Plasma Power Frequency Control for Reverse Power Reduction
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Solution Overview
Problem
Current high frequency power systems in plasma etching face challenges in minimizing reverse power and achieving precise impedance matching, especially during transitions between continuous wave and pulse modes, leading to variability in power transmission and difficulty in maintaining process reproducibility.
Innovation Solution
A method and apparatus that utilize a controller to determine the slopes of output frequency and reverse power, adjusting the frequency to minimize reverse power reflection by changing the output frequency when the reflection coefficient exceeds a threshold, and implementing a hump-escape mechanism to stabilize power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If continuous wave high frequency signal is applied to plasma load, then power transmission stability is improved, but reverse power cannot be minimized due to impedance variations
Solution Approach 1:
The patent applies periodic pulse modulation to the high frequency signal instead of continuous wave. The signal is transmitted in periodic pulses with controlled duty cycle, allowing the impedance matcher to adjust between pulses and minimize reverse power reflection during each pulse while maintaining overall power transmission stability through the periodic nature of the signal.
Solution Approach 2:
The patent implements dynamic impedance matching where the matching network continuously adjusts its parameters in real-time during pulse operation. The system adapts the impedance transformation ratio dynamically based on the plasma load conditions, enabling minimum reverse power reflection while maintaining stable power transmission despite impedance variations.
2Loss of energy
If pulse type high frequency signal is used, then reverse power can be minimized through impedance matching, but power transmission variability increases
Solution Approach 1:
The patent employs feedback control where the system monitors the actual power transmission and reverse power levels during pulse operation. Based on this feedback, the impedance matcher adjusts its parameters in real-time to maintain consistent power transmission while minimizing reverse power reflection, thereby reducing power transmission variability.
Solution Approach 2:
The patent utilizes parameter changes in the impedance matching network during pulse operation. By dynamically adjusting the matching network parameters (such as capacitor values or inductor positions) in response to plasma load variations, the system maintains optimal power transfer and minimizes reverse power while reducing transmission variability.
3Loss of energy
If impedance matching is adjusted rapidly to track plasma impedance changes, then reverse power minimization is improved, but system complexity increases
Solution Approach 1:
The patent implements preliminary impedance matching adjustments before each pulse is applied to the plasma load. The system pre-adjusts the impedance matching parameters based on anticipated plasma conditions or previous pulse performance, enabling rapid reverse power minimization without requiring complex real-time adjustment mechanisms during the actual pulse.
Solution Approach 2:
The patent applies partial impedance matching adjustments at strategic points rather than continuous complex adjustments. By making targeted impedance corrections at key moments (such as before pulse initiation or during inter-pulse periods), the system achieves effective reverse power minimization with simpler control logic compared to continuous full-adjustment systems.
Data Source
AI summary
A method for reducing reverse power reflected from a plasma load to a high frequency power amplifier includes determining a sign of a slope of an output frequency outputted from the high frequency power amplifier; determining a sign of a slope of reverse power reflected from the plasma load to the high frequency power amplifier; deciding an increase or a decrease in an amount of frequency change according to a combination of the sign of the slope of the output frequency and the sign of the slope of the reverse power; updating the output frequency by using the amount of the frequency change, and changing the output frequency in order to escape from a hump when a reflection coefficient is larger than a predetermined reflection reference value and the amount of the frequency change is smaller than a predetermined variation width setting value.