X-ray scatterometry apparatus for high aspect ratio feature measurement
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Solution Overview
Problem
Current methods for measuring the shape and spatial dimensions of small features in the semiconductor industry, such as optical scatterometry and CD-SEM, face challenges with high aspect ratio features due to issues with light penetration and depth measurement, while X-ray techniques offer partial solutions but require improvements in efficiency and accuracy.
Innovation Solution
An X-ray scatterometry system using transmission geometry with a sample-support, X-ray source, and detector-mount configured to direct and receive X-rays at orthogonal angles, allowing for simultaneous or sequential beam operation, and a processor to analyze signals for determining sample profiles, enhancing depth penetration and measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical scatterometry is used to measure small features, then measurement capability is provided, but depth penetration and high aspect ratio feature measurement are insufficient
Solution Approach 1:
The patent changes the wavelength parameter from optical range to X-ray range, enabling deep penetration into high aspect ratio features while maintaining measurement precision through diffraction analysis of the transmitted X-rays
2Measurement precision
If CD-SEM is used to measure feature dimensions, then top-down imaging capability is provided, but depth information and internal feature measurement are not available
Solution Approach 1:
The patent replaces the mechanical scanning electron beam with X-ray transmission and diffraction analysis, enabling non-contact measurement of internal and depth information through the sample while maintaining dimensional precision
3Measurement precision
If AFM probe tip is used to measure features, then individual feature measurement is provided, but probe tip cannot be inserted into features of interest
Solution Approach 1:
The patent replaces the mechanical AFM probe with a non-contact X-ray transmission system that can penetrate and measure features from the backside, providing complete accessibility to all feature types including high aspect ratio structures
4Measurement precision
If single wavelength X-ray beam is used, then measurement is provided, but measurement efficiency and accuracy are insufficient
Solution Approach 1:
The patent uses multiple discrete wavelengths in a periodic scanning approach, measuring diffraction at each wavelength and combining the data to achieve high precision profile determination while maintaining efficient measurement throughput
Solution Approach 2:
The patent dynamically adjusts the X-ray wavelength during measurement, scanning through a range of wavelengths to optimize the diffraction signal for different feature depths and dimensions, thereby improving both accuracy and efficiency
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
The system effectively measures cross-sectional shapes of high aspect ratio features by penetrating the entire sample depth and providing accurate profile determination, improving measurement efficiency and accuracy compared to existing techniques.
Implementation Method 1
an X-ray detector positioned in the second region on the detector-mount and configured to receive first and second diffracted beams of X-rays transmitted through the sample
Implementation Method 2
X-ray scatterometry system using transmission geometry with a sample-support, X-ray source, and detector-mount configured to direct and receive X-rays at orthogonal angles
Data Source
AI summary
Apparatus, including a sample-support that retains a sample in a plane having an axis, the plane defining first and second regions separated by the plane. A source-mount in the first region rotates about the axis, and an X-ray source on the source-mount directs first and second incident beams of X-rays to impinge on the sample at first and second angles along beam axes that are orthogonal to the axis. A detector-mount in the second region moves in a plane orthogonal to the axis and an X-ray detector on the detector-mount receives first and second diffracted beams of X-rays transmitted through the sample in response to the first and second incident beams, and outputs first and second signals, respectively, in response to the received first and second diffracted beams. A processor analyzes the first and the second signals so as to determine a profile of a surface of the sample.