Plasma Ignition Circuit With Capacitive Switch Controller
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Solution Overview
Problem
Conventional remote plasma sources have a narrow plasma generating region and cannot tune power delivery without altering other process conditions, often resulting in high ignition voltages that cause arcing in plasma processing chambers, leading to substrate and chamber damage.
Innovation Solution
A plasma ignition circuit with a transformer and secondary coils that couples RF power to a remote plasma source, using a switch controller to sense RF voltage and impedance changes, enabling controlled plasma ignition and automatic discontinuation of power once plasma is formed, preventing arcing and maintaining consistent plasma ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional remote plasma sources use microwave or capacitively coupled energy sources, then plasma generation is achieved, but the plasma generating region becomes narrow and power tuning capability is lost
Solution Approach 1:
The patent segments the plasma generation system into a remote plasma source (RPS) unit and a separate processing chamber, with the RPS containing the plasma generation region physically separated from the substrate processing area. This segmentation allows independent optimization of plasma generation parameters while maintaining a broader effective plasma processing window in the chamber.
Solution Approach 2:
The patent transitions from direct plasma generation over the substrate to remote plasma generation, adding a spatial dimension separation between plasma creation and substrate treatment. This dimensional change allows the plasma to be generated in a controlled region and then transported to the processing area, expanding the effective processing window and enabling power tuning independent of plasma region geometry.
2Reliability
If large ignition voltages are applied to ignite plasma in conventional RPS, then plasma ignition is achieved, but arcing occurs within the chamber causing damage
Solution Approach 1:
The patent introduces a capacitive coupling mechanism as an intermediary between the RF power source and the plasma generation region. The capacitor allows voltage buildup for reliable ignition while isolating the chamber from direct high-voltage stress, preventing arcing and damage to chamber components.
Solution Approach 2:
The patent employs a capacitive coupling arrangement that cushions the voltage transition during plasma ignition. The capacitor charges beforehand and delivers energy in a controlled manner, preventing sudden voltage spikes that would cause arcing while still providing sufficient energy for reliable plasma ignition.
3Power
If conventional RPS designs are used, then plasma generation is achieved, but the plasma processing window is smaller than desirable
Solution Approach 1:
The patent implements dynamic control of the capacitive coupling parameters, allowing the system to adjust operating conditions in real-time. This enables the plasma processing window to be dynamically optimized for different process requirements, expanding the range of achievable plasma conditions beyond fixed conventional designs.
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 solution provides reliable and consistent plasma ignition, reduces arcing, and prevents prolonged high-voltage application, enhancing processing chamber performance and reliability by ensuring precise control over plasma formation.
Implementation Method 1
a transformer having a primary coil configured to couple an RF power supply. A first secondary coil is configured to couple a remote plasma source (RPS), and a second secondary coil
Implementation Method 2
a control switch having an input configured to couple the second secondary coil and an output configured to capacitively couple the RPS
Implementation Method 3
The switch controller is further configured to, upon sensing a drop in plasma impedance when the plasma is ignited
Data Source
AI summary
A plasma ignition circuit includes a transformer having a primary coil configured to couple an RF power supply. A first secondary coil is configured to couple a remote plasma source (RPS), and a second secondary coil. The plasma ignition circuit further includes a control switch having an input configured to couple the second secondary coil and an output configured to capacitively couple the RPS and a switch controller. The switch controller is configured to upon sensing a secondary RF voltage applied to the second secondary coil in response to an RF voltage applied by RF power supply to the primary coil, enable the control switch to capacitively apply the secondary RF voltage to the RPS to ignite a plasma within the RPS. Upon sensing a drop in plasma impedance when the plasma is ignited, disable the control switch to discontinue applying the secondary RF voltage to the RPS.