Multi Charged Particle Beam Lens Layout for Stable Beam Position
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Solution Overview
Problem
In multi-charged particle 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 in limited spaces, resulting in drift and reduced positional accuracy.
Innovation Solution
A configuration with two or more-stage objective lenses, where one or no electrostatic correction lens is placed inside the magnetic field of each stage, and three or more correction lenses are used, including a magnetic correction lens outside the magnetic field and electrostatic correction lenses within, to stabilize beam irradiation and prevent secondary electron accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electrostatic lenses are placed inside the magnetic field of objective lenses to correct imaging state, then the beam array image rotation and magnification change are reduced, but secondary electrons accumulate and beam position becomes unstable
Solution Approach 1:
The patent extracts the electrostatic lenses from the magnetic field region of the objective lenses. By placing correction lenses outside the magnetic field, the harmful interaction between secondary electrons and electrostatic lenses is eliminated, while still achieving the necessary imaging correction through the coordinated arrangement of multiple lenses.
Solution Approach 2:
The patent introduces magnetic correction lenses as intermediary elements that can perform imaging correction without the secondary electron accumulation problem. These magnetic lenses act as mediators between the objective lenses and the beam array image, providing correction capability while avoiding the harmful effects experienced by electrostatic lenses placed in the magnetic field.
2Manufacturing precision
If multiple electrostatic correction lenses are placed in proximity inside the magnetic field to reduce rotation and magnification change, then imaging accuracy is improved, but the structural complexity and difficulty of construction increase
Solution Approach 1:
The patent extracts correction lenses from the constrained magnetic field region, placing them outside where there is more space available. This eliminates the need for complex vacuum sealing and insulation structures that would be required to house multiple electrostatic lenses in the limited space inside the magnetic field.
Solution Approach 2:
The patent employs multiple types of correction lenses (magnetic and electrostatic) with different functions and characteristics. Magnetic correction lenses handle certain aspects of imaging correction without requiring vacuum structures, while electrostatic lenses provide additional correction capabilities where needed, creating a more versatile and constructible system.
3Manufacturing precision
If two-stage objective lenses are used to achieve high reduction ratio and working distance, then beam array image dimensions and array pitch accuracy are improved, but the space available for placing correction lenses is limited
Solution Approach 1:
The patent extends the correction lens arrangement into the longitudinal dimension (optical axis direction) outside the magnetic field region. By placing correction lenses in sequence along the beam path rather than cramming them into the limited transverse space inside the magnetic field, the system achieves necessary correction capabilities without interfering with the two-stage objective lens configuration.
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, prevents secondary electron stagnation, and stabilizes the beam irradiation position, improving the accuracy and reliability of the multi-charged particle beam writing process.
Implementation Method 1
one or no electrostatic correction lens placed inside a magnetic field of each of the two or more-stage objective lenses
Implementation Method 2
inside the magnetic field of objective lenses
Implementation Method 3
a magnetic correction lens outside the magnetic field
Implementation Method 4
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 two or more-stage objective lenses each comprised of a magnetic lens, and configured to focus a multi charged particle beam on a substrate, which has passed through a limiting aperture member, and three or more correction lenses correcting an imaging state of the multi charged particle beam on the substrate. The three or more correction lenses are comprised of a first magnetic correction lens, and two or more correction lenses, the two or more correction lenses are placed inside a lens magnetic field of one of the two or more-stage objective lenses, and one or no electrostatic correction lens is placed inside a magnetic field of each of the two or more-stage objective lenses.