Multi Charged Particle Beam Spherical Aberration Correction
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Solution Overview
Problem
Multi-beam writing apparatuses face challenges in assessing and automatically adjusting spherical aberration, which distorts the beam shape from the ideal rectangular form to barrel or pincushion types due to the electron optical system's spherical aberration.
Innovation Solution
A multi charged particle beam writing apparatus that includes an emitter, an aperture plate forming multiple beams, a blanking plate for beam control, a limitation aperture plate, a stage for substrate irradiation, a detector for reflection particle detection, and aberration correction circuitry that calculates feature amounts of the aperture image to adjust spherical aberration using an aberration correction lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple beams are formed by passing an electron beam through an aperture member, then throughput is greatly improved by enabling irradiation with more beams at a time, but spherical aberration of the electron optical system causes distortion of the beam shape from the ideal rectangular form
Solution Approach 1:
The patent employs a feedback mechanism where a camera captures the actual beam shape formed by the aperture member, and a control unit compares the captured image with the ideal rectangular shape. Based on the deviation detected, the control unit automatically adjusts the spherical aberration correction lens to minimize the difference between the actual and ideal beam shapes, thereby maintaining manufacturing precision while using multiple beams for high throughput
Solution Approach 2:
The patent changes the optical parameters of the electron optical system by adjusting the spherical aberration correction lens. By modifying the lens parameters (such as excitation current or focal length), the system compensates for spherical aberration effects and restores the beam shape to the ideal rectangular form, resolving the contradiction between maintaining beam accuracy and achieving high throughput with multiple beams
2Device complexity
If spherical aberration is not corrected, then the system operates without complex adjustment mechanisms, but the beam shape distorts into barrel or pincushion types reducing writing precision
Solution Approach 1:
The system performs self-adjustment by automatically detecting its own beam shape distortion through the camera and control unit, then autonomously correcting the spherical aberration using the adjustable lens. This self-service mechanism eliminates the need for manual intervention or complex external adjustment equipment, maintaining low device complexity while ensuring high writing precision through automatic spherical aberration correction
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 accurate automatic adjustment of spherical aberration, ensuring the aperture image maintains a desired quadrilateral shape, thereby improving beam alignment and writing precision in semiconductor device manufacturing.
Implementation Method 1
a charged particle beam emitting unit that emits a charged particle beam
Implementation Method 2
under the influence of spherical aberration of an electron optical system provided with a writing apparatus
Implementation Method 3
a detector that detects a reflection charged particle from the substrate
Data Source
AI summary
In one embodiment, a multi charged particle beam writing apparatus includes an emitter that emits a charged particle beam, an aperture plate in which a plurality of openings are formed and that forms multiple beams by allowing the charged particle beam to pass through the plurality of openings, a blanking plate provided with a plurality of blankers that each perform blanking deflection on a corresponding beam included in the multiple beams, a stage on which a substrate irradiated with the multiple beams, a detector that detects a reflection charged particle from the substrate, feature amount calculation circuitry that calculates a feature amount of an aperture image based on a detection value of the detector, and aberration correction circuitry that corrects aberration of the charged particle beam based on the feature amount.