Booster Tube Plasma Source for Low Pressure Density
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Solution Overview
Problem
Traditional plasma sources face limitations in achieving high plasma strength at low pressures, leading to reduced radical transport and increased risk of arcing, and require costly Langmuir probe diagnostics for plasma gauging.
Innovation Solution
Incorporating a booster tube into the plasma source design to enhance plasma density through a positive feedback mechanism, and using plasma emission intensity measurement with low-cost light sensors to gauge plasma strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential pumping aperture is used to maintain low pressure in the downstream chamber, then the risk of arcing is reduced, but the transportation of radical species into the processing chamber is limited
Solution Approach 1:
The system is divided into two chambers: a plasma source chamber where plasma is generated at higher pressure, and a downstream processing chamber maintained at low pressure. A differential pumping aperture separates these chambers, allowing radical species to pass while maintaining pressure differential to prevent arcing.
2Reliability
If the downstream vacuum chamber pressure is kept low to avoid arcing, then electrical safety is improved, but plasma strength and radical density are reduced
Solution Approach 1:
The system separates plasma generation functions from processing functions by using two distinct chambers. The source chamber operates at higher pressure to maintain strong plasma, while the downstream chamber operates at low pressure to prevent arcing, with a differential pumping aperture connecting them.
3Area of stationary object
If a beam shaping aperture with wider openings is used to obtain a broader ion or electron beam, then beam coverage is improved, but the pressure difference between plasma source and downstream chamber is reduced
Solution Approach 1:
The system uses separate chambers connected by a differential pumping aperture, allowing the beam shaping aperture to have wider openings for broader beam coverage without compromising the pressure differential needed to maintain plasma strength and prevent arcing.
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 booster tube design increases plasma strength by 2-3 times at low pressures, reducing arcing risks and extending minimum operation pressure, while plasma emission intensity measurement provides a cost-effective and straightforward method for monitoring plasma strength.
Implementation Method 1
The booster chamber design disclosed in this invention greatly improves the plasma density at low pressure through a positive feedback mechanism
Implementation Method 2
The booster tube in this application has some similar properties as the traditional hollow cathode or hollow anode electrode
Implementation Method 3
A new and simple method to measure the strength of a remote plasma source is to use a light sensor, such as a photodiode, photoresistor or phototransistor, to detect the plasma emission
Data Source
AI summary
A method to improve plasma discharge efficiency by attaching one or more booster chambers to the main discharge chamber is disclosed here. The booster chamber functions as a plasma discharge amplification device for the main discharge chamber. It improves plasma density significantly, especially at pressure below 50 mTorr. Compared with traditional inductively coupled plasma (ICP) source, the strength of the plasma source enhanced with booster chamber has been improved several folds at low pressure conditions. Booster chamber can also be used as a convenient high speed plasma etching and deposition processing chamber for small samples. A method to gauge plasma strength by measuring plasma emission intensity has also been disclosed in this application.