Broadband Diffraction Alignment of Metrology Illumination-Detection Systems
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Solution Overview
Problem
Existing metrology techniques struggle to accurately measure small features in integrated circuits due to the use of wavelengths that are not available or usable for metrology, leading to inaccurate measurements and the need for indirect methods that do not account for distortions in the lithographic process.
Innovation Solution
A method for determining the alignment of an illumination-detection system in metrology devices using broadband radiation, involving the transformation of diffraction patterns into region coordinate systems to determine alignment parameters, ensuring accurate detector and measurement illumination alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visible or near-infrared radiation is used for metrology, then the pitch of the grating must be much coarser than actual product structures, but this results in indirect measurements that do not accurately reflect the dimensions of real product structures
Solution Approach 1:
The patent changes the wavelength parameter of the radiation used in metrology from visible/near-infrared to extreme ultraviolet (EUV) radiation with wavelengths of 13.5 nm or shorter. This parameter change allows the grating pitch to be reduced to match actual product structure dimensions while maintaining measurement accuracy, as EUV radiation provides the necessary resolution to directly measure sub-10nm features without requiring coarser gratings.
2Measurement precision
If EUV radiation with wavelength of 13.5 nm or shorter is used for metrology, then direct measurement of small product features becomes possible, but the alignment of illumination and detection systems becomes more difficult due to curved diffraction patterns
Solution Approach 1:
The patent applies preliminary action by performing alignment corrections before actual measurements are taken. The system first identifies curved diffraction patterns indicating misalignment, then applies correction values to adjust the illumination-detection system alignment. This preliminary alignment correction ensures that subsequent measurements are performed with properly aligned systems, eliminating the complexity of real-time alignment adjustments during measurement.
Solution Approach 2:
The patent implements feedback by using the observed curved diffraction patterns as indicators of alignment status. The system continuously monitors the diffraction pattern curvature and uses this feedback information to determine correction values for aligning the illumination and detection systems. This feedback mechanism automates the alignment process and reduces operational complexity by providing real-time alignment guidance based on diffraction pattern analysis.
3Measurement precision
If broadband radiation is used to obtain diffraction patterns, then alignment determination becomes possible through pattern transformation, but the transformation of each diffraction order to region coordinate systems increases processing complexity
Solution Approach 1:
The patent applies segmentation by dividing the broadband diffraction pattern into individual diffraction orders, each corresponding to a specific wavelength range. Each diffraction order is then independently transformed to its respective region coordinate system, allowing for precise alignment determination for each spectral component. This segmentation approach simplifies the overall processing by breaking down the complex broadband pattern analysis into manageable individual order transformations.
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
Improves the accuracy of metrology measurements by aligning detectors and measurement illuminations, allowing for precise detection of small features and overcoming distortions in the lithographic process.
Implementation Method 1
obtaining a diffraction pattern relating to diffraction of broadband radiation from a structure
Data Source
AI summary
Disclosed is a method of determining an illumination-detection system alignment of an illumination-detection system describing alignment of at least one detector and/or measurement illumination of a metrology apparatus in terms of two or more illumination-detection system alignment parameters, each illumination-detection system alignment parameter relating to a respective degree of freedom for aligning the detector and/or the measurement illumination. The method comprises obtaining a diffraction pattern relating to diffraction of broadband radiation from a structure; transforming each of one or more diffraction orders of the diffraction pattern to a respective region coordinate system, each region coordinate system comprising a first axis and a second axis, each region coordinate system being such that said first axis is aligned in relation to a direction of an intensity metric of each transformed diffraction order; and determining illumination-detection system alignment parameter values for the illumination-detection system alignment parameters.