Closed-Drift Ion Gun Magnetic Layout for Pole Erosion Control
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Solution Overview
Problem
Closed drift type ion guns experience erosion of magnetic poles due to ion collisions, leading to decreased discharge stability, contamination, and reduced etching rates, as the ions collide more frequently with the magnetic pole in curved portions of the ejection port.
Innovation Solution
The ion gun design includes an annular ejection port with a curved portion, where the magnetic field lines are configured to shift the plasma center inside the ejection port, reducing ion collisions with the magnetic poles by adjusting the position of the magnetic field line bottom and inclining the magnetic field vector, thereby minimizing erosion and improving beam efficiency and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the closed drift type ion gun uses a conventional ejection port design with linear and curved portions, then plasma generation and ion acceleration can be performed simultaneously, but the amount of ions colliding with the magnetic pole increases significantly in the curved portion, causing erosion and reduced discharge stability
Solution Approach 1:
The invention applies different magnetic field line configurations to different portions of the ejection port. Specifically, the magnetic field line bottom position and inclination angle are locally optimized: in the linear portion, the bottom is positioned at the centerline with 0° inclination, while in the curved portion, the bottom is positioned inside the centerline with a specific inclination angle (0-1.5°) to reduce ion collisions with the magnetic pole, thereby addressing the erosion problem locally without compromising overall plasma generation
Solution Approach 2:
The invention changes key magnetic field parameters including the position of the magnetic field line bottom and the inclination angle of magnetic field vectors. By adjusting these parameters differently in linear and curved portions of the ejection port, the ion trajectory is optimized to minimize collisions with the magnetic pole while maintaining effective plasma generation and ion acceleration
2Device complexity
If the magnetic pole is designed with conventional geometry, then the ion gun structure is simple, but the magnetic pole erodes over time due to ion collisions, leading to contamination and heat generation
Solution Approach 1:
The invention modifies the magnetic field configuration locally in the curved portion of the ejection port by positioning the magnetic field line bottom inside the centerline and setting a specific inclination angle. This local modification redirects ion trajectories away from the magnetic pole surface, significantly reducing sputtering erosion and material loss without requiring fundamental changes to the overall ejection port geometry
Solution Approach 2:
The invention converts the potentially harmful ion-magnetic pole collisions into a beneficial configuration where the magnetic field geometry itself guides ions away from the pole. By carefully designing the magnetic field line inclination and bottom position, the magnetic field that originally caused erosion is transformed into a protective element that shields the magnetic pole from direct ion impact
3Ease of manufacture
If the ejection port is designed with standard geometry, then manufacturing is straightforward, but ion beam uniformity and ejection efficiency are reduced due to increased collisions in curved portions
Solution Approach 1:
The invention implements localized magnetic field optimizations in the curved portion of the ejection port, where the magnetic field line bottom position and inclination angle are specifically adjusted. This local customization improves ion beam uniformity and ejection efficiency in the curved region without complicating the overall manufacturing process, as the changes are achieved through magnetic field configuration rather than complex geometric modifications
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 reduces the erosion of magnetic poles, enhances the stability and efficiency of the ion beam, and extends the maintenance cycle, resulting in improved operational performance and reduced running costs.
Implementation Method 1
a magnet configured to form a magnetic field space between the first portion and the second portion
Implementation Method 2
the magnetic field lines are configured to shift the plasma center inside the ejection port, reducing ion collisions with the magnetic poles
Data Source
AI summary
An ion gun according to one embodiment of the present invention has an anode, a cathode having a first portion and a second portion that face the anode, and a magnet that creates a spatial magnetic field between the first portion and the second portion. An annular gap including a curved portion is provided between the first portion and the second portion of the cathode. The magnet creates lines of magnetic field having the bottom inside with respect to the sectional center line of the gap between the first portion and the second portion of the curved portion.