Plasma RF Source Frequency Control for Reflection-Stable Processing
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Solution Overview
Problem
Existing plasma processing apparatuses experience significant reflection of source radio-frequency power, which affects the efficiency and stability of plasma generation.
Innovation Solution
A plasma processing apparatus with a substrate support and radio-frequency power supply that adjusts the source frequency based on interpulse and intrapulse feedback mechanisms to minimize reflection by identifying changes in the degree of reflection during overlapping pulse periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If source radio-frequency power is provided continuously to generate plasma, then plasma generation is maintained, but the degree of reflection of source radio-frequency power increases
Solution Approach 1:
The patent applies periodic action by providing bias energy in pulsed periods rather than continuously. The bias power supply provides a pulse of bias energy to the bias electrode in each of a plurality of pulse periods, creating periodic modulation of the plasma state. This periodic action allows the source radio-frequency power reflection to be reduced while maintaining plasma generation stability through the rhythmic adjustment of bias conditions.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the source frequency of source radio-frequency power in real-time based on feedback from the plasma state. The radio-frequency power supply sets a source frequency in each of a plurality of phase periods in each of a plurality of waveform cycles, with the frequency being adjusted based on changes in the degree of reflection. This dynamic adjustment allows the system to adapt to changing plasma conditions and minimize reflection while maintaining stable plasma generation.
2Loss of energy
If the source frequency is adjusted frequently to minimize reflection, then the degree of reflection is reduced, but the complexity of the control system increases
Solution Approach 1:
The patent implements feedback control by monitoring the degree of reflection of source radio-frequency power and using this information to adjust the source frequency. The radio-frequency power supply adjusts the source frequency based on a change in the degree of reflection of the source radio-frequency power, where the change in the degree of reflection is identified with the source frequency being set differently in preceding waveform cycles or overlap periods. This feedback mechanism enables automatic optimization of reflection without requiring complex external control systems.
Solution Approach 2:
The system performs self-service by using the reflection characteristics of the plasma load itself to determine the optimal source frequency. The radio-frequency power supply uses the measured degree of reflection as direct feedback to adjust its own operating frequency, eliminating the need for complex external control algorithms or additional sensors. The system essentially uses its own performance metric (reflection degree) to self-optimize its operation.
3Productivity
If multiple overlap periods with different source frequencies are used, then plasma generation efficiency is improved, but the difficulty of detecting and measuring reflection changes increases
Solution Approach 1:
The patent applies segmentation by dividing the continuous radio-frequency power supply into discrete phase periods within waveform cycles, and further dividing waveform cycles into separate overlap periods. The radio-frequency power supply sets different source frequencies in different phase periods and waveform cycles, creating a segmented approach to frequency control. This segmentation allows the system to measure reflection changes at specific intervals (in preceding waveform cycles or overlap periods) rather than requiring continuous measurement, thereby reducing measurement complexity while maintaining plasma generation 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
The apparatus effectively reduces the degree of reflection, enhancing plasma generation efficiency and stability by dynamically adjusting the source frequency in response to reflection changes.
Implementation Method 1
The radio-frequency power supply generates source radio-frequency power to generate plasma in the chamber
Implementation Method 2
The plasma processing apparatus uses bias RF power to draw ions in plasma generated in a chamber toward a substrate
Data Source
AI summary
A plasma processing apparatus includes a chamber, a substrate support, a radio-frequency power supply, and a bias power supply. The radio-frequency power supply generates source radio-frequency power to generate plasma in the chamber. The bias power supply provides a pulse of bias energy to a bias electrode in each of a plurality of pulse periods. The radio-frequency power supply sets, based on a change in a degree of reflection of the source radio-frequency power, a source frequency of the source radio-frequency power in each of a plurality of phase periods in each of a plurality of overlap periods. Each of the plurality of overlap periods overlaps a corresponding pulse period of the plurality of pulse periods. The degree of reflection is identified with the source frequency being set differently in identical phase periods in two or more preceding overlap periods.