Shielded Gas Inlet Structure for Thermally Unstable Ion Source Gases
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Solution Overview
Problem
Existing ion implantation systems face challenges in efficiently delivering thermally unstable gases like dimethylaluminum chloride (DMAC) to the arc chamber due to high temperatures, leading to degradation, plugging, and reduced productivity, especially when transitioning between different metal species.
Innovation Solution
The system employs shields positioned proximate to the gas inlet aperture to prevent thermal radiation from reaching the inlet, maintaining the gas inlet temperature below the decomposition point of DMAC, using materials like refractory metals, ceramics, and graphite to minimize heat transfer and plasma formation, ensuring stable gas delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the gas inlet is exposed to the arc chamber environment, then the ion source can operate at high temperatures (800 C) necessary for plasma generation, but the thermally unstable source gas (DMAC) degrades and decomposes at these temperatures
Solution Approach 1:
The gas delivery system is segmented into a hot zone (arc chamber) and a cold zone (gas inlet region) using a shield structure. The shield creates a thermal barrier that divides the temperature zones, allowing the arc chamber to operate at 800 C while the gas inlet region remains cool enough to prevent DMAC decomposition.
Solution Approach 2:
A shield structure acts as an intermediary element between the hot arc chamber and the cold gas inlet. This shield blocks thermal radiation from reaching the gas inlet, mediating the thermal interaction and preventing direct heat transfer that would cause gas degradation.
2Productivity
If thermally unstable gases like DMAC are delivered to the arc chamber, then aluminum ion beams can be generated, but the gases degrade and decompose due to high temperatures, causing plugging and reduced productivity
Solution Approach 1:
The shield serves as a thermal intermediary that protects the DMAC gas from direct exposure to high temperatures. By blocking thermal radiation, the shield prevents DMAC decomposition and plugging while still allowing the arc chamber to operate at temperatures necessary for efficient aluminum ion beam generation.
Solution Approach 2:
The harmful thermal radiation is extracted or removed from the gas inlet region by the shield. This separates the thermal environment from the gas delivery path, allowing DMAC to be delivered without degradation while maintaining the high-temperature plasma environment needed for ion production.
3Adaptability or versatility
If species transitions are performed in conventional systems, then different metal ions can be implanted, but significant time is lost waiting for the oven to cool down between species changes
Solution Approach 1:
The thermal zones are segmented so that the gas inlet region is thermally isolated from the arc chamber. This allows the gas delivery system to remain cool regardless of arc chamber temperature, enabling rapid species transitions without waiting for cooling, as the inlet region maintains low temperature continuously.
Solution Approach 2:
The shield pre-cools or maintains the gas inlet region at low temperature before gas delivery occurs. This preliminary thermal conditioning of the gas path allows immediate introduction of new species without cooling delays, as the inlet region is already at the appropriate temperature for thermally unstable gases.
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 allows for faster species transitions, reduces degradation of DMAC, prevents plugging, and maintains system productivity by shielding the gas inlet from thermal radiation, thereby ensuring consistent aluminum ion beam generation.
Implementation Method 1
shields positioned proximate to the gas inlet aperture to prevent thermal radiation from reaching the inlet
Implementation Method 2
using materials like refractory metals, ceramics, and graphite to minimize heat transfer
Data Source
AI summary
An ion source has arc chamber having one or more radiation generating features, an arc chamber body enclosing an internal volume, and at least one gas inlet aperture defined therein. A gas source provides a gas such as a source species gas or a halide through the gas inlet aperture. The source species gas can be an aluminum-based ion source material such as dimethylaluminum chloride (DMAC). One or more shields positioned proximate to the gas inlet aperture provide a fluid communication between the gas inlet aperture and the internal volume, minimize a line-of-sight from the one or more radiation generating features to the gas inlet aperture, and substantially prevent thermal radiation from reaching the gas inlet aperture from the one or more radiation generating features.