Multi-Electron Beam Lens Layout for Variable Landing Energy Focus
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Solution Overview
Problem
Existing multi-electron beam image acquisition systems face challenges in focusing primary and secondary electron beams at optimal landing energies, leading to potential crosstalk issues and limitations in image formation, especially when adjusting landing energy for different target objects.
Innovation Solution
A multi-electron beam image acquisition apparatus with a first electromagnetic lens to focus primary electron beams and a second electromagnetic lens to adjust the peak position of the magnetic field distribution, allowing for variable focusing of secondary electron beams without crosstalk, using a multi-stage electromagnetic lens configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed optical system is used to focus primary and secondary electron beams, then the system structure is simple, but it cannot achieve proper focusing when landing energy is changed
Solution Approach 1:
The patent introduces a variable focal length electromagnetic lens that can dynamically adjust its focusing power based on the landing energy of the primary electron beam. This dynamic adjustment capability allows the optical system to maintain proper focusing conditions across different landing energies without requiring complete reconfiguration of the optical path, thus resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The patent changes the operational parameters of the electromagnetic lens by adjusting its excitation current to vary the focal length according to the primary beam's landing energy. This parameter change approach enables the system to adapt to different energy conditions while maintaining a relatively simple optical structure, avoiding the need for multiple fixed lenses or complex mechanical adjustments.
2Manufacturing precision
If multiple electron beams are focused using a fixed optical system, then the system is simple, but crosstalk occurs between secondary electron beams
Solution Approach 1:
The variable focal length electromagnetic lens dynamically adjusts the focusing strength for each secondary electron beam based on its specific trajectory and energy characteristics. This dynamic control allows each beam to be focused precisely at its intended location without interfering with adjacent beams, thereby eliminating crosstalk while maintaining system simplicity.
Solution Approach 2:
The patent applies local quality control by allowing different regions of the electromagnetic lens to provide different focal lengths for different secondary electron beams. Each beam receives a customized focusing strength appropriate to its specific path and energy, ensuring precise local image formation without affecting other beams, thus preventing crosstalk.
3Measurement precision
If the focal length is fixed for all landing energies, then the optical system is simple, but proper focusing cannot be achieved at varying landing energies
Solution Approach 1:
The electromagnetic lens's focal length is changed by adjusting its excitation current parameter. This allows the lens to provide the appropriate focal length for each landing energy condition without requiring physical reconfiguration or multiple lenses. The parameter change approach maintains system simplicity while achieving precise focusing across different energy levels.
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 accurate focusing of electron beams at varying landing energies, preventing crosstalk and ensuring effective image formation on the substrate, enhancing the precision of pattern inspection in semiconductor manufacturing.
Implementation Method 1
a first electromagnetic lens configured to focus the multiple primary electron beams to form an image on the substrate
Implementation Method 2
a separator configured to separate multiple secondary electron beams, which are emitted from the substrate due to irradiation with the multiple primary electron beams, from the multiple primary electron beams
Implementation Method 3
a second electromagnetic lens configured to be able to variably adjust a peak position of a magnetic field distribution in a direction of a trajectory central axis of the multiple secondary electron beams, and to focus the multiple secondary electron beams to form an image on either one of a detection surface of the detector and a position conjugate to the detection surface
Data Source
AI summary
A multi-electron beam image acquisition apparatus includes a first electromagnetic lens configured to focus multiple primary electron beams to form an image on a substrate, and a second electromagnetic lens configured to be able to variably adjust a peak position of a magnetic field distribution in a direction of a trajectory central axis of multiple secondary electron beams, and to focus the multiple secondary electron beams to form an image on either one of a detection surface of a detector and a position conjugate to the detection surface. The first electromagnetic lens focuses, to form an image, the multiple secondary electron beams before they are separated from the multiple primary electron beams, and the second electromagnetic lens is arranged between a separator which separates the multiple secondary electron beams and an image forming point on which the multiple secondary electron beams are focused by the first electromagnetic lens.