Multi-Beam Writing Optics Layout for Stable Beam Positioning
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Solution Overview
Problem
In multi-beam electron beam writing apparatuses, the placement of electrostatic lenses within the magnetic field of objective lenses leads to challenges such as secondary electron accumulation, beam position instability, and difficulty in constructing complex vacuum structures, which affect the precision and stability of beam irradiation.
Innovation Solution
A multi-charged particle beam writing apparatus is designed with a configuration that includes a plurality of blankers, an acceleration lens, limiting aperture members, and multiple-stage objective lenses, where one or no electrostatic correction lens is placed within the magnetic field of each objective lens stage, allowing for focus correction and preventing secondary electron accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrostatic correction lenses are placed within the magnetic field of objective lenses to correct imaging state, then focus correction capability is improved, but secondary electron accumulation occurs and beam position stability deteriorates
Solution Approach 1:
The patent extracts the electrostatic correction lens from the magnetic field region of the objective lens. By placing the correction lens in a region free from magnetic field interference, the accumulation of secondary electrons is prevented and beam position stability is maintained while still achieving the required focus correction capability through the electrostatic lens's imaging state adjustment function.
Solution Approach 2:
The patent introduces a magnetic field-free region as an intermediary space between the objective lens and the correction lens. This intermediary region allows the electrostatic correction lens to operate without being influenced by the magnetic field, thereby preventing secondary electron accumulation while still enabling effective focus correction.
2Measurement precision
If electrostatic correction lenses are placed within the magnetic field of objective lenses, then focus correction is achieved, but device complexity increases due to vacuum seal and wire lead-out requirements
Solution Approach 1:
The patent extracts the electrostatic correction lens from the magnetic field region, which simplifies the vacuum structure by eliminating the need for complex vacuum seals and wire lead-outs that would be required to accommodate electrodes within the magnetic field region. The correction lens is placed in a simpler, magnet-free environment.
Solution Approach 2:
The patent uses electrostatic fields as a substitute for magnetic fields in the correction lens function. By employing electrostatic correction lenses instead of magnetic correction lenses, the system avoids the complexity of integrating magnetic components within the vacuum chamber while achieving the same imaging state correction objective.
3Manufacturing precision
If high reduction ratio imaging is performed to increase beam array image accuracy, then manufacturing precision is improved, but working distance requirements increase requiring more imaging stages
Solution Approach 1:
The patent merges the correction lens function with the existing imaging optical path. By integrating the electrostatic correction lens into the imaging system without adding extra imaging stages, the working distance is maintained while achieving both high reduction ratio imaging and focus correction simultaneously.
Solution Approach 2:
The electrostatic correction lens serves multiple functions: it corrects the imaging state (focus, magnification, rotation) and maintains the working distance requirements. This multi-functional component eliminates the need for separate correction mechanisms that would increase the overall system length.
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
This configuration secures space for focus correction lenses, stabilizes beam irradiation positions, and prevents secondary electron accumulation, enhancing the precision and stability of the beam irradiation process.
Implementation Method 1
an acceleration lens comprised of an electrostatic lens including a plurality of electrodes and configured to accelerate the multi charged particle beam
Implementation Method 2
two or more-stage objective lenses each comprised of a magnetic lens, and configured to focus the multi charged particle beam on a substrate
Data Source
AI summary
In one embodiment, a multi charged particle beam writing apparatus includes an acceleration lens comprised of an electrostatic lens including a plurality of electrodes and configured to accelerate a multi charged particle beam, two or more-stage objective lenses each comprised of a magnetic lens, and configured to focus the multi charged particle beam on a substrate, which has passed through a limiting aperture member, and three or more correction lenses including a first correction lens, a second correction lens and a third correction lens, and configured to correct an imaging state of the multi charged particle beam on the substrate. One or no electrostatic correction lens is placed in a magnetic field of each of the two or more-stage objective lenses. The first correction lens is an electrostatic correction lens that also serves as at least one of the plurality of electrodes of the acceleration lens.