Floating Probe Plasma Diagnosis with DC Cut-Off Capacitor
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Solution Overview
Problem
Current plasma diagnostic methods struggle to accurately calculate electron density in plasma spaces, particularly in negative plasma, where ion and electron densities differ, affecting the reliability of plasma treatment processes and semiconductor device fabrication.
Innovation Solution
A method and apparatus using floating probes with a processor to calculate electron density ratios by measuring both AC and DC components of probe currents, with a DC cut-off capacitor to isolate the AC component, and arranging probes in a two-dimensional plane matching the wafer shape, allowing for precise ion and electron temperature calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a floating probe is connected to a plasma medium through a capacitor to cut off DC component, then the influence on plasma medium is minimized and plasma potentials become static, but the ability to measure electron density accurately in negative plasma is lost
Solution Approach 1:
The probe current measurement is segmented into two separate measurements: one with DC component (for electron density) and one without DC component (for ion density and electron temperature). This segmentation allows each measurement to be optimized for its specific purpose while using the same floating probe setup.
Solution Approach 2:
The system performs periodic switching between two measurement modes: DC-coupled mode for electron density measurement and AC-coupled mode for ion density and electron temperature measurement. This periodic action enables comprehensive plasma characterization over time.
2Stability of the object's composition
If only AC component of probe current is measured using DC cut-off capacitor, then plasma potentials remain static, but electron density cannot be calculated in negative plasma where ion density equals electron density
Solution Approach 1:
The current measurement is divided into two separate measurement sequences: first measuring AC component only (with capacitor) for stable plasma potential, then measuring total current including DC component (without capacitor) for accurate electron density calculation in negative plasma.
Solution Approach 2:
The system first performs preliminary measurement of AC component to establish stable plasma potential conditions, then subsequently measures the DC component to calculate electron density, ensuring both stability and accuracy requirements are met in sequence.
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 enables accurate detection of spatial plasma characteristics and prediction of charging damage, enhancing the reliability of plasma treatment processes and semiconductor device fabrication by distinguishing between ion and electron densities.
Implementation Method 1
measuring both AC and DC components of probe currents, with a DC cut-off capacitor to isolate the AC component
Data Source
AI summary
To diagnose plasma in a plasma space, a plurality of floating probes are installed at a plurality of points, respectively, in a plasma space. An electron density ratio at each of the points is calculated by measuring a first probe current of each of the floating probes, the probe current including a DC component. A point ion density and a point electron temperature at each of the points are calculated by measuring a second probe current of each of the floating probes before the electron density ratio is calculated, the second probe current excluding the DC component.