Multilayer SEM Metrology for Buried Layer Feature Measurement
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Solution Overview
Problem
Existing metrology techniques struggle to accurately measure features at buried process layers within semiconductor devices, particularly due to interference from scattered electrons from other depth levels, leading to challenges in determining critical dimensions, line edge roughness, and overlay errors.
Innovation Solution
A method involving an SEM system with multiple detectors and varying landing energies is employed to generate composed images by pixel-by-pixel processing, allowing for the extraction of buried process layer information through techniques such as image subtraction and alignment with design layouts, enhancing image quality and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-energy SEM imaging is used, then the imaging process is simple and fast, but the measurement precision of buried process layer features is poor due to interference from scattered electrons at other depth levels
Solution Approach 1:
The imaging process is segmented into multiple energy level acquisitions, where the total imaging task is divided into separate measurements at different electron landing energies. Each energy level captures information from specific depth ranges, allowing selective imaging of buried process layers while excluding interference from other depths. The composed image is then generated by combining these segmented energy-level images through pixel-by-pixel processing.
Solution Approach 2:
The landing energy parameter of the electron beam is changed across multiple discrete levels to vary the penetration depth and scattering characteristics. By adjusting the electron beam energy, the system selectively probes different depth levels within the semiconductor structure. This parameter variation enables depth-resolved imaging, where lower energies provide surface information and higher energies provide buried layer information.
2Measurement precision
If multiple landing energy levels are used to image buried layers, then the clarity of buried process layer features is improved, but the measurement time and processing complexity increase
Solution Approach 1:
Image processing operations are performed preliminarily on the raw multi-energy images before final composition. Pre-processing steps such as noise filtering, contrast enhancement, and artifact removal are applied to each energy-level image individually, preparing the data for optimal combination. This preliminary action reduces the complexity of the subsequent composition process and improves the efficiency of generating the final composed image.
Solution Approach 2:
A composed image serves as an intermediary representation that synthesizes information from multiple energy levels. Rather than directly interpreting raw multi-energy data, the system creates this intermediate composed image through pixel-by-pixel processing, which then serves as the basis for accurate metrology measurements. This intermediary step consolidates the multi-energy information into a single, interpretable image that highlights buried process layer features.
3Manufacturing precision
If image composition from multiple detectors and energy levels is performed, then the accuracy of metrology characteristics is improved, but the data processing complexity increases
Solution Approach 1:
Images from multiple detectors operating at different energy levels are merged through pixel-by-pixel processing to create a composed image. The data from various sources are combined using mathematical operations that weight and integrate the information appropriately. This merging process consolidates redundant and complementary information, enhancing the signal from buried process layers while suppressing noise and artifacts from individual detector measurements.
Solution Approach 2:
The scattered electrons that cause interference in conventional imaging are converted into a benefit through multi-energy differentiation. By acquiring images at multiple energy levels, the system can identify and isolate the contribution of scattered electrons from deeper layers. The composition process exploits the different scattering signatures at various energies to extract useful information about buried process layers that would be obscured in single-energy images.
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 measurement of metrology characteristics like side wall angles, critical dimensions, and overlay errors by emphasizing features at buried layers, improving the accuracy of semiconductor manufacturing processes.
Implementation Method 1
obtain image data of an object with an SEM system, the image data acquired at multiple landing energy levels
Data Source
AI summary
Methods, apparatuses, and software are disclosed for multilayer metrology. One method includes obtaining image data of an object with an SEM system, with the image data acquired at multiple landing energy levels. A composed image is generated by performing pixel-by-pixel image processing of the image data. A metrology characteristic is determined from the composed image and metrology is performed on a feature based on the metrology characteristic.