Integrated Arc Chamber Ion Source for Longer Cathode Life
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Solution Overview
Problem
The lifetime of ion sources in ion implantation systems is limited by the sputtering of cathodes, particularly when generating multi-charged arsenic ion beams, leading to unwanted maintenance and downtime.
Innovation Solution
An ion source with a novel configuration of multiple electrode pairs and a source magnet that selectively form intersecting plasma columns, allowing for the controlled confinement and emission of plasma, thereby extending the ion source's lifetime by alternating the activation of electrode pairs and adjusting magnetic fields to optimize plasma confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a single cathode is used in the ion source, then the ion source structure is simple, but the lifetime is limited due to cathode sputtering
Solution Approach 1:
The ion source is divided into multiple independent arc chambers, each containing its own cathode and electrode pair. This segmentation allows one cathode to be replaced while others continue operating, extending the overall system lifetime without requiring complete system shutdown or complex replacement mechanisms.
Solution Approach 2:
The patent implements a system where cathodes can be individually replaced when sputtered, while the rest of the ion source remains operational. The spent cathodes are discarded and replaced with fresh ones, allowing continuous operation and extending the effective lifetime of the ion source through progressive replacement rather than simultaneous failure.
2Duration of action of stationary object
If multiple electrode pairs are used to extend lifetime, then the ion source lifetime is extended, but the device complexity increases
Solution Approach 1:
Multiple arc chambers are integrated into a single ion source structure that shares common components such as the vacuum envelope, power supply system, and control electronics. This merging approach allows multiple electrode pairs to function simultaneously while avoiding proportional increases in overall system complexity.
Solution Approach 2:
The multiple electrode pairs are designed with identical or similar configurations, allowing them to perform the same function of generating ion beams. This universality simplifies the design and operation, as each electrode pair can be independently controlled but follows the same operational principles, reducing the complexity burden of having multiple systems.
3Duration of action of stationary object
If cathode thickness is increased to protect the filament, then the filament lifetime is extended, but the electron emission efficiency decreases
Solution Approach 1:
The cathode structure is segmented into a thin protective cap layer and a thicker emitter body. The thin cap provides sufficient protection against sputtering while maintaining good thermal contact with the filament, allowing efficient electron emission without requiring excessive thickness that would insulate the filament and reduce emission efficiency.
Solution Approach 2:
The cathode cap thickness is optimized to a specific range that balances protection and thermal conductivity. By controlling the thickness parameter within an optimal range, the system achieves both extended filament lifetime through protection and maintained electron emission efficiency through adequate thermal coupling.
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 ion source's lifetime is significantly extended, reducing downtime and increasing productivity by allowing for selective activation of electrode pairs and controlled plasma confinement, thus improving the ion implantation process.
Implementation Method 1
a source magnet configured to selectively confine the plasma to the plasma column along the plasma column axis
Implementation Method 2
each of the plurality of electrode pairs are configured to selectively form a respective plasma therebetween based, at least in part, on an electrical potential supplied therebetween
Implementation Method 3
An ion source with multiple integrated arc chambers... generates ions of desired atomic or molecular dopant species
Data Source
AI summary
An ion source has an arc chamber and multiple electrode pairs that define a respective plasma column axis within the arc chamber. A source magnet surrounds the arc chamber and defines pole pairs, each respectively associated with the electrode pairs to confine a plasma to the respective plasma column axis. The source magnet can be an electromagnet or a permanent magnet. The electromagnet has coils and a magnetic core to define the pole pairs and confine the plasma to the respective plasma column based on a coil current supplied to the coils. The magnetic core can have movable core members to magnetically couple each of the plurality of pole pairs. The permanent magnet has a magnetic core and movable core members to selectively magnetically couple the permanent magnet to each of the plurality of pole pairs.