EUV Metrology Apparatus Multi-Waveband Spectroscopic Grating
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Solution Overview
Problem
Current metrology techniques for measuring critical dimension (CD) and overlay in semiconductor manufacturing face challenges with low accuracy, cross-talk between parameters, and the inability to handle small target sizes and complex 3D structures, especially as technology advances and feature sizes shrink.
Innovation Solution
A metrology apparatus and method utilizing EUV radiation with a spectroscopic grating system that analyzes radiation in multiple wavebands simultaneously, including EUV, VUV, DUV, and visible, to enhance measurement accuracy by exploiting the broadband nature of the EUV source, allowing for simultaneous spectral information collection without increasing measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical scatterometers are used for CD measurement, then measurement throughput is high, but measurement accuracy is low and cross-talk between parameters occurs
Solution Approach 1:
The patent changes the fundamental parameter of radiation wavelength from optical to EUV range, enabling new measurement capabilities. This parameter change allows access to previously unmeasurable structural parameters and eliminates cross-talk issues while maintaining high throughput through the broadband nature of EUV sources
Solution Approach 2:
The patent introduces a new dimension of measurement by utilizing multiple wavebands (EUV, VUV, DUV, visible) simultaneously. This multi-dimensional approach enables independent measurement of multiple parameters including CD, overlay, and 3D structure properties without the cross-talk that plagues conventional single-waveband optical methods
2Area of stationary object
If small target metrology is used to reduce target size, then targets can be positioned in amongst product features, but measurement accuracy for CD and overlay is compromised
Solution Approach 1:
By changing to EUV radiation with its distinctive broadband characteristics, the patent enables accurate measurement of small targets without sacrificing precision. The EUV wavelength range provides enhanced sensitivity to small feature dimensions and allows for accurate characterization of compact target structures that would be difficult to measure with conventional optical methods
3Difficulty of detecting and measuring
If known CD metrology techniques are used for small features, then measurement can be performed, but accuracy and precision deteriorate as features shrink to 3D structures
Solution Approach 1:
The patent employs EUV radiation parameters that are specifically suited for measuring small and complex 3D structures. The shorter wavelength and broadband nature of EUV radiation provide enhanced resolution and the ability to characterize vertical profile and 3D geometry accurately, overcoming the limitations of conventional optical techniques
Solution Approach 2:
The patent segments the measurement approach by using different wavebands (EUV, VUV, DUV, visible) to measure different aspects of the structure. This segmentation allows independent optimization for measuring specific parameters like CD, overlay, and 3D shape, improving overall precision for complex structures
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 improves the accuracy and precision of CD and overlay measurements by leveraging the strengths of EUV radiation, reducing errors from cross-correlation issues and enabling more accurate modeling of small target structures, while maintaining modest cost and complexity.
Implementation Method 1
a first detection system comprising a first spectroscopic grating and a first detector, the first spectroscopic grating being arranged to receive said radiation after interaction with the structure, the first detector being arranged to detect a spectrum in a first waveband by receiving one or more higher orders of radiation diffracted by said first spectroscopic grating
Implementation Method 2
a second detection system arranged to receive at least a portion of zero order radiation reflected by the first spectroscopic grating and to analyze said zero order radiation in one or more other wavebands
Data Source
AI summary
A metrology apparatus uses radiation (304) in an EUV waveband. A first detection system (333) includes a spectroscopic grating (312) and a detector (313) for capturing a spectrum of the EUV radiation after interaction with a target (T). Properties of the target are measured by analyzing the spectrum. The radiation (304) further includes radiation in other wavebands such as VUV, DUV, UV, visible and IR. A second detection system (352, 372, 382) is arranged to receive at least a portion of radiation (350) reflected by the first spectroscopic grating and to capture a spectrum (SA) in one or more of said other wavebands. The second waveband spectrum can be used to enhance accuracy of the measurement based on the EUV spectrum, and/or it can be used for a different measurement. Other types of detection, such as polarization can be used instead or in addition to spectroscopic gratings.