Pulse-Modulated RF Power Control for Plasma Stability
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Solution Overview
Problem
Conventional RF power control methods lead to unstable output power due to fluctuations in reflected power, affecting plasma stability and process homogeneity in plasma treatment chambers, and can result in plasma loss and reduced product quality.
Innovation Solution
A pulse modulated RF power control method that maintains constant power amplitude by adjusting the duty ratio of pulse power, using output amplitude control and duty control to stabilize plasma density and suppress reflected power, thereby stabilizing the plasma atmosphere and reducing unnecessary matching operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the peak forward power is changed along with the fluctuation of the reflected power, then the reflected power can be suppressed, but the output power becomes unstable and plasma stability is affected
Solution Approach 1:
The patent segments the power control into two independent parts: peak forward power control and duty ratio control. The peak forward power is kept constant to ensure output stability, while the duty ratio is adjusted independently to suppress reflected power. This segmentation resolves the contradiction by allowing each parameter to fulfill its specific function without interfering with the other.
Solution Approach 2:
The patent applies dynamics by making the duty ratio variable while keeping the peak forward power constant. The duty ratio dynamically adjusts in response to reflected power fluctuations, allowing the system to adapt to changing conditions without compromising output power stability. This dynamic adjustment of only the necessary parameter resolves the contradiction.
2Stability of the object's composition
If the forward power is controlled to be constant, then the output power stability is maintained, but the plasma state changes when reflected power increases, causing matching deviation
Solution Approach 1:
The duty ratio serves as an intermediary parameter that mediates between the constant peak forward power and the varying plasma conditions. When reflected power increases indicating plasma state changes, the duty ratio adjusts to compensate, maintaining both output stability and plasma adaptability. This intermediary mechanism resolves the contradiction by providing a buffer between the fixed power level and changing plasma conditions.
3Reliability
If the output power is lowered to protect the RF power supply device from increased reflected power, then the device is protected, but plasma activation is lost and process development is interrupted
Solution Approach 1:
The patent segments the protection mechanism from the power delivery mechanism. The peak forward power remains high to maintain plasma activation and productivity, while the duty ratio is reduced to limit average power and protect the device from excessive reflected power. This segmentation allows simultaneous achievement of device protection and plasma activation.
Solution Approach 2:
The patent uses periodic action through pulse modulation with variable duty ratio. Instead of continuously lowering power, the system delivers high peak power in periodic pulses with adjusted width. This periodic delivery maintains plasma activation during pulse periods while reducing average power to protect the device, resolving the contradiction between protection and activation.
Data Source
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AI summary
In a pulse power control, power amplitude (peak power) of output power is controlled to be constant against the fluctuation of the power, whereby it is possible to avoid an effect on a load, which is caused by the fluctuation of the power amplitude of the output power. The pulse modulated RF power control method includes an output amplitude control step for controlling amplitude of a pulse output, and a duty control step for controlling a duty ratio of the pulse output. The output amplitude control step performs a constant amplitude control to control an amplitude value of the pulse output so that the amplitude value becomes equal to a set amplitude value. The constant amplitude control according to the output amplitude control, for instance, gives a feedback of the amplitude value of the pulse output outputted by the power control, obtains a difference value between the feedback value and the set amplitude value, and controls the amplitude value of the pulse output so that the difference value becomes zero.