Multi-Frequency Plasma RF Synchronization for Stable Processing
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Solution Overview
Problem
Existing plasma processing systems experience RF power instability and plasma perturbations due to unsynchronized RF signal pulsing, which affects process results and device yield, particularly in high-density, high-performance device fabrication.
Innovation Solution
Proactively synchronize and set the RF power levels of higher frequency RF signals in response to the pulsing states of the base RF signal, minimizing RF power perturbations by using a master RF power supply or external control circuit to coordinate pulsing among multiple RF generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple RF signals are pulsed independently without synchronization, then each RF signal can be controlled separately to optimize individual processing parameters, but RF power instability and plasma perturbations occur during transitions
Solution Approach 1:
The patent merges the control of multiple independent RF signals by introducing a master RF power supply that synchronizes the pulsing of all RF signals. The master RF power supply generates a master pulse signal that coordinates the pulsing timing of multiple RF generators, ensuring they transition simultaneously rather than independently. This combining of control functions eliminates the plasma perturbations caused by unsynchronized transitions while maintaining the ability to optimize individual RF power levels for each signal.
Solution Approach 2:
The system performs preliminary action by proactively synchronizing RF signal transitions before plasma perturbations can occur. The master RF power supply anticipates the need for coordinated transitions by establishing a master pulse signal that pre-coordinates all RF signal changes. This preliminary synchronization prevents the reactive compensation cycles that previously caused instability, as all RF signals transition together rather than sequentially.
2Reliability
If RF signals are synchronized with a master pulse signal, then plasma stability is improved by minimizing power perturbations, but system complexity increases due to coordination requirements
Solution Approach 1:
The master RF power supply serves multiple functions simultaneously: it generates the master pulse signal for synchronization, provides power to at least one RF generator, and coordinates the pulsing of multiple RF signals. This multi-functionality reduces the need for separate dedicated synchronization hardware, as the master RF power supply inherently performs both power delivery and synchronization control, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The master pulse signal acts as an intermediary that mediates between the control systems of multiple RF generators. Rather than requiring direct complex inter-communication between all RF signal controllers, the master pulse signal serves as a simple timing reference that all systems follow. This intermediary approach simplifies the control architecture compared to implementing full distributed synchronization protocols.
3Reliability
If reactive compensation is used to detect and correct plasma condition changes, then plasma stability can be restored after perturbations, but RF power perturbations occur during the detection and compensation delay
Solution Approach 1:
The system performs preliminary synchronization of all RF signal transitions before plasma perturbations can occur. By proactively coordinating all RF power changes to happen simultaneously under master control, the system prevents the initial plasma condition changes that would otherwise require reactive compensation. This eliminates the detection and compensation delay entirely, as the perturbations are prevented rather than corrected after the fact.
Solution Approach 2:
The master synchronization system applies preliminary anti-action by preventing plasma perturbations before they can occur. Instead of allowing unsynchronized RF transitions to create plasma instability and then compensating for it, the system preemptively coordinates all transitions to avoid creating instability in the first place. This preliminary preventive measure eliminates the need for reactive compensation cycles and their associated delays.
Data Source
AI summary
Methods and apparatus for processing a substrate in a multi-frequency plasma processing chamber are disclosed. The base RF signal pulses between a high power level and a low power level. Each of the non-base RF generators, responsive to a control signal, proactively switches between a first predefined power level and a second predefined power level as the base RF signal pulses. Alternatively or additionally, each of the non-base RF generators, responsive to a control signal, proactively switches between a first predefined RF frequency and a second predefined RF frequency as the base RF signal pulses. Techniques are disclosed for ascertaining in advance of production time the first and second predefined power levels and/or the first and second predefined RF frequencies for the non-base RF signals.