Foil Liner Thermal Gradient Control for Ion Sources
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Solution Overview
Problem
Indirectly heated cathode ion sources face challenges in maintaining a temperature gradient between the plasma and the ion source chamber, which is critical for species like carbon and boron trifluoride, as existing liners do not allow for easy variation of plasma temperature without affecting the ion source chamber temperature, and are costly and difficult to replace.
Innovation Solution
A foil liner comprising a plurality of stacked foil layers, which can be made of electrically conductive or insulating materials, is introduced to create a thermal gradient by varying the spacing and material composition between the plasma and the ion source chamber, allowing for easy assembly and replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a solid liner is used to protect the ion source chamber, then the lifetime of the ion source is extended, but the ability to maintain a temperature gradient between plasma and chamber is compromised
Solution Approach 1:
The liner is divided into multiple thin foil layers (typically 3-7 layers) rather than using a single solid piece. This segmentation allows the liner to maintain structural integrity for protection while creating thermal isolation between the plasma-facing surface and the chamber wall, enabling temperature gradient control.
Solution Approach 2:
The liner uses composite construction with multiple foil layers of different materials (e.g., tungsten, molybdenum, nickel) with different thermal conductivities. This allows optimization of both protective function and thermal management by selecting materials with appropriate thermal properties for each layer.
2Reliability
If tungsten liners are used for their electrical conductance and high temperature resistance, then the ion source performance is improved, but the cost and difficulty of replacement increase
Solution Approach 1:
The liner is designed as multiple thin foil layers that can be individually handled and replaced. When degradation occurs, the entire multi-layer assembly can be quickly removed and replaced as a unit, significantly reducing replacement time and labor costs compared to traditional solid liners.
Solution Approach 2:
The multi-foil liner assembly is designed as a replaceable component with lower individual material cost compared to traditional solid tungsten liners. The foils can be manufactured more economically and replaced frequently without significant cost penalty, accepting shorter service life in exchange for lower operational cost.
3Reliability
If traditional solid liners are used, then electrical conductance is maintained, but thermal management flexibility is reduced
Solution Approach 1:
Different regions of the liner have different thermal properties through varying foil layer configurations. The number of layers, material composition, and spacing can be optimized for specific zones within the ion source chamber to achieve desired thermal management for different operational conditions.
Solution Approach 2:
The liner design allows dynamic adjustment of thermal properties by modifying the spacing between foil layers or adding/removing layers based on operational requirements. This provides flexibility to adapt thermal management to different plasma conditions and species being processed.
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 foil liner effectively manages the temperature gradient between the plasma and the ion source chamber, enhancing the uniformity, lifetime, and reducing costs by allowing for easy replacement and customization of the liner to achieve desired operating conditions.
Implementation Method 1
The spacing between adjacent foil layers may create a thermal gradient such that the temperature of the plasma is hotter than the temperature of the ion source chamber
Implementation Method 2
Tungsten liners are also thermally conductive, so the heat of the plasma is typically transferred to the ion source chamber
Implementation Method 3
one or more of the plurality of stacked foil layers comprises an insulating material
Data Source
AI summary
A foil liner comprising a plurality of foil layers is disclosed. The foil layers may each be an electrically conductive material that are stacked on top of each other. The spacing between adjacent foil layers may create a thermal gradient such that the temperature of the plasma is hotter than the temperature of the ion source chamber. In other embodiments, the foil layers may be assembly to sink the heat from the plasma so that the plasma is cooler than the temperature of the ion source chamber. In some embodiments, gaps or protrusions are disposed on one or more of the foil layers to affect the thermal gradient. In certain embodiments, one or more of the foil layers may be constructed of an insulating material to further affect the thermal gradient. The foil liner may be easily assembled, installed and replaced from within the ion source chamber.