Tubular Cathode Ion Source for High-Efficiency 11B+ Production
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Solution Overview
Problem
Existing ion sources, such as hot-cathode ion sources, have limited efficiency in producing specific ion species like 11B+, with efficiencies often no greater than 35% of the total extracted current, which restricts the precision and effectiveness of ion implantation in semiconductor manufacturing.
Innovation Solution
The use of a tubular cathode in ion sources, which generates a high-density plasma and expands it towards an extraction aperture, allowing for increased beam currents and efficiencies up to 50% or more, by optimizing the plasma generation and extraction process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a hot-cathode ion source with indirectly heated cathode is used, then ion species can be generated for implantation, but the efficiency in producing specific ion species (e.g., 11B+) is limited to no greater than 35% of total extracted current
Solution Approach 1:
The patent changes the cathode heating method from indirect heating to direct heating, and modifies the cathode geometry to a tubular shape with specific dimensions. These parameter changes enable direct electron bombardment of the cathode surface, creating a high-density plasma region that significantly improves ion production efficiency while maintaining doping precision through controlled extraction
2Duration of action of stationary object
If conventional cathode structures are used, then the ion source can operate, but maintenance intervals are frequent and source failure occurs due to high bias power and thermal stress
Solution Approach 1:
The patent segments the cathode into a tubular structure with specific geometric parameters, separating the heating function from the ion generation function. The direct heating approach confines thermal effects to the cathode surface while the plasma generation occurs in a controlled region, reducing thermal stress on the overall structure and extending maintenance intervals while improving source stability
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 approach results in higher throughput and longer maintenance intervals, with a B+ fraction of at least 50%, improved plasma stability and uniformity, and reduced source failure due to lower bias power and mechanical/thermal isolation.
Implementation Method 1
generates a high-density plasma and expands it towards an extraction aperture
Implementation Method 2
hot-cathode ion source utilizing an indirectly heated cathode (IHC) to ionize a feed gas
Implementation Method 3
a series of electrodes configured to extract ions from the source chamber
Data Source
AI summary
Provided herein are approaches for increasing efficiency of ion sources. In some embodiments, an apparatus, such as an ion source, may include a chamber housing having a first end wall and a second end wall, and an extraction plate coupled to at least one of the first end wall and the second end wall. The extraction plate may include an extraction aperture. The apparatus may further include a tubular cathode extending between the first end wall and the second end wall.