Inter-Period Control for Plasma Power Delivery
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Solution Overview
Problem
Current plasma power delivery systems face challenges in accurately controlling power and impedance due to the nonlinear nature of the plasma load, leading to interference and suboptimal performance, especially with the need for high bandwidth and independent control of generator and match network components.
Innovation Solution
An inter-period control system that adjusts output patterns based on measurements from past repetition periods, combined with an intra-period controller for real-time adjustments, allowing for precise control of power and impedance matching to achieve consistent and accurate power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional control schemes with high bandwidth requirements are used to follow prescribed modulation waveforms, then power delivery accuracy is improved, but device complexity and measurement system requirements increase
Solution Approach 1:
The system performs measurements and control adjustments in advance during previous repetition periods before the actual power delivery phase. By predicting plasma impedance based on prior period measurements and pre-adjusting generator frequency and match network settings, the system achieves accurate power delivery without requiring high bandwidth real-time control systems.
Solution Approach 2:
The control system operates in a periodic manner synchronized with the waveform repetition rate. Measurements are taken at specific phases of previous repetition periods, and control adjustments are applied in a periodic cycle that matches the plasma processing waveform, enabling accurate control through regular periodic updates rather than continuous high-bandwidth operation.
2Reliability
If narrowband measurement systems are used to limit intermodulation interference, then measurement reliability is improved, but control bandwidth and response capability are reduced
Solution Approach 1:
The narrowband measurement system performs impedance measurements during previous repetition periods before the main power delivery phase. By completing measurements and control adjustments in advance, the system maximizes the use of narrowband measurement capabilities without sacrificing response speed, as the control actions are prepared beforehand rather than requiring fast real-time responses.
3Adaptability or versatility
If independent control of generator and match network is implemented, then adaptability is improved, but device complexity and control difficulty increase
Solution Approach 1:
The control system merges the control of generator frequency and match network impedance into a unified control algorithm. By calculating the required generator frequency adjustment and match network setting together based on predicted plasma impedance, the system achieves coordinated control of multiple components through a single integrated control logic, reducing overall control complexity while maintaining adaptability.
Solution Approach 2:
The system implements feedback control by measuring actual plasma impedance during operation and using these measurements to adjust generator frequency and match network settings in subsequent repetition periods. This feedback mechanism enables the independent control components to work together adaptively, with the control algorithm automatically coordinating their settings based on real-time plasma conditions.
4Ease of operation
If human operators manually monitor and adjust system parameters, then ease of operation is improved, but productivity and response time are reduced
Solution Approach 1:
The control system performs autonomous measurements, calculations, and adjustments without requiring human operator intervention. The system automatically monitors plasma impedance, predicts optimal settings, and adjusts generator and match network parameters independently, eliminating the need for manual monitoring while significantly increasing productivity and response speed compared to human-operated systems.
Data Source
AI summary
A generator produces output such as delivered power, voltage, current, forward power etc. that follows a prescribed pattern of output versus time where the pattern repeats with a repetition period by controlling sections of the pattern based on measurements taken one or more repetition periods in the past. A variable impedance match network may control the impedance presented to a radio frequency generator while the generator produces the output that follows the prescribed pattern of output versus time where the pattern repeats with a repetition period by controlling variable impedance elements in the match during sections of the pattern based on measurements taken one or more repetition periods in the past.