SEM Backscattered Electron Detector Signal Switching
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Solution Overview
Problem
Conventional three-dimensional shape measuring devices using scanning electron microscopes with multiply-segmented backscattered electron detectors require multiple signal amplifiers, A/D converters, and frame memories, leading to a larger and more costly system, and suffer from quantization errors due to brightness adjustments in three-dimensional shape measurement.
Innovation Solution
A scanning electron microscope configuration that includes a means for switching detection signals from segmented backscattered electron detectors, frame memories equal to the number of detector divisions, and mechanisms for adjusting brightness and contrast to minimize offset and saturation, allowing for three-dimensional shape measurement with reduced hardware requirements and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple signal amplifiers, A/D converters, and frame memories are provided for each segmented detector element, then three-dimensional shape measurement capability is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple detector elements into a single integrated backscattered electron detector with segmented structure. Instead of providing separate signal amplifiers, A/D converters, and frame memories for each segment, the invention uses a shared signal processing chain that sequentially processes signals from different segments, thereby reducing the total number of components while maintaining 3D measurement capability
Solution Approach 2:
The signal processing components (amplifier, A/D converter, frame memory) are designed to serve multiple detector elements sequentially. The same hardware resources are reused for processing signals from different segments at different time intervals, making the system multi-functional rather than requiring dedicated components for each segment
2Illumination intensity
If brightness adjustment is applied in three-dimensional shape measurement, then image quality is improved, but quantization errors occur due to offset and saturation
Solution Approach 1:
The patent performs preliminary actions by acquiring dark current data and reference images before actual measurement. The dark current offset is measured and stored in advance, then subtracted from subsequent measurements to prevent quantization errors. This preliminary calibration ensures that brightness adjustment does not introduce measurement errors
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring signal levels and adjusting brightness/contrast parameters based on measured data. The dark current subtraction and reference image comparison provide feedback loops that compensate for offset and saturation effects, maintaining measurement precision while allowing brightness adjustment
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 configuration simplifies the system, reduces costs, and minimizes quantization errors, enabling efficient three-dimensional shape measurement without the need for dedicated devices, while maintaining high measurement accuracy by optimizing brightness and contrast settings.
Implementation Method 1
a backscattered electron emitted from the sample 4 is detected by a backscattered electron detector 6
Data Source
AI summary
In three-dimensional shape measurement, a backscattered electron detection signal and selection signal generator in a control section controls, by selection signal, a signal switching section and a frame memory so that: detection signals from respective semiconductor elements are sequentially switched in the signal switching section in synchronization with a scanning frame of an electron beam on a sample; and the detection signals from the respective semiconductor elements can be sequentially recorded in recording addresses in the frame memory which correspond to the respective semiconductor elements. After four electron beam scanning sessions, each image data for three-dimensional shape measurement is recorded in the frame memory, and processed in a computing processing section for three-dimensional shape measurement, and the result can be displayed in a display section. The backscattered electron detection signal and selection signal generator in the control section is configured to include, for example, a counter updated in frame scanning units, and can be composed of a very simple circuit or software.