SWIR Optical Metrology for VOIT Layer Measurement
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Solution Overview
Problem
Optical metrology techniques based on visible wavelengths face challenges with lower signal intensities and higher noise when measuring semiconductor samples with reduced transparency to visible wavelengths but increased transparency to short-wave infrared (SWIR) wavelengths, affecting measurement accuracy and throughput.
Innovation Solution
An optical metrology tool utilizing both short-wave infrared (SWIR) and non-SWIR illumination sources, with multiple imaging channels and detectors sensitive to various wavelength ranges, including SWIR, to enhance measurement accuracy and robustness by decoupling overlay errors from feature asymmetries and allowing non-destructive characterization of samples with visibly-opaque IR-transparent layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visible wavelength illumination is used for optical metrology, then the measurement system can operate with conventional visible detectors, but the signal intensity decreases and noise increases when measuring samples with reduced visible transparency
Solution Approach 1:
The patent changes the wavelength parameter of the illumination light from visible range to SWIR range (1000-3000 nm). This parameter change enables the light to penetrate VOIT layers that are opaque to visible light, thereby restoring signal intensity and improving measurement reliability without requiring changes to the fundamental optical metrology approach
Solution Approach 2:
The patent transitions from using conventional visible wavelength detection to SWIR wavelength detection, effectively moving to a different spectral dimension. This dimensional shift in the electromagnetic spectrum allows the measurement system to access samples through VOIT layers that block visible light, resolving the signal intensity problem while maintaining measurement accuracy
2Reliability
If visible wavelength illumination is used, then the system structure remains simple with single wavelength detection, but measurement robustness decreases due to sensitivity to feature asymmetries
Solution Approach 1:
The patent utilizes the unique interaction properties of SWIR light with semiconductor materials and VOIT layers. The longer SWIR wavelengths reduce sensitivity to feature asymmetries and provide more robust measurements, while the parameter change itself (wavelength selection) is the primary mechanism rather than adding complex system components
Solution Approach 2:
The patent employs multiple imaging channels with different wavelength ranges (including both SWIR and non-SWIR) to perform measurements. By using partial wavelength ranges selectively, the system achieves robustness against feature asymmetries while managing complexity through targeted rather than comprehensive multi-wavelength coverage
3Measurement precision
If multiple imaging channels with different wavelength ranges are used, then measurement accuracy and robustness improve, but the device complexity increases
Solution Approach 1:
The patent integrates multiple imaging channels with different wavelength ranges into a single optical metrology tool. Each channel serves a specific function (SWIR for penetrating VOIT layers, non-SWIR for surface measurements), and the system provides universal measurement capability across different sample types and measurement requirements, justifying the increased complexity through enhanced functionality
Solution Approach 2:
The patent divides the measurement system into separate imaging channels, each optimized for specific wavelength ranges and measurement tasks. This segmentation allows independent optimization of each channel while maintaining overall system coordination through the controller, managing complexity through modular architecture
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 measurement accuracy and robustness by using SWIR wavelengths, which reduce sensitivity to feature asymmetries and enable direct, non-destructive metrology of samples with VOIT layers, enhancing the sensitivity and accuracy of overlay and optical critical dimension measurements.
Implementation Method 1
short-wave infrared (SWIR) wavelengths, which reduce sensitivity to feature asymmetries and enable direct, non-destructive metrology of samples with VOIT layers
Implementation Method 2
a first detector to image the sample based on illumination with a first wavelength range, where the first wavelength range includes at least some wavelengths in the SWIR spectral range
Data Source
AI summary
An optical metrology tool may include one or more illumination sources to generate illumination having wavelengths both within a short-wave infrared (SWIR) spectral range and outside the SWIR spectral range, illumination optics configured to direct the illumination to a sample, a first imaging channel including a first detector configured to image the sample based on a first wavelength range including at least some wavelengths in the SWIR spectral range, a second imaging channel including a second detector configured to image the sample based on a second wavelength range including at least some wavelengths outside the SWIR spectral range, and a controller. The controller may receive first images of the sample from the first detector, receive second images of the sample from the second detector, and generate an optical metrology measurement of the sample based on the first and second images.