Plasma Impedance Stabilization via Counter-Phase RF Injection
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Solution Overview
Problem
Conventional impedance match circuits in plasma processes for semiconductor fabrication struggle to accurately control RF power due to delays in responding to rapid fluctuations in plasma impedance, leading to impedance mismatches and potential reactor shutdowns.
Innovation Solution
A method is introduced where stabilization RF power is applied to the plasma reactor to counteract sensed changes in plasma impedance, using RF power generators of specific frequencies to manage both resistive and capacitive components of impedance, allowing for real-time adjustment of power levels to maintain impedance stability without relying on impedance match circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional impedance match circuits are used to maintain impedance match for RF generator, then the RF generator is protected from reflected power damage, but the response delay of the impedance match circuit causes failure to follow rapid plasma impedance changes, leading to impedance mismatch and reactor shutdown
Solution Approach 1:
The patent replaces the mechanical impedance match circuit with an electrical field-based solution. A counter-phase RF signal is generated and injected into the plasma chamber to actively cancel impedance variations. This electrical field approach eliminates the mechanical response delay inherent in traditional impedance match circuits, enabling real-time compensation of plasma impedance fluctuations without moving parts or tuning elements.
Solution Approach 2:
The patent dynamically changes the RF signal parameters (frequency, phase, amplitude) to match and counteract plasma impedance variations. By continuously adjusting the counter-phase signal parameters based on real-time plasma conditions, the system maintains optimal impedance match across a wide range of operating conditions, overcoming the fixed parameter limitations of conventional circuits.
2Reliability
If variable reactance impedance match circuit is used, then impedance matching is maintained, but the mechanical limitations of variable reactance elements cause response time on the order of one second
Solution Approach 1:
The invention eliminates mechanical variable reactance elements entirely by using electronic signal generation and injection. The counter-phase RF signal is generated electronically and can be adjusted instantaneously, replacing the slow mechanical tuning process with rapid electrical control. This substitution reduces response time from seconds to microseconds.
Solution Approach 2:
The patent employs periodic RF signaling at the plasma frequency to continuously monitor and counteract impedance variations. By using periodic signals that match the plasma oscillation frequency, the system achieves rapid, repetitive adjustment cycles that far exceed the response capability of mechanical systems, maintaining continuous impedance match without mechanical inertia.
3Reliability
If tuned frequency impedance match system is used, then impedance matching is achieved, but mechanical limitations of frequency tuning elements cause response time on the order of 100 milliseconds
Solution Approach 1:
The patent replaces mechanical frequency tuning elements with electronic frequency synthesis and signal generation. The counter-phase RF signal frequency is controlled electronically, allowing instantaneous frequency adjustment without mechanical movement. This electronic control mechanism eliminates the 100-millisecond response delay inherent in mechanical tuning systems.
Solution Approach 2:
The invention implements dynamic frequency and phase control of the RF signal through electronic modulation. The system continuously adapts the signal characteristics in real-time based on plasma conditions, enabling rapid response to impedance changes. This dynamic electronic control replaces static or slowly-adjusting mechanical tuning elements, achieving millisecond or microsecond response times.
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 effectively reduces reflected power at the RF generator, stabilizes plasma conditions, and prevents impedance mismatches, ensuring accurate RF power delivery and protecting the RF generator from damage by maintaining a stable impedance match.
Implementation Method 1
an RF generator is coupled to a plasma chamber through a capacitor
Implementation Method 2
The amount of RF power delivered to the plasma is affected by fluctuations in plasma impedance
Implementation Method 3
an RF generator is coupled to a plasma chamber through a capacitor
Data Source
AI summary
A workpiece is processed in a plasma reactor chamber using stabilization RF power delivered into the chamber, by determining changes in load impedance from RF parameters sensed at an RF source or bias power generator and resolving the changes in load impedance into first and second components thereof, and changing the power level of the stabilization RF power as a function one of the components of changes in load impedance.