Multi-beam Writing Aberration Correction via Grating and Correction Lenses
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Solution Overview
Problem
In multi-beam writing apparatuses, large beam sizes lead to significant aberrations, necessitating large aperture diameters for blanking, which in turn require higher blanking voltages, and existing correction methods only address lower-order spherical aberrations while increasing higher-order aberrations.
Innovation Solution
A multi-charged particle beam writing apparatus is designed with a stage for continuous movement of a target object, an emission unit, an aperture member with multiple openings, a blanking plate for beam deflection, a grating lens to correct spherical aberrations, and a correction lens to address high-order spherical aberrations, allowing for reduced aperture diameter and lower blanking voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the beam size of multi-beams is increased to improve throughput, then productivity increases, but spherical aberration becomes larger
Solution Approach 1:
The patent applies parameter changes by modifying the excitation amounts of the grating lens and correction lens to dynamically adjust and correct spherical aberrations. By changing the lens parameters (excitation amounts) based on the multi-beam conditions, the system maintains high throughput while correcting the aberrations that arise from large beam sizes.
2Manufacturing precision
If the aperture diameter is increased to reduce spherical aberration, then manufacturing precision improves, but blanking voltage must be increased
Solution Approach 1:
The patent resolves this contradiction by changing the approach from geometric parameter changes (aperture diameter) to optical parameter changes (lens excitation amounts). By using the grating lens and correction lens with adjusted excitation amounts, the system achieves spherical aberration correction without increasing the aperture diameter, thereby avoiding the need for higher blanking voltages.
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 corrects both low-order and high-order spherical aberrations, reducing trajectory displacement and enabling smaller aperture diameters and lower blanking voltages, thereby improving the efficiency and precision of multi-beam writing.
Implementation Method 1
a first grating lens, using the aperture member as gratings, configured to correct spherical aberration of the charged particle beam
Implementation Method 2
a correction lens configured to correct high order spherical aberration produced by the first grating lens
Implementation Method 3
a foil lens, arranged between the illumination lens and the aperture member, configured to correct spherical aberration of the charged particle beam
Implementation Method 4
a blanking plate in which there are arranged a plurality of blankers configured to respectively perform blanking deflection for a corresponding beam in the multiple beams
Data Source
AI summary
A multi charged particle beam writing apparatus includes an aperture member to form multiple beams, a blanking plate in which there are arranged a plurality of blankers to respectively perform blanking deflection for a corresponding beam in the multiple beams having passed through a plurality of openings of the aperture member, a blanking aperture member to block each beam having been deflected to be in OFF state by at least one of the plurality of blankers, a first grating lens, using the aperture member as gratings, to correct spherical aberration of the charged particle beam, and a correction lens configured to correct high order spherical aberration produced by the first grating lens.