X-Ray Scatterometry Decomposition for High-Aspect Ratio Metrology
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Solution Overview
Problem
Current metrology systems face challenges in accurately measuring complex, high-aspect ratio semiconductor structures due to limitations in penetration depth and sensitivity, especially with optical methods, which struggle with opaque materials and three-dimensional geometries, leading to biased and inaccurate results.
Innovation Solution
The implementation of X-Ray scatterometry measurement systems that decompose complex structures into simpler sub-structures and measurement areas, allowing for independent simulation and modeling of scattering responses to enhance measurement accuracy and reduce the influence of incidental structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical scatterometry is used to measure complex high-aspect ratio structures, then non-destructive measurement is achieved, but penetration depth and sensitivity are insufficient
Solution Approach 1:
The patent segments the complex measurement problem into two parts: (1) using optical scatterometry for non-destructive surface measurement, and (2) using destructive cross-sectional preparation for deep internal structure measurement. This segmentation allows each method to be applied where it is most effective, resolving the contradiction between non-destructive capability and penetration depth.
Solution Approach 2:
The patent introduces cross-sectional preparation as an intermediary step that bridges the gap between optical measurement limitations and the need for deep structure characterization. By preparing physical cross-sections, the system enables transmission electron microscopy to measure internal structures that optical methods cannot penetrate, while still maintaining process correlation through the use of identical target structures.
2Length of moving object
If complex three-dimensional structures are measured with optical radiation, then depth penetration is improved, but sensitivity to small anomalies is lost
Solution Approach 1:
The patent transitions from three-dimensional optical measurement to two-dimensional cross-sectional measurement. By preparing thin cross-sectional samples and measuring them in transmission electron microscopy, the system achieves both deep penetration (through the thin section) and high sensitivity (to nanoscale features in the cross-section), resolving the contradiction between depth and sensitivity in 3D measurement.
3Loss of information
If multiple parameters are used to characterize complex structures, then measurement completeness is improved, but parameter correlation increases
Solution Approach 1:
The patent replaces optical measurement methods with transmission electron microscopy for cross-sectional measurement. TEM provides direct imaging of internal structures with high resolution, allowing multiple parameters (layer thicknesses, material compositions, structural dimensions) to be measured simultaneously with high accuracy and minimal parameter correlation, as each parameter can be directly observed and measured independently in the cross-sectional view.
4Measurement precision
If destructive sample preparation is performed to achieve deep structure measurement, then measurement accuracy is improved, but measurement time and process complexity increase
Solution Approach 1:
The patent performs cross-sectional preparation in advance on dedicated target structures that are fabricated alongside the device structures. These pre-prepared cross-sections can then be stored and measured later using transmission electron microscopy, allowing deep structure measurement without adding time to the critical device fabrication process. The preliminary action of preparing targets in advance decouples the measurement time from the fabrication timeline.
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 more efficient and accurate measurement of high-aspect ratio structures by improving sensitivity and reducing parameter correlation, thereby increasing device yield and reducing the need for destructive sample preparation.
Implementation Method 1
an x-ray illumination source configured to emit an amount of x-ray illumination light
Implementation Method 2
an amount of x-ray light reflected from or transmitted through the semiconductor wafer is detected
Data Source
AI summary
Methods and systems for more efficient X-Ray scatterometry measurements of on-device structures are presented herein. X-Ray scatterometry measurements of one or more structures over a measurement area includes a decomposition of the one or more structures into a plurality of sub-structures, a decomposition of the measurement area into a plurality of sub-areas, or both. The decomposed structures, measurement areas, or both, are independently simulated. The scattering contributions of each of the independently simulated decomposed structures are combined to simulate the actual scattering of the measured structures within the measurement area. In a further aspect, measured intensities and modelled intensities including one or more incidental structures are employed to perform measurement of structures of interest. In other further aspects, measurement decomposition is employed to train a measurement model and to optimize a measurement recipe for a particular measurement application.