Plasma RF Power Delivery Using Inter-Period Waveform Control
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Solution Overview
Problem
Plasma processing systems face challenges in controlling power delivery due to the nonlinear nature of the plasma load, which creates intermodulation products that interfere with measurement systems, and require high bandwidth for traditional control schemes, making it difficult to track and control power effectively.
Innovation Solution
A power delivery system that uses an inter-period controller to produce output patterns based on past measurements, allowing for lower bandwidth control by comparing output values from previous periods to generate error signals, combined with an intra-period controller for adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional control schemes are used with high bandwidth requirements, then power control precision can be maintained, but the system becomes vulnerable to intermodulation interference and requires complex measurement systems
Solution Approach 1:
The patent applies periodic action by using a repetitive waveform approach where the modulation waveform is repeated at a waveform repetition rate. The control system uses measurements from previous waveform periods to control the current period, creating a periodic control cycle that avoids the need for continuous high-bandwidth measurements while maintaining control precision through the repetitive nature of the waveform and the nonlinear characteristics of the plasma load
Solution Approach 2:
The patent implements preliminary action by measuring power and other parameters during the current waveform period and using those measurements to control the next waveform period. This advance preparation of control data from previous periods allows the system to anticipate and compensate for plasma load variations before they affect the current period, reducing vulnerability to intermodulation interference
2Reliability
If narrowband measurement systems are used to limit interference, then system robustness improves, but control bandwidth is reduced making it difficult to track rapid power changes
Solution Approach 1:
The system uses periodic action by operating the measurement and control systems at the waveform repetition rate rather than requiring continuous high-bandwidth measurements. The repetitive waveform approach allows the use of narrowband measurement systems tuned to specific frequency components, limiting interference while maintaining effective control through the periodic nature of the plasma processing operation
Solution Approach 2:
The patent applies copying by using measurements from previous waveform periods as the basis for controlling the current period. Instead of requiring real-time high-bandwidth measurements, the system copies control parameters from previously measured and optimized waveform cycles, allowing narrowband measurement systems to suffice while maintaining control effectiveness through the repetitive waveform pattern
3Adaptability or versatility
If multiple parameters are controlled simultaneously (power, impedance, source impedance), then system versatility improves, but control complexity increases making tracking difficult
Solution Approach 1:
The patent implements universality by using a single repetitive waveform control approach that simultaneously controls multiple parameters including power, impedance, and source impedance. The modulation waveform and control system are designed to handle multiple parameter variations within the same periodic cycle, allowing one control mechanism to perform multiple functions and control diverse plasma processing parameters without requiring separate control systems for each parameter
Solution Approach 2:
The system applies preliminary action by measuring multiple parameters (power, impedance, source impedance) during the current waveform period and using all those measurements together to control the next waveform period. This advance preparation allows the control system to coordinate multiple parameter adjustments in advance, reducing the complexity of simultaneous real-time control while maintaining system versatility
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.