction orders while blocking others. By using the diffraction grating to separate radiation into different orders and detecting only the first order (which contains the position information), the system achieves high signal detection capability with a small detector area. This extraction approach prevents collection of zeroth order scattered light that would contribute to dark current, thereby maintaining low dark current levels while improving signal detection.
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 solution enhances the dynamic range and reduces dark current detection, allowing for more accurate and efficient alignment and positioning in lithographic processes, particularly when measuring through opaque layers, without compromising the sensor's pitch flexibility or increasing size within the alignment sensor module.
Implementation Method 1
an optical collection system configured to collect diffracted or scattered radiation from a metrology mark on a substrate
Implementation Method 2
an optical collection system configured to collect diffracted or scattered radiation from a metrology mark on a substrate
Implementation Method 3
at least one optical guide for guiding the at least one parameter-sensitive signal, separated from the at least one noise signal, from the processing system to a detection system outside of the housing
Implementation Method 4
A metrology sensor system that separates parameter-sensitive signals from noise signals using an obscuration located outside the housing, allowing for adjustable and tunable blocking of noise signals
Data Source
AI summary
Disclosed is a metrology sensor system, such as a position sensor. The system comprises an optical collection system configured to collect diffracted or scattered radiation from a metrology mark on a substrate, said collected radiation comprising at least one parameter-sensitive signal and noise signal which is not parameter-sensitive, a processing system operable to process the collected radiation; and a module housing. An optical guide is provided for guiding the at least one parameter-sensitive signal, separated from the noise signal, from the processing system to a detection system outside of the housing. A detector detects the separated at least one parameter-sensitive signal. An obscuration for blocking zeroth order radiation and/or a demagnifying optical system may be provided between the optical guide and the detector.