Multi-Angle X-Ray Scatterometry for 3D IC Profile Metrology
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Solution Overview
Problem
Current metrology techniques for measuring critical dimensions of integrated circuits face limitations such as charging issues, radiation damage, incompatibility with low-k dielectrics, and difficulty in measuring three-dimensional profiles, especially with optical critical dimension metrology and grazing-incidence small-angle scattering, which are unable to provide sufficient sensitivity and depth for advanced IC fabrication.
Innovation Solution
The use of multi-angle X-ray reflectance scatterometry (XRS) with low-energy X-ray beams and a converging beam geometry to simultaneously impinge multiple angles and azimuthal angles on periodic structures, allowing for the detection of scattered light in two directions and providing precise measurements of two- and three-dimensional periodic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical critical dimension (OCD) metrology is used to measure small features, then the measurement can be performed with available optical systems, but the relatively long wavelength used is significantly larger than the device feature size which does not provide a simple and direct measurement and compromises measurement sensitivity
Solution Approach 1:
The patent replaces optical metrology systems with X-ray metrology systems. X-rays have wavelengths comparable to or smaller than IC feature sizes, providing direct and sensitive measurements without the fundamental wavelength limitations that plague optical systems. This substitution enables accurate measurement of sub-10nm features that are beyond the capability of conventional optical OCD metrology.
Solution Approach 2:
The patent changes the fundamental parameter of the measurement system by transitioning from optical wavelengths to X-ray wavelengths. This parameter change allows the probing radiation to have dimensions comparable to the features being measured, thereby improving measurement sensitivity and providing direct measurement capability for advanced IC nodes.
2Measurement precision
If shorter wavelength radiation is used to reduce circuit feature size measurement limitations, then measurement precision improves, but transmission in solids or low vacuum becomes extremely low causing low probing depth and requiring stringent vacuum requirements
Solution Approach 1:
The patent selects X-ray wavelengths in the range of approximately 0.1 to 10 nanometers, which provides an optimal balance between having wavelengths small enough to resolve sub-10nm features and being energetic enough to penetrate through solid samples and low-vacuum environments. This parameter optimization resolves the contradiction between measurement precision and transmission/penetration depth.
3Measurement precision
If grazing-incidence small-angle scattering (GISAS) is used to measure nanostructured surfaces, then the technique can study surfaces and thin films, but the incident beam is directed mostly along only the top surfaces which limits information for measuring 3D structures
Solution Approach 1:
The patent extends the measurement capability from primarily surface-level information to three-dimensional structural information by utilizing X-ray scattering at multiple angles and azimuthal angles. This dimensional extension of the measurement approach enables reconstruction of complete 3D profiles including sidewalls, trenches, and complex vertical structures that are inaccessible to conventional GISAS techniques.
4Measurement precision
If CD-SEM metrology is used to measure IC features, then the technique can provide surface measurements, but it is essentially a surface technique making it difficult to measure three dimensional (3D) profiles and has charging problems that limit achievable resolution
Solution Approach 1:
The patent replaces electron-based CD-SEM metrology with X-ray-based scatterometry. This substitution eliminates charging problems inherent to electron microscopy and enables non-destructive measurement of 3D profiles through scattering signals that contain information about vertical structures, sidewalls, and complex three-dimensional geometries.
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 accurate measurement of complex 2D and 3D periodic structures with higher sensitivity and stability, overcoming the limitations of existing methods by providing direct sensitivity to structural dimensions and enabling non-destructive, high-precision analysis of critical dimensions in semiconductor devices.
Implementation Method 1
impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam
Implementation Method 2
A monochromator is provided for focusing the X-ray beam to provide an incident X-ray beam to the periodic structure which simultaneously has a plurality of incident angles and a plurality of azimuthal angles
Data Source
Figure 1~2
Figure 3~4B
Figure 5(A)~5(C)
AI summary
Methods and systems for measuring periodic structures using multi-angle X-ray reflectance scatterometry (XRS) are disclosed. For example, a method of measuring a sample by X-ray reflectance scatterometry involves 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. The method also involves collecting at least a portion of the scattered X-ray beam.