RF Match Impedance Scanning for Pulsed Plasma Load Tracking
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Solution Overview
Problem
Conventional plasma processing systems face challenges in maintaining efficient RF power delivery due to rapidly changing plasma load impedance values, leading to inter-modulation distortion and undesirable variations in plasma processing results.
Innovation Solution
The method involves delivering an RF signal through an RF match set to a first matching point, while simultaneously applying a voltage waveform. The RF match measures impedance-related data at specific time intervals, calculates a combined impedance parameter, and adjusts its matching parameter to achieve a second matching point, thereby compensating for the varying impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RF matching is used with rapidly changing plasma load impedance, then the RF matching network cannot adjust quickly enough, but inter-modulation distortion and reflected power increase
Solution Approach 1:
The patent implements a feedback mechanism where the RF matching network continuously measures impedance-related data during plasma processing, calculates combined impedance parameters, and adjusts matching parameters in real-time based on these measurements. This closed-loop feedback system enables the RF match to track rapidly changing plasma load impedance values and maintain optimal matching points, thereby resolving the contradiction between processing reliability and system complexity by making the system adaptive rather than static
Solution Approach 2:
The patent transforms the static RF matching system into a dynamic one by enabling continuous adjustment of matching parameters during plasma processing. The RF matching network now operates dynamically by measuring impedance at different time intervals, calculating combined impedance parameters that account for rapid changes, and adjusting matching points accordingly. This dynamic operation allows the system to adapt to rapidly changing plasma conditions without requiring overly complex additional hardware
2Adaptability or versatility
If DC voltage pulsing is applied to control plasma sheath, then plasma sheath toggling is achieved, but plasma load impedance varies rapidly over time
Solution Approach 1:
The patent applies preliminary action by measuring impedance-related data at specifically timed intervals before the plasma load impedance changes too rapidly. The system measures impedance during periods when the plasma sheath state is relatively stable (such as during DC pulse off-periods or at specific phases of sheath toggling), calculates combined impedance parameters in advance, and uses these pre-calculated values to adjust matching parameters proactively before the next rapid impedance change occurs. This preliminary measurement and calculation approach allows the system to anticipate and prepare for upcoming impedance variations
Solution Approach 2:
The patent implements periodic action by measuring impedance-related data at regular, periodic intervals during DC voltage pulsing operations. Rather than attempting to continuously track every instantaneous impedance change, the system samples impedance at periodic moments when the plasma sheath is in predictable states, calculates combined impedance parameters from these periodic measurements, and adjusts matching parameters accordingly. This periodic sampling strategy enables the system to handle rapid impedance changes caused by plasma sheath toggling without requiring measurement speeds that exceed practical implementation capabilities
3Measurement precision
If impedance measurement is performed during rapid plasma load changes, then accurate impedance tracking is achieved, but measurement and adjustment time increases
Solution Approach 1:
The patent applies partial action by measuring only specific impedance-related parameters at selected time intervals rather than attempting to continuously measure and process all impedance components. The system selectively measures impedance during periods when the plasma load is relatively stable or at critical transition points, calculates combined impedance parameters from these partial measurements, and uses them to make timely matching adjustments. This selective, partial measurement approach maintains sufficient measurement precision for effective impedance tracking while avoiding the time penalties of continuous, exhaustive measurement
Solution Approach 2:
The patent implements multi-functionality by designing the RF matching network to simultaneously perform multiple functions: measuring impedance-related data, calculating combined impedance parameters, adjusting matching parameters, and maintaining plasma processing—all within the same operational framework. The system integrates these functions so that a single impedance measurement campaign serves multiple purposes: characterizing plasma load conditions, determining optimal matching points, and validating processing stability. This multi-functional approach eliminates the need for separate measurement and adjustment cycles, thereby reducing total time loss while maintaining measurement precision
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the stability and efficiency of RF power delivery to the plasma load, reducing inter-modulation distortion and ensuring consistent plasma processing results across different systems and chambers.
Implementation Method 1
A plasma is formed in a processing chamber and ions from the plasma are accelerated towards a surface of a substrate
Implementation Method 2
A typical Reactive Ion Etch (RIE) plasma processing chamber includes a radio frequency (RF) bias generator, which supplies an RF voltage to a power electrode
Implementation Method 3
measuring, by an output sensor of the RF match, a first set of impedance related data of the plasma processing system over a first time period
Implementation Method 4
During operation, the DC voltage pulses cause a generated plasma sheath to toggle between states that includes a thick plasma sheath and state where no plasma sheath exists
Data Source
AI summary
Embodiments of the disclosure include a method of processing a substrate in a plasma processing system, comprising delivering an RF signal, by an RF generator, through an RF match to an electrode assembly disposed within the plasma processing system, wherein while delivering the RF signal the RF match is set to a first matching point, and delivering a voltage waveform, by a waveform generator, to the electrode assembly disposed within the plasma processing system while the RF signal is delivered to the electrode assembly. The method includes receiving, by the RF match, a synchronization signal from a RF generator or the waveform generator, measuring, by an output sensor of the RF match, a first set of impedance related data of the plasma processing system over a first time period, the first time period beginning after a first delay triggered by a first portion of a first waveform pulse of the synchronization signal, measuring, by the output sensor of the RF match, a second set of impedance related data of the plasma processing system over a second time period, the second time period beginning after a second delay triggered by the first portion of the first waveform pulse of the synchronization signal, calculating, by the RF match, a combined impedance parameter based on the measured first set of impedance related data and the measured second set of impedance related data, and adjusting a matching parameter within the RF match based on the calculated combined impedance parameter to achieve a second matching point.