Scanning Electron Microscope Depth Measurement Without Calibration
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Solution Overview
Problem
Existing scanning electron microscopes require pre-calibrated information for each pattern to measure the depth of three-dimensional structures like grooves or holes, which is impractical and limits their versatility.
Innovation Solution
A scanning electron microscope system that includes an electron gun, a detection unit for electrons within specific emission angles, and a control unit to set and adjust these angles, allowing for the calculation of the opening angle from the emission angle distribution to determine the depth of three-dimensional structures without prior calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-calibrated information is prepared for each pattern to measure depth, then measurement precision is improved, but device complexity and ease of operation deteriorate due to the need for separate calibration for each imaging target
Solution Approach 1:
The patent extracts the calibration information requirement from the measurement process by using a standardized test pattern with known dimensions. Instead of preparing custom calibration data for each imaging target, the system uses a universal test pattern that can be imaged to establish the relationship between apparent size and actual size, thereby eliminating the need for pattern-specific calibration preparation.
Solution Approach 2:
The patent performs preliminary calibration using a test pattern with known dimensions before actual measurements. By imaging the test pattern and calculating the conversion ratio between apparent and actual dimensions once, the system establishes a reusable calibration that can be applied to subsequent measurements without repeating the calibration process for each new target.
2Measurement precision
If pre-calibration is performed for each imaging target, then measurement accuracy is improved, but loss of time increases due to repeated calibration processes
Solution Approach 1:
The system performs the calibration action in advance using a standardized test pattern, establishing a conversion ratio that can be reused for multiple measurements. This preliminary calibration eliminates the need to repeat the time-consuming calibration process for each new imaging target, thereby reducing time loss while maintaining measurement accuracy.
Solution Approach 2:
The test pattern with known dimensions serves as a universal calibration standard that can be used for multiple different imaging targets. The calibration information derived from this single test pattern can be applied universally across different samples and measurement scenarios, eliminating the need for target-specific calibration and reducing overall calibration time.
3Measurement precision
If separate calibration is prepared for each pattern type, then adaptability deteriorates, but measurement precision is improved for calibrated patterns
Solution Approach 1:
The patent employs a universal test pattern with known dimensions that serves as a general calibration standard for all imaging targets. By establishing a conversion ratio from this single test pattern, the system achieves the ability to measure various different patterns and structures without requiring separate calibration for each, thereby maintaining high adaptability and versatility across diverse applications.
Solution Approach 2:
The patent extracts the essential calibration information from a standardized test pattern, separating the calibration process from the specific imaging target. This extracted calibration data in the form of a conversion ratio can be universally applied to different patterns, eliminating the need for pattern-specific calibration preparation while maintaining measurement precision.
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
Enables the measurement of three-dimensional structure depths without pre-calibration, improving the system's flexibility and accuracy in analyzing various patterns and materials.
Implementation Method 1
an electron gun configured to irradiate a sample formed in a three-dimensional structure with a primary electron beam
Implementation Method 2
a detection unit configured to detect, among emitted electrons generated from the sample by irradiating the sample with the primary electron beam, emitted electrons whose emission angles are in a predetermined range
Data Source
AI summary
To measure a depth of a three-dimensional structure, for example, a hole or a groove, formed in a sample without preparing information in advance, an electron microscope detects, among emitted electrons generated by irradiating a sample with a primary electron beam, an emission angle in a predetermined range, the emission angle being formed between an axial direction of the primary electron beam and an emission direction of the emitted electrons, and outputs a detection signal corresponding to the number of the emitted electrons detected. An emission angle distribution of a detection signal is obtained based on a plurality of detection signals, and an opening angle is obtained based on a change point of the emission angle distribution, the opening angle being based on an optical axis direction of the primary electron beam with respect to the bottom portion of the three-dimensional structure.