Triode Ion Accelerator Bevelled Aperture Aberration Control
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Solution Overview
Problem
Conventional ion beam accelerators face challenges in producing low energy ion beams with high current density and low divergence, which are essential for modern semiconductor and thin film device fabrication, as they suffer from significant spherical aberrations and mechanical weakness due to thin electrodes, making it difficult to achieve uniformity and symmetry in processing large substrates.
Innovation Solution
The use of a triode ion accelerator with a bevelled aperture in the first electrode and opposing potentials between electrodes, along with a ground electrode, significantly reduces spherical aberrations and allows for larger apertures, resulting in a low divergence, high power density ion beam. This configuration, known as an accel-decel system, enhances beam collimation and robustness while maintaining sufficient output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin electrodes are used in conventional ion beam accelerators, then the device complexity is reduced and manufacturing is easier, but the mechanical strength and robustness deteriorate, making the electrodes vulnerable to plasma heat load
Solution Approach 1:
The patent changes the geometric parameters of the electrode apertures by introducing a bevelled configuration with specific angles (alpha and beta) and dimensional ratios (d1/d2). This geometric modification allows the electrode to maintain mechanical strength while still achieving the required ion beam extraction and acceleration functions, resolving the contradiction between ease of manufacture and mechanical strength.
2Device complexity
If conventional accelerator designs are used, then the device structure is simple, but spherical aberrations increase, reducing beam quality and uniformity
Solution Approach 1:
The patent modifies the aperture geometry parameters by introducing bevels with specific angles and dimensional relationships. This changes the electric field distribution within the aperture, reducing spherical aberrations and improving beam uniformity without significantly increasing device complexity.
Solution Approach 2:
The bevelled aperture introduces asymmetric geometry to what would otherwise be a symmetric circular opening. This asymmetric shape modifies the electric field lines and ion trajectories, reducing spherical aberrations and improving beam quality while maintaining a relatively simple overall device structure.
3Quantity of substance
If larger apertures are used in the first electrode, then the ion beam current increases, but spherical aberrations increase, reducing beam collimation
Solution Approach 1:
The patent changes the aperture geometry by introducing a bevelled configuration with specific angular and dimensional parameters. This allows larger aperture openings to be used while the bevel geometry controls the electric field distribution, maintaining beam collimation and reducing spherical aberrations even with increased aperture size for higher current.
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 achieves a low divergence, reduced spherical aberration ion beam with sufficient power density, improving uniformity and symmetry in substrate processing, and increases the robustness and reliability of the ion accelerator, reducing manufacturing costs and vulnerability to plasma heat load.
Implementation Method 1
accelerating a beam of positive ions from a plasma source through an externally applied electric field
Implementation Method 2
the ions are formed by electron impact ionisation and move within the chamber by random thermal motion
Data Source
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AI summary
An apparatus (200) for accelerating an ion beam comprising: a) a first electrode (202) having a proximal side and a distal side and having at least one aperture (201) therethrough, the wall of the aperture being shaped such that the radius of the aperture on the distal side of the first electrode is greater than that on the proximal side of the electrode; b) a second electrode (204) located such that it is adjacent to but spaced from the distal side of the first electrode and having at least one aperture therethrough; and c) a third electrode (206) located such that it is adjacent to and spaced from the second electrode and having at least one aperture therethrough, said at least one apertures in each electrode being aligned with corresponding apertures in the other electrodes; wherein the electrodes are arranged such that there is a potential difference between the first and second electrodes and a potential difference between the second and third electrodes.