Electron Beam Device Stray Light Suppression
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Solution Overview
Problem
In electron beam devices with two columns, including an irradiation optical system and an imaging optical system, the adjustment of optical axes is challenging due to stray light from ultraviolet rays entering the sensor, leading to a blurry photoelectron image.
Innovation Solution
An electron beam device with a stray light suppression part between the sensor and the stage, which uses a negative voltage to invert the electron beam and form a mirror electron image, and a light irradiation unit to enhance photoelectron image sharpness by suppressing stray light with a cylindrical or shielding part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the intensity of ultraviolet light is increased to secure the contrast of the photoelectron image, then the photoelectron image contrast is improved, but stray light enters the sensor making a clear photoelectron image unobtainable
Solution Approach 1:
The harmful stray light is extracted and removed from the optical path by introducing a stray light suppression part (blackening treatment) between the sensor and the sample stage, allowing the ultraviolet light intensity to be increased without compromising image quality
Solution Approach 2:
A stray light suppression part (blackening treatment) is introduced as an intermediary element between the ultraviolet light source and the sensor to block stray light while allowing the desired photoelectron signal to pass through
2Ease of operation
If photoelectrons are used for optical axis adjustment, then the imaging optical system can be adjusted, but the photoelectron image has lower intensity and poor contrast
Solution Approach 1:
The intensity parameter of ultraviolet light is increased to enhance photoelectron generation, and combined with stray light suppression, this resolves the low intensity problem while maintaining optical axis adjustment functionality
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 sharper photoelectron images for accurate optical axis adjustment, improving the clarity and contrast of images obtained in the electron beam device.
Implementation Method 1
a light irradiation unit (50) that irradiates the sample (30) with light containing ultraviolet rays
Implementation Method 2
a sample voltage control unit (44) that applies a negative voltage to the sample (30) so that, before the electron beam reaches the sample (30), the electron orbit inverts
Data Source
AI summary
In an electron beam device provided with two columns including an irradiation optical system and an imaging optical system, a photoelectron image for use in adjusting the irradiation optical system is made sharper. The electron beam device includes: an irradiation optical system which irradiates a sample placed on a stage with an electron beam; a light irradiation unit 50 which irradiates the sample with light containing ultraviolet rays; a sample voltage control unit 44 which applies a negative voltage to the sample so that, before the electron beam reaches the sample, the electron orbit inverts; and an imaging optical system which acquires a mirror electron image by forming an image of mirror electrons reflected by application of the negative voltage. In the electron beam device, the imaging optical system includes a sensor 32 which obtains a mirror electron image and a stray light suppression part 27 which is provided between the sensor and the stage 31 and which suppresses reaching the sensor of the light emitted from the light irradiation unit.