Ellipsometer Wavefront Splitting for Instantaneous Polarization Measurement
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Solution Overview
Problem
Current spectroscopic and monochromatic ellipsometers and scatterometers face limitations in measurement precision due to light source intensity instabilities, mechanical vibrations from rotating components, and the inability to adjust acquisition time based on intensity, making it difficult to measure materials with varying reflectivity or spot sizes, and they often introduce systematic errors and reduce measurement quality.
Innovation Solution
An ellipsometer or scatterometer design that uses a wavefront splitting optical beam splitter to create three collimated split beams, which are then modified to form six polarized beams, allowing for instantaneous measurements without polarization modulation, with a detection system capable of adapting acquisition time based on intensity and featuring a spectrometer for spectral dispersion and imaging, enabling high-frequency measurements across a wide spectral band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If temporal polarization modulation is used to acquire polarization components, then measurement capability is improved, but measurement precision deteriorates due to light source intensity instabilities
Solution Approach 1:
The detection arm is divided into multiple independent detection channels (at least two channels), each detecting light with a different polarization state simultaneously. This segmentation eliminates the need for temporal modulation and allows direct simultaneous measurement of polarization components, resolving the contradiction between measurement capability and precision.
2Adaptability or versatility
If rotating polarization modulators are used to vary polarization state, then polarization measurement capability is improved, but mechanical reliability deteriorates due to vibrations and long-term reliability issues
Solution Approach 1:
The patent replaces mechanical rotating polarization modulators with a non-mechanical optical system using beam splitters and mirrors to create multiple detection channels. This substitution eliminates mechanical vibrations and improves long-term reliability while maintaining polarization measurement capability.
3Device complexity
If fixed modulation period acquisition is used, then polarization modulation is simplified, but adaptability deteriorates due to inability to adjust acquisition time for different intensities
Solution Approach 1:
The detection system is segmented into multiple independent channels that simultaneously detect different polarization states. This allows the acquisition time to be independently optimized for each channel based on its specific intensity requirements, providing adaptability without increasing overall system complexity.
4Device complexity
If temporal modulation approach is used, then polarization analysis is simplified, but measurement speed deteriorates due to minimum duration being half the modulation period
Solution Approach 1:
The patent segments the detection into multiple simultaneous channels, enabling instantaneous measurement of all polarization components. This eliminates the temporal sequencing requirement and doubles the measurement rate by removing the half-modulation-period minimum duration constraint.
5Measurement precision
If wavefront splitting is used to create multiple beams, then measurement precision is improved, but device complexity increases due to additional optical components
Solution Approach 1:
The wavefront splitting optical beam splitter serves multiple functions simultaneously: it divides the incident beam into multiple beams with different polarization states, directs them to appropriate detection channels, and enables precise polarization measurement. This multi-functionality reduces the need for additional separate components, offsetting the initial complexity increase.
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 design enhances measurement precision and quality by reducing systematic errors, allowing for faster and more accurate ellipsometry and scatterometry measurements across a wide spectral range, particularly suitable for time-resolved processes and materials with varying reflectivity, while avoiding mechanical vibrations and intensity-related issues.
Implementation Method 1
a wavefront splitting optical beam splitter arranged to receive a secondary light beam formed by reflection or transmission of the incident light beam polarized on the sample
Implementation Method 2
a polarization modification optical device adapted to receive the three collimated split beams and form three polarized beams according to three distinct polarization states
Implementation Method 3
a polarization splitter optical device arranged and oriented to receive the three polarized beams according to three distinct polarization states and to form six separate beams propagating along six angularly separated optical axes
Implementation Method 4
the imaging spectrometer being adapted to spectrally disperse the six images and simultaneously form six spatially separated spectral sub-images on an image detector
Implementation Method 5
an optical illumination system adapted to direct the incident light beam polarized towards a sample along an incident optical axis in a plane of incidence
Implementation Method 6
a detection system suitable for detecting the six separate beams and a processing system suitable for extracting a scatterometry or ellipsometry measurement therefrom
Data Source
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Figure 5~6
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AI summary
The invention relates to an ellipsometer or scatterometer comprising a light source (1), a polarizer (5), an optical illumination system (2, 4) suitable for directing an incident polarized light beam (11) towards a sample (6), a wavefront-division optical beam splitter (20) arranged to receive a secondary light beam (12) produced by reflection, transmission or diffraction, the wavefront-division optical beam splitter (20) being oriented to form three collimated split beams, an optical polarization modification device (25) and an optical polarization splitting device (26) to form six angularly split beams, a detection system suitable for detecting the six split beams, and a processing system suitable for deducing therefrom an ellipsometric or scatterometric measurement.