Biased Tungsten Liner Elements for Ion Source Efficiency
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Solution Overview
Problem
Ion source housings in semiconductor manufacturing are prone to damage due to harsh conditions, leading to reduced operational life and increased maintenance costs, and existing liners only provide partial protection while not improving power efficiency.
Innovation Solution
Biased tungsten liner elements are inserted into the ion source chamber, creating a perpendicular electrical field to the magnetic field, which enhances ion extraction efficiency and prolongs the life of the ion source, indirectly heated cathode, and repeller by directing hotter ions towards the aperture, thus increasing ion production or reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If traditional ion source housing is used without biased liner elements, then the structure is simple and easy to manufacture, but the housing is damaged by harsh conditions reducing operational life
Solution Approach 1:
A biased liner element is introduced as an intermediary component between the harsh plasma environment and the ion source housing. This liner element protects the housing from damage while being replaceable, thus extending the housing's operational life without permanently complicating the overall structure.
Solution Approach 2:
The liner element is designed as a sacrificial, replaceable component that can be easily replaced when worn. This allows the expensive housing to be preserved while replacing only the cheaper, shorter-lived liner element, effectively extending the operational life of the overall system.
2Duration of action of stationary object
If biased liner elements are inserted to protect components, then the operational life of cathode and repeller is extended, but the device complexity increases
Solution Approach 1:
The biased liner element serves multiple functions simultaneously: it protects the housing from plasma damage, extends the life of the cathode and repeller by controlling ion trajectories, and improves ion extraction efficiency. This multi-functionality justifies the added complexity by delivering multiple benefits from a single component.
3Productivity
If biased liner elements are used to direct hotter ions toward aperture, then ion production efficiency increases, but the device complexity and power consumption increase
Solution Approach 1:
The liner element is biased at a specific voltage potential (different from both the housing and plasma potential) to create an electric field that modifies ion trajectories. This parameter change in voltage creates a more efficient ion extraction process, directing hotter ions toward the aperture and improving overall ion production efficiency while managing power consumption.
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 biased liner elements increase ion source efficiency, allowing more ions to be produced at a given power level or the same number at a lower power level, while extending the life of critical components like the indirectly heated cathode and repeller, reducing maintenance needs and operational costs.
Implementation Method 1
The current passing through the filament 30 heats it sufficiently (i.e. above 2000° C.) so as to produce thermo-electrons. As these electrons bombard the cathode, the cathode heats significantly, often to temperatures over 2000° C.
Implementation Method 2
The cathode, which is referred to as an indirectly heated cathode (IHC), then emits thermo-electrons into the ion chamber 14
Implementation Method 3
A magnetic field is preferably created in the direction 62, typically by using magnetic poles located outside the chamber. The effect of the magnetic field is to confine the emitted electrons within magnetic field lines. A second effect is to cause the electrons to move from the cathode toward the opposite end of the chamber in a spiraling fashion
Implementation Method 4
The arc supply 50 is used to bias the ion chamber housing 10 positively as compared to the cathode. This difference in voltage causes the electrons emitted from the cathode 20 to be accelerated toward the housing 10
Implementation Method 5
Biased tungsten liner elements are inserted into the ion source chamber, creating a perpendicular electrical field to the magnetic field, which enhances ion extraction efficiency and prolongs the life of the ion source, indirectly heated cathode, and repeller by directing hotter ions towards the aperture
Data Source
AI summary
Liner elements to protect the ion source housing and also increase the power efficiency of the ion source are disclosed. Two liner elements, preferably constructed from tungsten, are inserted into the ion source chamber, one placed against each of the two sidewalls. These inserts are electrically biased so as to induce an electrical field that is perpendicular to the applied magnetic field. Such an arrangement has been unexpectedly found to increase the life of not only the ion chamber housing, but also the indirectly heated cathode (IHC) and the repeller. In addition, the use of these biased liner elements also improved the power efficiency of the ion source; allowing more ions to be generated at a given power level, or an equal number of ions to be generated at a lower power level.