X-ray Scatterometry for High-Aspect-Ratio Stack Tilt
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Solution Overview
Problem
Current techniques face challenges in accurately measuring the shift and tilt of high aspect ratio (HAR) structures, particularly in stacked configurations, which are crucial for advanced memory technologies like 3D NAND flash, due to limitations in X-ray scatterometry measurements.
Innovation Solution
The method involves generating and directing an X-ray beam to samples with HAR structures, measuring X-ray scatter profiles as a function of tilt angle, and estimating the shift and characteristic tilt using regression models, including machine learning approaches, to improve accuracy and precision in determining structural parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional X-ray scatterometry measurements are used to measure shift and tilt of stacked HAR structures, then the measurement process is simple, but the measurement precision is insufficient
Solution Approach 1:
The patent implements dynamic measurement by rotating the sample stage to acquire X-ray scatter profiles at multiple tilt angles (ω1, ω2, ..., ωn). This dynamic approach allows the measurement system to capture structural information from different orientations, enabling accurate determination of both shift and tilt parameters of stacked HAR structures through computational analysis of the varying scatter patterns
Solution Approach 2:
The patent transitions from conventional single-angle measurement to multi-dimensional measurement by introducing the tilt angle dimension. By measuring X-ray scatter profiles as a function of tilt angle in addition to the standard in-plane rotation, the system creates a three-dimensional measurement space (q_x, q_y, ω) that provides sufficient information to independently determine both lateral shift and angular tilt parameters
2Measurement precision
If multiple measurement angles are used to improve measurement accuracy, then the measurement precision improves, but the measurement time increases
Solution Approach 1:
The patent applies partial action by selecting a specific, optimized set of tilt angles (ω1, ω2, ..., ωn) that provides sufficient measurement information without requiring exhaustive angular sampling. This selective approach achieves the necessary measurement precision for determining shift and tilt parameters while minimizing the total measurement time by avoiding redundant angular positions
3Measurement precision
If regression models including machine learning are used to estimate shift and tilt, then the estimation accuracy improves, but the data processing complexity increases
Solution Approach 1:
The patent replaces traditional mechanical/physical estimation methods with computational regression models and machine learning algorithms. By substituting complex physical analysis with data-driven statistical models that correlate measured X-ray scatter profiles at multiple tilt angles to structural parameters, the system achieves high estimation accuracy while the computational complexity is managed through optimized algorithm selection and training
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 shifts and tilts between stacked HAR structures, enhancing process control and providing reliable data for physical models, thereby improving the accuracy and throughput of X-ray scatterometry analysis.
Implementation Method 1
X-ray scatter profiles are measured, that are emitted from the sample location in response to the X-ray beam as a function of tilt angle between the sample and the X-ray beam
Data Source
AI summary
A method for X-ray measurement includes generating and directing an X-ray beam to a sample including at least first and second layers stacked on one another, the X-ray beam incident on a sample location at which the first and second layers include respective first and second high aspect ratio (HAR) structures. X-ray scatter profiles are measured, that are emitted from the sample location in response to the X-ray beam as a function of tilt angle between the sample and the X-ray beam. A shift is estimated, between the first and second layers and a characteristic tilt of the first and second layers, based on the X-ray scatter profiles measured as a function of the tilt angle.