Electron Beam Detector Voltage Control for Axial Shift
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Solution Overview
Problem
Existing electron beam irradiation apparatuses face axial misalignment and aberration due to asymmetric electric fields generated by backscattered electron detectors, which affect the accuracy and resolution of semiconductor device measurements.
Innovation Solution
An electron beam irradiation apparatus with a scanning deflector and multiple backscattered electron detectors, where a controller device adjusts the voltage applied to the detectors to compensate for image shifts caused by the electric fields, ensuring axial symmetry and maintaining high signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high voltage is applied to backscattered electron detectors to detect reflected electrons with high efficiency, then detection efficiency is improved, but axial misalignment and aberration occur due to asymmetric electric fields
Solution Approach 1:
The patent applies asymmetry principle by intentionally introducing a correcting electric field with opposite asymmetry to counterbalance the asymmetric distortion caused by detector electric fields. The correcting electrode is positioned asymmetrically relative to the optical axis, creating a controlled asymmetric field that compensates for the asymmetric misalignment and aberration induced by the backscattered electron detectors.
Solution Approach 2:
The patent employs parameter changes by adjusting the voltage applied to the correcting electrode to dynamically control the strength and distribution of the correcting electric field. By varying the voltage parameter, the system can adaptively compensate for axial misalignment and aberration under different operating conditions, maintaining image quality while detectors operate at optimal high voltage.
2Adaptability or versatility
If multiple backscattered electron detectors are arranged axially symmetrically to detect reflected electrons in respective directions, then detection coverage is improved, but electric field asymmetry causes image shifts and aberration
Solution Approach 1:
The patent introduces a correcting electrode as an intermediary element that mediates between the backscattered electron detectors and the electron beam optical system. This correcting electrode generates an electric field that acts as a buffer to counterbalance the asymmetric influences from the detectors, thereby preserving both the multi-directional detection capability and the positional accuracy of the formed image.
3Measurement precision
If voltages are applied to backscattered electron detectors to generate electric fields for electron detection, then electron signal detection is improved, but axial shift and aberration occur affecting measurement accuracy
Solution Approach 1:
The patent implements preliminary anti-action by pre-introducing a correcting electric field through the correcting electrode that opposes and counterbalances the asymmetric electric fields generated by the backscattered electron detectors before they can cause significant axial misalignment and aberration. This proactive compensation maintains beam optical alignment while allowing detectors to operate at optimal voltage for sensitive electron signal detection.
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
The solution effectively suppresses axial shifts and aberrations, enhancing the resolution and accuracy of semiconductor device measurements by utilizing the electric field generated by the detectors for correction and focal distance adjustment.
Implementation Method 1
influences the electric fields based on applied voltages have upon the electron beam
Implementation Method 2
a scanning deflector adapted to scan the electron beam emitted from an electron source
Data Source
AI summary
The present invention has for its object to provide an electron beam irradiation apparatus which can suppress influences the electric fields generated by a plurality of backscattered electron detectors have. To attain the above object, an electron beam irradiation apparatus equipped with a scanning deflector comprises a plurality of backscattered electron detectors, a power source for detectors which applies voltages to the plural backscattered electron detectors, respectively, and a controller device which adjusts application voltages the power source for detectors delivers, on the basis of an image shift when the voltages are applied to the plural backscattered electron detectors.