Pulsed RF Power Feedback for Coherent Multi-Generator Plasma Control
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Solution Overview
Problem
Current pulsed RF systems lack closed-loop power delivery solutions, leading to inefficiencies and reduced accuracy and reproducibility in power delivery due to dynamic impedance variations, especially in plasma etching processes, which are critical for semiconductor fabrication.
Innovation Solution
A radio frequency (RF) control system with a power amplifier, sensors, and energy detection circuits that generate control signals to adjust the RF signal based on real-time energy and power feedback, along with a coordination module for phase coherence between multiple RF generators to synchronize energy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pulsed RF systems operate without closed-loop feedback, then device complexity is reduced, but manufacturing precision and reliability deteriorate due to dynamic impedance variations
Solution Approach 1:
The patent implements closed-loop feedback control by measuring actual RF power delivered to the plasma load and comparing it with the desired power level. The system dynamically adjusts the RF generator output based on real-time measurements, compensating for impedance variations and ensuring accurate power delivery throughout the pulse cycle.
Solution Approach 2:
The system transitions from static open-loop control to dynamic closed-loop control, where control parameters are continuously adjusted based on real-time system state. The feedback mechanism enables the system to adapt to changing plasma conditions and impedance variations during pulsed operation.
2Adaptability or versatility
If multiple RF generators are used to control plasma parameters, then adaptability improves, but device complexity and difficulty of detecting and measuring increase
Solution Approach 1:
Each RF generator is equipped with independent feedback control that monitors its own power delivery and plasma load conditions. This per-generator feedback approach enables precise control of multiple plasma parameters while maintaining manageable system complexity through modular control architecture.
Solution Approach 2:
The control system is divided into independent control channels for each RF generator, with each channel having its own feedback loop. This segmentation allows each generator to be controlled independently for specific plasma parameters while the overall system benefits from coordinated operation.
3Device complexity
If power measurement samples at slow rates, then device complexity is reduced, but measurement precision deteriorates due to missing RF transients
Solution Approach 1:
The system preemptively addresses the problem of missing transients by implementing high-rate sampling that captures all RF power variations throughout the pulse cycle. This prevents information loss before it can occur, ensuring complete measurement of power delivery including all transient events.
Solution Approach 2:
The sampling system operates at a rate synchronized with the RF pulse frequency and higher, taking multiple measurements per pulse cycle. This periodic high-rate sampling ensures that all transient events are captured while maintaining manageable data processing requirements through synchronized timing.
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 precise control of RF power delivery, improving the accuracy and reproducibility of power transfer to the plasma load, even during dynamic impedance changes, thereby enhancing the consistency and efficiency of plasma etching processes.
Implementation Method 1
A sensor outputs a sensor signal based on the RF signal. An energy detection circuit determines an energy of the RF signal in accordance with the sensor signal.
Data Source
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AI summary
A RF power supply system for delivering periodic RF power to a load. A power amplifier outputs a RF signal to the load. A sensor measures the RF signal provided to the load and outputs signals that vary in accordance with the RF signal. A first feedback loop enables control the RF signal based upon power determined in accordance with output from the sensor. A second feedback loop enables control the RF signal based upon energy measured in accordance with signals output from the sensor. Energy amplitude and duration provide control values for varying the RF signal. The control system and techniques are applicable to both pulsed RF power supplies and in various instances to continuous wave power supplies.