Ion Energy Analyzer Two-Stage Voltage Sweep for Complete Plasma Measurement
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Solution Overview
Problem
Existing methods for measuring ion energy distribution in plasma processing systems face inefficiencies and power consumption issues with descending voltage sweeps, particularly due to incomplete data collection in low energy regions.
Innovation Solution
A two-stage voltage scanning method is employed, where ion current is sampled during both an ascending and descending voltage sweep, using a high voltage generating circuit with a discharge resistor to ensure complete ion energy distribution measurement across a wide range of energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a descending voltage sweep is used for ion energy distribution measurement, then power consumption is reduced, but measurement completeness in low energy regions deteriorates
Solution Approach 1:
The voltage sweep is divided into two distinct stages: an ascending voltage sweep stage and a descending voltage sweep stage. Each stage collects ion current data for different energy regions. The ascending sweep captures low energy region data, while the descending sweep captures high energy region data. By segmenting the measurement process into these two phases, the system achieves complete energy distribution coverage while maintaining power efficiency during the descending stage.
Solution Approach 2:
The ascending voltage sweep is performed first to collect ion current data in the low energy region before transitioning to the descending voltage sweep. This preliminary action ensures that low energy data is captured before the voltage drops, which would otherwise miss this critical region. The preliminary ascending sweep prepares the measurement baseline, enabling subsequent efficient descending sweep measurement.
2Loss of information
If a continuous voltage sweep from zero to maximum is used, then complete ion energy distribution measurement is achieved, but power consumption increases
Solution Approach 1:
The system employs periodic voltage sweeps alternating between ascending and descending phases. Each measurement cycle consists of an ascending sweep followed by a descending sweep. This periodic action pattern allows the system to reuse the voltage infrastructure efficiently, capturing necessary data in both directions while minimizing the time spent at high power consumption levels compared to continuous ascending sweeps.
3Use of energy by moving object
If ion current is sampled only during descending voltage sweep, then power consumption is reduced, but data accuracy in low energy regions deteriorates
Solution Approach 1:
The sampling process is segmented into two distinct phases corresponding to ascending and descending voltage sweeps. During the ascending sweep phase, ion current is sampled to accurately capture low energy region data. During the descending sweep phase, ion current is sampled to capture high energy region data. This segmentation ensures that each energy region is measured during the optimal voltage transition phase, maintaining measurement precision across the entire energy distribution.
Solution Approach 2:
Different sampling strategies are applied to different energy regions. Low energy region sampling is performed during the ascending voltage sweep when the voltage is increasing, while high energy region sampling is performed during the descending voltage sweep. This local quality approach tailors the measurement conditions to the specific energy region being measured, ensuring optimal accuracy for each region while maintaining overall power efficiency.
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 comprehensive ion energy distribution measurement with reduced power consumption, enabling longer sensor operation and accurate data collection across both high and low energy regions.
Implementation Method 1
a high voltage generating circuit within the substrate and configured to take the output voltage of a battery to power the high voltage generating circuit and apply a voltage sweep to a first conductive grid
Implementation Method 2
sampling ion current during a first stage while a first voltage is being charged on the first grid from the floating ground potential to a plateau voltage
Implementation Method 3
sampling ion current during a second stage while a second voltage applied to the first grid is discharging through the resistor from a predetermined voltage generated by the high voltage generating circuit to the plateau voltage
Data Source
AI summary
Methods for obtaining ion energy distribution measurements in a plasma processing system are described. A substrate is placed in the system with an ion energy analyser embedded within it. The analyser consists of multiple conductive grids and a collection electrode, separated by insulating layers. A high-voltage generating circuit within the substrate is powered by a battery and applies voltage to the first grid. A high-voltage switch discharges the first grid to a floating ground, with a resistor in parallel. Ion current is sampled in two stages: first, while charging the first grid from floating ground to a plateau voltage, and second, while discharging through the resistor from a predetermined voltage to the plateau voltage. This setup allows for precise measurement of ion energy distribution at the substrate surface during plasma processing.