Plasma Potential Probe Sensitivity Tuning Without Back-Side Capacitance
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Solution Overview
Problem
Existing plasma potential measuring devices suffer from reduced detection sensitivity due to back-side capacitance and fixed detection sensitivity, necessitating circuit changes when sensitivity is too high or low.
Innovation Solution
A plasma potential measuring device with a detection electrode that adjusts its reference potential using a potential changing circuit, and optionally includes a first electrode virtually short-circuited with the detection electrode to mitigate back-side capacitance effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an ITO shield electrode is disposed to cover the insulating film on the back surface of the probe electrode, then electromagnetic shielding is improved, but back-side capacitance is formed which reduces detection sensitivity
Solution Approach 1:
The harmful back-side capacitance effect is extracted and eliminated by removing the ITO shield electrode from the probe electrode structure. The patent applies electromagnetic shielding through a separate shield electrode positioned away from the probe electrode, thus eliminating the capacitance interference while maintaining shielding functionality.
Solution Approach 2:
A separate shield electrode is introduced as an intermediary element to provide electromagnetic shielding without directly contacting the probe electrode. This mediator approach allows shielding functionality to be decoupled from the probe structure, preventing back-side capacitance formation while maintaining electromagnetic interference protection.
2Adaptability or versatility
If the detection sensitivity is set too high or too low, then the fixed sensitivity configuration cannot adapt to different plasma conditions, but changing the amplifier circuit is required which increases device complexity
Solution Approach 1:
The detection sensitivity is adjusted by changing the reference potential parameter rather than modifying the amplifier circuit. By varying the reference potential applied to the probe electrode, the system can adapt to different plasma conditions and sensitivity requirements without requiring physical circuit changes, thus maintaining low device complexity while achieving high adaptability.
3Object-affected harmful factors
If the probe electrode structure includes an insulating film and shield electrode configuration, then electromagnetic shielding is achieved, but the structure becomes more complex and back-side capacitance is introduced
Solution Approach 1:
The electromagnetic shielding function is segmented from the probe electrode structure itself. Instead of integrating the shield electrode directly with the probe electrode (which creates back-side capacitance), the shielding function is separated into a distinct component positioned away from the probe, thus reducing structural complexity and eliminating capacitance interference while maintaining shielding effectiveness.
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
Accurate detection of plasma state by adjusting detection sensitivity through reference potential changes, minimizing back-side capacitance influence, and improving measurement accuracy.
Implementation Method 1
a back-side capacitance can be formed between the probe electrode and the ITO shield electrode
Implementation Method 2
a potential changing circuit for changing a reference potential of the detection electrode
Data Source
AI summary
A plasma potential measuring device, including: a detection electrode 162b which is disposed so as to face a plasma P generated in a chamber and at which an electric charge corresponding to an electric potential of the plasma is induced; a potential changing circuit 203 for changing a reference potential of the detection electrode 162b; and a detection circuit 202 for detecting an amount of electric charge or potential induced at the detection electrode 162b.