Transformer Coupled Plasma Pulsing With Capacitive Tuning
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Solution Overview
Problem
Substrate processing systems face challenges in efficiently controlling plasma etching processes due to limitations in existing feedback control systems, particularly when operating in mixed mode pulsing modes with varying duty cycles and frequencies, which affect impedance matching and power splitting, leading to suboptimal etching performance.
Innovation Solution
The system employs a controller with adaptive feedback and feedforward control mechanisms, utilizing variable capacitors and neural networks to adjust pulsing frequencies and duty cycles, enabling precise impedance matching and power splitting across coils, and incorporating learning capabilities to achieve stable plasma conditions quickly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing feedback control systems are used for plasma etching, then basic control functionality is provided, but control precision and response speed are insufficient when operating in mixed mode pulsing modes with varying duty cycles and frequencies
Solution Approach 1:
The control system dynamically adjusts impedance matching parameters and power splitting ratios in real-time based on the pulsing mode configuration (duty cycle and frequency). The system transitions from static control to dynamic control by continuously monitoring plasma conditions and adjusting matching network parameters adaptively to maintain optimal performance across varying operating conditions.
Solution Approach 2:
The system implements a closed-loop feedback control mechanism where plasma parameters (such as reflected power, VSWR, or plasma impedance) are continuously measured and fed back to the controller. The controller then adjusts the impedance matching parameters and power splitting ratios based on this feedback to maintain precise control despite variations in duty cycle and frequency, thereby improving control precision.
2Manufacturing precision
If impedance matching is optimized for specific duty cycles and frequencies, then etching performance is improved, but the system cannot adapt to varying pulsing modes
Solution Approach 1:
The system changes operating parameters (impedance matching values and power splitting ratios) dynamically based on the selected pulsing mode. When duty cycle or frequency changes, the control system automatically adjusts the matching network parameters and power distribution to optimize etching performance for each specific operating condition, rather than being fixed for a single configuration.
Solution Approach 2:
The control system is designed to handle multiple pulsing modes (different duty cycles and frequencies) within a single unified control architecture. The impedance matching network and power splitting mechanism are configured to be universally adaptable across various operating conditions, allowing the system to maintain optimal etching performance regardless of which pulsing mode is active.
3Stability of the object's composition
If power is continuously applied to maintain plasma, then plasma stability is maintained, but energy efficiency decreases during low-duty-cycle pulsing modes
Solution Approach 1:
The system employs periodic pulsed power delivery to the plasma rather than continuous power application. During low-duty-cycle modes, power is delivered in controlled pulses with appropriate timing and duration to maintain plasma stability only when needed for the etching process, reducing energy consumption during non-processing intervals while preserving plasma stability during active etching periods.
Solution Approach 2:
The control system performs preliminary actions by pre-configuring impedance matching and power splitting parameters before initiating plasma pulsing. This allows the system to quickly establish stable plasma conditions at the start of each pulse and efficiently transition between pulsed and non-pulsed states, minimizing energy waste during transitions and maintaining plasma stability with reduced overall energy consumption.
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 allows for rapid and precise control of plasma etching processes, improving etching efficiency and stability across a wide range of pulsing frequencies and duty cycles, reducing the time required to reach setpoints and minimizing oscillations, thereby enhancing the overall performance of substrate processing systems.
Implementation Method 1
The inductively-coupled plasma may be generated by coils arranged outside of a processing chamber adjacent to a dielectric window. Process gas flowing inside the processing chamber is ignited to create plasma.
Implementation Method 2
A tuning circuit receives an output of the first pulsing circuit, includes a first variable capacitor, and has an output in communication with the coil to generate plasma in the processing chamber.
Implementation Method 3
A controller includes a data acquisition module to generate feedback. A feedback control module controls at least one of the first frequency and the first variable capacitor based on the feedback and a gain value.
Data Source
AI summary
A substrate processing system includes a processing chamber including a substrate support to support a substrate. A coil is arranged around the processing chamber. A first RF source provides first RF power at a first magnitude and a first frequency. A first pulsing circuit applies a duty cycle to the first RF source. A tuning circuit receives an output of the first pulsing circuit, includes a first variable capacitor, and has an output in communication with the coil to generate plasma in the processing chamber. A controller includes a data acquisition module to generate feedback. A feedback control module controls at least one of the first frequency and the first variable capacitor based on the feedback and a gain value. The controller selects the gain value based on at least one of the first frequency and the duty cycle.