Pulsed Charged Particle Beam Scanning for Fringe-Free Dose Control
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Solution Overview
Problem
In charged particle beam apparatuses like transmission electron microscopes, adjusting the illumination dose of the electron beam requires changes in condenser lens excitation and aperture size, leading to axis alignment and aberration correction adjustments, and results in optical system changes that can cause bright and dark fringes on the scan image.
Innovation Solution
A charged particle beam apparatus with a pulse mechanism and deflector system controlled to satisfy T=n×t, where T is the dwell time and t is the cycle of pulses, allowing for precise control of illumination dose without altering condenser lens excitation or aperture size, preventing bright and dark fringes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the excitation of the condenser lens is changed to adjust illumination dose, then the illumination dose can be adjusted, but axis alignment and adjustment of the aberration correction apparatus are needed
Solution Approach 1:
The patent applies periodic action by using a pulse mechanism to illuminate the specimen with pulsed electron beams instead of continuous illumination. By controlling the pulse width and repetition frequency, the illumination dose can be adjusted without changing condenser lens excitation or aperture size, thereby avoiding the need for axis alignment and aberration correction adjustments.
2Use of energy by moving object
If the size of the aperture is changed to adjust illumination dose, then the illumination dose can be adjusted, but the aperture has to be adjusted and the convergence angle of the electron beam changes
Solution Approach 1:
The patent uses periodic pulsed illumination to control the illumination dose by adjusting pulse width and repetition frequency rather than changing aperture size. This approach maintains a fixed aperture and convergence angle, eliminating the need for mechanical aperture adjustments and associated complexity.
3Use of energy by moving object
If the illumination dose of the electron beam is changed, then the illumination dose can be adjusted, but the conditions of the optical system change and in some cases the optical system has to be adjusted
Solution Approach 1:
The patent employs periodic pulsed electron beam illumination where the illumination dose is controlled by varying pulse parameters (width and repetition frequency) rather than changing optical system conditions. This maintains stable optical system settings while achieving flexible dose control, improving adaptability without requiring optical re-adjustment.
Data Source
AI summary
A charged particle beam apparatus for scanning a specimen with a charged particle beam and acquiring a scan image. The charged particle beam apparatus including: an optical system that includes a pulse mechanism for illuminating the specimen with pulses of the charged particle beam, and a deflector that deflects the charged particle beam and scans the specimen with the deflected charged particle beam; and a control unit that controls the optical system. The control unit controls the optical system so as to satisfy T=n×t (n is a natural number). T represents a dwell time of the charged particle beam in each pixel of the scan image, and t represents a cycle of pulses of the charged particle beam.