Scanning Electron Microscope Drift Correction
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Solution Overview
Problem
Scanning electron microscopes face challenges in obtaining clear images and precise dimension measurements at high magnification due to image drift caused by sample charging, leading to image blur and reduced measurement accuracy.
Innovation Solution
A scanning electron microscope system that includes an image recording unit, a correction analyzing handling unit, and a data handling unit to calculate and correct image drift rates, superimpose field images, and form clear frame images, enabling accurate pattern dimension measurement on semiconductor or insulating substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high magnification observation is performed to measure fine pattern dimensions, then measurement precision is improved, but image drift occurs causing image blur and reducing measurement accuracy
Solution Approach 1:
The system performs preliminary drift rate calculations between frame images before correcting the field images. By anticipating and calculating the drift that will occur during high magnification observation, the system can pre-compensate for these movements, ensuring that the final measurement is not affected by image drift-induced blur.
Solution Approach 2:
The system continuously monitors image drift by calculating drift rates between sequentially acquired frame images, then uses this feedback information to correct the positions of field images. This closed-loop feedback mechanism ensures that even as drift occurs during observation, the system can dynamically adjust and maintain measurement accuracy.
2Measurement precision
If multiple frame images are acquired to improve measurement accuracy, then measurement precision is improved, but image drift causes blur that reduces the effectiveness of image accumulation
Solution Approach 1:
The system calculates drift rates between frame images before performing image accumulation. By determining the drift characteristics in advance, the system can apply appropriate corrections to each field image before superimposition, ensuring that the accumulated image maintains clarity and does not suffer from drift-induced blur that would otherwise negate the benefits of multiple image acquisition.
Solution Approach 2:
The drift rate calculation between frame images provides continuous feedback about image movement. This feedback is used to dynamically adjust the positioning and alignment of field images during accumulation, ensuring that each contributed image is properly registered. This prevents information loss due to blur while maintaining the measurement precision benefits of multiple image acquisition.
3Reliability
If frame images are corrected using drift rate between frames, then image stability is improved, but drift within field images remains causing measurement errors
Solution Approach 1:
The system segments the correction process into two distinct levels: first correcting drift between entire frame images, then separately correcting drift within individual field images. This segmentation allows each level of drift to be addressed with appropriate correction methods, ensuring that both inter-frame and intra-field drift are compensated to achieve high measurement precision.
Solution Approach 2:
The system applies different correction approaches to different parts of the image data. Frame-level drift correction addresses global image movement, while field-level drift correction addresses local variations within each field image. This local quality approach ensures that measurement precision is maintained across the entire observation area, accounting for both macro and micro drift effects.
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 achieves clear images and high precision in measuring pattern dimensions on substrates, even with image drift, by correcting field image shifts and forming new frame images, thereby improving measurement accuracy to 0.5 nm or lower.
Implementation Method 1
a sample is irradiated with an electron beam which has been finely narrowed, and a secondary electron and a backscattered electron generated by the irradiation of the electron beam are detected
Implementation Method 2
a deflector which scans an electron emitted from the electron beam source
Implementation Method 3
The major factor of generating image drift is the charging of the sample due to the irradiation of the electron beam
Data Source
AI summary
Provided is a scanning electron microscope including: an image recording unit (112) which stores a plurality of acquired frame images; a correction analyzing handling unit (113) which calculates a drift amount between frame images and a drift amount between a plurality of field images constituting a frame image; and a data handling unit (111) which corrects positions of respective field images constituting the plurality of fields images according to the drift amount between the field images and superimposes the field images on one another so as to create a new frame image. This provides a scanning electron microscope which can obtain a clear frame image even if an image drift is caused during observation of a pattern on a semiconductor substrate or an insulating object.