Grooved Cathode for Ion Source Electron Focusing
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Solution Overview
Problem
Ion source cathodes in ion implanters experience reduced lifespan due to erosion, leading to a concave surface that increases output but is difficult to maintain and control, especially as the cathode ages, resulting in limited duration of increased performance.
Innovation Solution
A cathode with electron production and focusing grooves, where each groove has an angled surface relative to the planar portion, mimicking a concave surface to enhance ion plasma focusing without the structural challenges of a true concave surface, allowing for increased output without premature wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a concave surface cathode is used to focus electrons and increase ion source output, then the ion source output increases by 40-50%, but the cathode lifespan decreases due to thinner center and premature failure
Solution Approach 1:
The cathode surface is segmented into multiple grooves rather than forming a single continuous concave surface. This segmentation allows the cathode to achieve electron focusing benefits while maintaining structural integrity and uniform thickness, preventing premature failure at thin centers.
Solution Approach 2:
The grooves are positioned specifically in regions where electron focusing is needed, while the broader cathode structure maintains uniform thickness for durability. This localized modification achieves the desired electron concentration effect without compromising overall cathode strength and lifespan.
2Productivity
If a concave surface cathode is used to focus electrons, then ion source output increases, but the thermal mass increases making heating and temperature control difficult
Solution Approach 1:
By segmenting the cathode into grooves rather than creating a solid concave structure, the overall thermal mass is reduced while still providing the necessary electron focusing capability. This allows for more efficient heating and better temperature control during operation.
Solution Approach 2:
The cathode structure is changed from a solid concave surface to a grooved surface, altering the thermal parameters (reducing thermal mass) while maintaining the electrical function of electron focusing. This parameter change enables better temperature control.
3Ease of manufacture
If a planar cathode surface is used, then the cathode structure is simple and easy to manufacture, but the ion source output is lower due to lack of electron focusing
Solution Approach 1:
The cathode surface is segmented into grooves that can be formed using standard manufacturing techniques, maintaining relative manufacturing simplicity while adding the electron focusing capability needed to increase ion source output.
Solution Approach 2:
The grooves introduce curved surfaces that focus electrons, transitioning from a completely planar surface to one with controlled curvature elements. This provides electron focusing benefits while remaining manufacturable through conventional processes.
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 cathode design provides a 40-50% increase in ion source output compared to a planar cathode, maintaining performance while extending the cathode's lifespan by distributing wear evenly across the surface.
Implementation Method 1
the concave surface of the cathode focuses the thermionic electrons in a central region of the plasma
Implementation Method 2
generate an ion plasma by injecting electrons into a source gas
Data Source
AI summary
A cathode having electron production and focusing grooves for an ion source of an ion implanter system, the ion source and a related method are disclosed. In one embodiment, the cathode includes a working surface having a plurality of electron production and focusing grooves positioned therein. A repeller of the ion source may be similarly structured.