Pulsed RF Power Feedback Control for Coherent Plasma Delivery
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Solution Overview
Problem
Current pulsed RF power delivery systems lack closed-loop feedback control, leading to inefficiencies and variability in power delivery due to dynamic impedance variations in plasma etching processes, which limits their use in volume manufacturing and precision control of plasma parameters like ion flux and ion energy.
Innovation Solution
A radio frequency (RF) control system that includes a power amplifier with energy detection and adjustment circuits, along with a coordination module for phase coherence between multiple RF power supplies, enabling precise control of RF signals and energy delivery to the plasma load through continuous monitoring and feedback loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pulsed RF power delivery systems are used without closed-loop feedback control, then device complexity is reduced, but manufacturing precision and reliability of plasma parameter control deteriorate
Solution Approach 1:
The patent implements closed-loop feedback control by continuously monitoring forward and reflected power through sensors and adjusting the RF power supply output accordingly. The system measures actual power delivery, compares it to desired values, and dynamically corrects deviations through feedback signals to the power amplifier, ensuring precise plasma parameter control despite impedance variations.
Solution Approach 2:
The system dynamically adapts to changing plasma conditions by continuously adjusting RF power delivery parameters in real-time. The feedback control mechanism enables the system to respond to dynamic impedance changes in the plasma chamber, maintaining optimal power transfer and plasma parameter stability throughout the pulsed operation cycle.
2Manufacturing precision
If multiple RF power supplies are used to control plasma parameters, then manufacturing precision of plasma parameters improves, but device complexity and difficulty of coordination increase
Solution Approach 1:
The patent combines multiple RF power supplies into a coordinated system where each amplifier is integrated with sensors and feedback control circuits. The system merges the control of multiple power sources through a unified feedback mechanism that monitors total power delivery and individual amplifier outputs, enabling precise plasma parameter control while managing complexity through integrated design.
Solution Approach 2:
Each RF power amplifier is equipped with feedback control that monitors its output and the overall system state. The feedback signals from sensors measuring forward and reflected power are used to dynamically adjust each amplifier's output, ensuring coordinated operation and precise control of plasma parameters even with multiple power supplies.
3Device complexity
If sensors sample power at slow rates in pulsed mode operation, then device complexity is reduced, but measurement precision and reliability of power delivery control deteriorate
Solution Approach 1:
The system employs periodic sampling of power parameters synchronized with the pulsed RF operation cycle. Sensors take measurements at specific phases of the pulse waveform, capturing critical power delivery information including peak and average power. This periodic sampling approach, coordinated with the pulse timing, provides sufficient measurement precision without requiring continuous high-rate sampling.
Solution Approach 2:
The feedback control system performs preliminary measurements of forward and reflected power during each pulse cycle to predict and adjust power delivery before significant deviations occur. By sampling at strategically chosen moments during the pulse waveform, the system proactively maintains accurate power control without requiring excessively high sampling rates.
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.