Charged Particle Beam Microscope Adaptive Signal Processing
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Solution Overview
Problem
Current charged particle beam microscopes face challenges in acquiring high-resolution images of small defects in semiconductor devices and magnetic disks due to reduced contrast and prolonged image acquisition times, especially when observing features like hole or groove bottoms, where the number of secondary electrons is low, leading to attenuated detecting signals and weakened image contrast.
Innovation Solution
A charged particle beam microscope incorporating a beam dwell integration selector and frame integration selector to determine optimal integration methods, allowing for efficient detection and integration of secondary particles, thereby enhancing image contrast and reducing acquisition time by switching between electron counting and analog signal detection methods based on the number of secondary electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of secondary electrons is low (as in hole or groove bottom observation), then the image contrast is weakened and signal-to-noise ratio is reduced, but increasing beam current or dwell time to improve signal strength prolongs the image acquisition time
Solution Approach 1:
The patent applies dynamics by dynamically switching between electron counting mode and analog signal detection mode based on the detected number of secondary electrons. The system adaptively adjusts the signal processing method in real-time: when secondary electron count is low (as in hole/groove bottom regions), it uses electron counting with frame integration to maximize contrast; when count is high, it switches to analog mode for faster acquisition, thus resolving the contradiction between image contrast and acquisition time.
Solution Approach 2:
The patent changes the detection parameter (electron counting vs. analog signal detection) based on the secondary electron signal strength. By monitoring the number of detected secondary electrons and adjusting the processing mode accordingly, the system optimizes both image contrast and acquisition time differentially across different regions of the sample, allowing high contrast where needed without universally prolonging acquisition time.
2Measurement precision
If electron counting method is used to improve signal-to-noise ratio in low secondary electron regions, then image contrast is enhanced, but the processing complexity and time per pixel increases
Solution Approach 1:
The patent applies local quality by applying different signal processing methods to different regions based on local secondary electron yield. Electron counting with frame integration is applied locally to regions with low secondary electron emission (hole bottoms, groove bottoms), while standard analog processing is used in regions with high emission. This localized approach enhances S/N ratio only where necessary without increasing overall processing complexity across the entire image.
Solution Approach 2:
The system dynamically selects the processing mode (electron counting vs. analog) based on real-time measurement of secondary electron signal strength. This dynamic adaptation allows the system to use the more complex electron counting method only when and where it is needed (low signal regions), thereby improving S/N ratio selectively without universally increasing processing complexity.
3Productivity
If the beam current is increased to reduce image acquisition time, then productivity is improved, but the resolution deteriorates due to increased probe diameter
Solution Approach 1:
The patent uses dynamics by adaptively switching between electron counting mode and analog mode based on signal strength. This allows the system to maintain high resolution (using low beam current with electron counting) in regions where it is needed for contrast, while potentially using faster analog processing in high-signal regions. The key is that electron counting enables efficient use of low beam current by maximizing signal utilization, thus maintaining resolution without sacrificing excessive acquisition time.
Solution Approach 2:
The patent replaces the mechanical approach of increasing beam current to improve signal strength with an electronic signal processing approach (electron counting and frame integration). Instead of physically increasing the beam current (which would increase probe diameter and reduce resolution), the system uses digital/electronic methods to amplify and process the weak signal from low secondary electron regions, thereby maintaining both resolution and acquisition 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 microscope effectively acquires images with emphasized contrast of hole or groove bottoms in a short time, improving signal-to-noise ratio and enabling high-resolution inspections of semiconductor devices and magnetic disks by dynamically selecting integration methods tailored to the number of secondary electrons detected.
Implementation Method 1
a charged particle source 111 of generating an electron beam 110
Implementation Method 2
an electromagnetically superposing type objective lens 113 of converging the electron beam 110
Implementation Method 3
a detector 119 of detecting a subsidiary particle 118 caused by the secondary particle 115
Data Source
AI summary
This charged particle beam microscope is characterized by being provided with selection means (153, 155) for a measurement processing method for detected particles (118) and by this means selecting a different measurement processing method for a scanning region with a large number of secondary electrons (115) emitted from a sample (114) and for a region with a small number of secondary electrons. Thus, in sample scanning using a charged particle beam microscope, an image in which the contrast of bottom holes and channel bottoms with few emitted secondary electrons is emphasized and images that emphasize shadow contrast can be acquired in a short period of time.