Multi-Angle X-Ray Scatterometry for 3D IC Profile Measurement
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Solution Overview
Problem
Current metrology techniques, such as CD-SEM and OCD, face challenges in measuring critical dimensions of ever-smaller integrated circuit features due to limitations like charging issues, radiation damage, incompatibility with low-k dielectrics, and difficulty in measuring three-dimensional profiles, while XRS methods are limited by incident beam angles and wavelengths, making it hard to achieve precise dimensional control for next-generation IC fabrication.
Innovation Solution
The use of multi-angle X-ray reflectance scatterometry systems that impinge an X-ray beam with multiple incident and azimuthal angles on a sample, allowing for the detection of scattered light to infer the shape and pitch of periodic structures, providing precise measurements of two- and three-dimensional profiles using low-energy X-rays and a toroidal multilayer monochromator to focus the beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD-SEM metrology is used to measure IC features, then surface topology can be observed, but charging problems limit achievable resolution and radiation damage causes dimensional shrinking
Solution Approach 1:
The patent replaces electron-based CD-SEM metrology with X-ray-based scatterometry. X-rays have different interaction mechanisms with matter compared to electrons, avoiding charging effects and radiation-induced dimensional changes. The X-ray beam interacts with the sample through scattering and absorption, providing measurement capability without the harmful side effects of electron beam metrology.
Solution Approach 2:
The patent changes the fundamental measurement parameter from electron beam interaction to X-ray interaction. By using X-rays with appropriate energy levels and multiple incident angles, the system achieves measurement capability that is insensitive to charging and radiation damage effects that plague electron-based methods.
2Measurement precision
If optical critical dimension (OCD) metrology is used, then measurement can be performed with current technology, but the long wavelength does not provide direct measurement and extensive modeling is required
Solution Approach 1:
The patent uses X-ray wavelengths that are comparable to or smaller than the IC feature dimensions, providing direct measurement capability without requiring extensive modeling and interpolation. The shorter wavelength enables direct observation of critical dimensions while reducing the complexity of data interpretation compared to optical methods.
3Loss of information
If GISAS technique is used with small incident angles, then scattered probe can be collected, but information about 3D structures is limited since beam is directed mostly along top surfaces
Solution Approach 1:
The patent employs a dynamic multi-angle X-ray scatterometry system that varies the incident angle to optimize information collection from different depths and orientations of the sample. By dynamically adjusting the incident angle, the system overcomes the limitation of fixed small-angle GISAS and achieves comprehensive 3D structural information.
Solution Approach 2:
The patent transitions from single-angle to multi-angle X-ray scatterometry, adding the angular dimension as a variable parameter. This enables the system to probe different depths and orientations within the sample, achieving comprehensive 3D structural information that cannot be obtained with fixed small-angle illumination.
4Measurement precision
If shorter wavelength radiation is used to reduce circuit feature size measurement limitations, then measurement precision improves, but transmission in solids and low vacuum becomes extremely low
Solution Approach 1:
The patent optimizes the X-ray energy parameter to achieve an optimal balance between measurement precision and transmission. By selecting appropriate X-ray energy levels and incident angles, the system achieves sufficient penetration through solids and low vacuum while maintaining the short wavelength needed for high-precision measurement of small IC features.
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 enables precise and stable measurement of complex 2D and 3D periodic structures, overcoming the limitations of existing techniques by providing direct sensitivity to critical dimensions, enhancing measurement sensitivity and accuracy for IC feature control.
Implementation Method 1
x-ray reflectance scatterometry
Implementation Method 2
a monochromator positioned between the X-ray source and the sample holder. The monochromator is for focusing the X-ray beam
Implementation Method 3
impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam
Data Source
AI summary
A system and method for measuring a sample by X-ray reflectance scatterometry. The method may include impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam, the incident X-ray beam simultaneously providing a plurality of incident angles and a plurality of azimuthal angles; and collecting at least a portion of the scattered X-ray beam.