Semiconductor X-Ray Scattering Parameterization Using 3D Tomography
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Solution Overview
Problem
Current x-ray scattering measurements for semiconductor wafers face challenges in accurately determining shape deviations due to ambiguities in reference spectra and inability to separate foreground and background contributions, leading to potential failures in identifying unexpected process deviations.
Innovation Solution
The method involves performing slice-and-image tomographic measurements to obtain three-dimensional volume images of semiconductor structures, which are then used to parameterize x-ray scattering measurements. This approach allows for the determination of one or more parameter values associated with the x-ray scattering measurement, enabling more accurate in-line wafer metrology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If CD-SAXS measurements are used for in-line quality checks, then measurement speed is improved, but measurement precision deteriorates due to ambiguities in reference spectra and inability to separate foreground and background contributions
Solution Approach 1:
The patent performs slice-and-image tomographic measurements in advance to obtain three-dimensional volume images of the semiconductor structures. These 3D images are then used to pre-determine parameter values (such as shape parameters, size parameters, and background characteristics) that will be used to parameterize the subsequent CD-SAXS measurements. This preliminary action allows the fast CD-SAXS measurements to be accurately interpreted by providing pre-established reference data about the actual structure geometry and background contributions.
Solution Approach 2:
The patent introduces three-dimensional volume images obtained from slice-and-image tomography as an intermediary between the CD-SAXS measurement and the shape deviation determination. These 3D images serve as a mediator that provides detailed structural information to parameterize the CD-SAXS measurement, enabling the separation of foreground (semiconductor structure) and background (substrate, other structures) contributions. This intermediary resolves the ambiguity in reference spectra by providing actual structural data.
2Ease of operation
If reference spectra are used to determine shape deviations, then measurement process is simplified, but reliability deteriorates because multiple different shape deviations can result in the same reference spectrum variation
Solution Approach 1:
The patent uses slice-and-image tomographic measurements to directly determine parameter values describing the actual semiconductor structures (such as pillar diameter, height, spacing, and shape parameters). These measured parameter values are then used to parameterize the reference spectra, creating a direct mapping between actual structure parameters and expected scattering patterns. This approach changes the parameter determination method from indirect spectral fitting to direct tomographic measurement, eliminating the ambiguity where multiple shape deviations produce the same spectral variation.
3Productivity
If CD-SAXS measurements are performed on wafers with underlying structures, then throughput is maintained, but measurement precision deteriorates due to background contributions that cannot be separated from foreground signals
Solution Approach 1:
The patent performs slice-and-image tomographic measurements to obtain three-dimensional volume images that capture both the semiconductor structures of interest and the background structures (substrate, other layers, or features). From these 3D images, parameter values describing the background contributions are determined in advance. These pre-determined background parameters are then used to subtract or account for background effects in the CD-SAXS measurements, enabling accurate shape deviation determination even in the presence of underlying structures.
Solution Approach 2:
The patent segments the total scattering signal into foreground (semiconductor structure) and background (substrate, other structures) contributions by using parameter values derived from slice-and-image tomography. The 3D volume images allow separate characterization of the target structures and the background, enabling the measurement system to distinguish between signals originating from the semiconductor structures being measured and those from surrounding or underlying structures. This segmentation resolves the issue of unable to separate foreground and background contributions.
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 technique enhances the accuracy and reliability of in-line wafer metrology by resolving ambiguities in x-ray scattering measurements and providing a means to separate foreground and background contributions, thus improving the detection of shape deviations and maintaining high throughput.
Implementation Method 1
x-ray scattering measurements performed on wafers that include semiconductor structures
Implementation Method 2
performing a slice-and-image tomographic measurement to obtain one or more three-dimensional volume images
Data Source
AI summary
Semiconductor structures can be investigated, e.g., in an in-line quality check. An x-ray scattering measurement, e.g., CD-SAXS, can be used for wafer metrology. The x-ray scattering measurement can be configured based on a slice-and-imaging tomographic measurement using a dual-beam device, e.g., including a focused ion beam device and a scanning electron microscope.