Metrology Device Aperture Configuration for Periodic Structure Measurement
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Solution Overview
Problem
Current metrology devices face challenges in accurately measuring periodic structures on substrates due to limitations in capturing complementary diffraction orders, particularly with spatially coherent illumination, which leads to increased optical crosstalk and computational complexity, affecting measurement precision and throughput.
Innovation Solution
A metrology method and device that utilize spatially incoherent or multimode illumination, configuring the illumination and detection aperture profiles based on the pitch-to-wavelength ratio to capture at least 80% of complementary diffraction orders within separated detection regions, allowing for simultaneous measurement of both +1st and -1st diffraction orders and reducing optical crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If spatially coherent illumination is used to measure periodic structures, then measurement capability is provided, but optical crosstalk increases and measurement precision deteriorates
Solution Approach 1:
The patent changes the illumination coherence parameter from spatially coherent to spatially incoherent or partially coherent illumination. This parameter change reduces optical crosstalk between adjacent diffraction orders while maintaining the ability to measure periodic structures, thereby improving measurement precision without sacrificing measurement capability.
2Loss of information
If complementary diffraction orders are captured with coherent illumination, then measurement information is obtained, but computational complexity increases
Solution Approach 1:
The patent changes the illumination coherence parameter to spatially incoherent or partially coherent illumination, which simplifies the computational model required for data analysis. This parameter change reduces computational complexity while maintaining adequate measurement information through the capture of complementary diffraction orders.
3Loss of information
If illumination aperture is increased to capture more diffraction orders, then measurement completeness improves, but optical crosstalk increases
Solution Approach 1:
The patent changes the illumination coherence parameter from coherent to incoherent or partially coherent, which allows for increased illumination aperture to capture more diffraction orders without proportionally increasing optical crosstalk. The incoherent illumination reduces the interference effects that cause crosstalk, enabling more complete measurement information to be obtained.
4Productivity
If measurement throughput is increased by using simplified illumination, then productivity improves, but measurement precision may deteriorate
Solution Approach 1:
The patent implements spatially incoherent or partially coherent illumination, which simplifies the measurement system and increases throughput while maintaining or improving precision through reduced optical crosstalk. This parameter change achieves both higher productivity and maintained measurement precision simultaneously.
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 enhances measurement precision, reduces computational complexity, and increases throughput by minimizing optical crosstalk and aberration corrections, enabling more efficient and accurate determination of periodic structure parameters.
Implementation Method 1
diffracted radiation of at least a pair of complementary diffraction orders is captured within the detection aperture profile
Data Source
AI summary
Disclosed is a method of measuring a periodic structure on a substrate with illumination radiation having at least one wavelength, the periodic structure having at least one pitch. The method comprises configuring, based on a ratio of said pitch and said wavelength, one or more of: an illumination aperture profile comprising one or more illumination regions in Fourier space; an orientation of the periodic structure for a measurement; and a detection aperture profile comprising one or more separated detection regions in Fourier space. This configuration is such that: i) diffracted radiation of at least a pair of complementary diffraction orders is captured within the detection aperture profile, and ii) said diffracted radiation fills at least 80% of the one or more separated detection regions. The periodic structure is measured while applying the configured one or more of illumination aperture profile, detection aperture profile and orientation of the periodic structure.