Plasma Electrode Waveform Synchronization to Reduce RF Power Reflection
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Solution Overview
Problem
Conventional plasma processing systems face issues with inter-modulation distortion (IMD) and high reflected RF power due to the interaction between RF and DC pulsed voltage waveforms, leading to inconsistent plasma processing results across different chambers and systems, as conventional impedance matching components fail to adjust to rapidly changing plasma load impedance.
Innovation Solution
Synchronize the pulsed RF waveform with the pulsed voltage waveform such that the RF waveform is provided only during specific stages of the voltage waveform, namely the ion current or sheath collapse stage, to stabilize the plasma processing conditions and improve impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional impedance matching components are used to deliver RF power to the plasma load, then the system can operate with standard matching networks, but the rapidly changing plasma load impedance causes inter-modulation distortion and high reflected RF power
Solution Approach 1:
The patent applies periodic pulsed voltage waveforms to the plasma load, creating cyclic transitions between different impedance states. By synchronizing the RF waveform delivery with these periodic pulses and confining RF to specific stages (ion current or sheath collapse), the system achieves consistent plasma processing while avoiding the harmful inter-modulation distortion that occurs with continuous RF delivery during rapid impedance changes.
2Productivity
If RF waveform is delivered continuously during plasma processing, then continuous plasma generation is maintained, but impedance variations cause varying RF power delivery and processing inconsistencies
Solution Approach 1:
The patent segments the RF waveform delivery into distinct stages synchronized with the pulsed voltage waveform. RF power is delivered only during specific stages (either ion current stage or sheath collapse stage) rather than continuously, allowing the system to maintain productivity while achieving manufacturing precision by avoiding processing during impedance transition periods.
Solution Approach 2:
The patent implements periodic pulsed voltage waveforms that create cyclic plasma states, with RF delivery synchronized to specific periods. This periodic approach maintains overall plasma generation continuity while ensuring consistent processing results by delivering RF power during stable plasma conditions rather than during transient impedance changes.
3Adaptability or versatility
If DC pulsed voltage waveform is applied to control plasma sheath, then plasma sheath toggling between thick and no-sheath states is achieved, but plasma load impedance changes rapidly over time
Solution Approach 1:
The patent implements a synchronization mechanism that acts as a feedback system, detecting the stage of the pulsed voltage waveform and adjusting RF waveform delivery accordingly. This feedback approach automatically adapts the RF delivery timing to the current plasma state, providing versatile plasma sheath control while eliminating the need for complex manual impedance matching adjustments.
Solution Approach 2:
The patent uses periodic pulsed voltage waveforms to create predictable, cyclic plasma states with distinct phases. This periodic behavior simplifies the impedance matching problem by creating regular, repeating patterns that can be synchronized with RF delivery, reducing device complexity compared to attempting to continuously track and adapt to arbitrary impedance changes.
4Power
If RF matching network is designed for 50 Ω load, then maximum power delivery efficiency is achieved under matched conditions, but reflected power increases when plasma impedance deviates from 50 Ω
Solution Approach 1:
The patent applies periodic pulsed voltage waveforms that create distinct plasma stages with relatively stable impedance characteristics during each stage. By synchronizing RF delivery to occur only during these stable stages (ion current or sheath collapse) rather than during transitions, the system maintains power delivery efficiency while minimizing reflected power that would occur during rapid impedance changes.
Solution Approach 2:
The patent segments RF power delivery into discrete time windows corresponding to specific plasma stages. This segmentation allows the system to deliver RF power efficiently during stable impedance periods while avoiding power reflection during impedance transitions, effectively separating the power delivery function from the impedance variation periods.
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 synchronization method reduces IMD and reflected RF power, enhancing the consistency and precision of plasma processing results by minimizing impedance variations and improving power delivery efficiency.
Implementation Method 1
applying a pulsed radio frequency (RF) waveform to a reactive species to generate a plasma in a processing region of a processing chamber
Data Source
AI summary
Embodiments of the present disclosure generally relate to a system used in a semiconductor device manufacturing process. More specifically, embodiments provided herein generally include apparatus and methods for synchronizing and controlling the delivery of an RF bias voltage signal and a pulsed voltage waveform to one or more electrodes within a plasma processing chamber. Embodiments of the disclosure include a method and apparatus for synchronizing a pulsed radio frequency (RF) waveform to a pulsed voltage (PV) waveform, such that the pulsed RF waveform is on during a first stage of the PV waveform and off during a second stage. The first stage of the PV waveform includes a sheath collapse stage. The second stage of the PV waveform includes an ion current stage.