Charged Particle Beam Trajectory Correction via Zeroed Optical Element
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Solution Overview
Problem
Existing charged particle beam apparatuses face challenges in maintaining high resolution and reproducibility during three-dimensional observation, particularly when tilting the beam, due to off-axis chromatic and coma aberrations, which require complex correction methods involving multiple optical elements and non-linear adjustments.
Innovation Solution
A charged particle beam apparatus with a trajectory monitoring unit that includes an optical element and a trajectory correcting deflector, where the applied voltage and excitation current are adjusted to zero, allowing for precise control of the beam trajectory and correction of aberrations, thereby maintaining high resolution and reducing positional shifts during beam tilt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a deflector is used to tilt the beam for three-dimensional observation, then mechanical operation is eliminated and observation without mechanical tilt is achieved, but off-axis aberration occurs, beam diameter increases, and resolution deteriorates
Solution Approach 1:
The patent introduces a trajectory correcting deflector as an intermediary device between the main deflector and the objective lens. This intermediary component generates counter-aberrations to compensate for the off-axis aberrations produced by the main deflector, thereby maintaining beam quality and resolution during tilted observation without requiring mechanical stage movement
2Manufacturing precision
If aberration correcting lenses with great spherical aberration are used to generate deflected coma aberration, then off-axis chromatic aberration is corrected, but beam trajectory changes from paraxial trajectory and incident angle changes, requiring non-linear control
Solution Approach 1:
The patent implements a feedback control mechanism that monitors the actual beam trajectory and incident angle after passing through the aberration correcting lens, then adjusts the trajectory correcting deflector parameters in real-time to compensate for deviations from the ideal paraxial trajectory, enabling accurate control despite non-linear effects
Solution Approach 2:
The patent dynamically adjusts multiple parameters including the excitation current of the trajectory correcting deflector, the applied voltage to optical elements, and the timing of corrections to optimize beam trajectory for each specific tilt angle, transforming the non-linear control problem into a series of optimized parameter sets
3Manufacturing precision
If multiple optical elements and complex correction methods are used to correct off-axis chromatic and coma aberrations, then resolution is maintained during beam tilt, but device complexity and adjustment difficulty increase
Solution Approach 1:
The patent combines the functions of multiple separate optical elements into an integrated trajectory correction system. By merging the aberration correction function with the beam deflection function in a unified deflector system, the patent reduces the number of separate components while maintaining comprehensive correction of both chromatic and coma aberrations
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 enables effective monitoring and correction of the beam trajectory, improving reproducibility and resolution even at large tilt angles, and reducing positional shifts during beam tilt, enhancing the overall performance of the charged particle beam apparatus.
Implementation Method 1
a trajectory correcting deflector, wherein an applied voltage and an excitation current of the optical element are set to zero after a trajectory correction of the primary charged particle beam
Implementation Method 2
includes an optical element having a lens action and a trajectory correcting deflector
Data Source
AI summary
There is provided a charged particle beam apparatus that includes a trajectory monitoring unit which is disposed above an objective lens (14) and which includes an optical element (12) having a lens action and a trajectory correcting deflector (10). An applied voltage and an excitation current of the optical element (12) are set to zero after a trajectory correction of a primary charged particle beam (30). Accordingly, the lens action and an aberration of the optical element (12) have no influence on resolution.