Charged Particle Beam Focus and Astigmatism Interlock
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Solution Overview
Problem
Charged particle beam apparatuses face challenges in achieving high resolution and wide scanning regions due to focal point shortening, leading to image blur and distortion at the periphery, which limits inspection speed and throughput, especially in semiconductor wafer fabrication processes.
Innovation Solution
A charged particle beam apparatus with integrated means for adjusting focus and astigmatism in interlocked relation to scanning position, using a stigmator and deflector to correct aberrations and distortions, allowing for high resolution imaging over a wide field of view and improved inspection speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focal point of the objective lens is shortened to achieve high resolution powering, then image resolving power is improved, but the scanning region becomes limited due to blur and distortion at the peripheral portion
Solution Approach 1:
The patent implements dynamic adjustment of focus and astigmatism correction based on the scanning position. As the charged particle beam scans across the specimen, the focus and astigmatism correction amounts are continuously adjusted according to the beam's position, allowing the system to maintain high resolution across a wider scanning region rather than being limited to the central area where fixed focus settings work adequately.
Solution Approach 2:
The patent changes the focus and astigmatism correction parameters dynamically based on scanning position. By adjusting these optical parameters as functions of the beam position, the system adapts to the varying aberrations encountered at different locations in the scanning region, thereby extending the usable scanning area while maintaining high resolution.
2Productivity
If the scanning region is expanded to improve inspection speed and throughput, then productivity is improved, but image quality deteriorates due to blur and distortion at the peripheral portion
Solution Approach 1:
The patent implements dynamic adjustment of focus and astigmatism correction based on the scanning position. As the charged particle beam scans across the specimen, the focus and astigmatism correction amounts are continuously adjusted according to the beam's position, allowing the system to maintain high resolution across a wider scanning region rather than being limited to the central area where fixed focus settings work adequately.
Solution Approach 2:
The patent changes the focus and astigmatism correction parameters dynamically based on scanning position. By adjusting these optical parameters as functions of the beam position, the system adapts to the varying aberrations encountered at different locations in the scanning region, thereby extending the usable scanning area while maintaining high resolution.
3Device complexity
If focus and astigmatism are adjusted only at the central portion, then device complexity is reduced, but measurement precision deteriorates at the peripheral portion
Solution Approach 1:
The patent implements dynamic adjustment of focus and astigmatism correction based on the scanning position. As the charged particle beam scans across the specimen, the focus and astigmatism correction amounts are continuously adjusted according to the beam's position, allowing the system to maintain high resolution across a wider scanning region rather than being limited to the central area where fixed focus settings work adequately.
Solution Approach 2:
The patent employs automatic adjustment mechanisms that utilize detection signals from the specimen to self-correct focus and astigmatism at different scanning positions. This automated approach reduces the need for manual intervention while maintaining high image quality across the entire scanning region, effectively balancing complexity and performance.
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
Enables high-resolution imaging with a wide scanning region, enhancing inspection speed and throughput by maintaining image quality across the entire scanning area, thereby addressing the limitations of existing technologies.
Implementation Method 1
means for adjusting astigmatism
Implementation Method 2
the focal point of the objective lens becomes shorter to ensure that a charged particle beam can be reduced in aberration
Implementation Method 3
the magnetic field and electric field of a deflector becomes irregular towards the peripheral portion and distortion takes place
Data Source
AI summary
A charged particle beam apparatus is provided which has high resolving power and a wide scanning region (observation field of view). The apparatus has a unit for adjusting the focus, a unit for adjusting astigmatism, a unit for controlling and detecting scanning positions and a controller operative to control the focus adjustment and astigmatism adjustment at a time in interlocked relation to the scanning positions, thereby assuring compatibility between the high resolving power and the observation view field of a wide area.