CD-SEM Edge Detection Correction for Scanning Direction Errors
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Solution Overview
Problem
Current semiconductor inspection techniques, such as CD-SEM, face challenges in accurately measuring pattern edge positions due to variations in secondary electron generation intensity and distribution caused by electron beam scanning direction and pattern edge orientation, leading to errors in edge detection and measurement accuracy, especially for fine patterns less than 32 nm.
Innovation Solution
The method involves pre-characterizing and correcting secondary electron signal differences based on electron beam scanning direction and pattern edge orientation, using a library to adjust the scanning error, allowing for accurate measurement of pattern edges in all directions by compensating for scanning position and direction errors during the measurement process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the electron beam scanning direction is changed to measure pattern edges in all directions, then measurement coverage is improved, but measurement precision deteriorates due to variations in secondary electron generation intensity and distribution
Solution Approach 1:
The patent changes the parameters of secondary electron signal processing by introducing direction-dependent correction values. The system adjusts the signal intensity and distribution parameters based on the scanning direction and pattern edge orientation, allowing accurate measurement across all directions while compensating for the variations in secondary electron generation
Solution Approach 2:
The system implements a feedback mechanism by comparing the measured pattern edge positions with the stored correction values in the library. The correction values are applied based on the detected scanning direction and pattern edge orientation, creating a closed-loop system that compensates for measurement errors and maintains precision across different measurement conditions
2Measurement precision
If the electron beam is constantly scanned vertically to the pattern edge direction, then measurement precision is improved, but device complexity increases due to the need for dynamic scanning direction control
Solution Approach 1:
The system performs preliminary action by pre-characterizing the secondary electron signal variations for different scanning directions and pattern edge orientations. These correction values are stored in a library before actual measurement, eliminating the need for real-time dynamic scanning direction control and reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent creates a virtual model of the secondary electron signal characteristics by copying and storing correction values for different scanning conditions in a library. This virtual model allows the system to compensate for direction-dependent variations without requiring complex real-time control of the electron beam scanning direction
3Adaptability or versatility
If the scanning direction is changed to accommodate different pattern orientations, then adaptability is improved, but measurement precision deteriorates due to scanning position and direction errors
Solution Approach 1:
The system compensates for scanning position and direction errors by changing the parameters of the measurement data through correction values. These correction values adjust the measured edge positions based on the scanning direction and pattern orientation, maintaining accuracy across all pattern orientations while allowing flexible scanning
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 significantly reduces measurement errors in pattern edge positions, enabling high-accuracy detection of fine pattern edges with sub-nanometer precision across all directions, thereby improving the control and accuracy of semiconductor pattern dimensions.
Implementation Method 1
The CD-SEM is an apparatus in which the dimension of a pattern formed on a sample is measured on the basis of secondary electrons obtained by scanning an electron beam, a kind of charged-particle beam, on the sample
Data Source
AI summary
One of principal objects of the present invention is to provide a sample dimension measuring method for detecting the position of an edge of a two-dimensional pattern constantly with the same accuracy irrespective of the direction of the edge and a sample dimension measuring apparatus. According to this invention, to accomplish the above object, it is proposed to correct the change of a signal waveform of secondary electrons which depends on the direction of scanning of an electron beam relative to the direction of a pattern edge of an inspection objective pattern. It is proposed that when changing the scanning direction of the electron beam in compliance with the direction of a pattern to be measured, errors in the scanning direction and the scanning position are corrected. In this configuration, a sufficient accuracy of edge detection can be obtained irrespective of the scanning direction of the electron beam.