Charged Beam Device Scan Speed Switching
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Solution Overview
Problem
Charged beam devices face challenges in achieving high accuracy and throughput during focus and astigmatism correction due to charge-up on insulating materials, leading to measurement errors and reduced image precision.
Innovation Solution
A charged beam device with a switchable scan speed and interval, allowing for high-speed focus and astigmatism correction using a larger scan speed and integral multiple scan line intervals, and returning to skipped positions, reduces charge-up and improves image accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charged beam scans the sample surface at a low scan speed to improve image quality and reduce charge-up effects, then measurement accuracy improves, but inspection throughput deteriorates
Solution Approach 1:
The patent applies dynamics by making the scan speed variable rather than fixed. The control unit dynamically adjusts scan speed based on the inspection stage: using high scan speed for focus/astigmatism correction and low scan speed for actual measurement. This resolves the contradiction by allowing the system to optimize for speed when necessary and for accuracy when critical.
Solution Approach 2:
The patent implements periodic action through multi-frame scanning where the charged beam scans the same region multiple times at different scan speeds. Focus/astigmatism correction uses high-speed scanning repeated across multiple frames, while measurement uses low-speed scanning. This periodic alternation between high-speed and low-speed scanning modes allows the system to achieve both high throughput and high measurement accuracy.
2Ease of operation
If the same scan speed is used for both focus/astigmatism correction and measurement, then device operation is simplified, but charge-up on insulating materials causes focus measurement errors
Solution Approach 1:
The patent makes scan speed dynamic by implementing different scan speeds for different operational stages. During focus/astigmatism correction, high scan speed is used to minimize charge-up accumulation. During actual measurement, low scan speed is used to ensure image quality. The control unit automatically manages this dynamic adjustment, maintaining operational simplicity while eliminating measurement errors.
Solution Approach 2:
The patent segments the inspection process into distinct stages with different scan speed requirements: focus/astigmatism correction stage and measurement stage. Each stage is independently optimized with appropriate scan speed settings. This segmentation allows the system to address charge-up issues during correction without compromising measurement accuracy, while the automated control maintains ease of operation.
3Measurement precision
If high scan speed is used during focus/astigmatism correction, then charge-up effects are reduced and measurement accuracy improves, but image signal-to-noise ratio deteriorates
Solution Approach 1:
The patent uses periodic action through multi-frame scanning to compensate for the noise introduced by high-speed scanning during focus/astigmatism correction. By repeatedly scanning the same region multiple times at high speed and combining the frames, the system maintains low charge-up effects while improving the signal-to-noise ratio through signal accumulation. This allows high scan speed to be used without sacrificing image quality.
Solution Approach 2:
The patent maintains continuity of useful action by performing multiple frames of high-speed scanning continuously during focus/astigmatism correction. Rather than using a single low-speed scan that would accumulate charge, the system continuously performs multiple high-speed scans, ensuring that the useful action of focus correction is maintained while minimizing charge-up effects and improving signal quality through frame accumulation.
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 enhances the accuracy of focus and astigmatism correction, resulting in precise pattern images and improved reproducibility of measurements, while maintaining high throughput.
Implementation Method 1
a charged beam generator; a deflection control portion which allows a charged beam generated by the charged beam generator to scan
Implementation Method 2
there occur focus measurement errors in the automatic focus/astigmatism correction step due to charge-up on a wafer surface
Data Source
AI summary
In order to provide a charged beam device capable of obtaining a precise image of a sample surface pattern while improving the accuracy of automatic focus/astigmatism correction, there are provided an electron gun (1), a deflection control portion (8) which allows an electron beam to scan, a focus control portion (10) and an astigmatism correction portion (3) for the electron beam, an image processing portion (11), and a switching portion (9) which switches scan conditions when obtaining pattern information of the sample (1001) surface and scan conditions when performing the automatic focus/astigmatism correction, and a scan speed and scan procedures are switched between when obtaining the pattern information and when performing the automatic focus/astigmatism correction.