Radiation Receiving System for Lithographic Metrology
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Solution Overview
Problem
Current scatterometers in lithographic processes require sequential measurement of multiple wavelengths, leading to increased time and decreased throughput due to limitations in simultaneous spectral and spatial resolutions, especially when dealing with deep ultraviolet or extreme ultraviolet radiation and opaque materials.
Innovation Solution
A radiation receiving system comprising a plurality of inputs, optical elements, and a spectrometer that can simultaneously process radiation from multiple sources, allowing for simultaneous measurement of scattered radiation across various wavelengths and improving resolution and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential measurement of multiple wavelengths is used, then measurement completeness is improved, but measurement time increases and throughput decreases
Solution Approach 1:
The system segments the spectral measurement task by dividing it into multiple spatial channels, each detecting a specific wavelength range simultaneously. This allows the complete spectrum to be measured in parallel across multiple detectors rather than sequentially through a single detector.
Solution Approach 2:
The invention transitions from sequential temporal measurement to simultaneous spatial measurement by adding spatial dimensionality. Multiple detectors are arranged to receive different wavelength components at the same time, converting a time-based measurement problem into a space-based solution.
2Measurement precision
If spectral resolution is increased, then wavelength discrimination is improved, but device complexity increases
Solution Approach 1:
The spectral resolution requirement is segmented across multiple detectors rather than concentrated in a single high-resolution spectrometer. Each detector handles a portion of the spectrum, reducing the resolution demand per detector while maintaining overall spectral discrimination capability.
Solution Approach 2:
The invention replaces complex mechanical spectral scanning systems with a static optical arrangement using diffraction gratings and multiple detectors. This eliminates moving parts and complex control mechanisms while achieving high spectral resolution through spatial separation of wavelengths.
3Measurement precision
If spatial resolution is increased, then target structure detail is improved, but field of view decreases
Solution Approach 1:
The field of view is segmented into multiple spatial zones, each corresponding to a specific detector. This allows high spatial resolution within each zone while collectively covering a broader overall field of view through the array of detectors.
Solution Approach 2:
The system uses spatial arrangement of multiple detectors to simultaneously achieve high resolution in the spectral dimension and broad coverage in the spatial dimension. By distributing detectors across different positions and angles, the system resolves the trade-off between resolution and field of view.
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
Enables faster and more efficient metrology measurements by allowing simultaneous detection of radiation across multiple wavelengths, enhancing processing throughput and overcoming limitations of existing spectrometers in terms of resolution and field of view.
Implementation Method 1
a first optical element operable to receive radiation from each of the plurality of inputs
Implementation Method 2
a second optical element operable to receive radiation from the first optical element and to scatter the radiation
Implementation Method 3
a third optical element operable to direct the scattered radiation onto a detector
Data Source
AI summary
A radiation receiving system for an inspection apparatus, used to perform measurements on target structures on lithographic substrates as part of a lithographic process, comprises a spectrometer with a number of inputs. The radiation receiving system comprises: a plurality of inputs, each input being arranged to provide radiation from a target structure; a first optical element operable to receive radiation from each of the plurality of inputs; a second optical element operable to receive radiation from the first optical element and to scatter the radiation; and a third optical element operable to direct the scattered radiation onto a detector. The second optical element may for example be a reflective diffraction grating that diffracts incoming radiation into an output radiation spectrum.