Adjusting Electron Beam Trajectories in Multi-Beam Inspection
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Solution Overview
Problem
In image acquisition apparatuses using multiple electron beams, the adjustment of primary and secondary optical systems is interdependent, creating a contradiction where the completion of one system is dependent on the completion of the other, making simultaneous adjustment challenging and affecting the accuracy of secondary electron image acquisition.
Innovation Solution
The method involves extracting one primary electron beam at a time from multiple beams, adjusting its trajectory using primary electron optics, and then adjusting the secondary electron trajectory using secondary electron optics, with a movable detector guiding secondary electrons to a wide-area detector for alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the adjustment of the secondary optical system is completed first, then the primary optical system can be adjusted, but the secondary electron image cannot be obtained without completed secondary optical system adjustment
Solution Approach 1:
A movable detector is introduced as an intermediary device to temporarily guide secondary electrons during the adjustment process. This detector can be positioned at different locations to first enable primary optical system adjustment, then moved to allow secondary optical system adjustment, resolving the interdependence contradiction between the two systems
2Manufacturing precision
If the adjustment of the primary optical system is completed first, then the secondary optical system can be adjusted, but the secondary electrons deviate from the optical path without completed primary optical system adjustment
Solution Approach 1:
The adjustment process is segmented into distinct phases: first adjusting the primary optical system with the movable detector in position, then adjusting the secondary optical system after moving the detector. This segmentation allows each subsystem to be adjusted independently without interference, reducing the overall complexity of simultaneous adjustment
3Productivity
If multiple beams are adjusted simultaneously, then the adjustment time is reduced, but the interdependence between primary and secondary systems creates adjustment conflicts
Solution Approach 1:
The adjustment process uses periodic action by sequentially adjusting different beams in a structured sequence rather than simultaneously. The movable detector is periodically repositioned to facilitate different adjustment phases, ensuring reliable adjustment while maintaining reasonable efficiency through systematic progression
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 allows for precise adjustment of both primary and secondary electron beams, enabling accurate secondary electron image acquisition and improving pattern inspection accuracy in semiconductor wafer manufacturing.
Implementation Method 1
multiple secondary electrons emitted due to irradiation of a target object surface with multiple primary electron beams
Implementation Method 2
adjusting a trajectory of the one primary electron beam using a primary electron optics
Implementation Method 3
adjusting a trajectory of the secondary electrons using a secondary electron optics such that the secondary electrons corresponding to the one primary electron beam are detected
Data Source
AI summary
According to one aspect of the present invention, an optical system adjustment method of an image acquisition apparatus includes: extracting one primary electron beam after another from primary electron beams at a plurality of preset positions among multiple primary electron beams; and adjusting, a first detector being capable of individually detecting multiple secondary electrons emitted due to irradiation of a target with the multiple primary electron beams, a trajectory of the one primary electron beam using a primary electron optics while detecting secondary electrons corresponding to the one primary electron beam for each of the primary electron beams extracted one by one using a movable second detector having an inspection surface of a size capable of detecting the multiple secondary electrons as a whole and arranged on an optical path for guiding the multiple secondary electrons to the first detector.