Transformer Coupled Capacitive Tuning Circuit for Plasma Etch Chambers
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Solution Overview
Problem
Existing transformer coupled capacitive tuning (TCCT) circuits for inductively coupled plasma (ICP) chambers face limitations in high-speed impedance switching, which hinders their ability to support mixed mode pulsing (MMP) operations due to slow capacitance value variations in motor-controlled vacuum capacitors.
Innovation Solution
The implementation of switched capacitor circuits with motor-controlled vacuum capacitors and high-power MOSFET switches allows for dynamic impedance matching by varying capacitance values at high switching speeds between 10 Hz and 1 kHz, enabling faster impedance adjustments during pulsed plasma operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If motor-controlled vacuum capacitors are used for impedance matching, then impedance matching capability is achieved, but switching speed is slow
Solution Approach 1:
The patent divides the capacitance adjustment function into multiple discrete capacitor elements (first capacitor, second capacitor, third capacitor, fourth capacitor) that can be independently switched. This segmentation allows the system to achieve multiple capacitance values by combining different capacitor elements, thereby enabling fast impedance switching without requiring a single complex motor-controlled variable capacitor.
Solution Approach 2:
The patent replaces the mechanical motor-controlled capacitor mechanism with electronic switching devices (MOSFETs). Instead of using a motor to physically adjust the capacitance of a vacuum capacitor, the system uses electronic switches to connect or disconnect fixed capacitor elements, achieving much faster switching speeds without mechanical movement.
2Adaptability or versatility
If fast switching is implemented for mixed mode pulsing operations, then operational versatility is improved, but impedance matching response time must be reduced
Solution Approach 1:
The patent implements a dynamic impedance matching system where the capacitance values can be rapidly changed in real-time during plasma operations. The electronic switching mechanism allows the system to adapt impedance values dynamically during different phases of mixed mode pulsing, enabling the plasma process to respond quickly to changing conditions without the time delays associated with mechanical capacitor adjustment.
Solution Approach 2:
The patent enables periodic switching of capacitance values to support mixed mode pulsing operations. The system can alternate between different capacitance configurations at controlled frequencies, allowing for periodic modulation of the plasma discharge characteristics. This periodic action is essential for implementing complex pulsing patterns required in advanced plasma processing.
3Speed
If multiple capacitor circuits are used for fast switching, then switching speed is improved, but circuit complexity increases
Solution Approach 1:
The patent combines multiple capacitor elements (first capacitor, second capacitor, third capacitor, fourth capacitor) with switching devices to create a unified switched capacitor circuit. By merging these discrete components into an integrated circuit architecture, the system achieves fast switching capability while managing complexity through systematic design. The capacitors are strategically positioned and connected to provide multiple capacitance values without requiring an excessive number of independent circuit paths.
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 enhances the impedance matching response times and overall performance of TCCT circuits, facilitating effective mixed mode pulsing operations by rapidly adjusting capacitance values to match the impedance of coils and plasma changes.
Implementation Method 1
a first switched capacitor circuit including a first terminal, a second terminal, a first capacitor connected to at least one of the first terminal and the second terminal, a second capacitor connected to at least one of the first terminal and the second terminal, and a first switch in communication with at least one of the first capacitor and the second capacitor to vary a capacitance value between the first terminal and the second terminal
Implementation Method 2
Dry etching may be performed using plasma generated by inductively-coupled plasma (ICP). 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.
Data Source
AI summary
A transformer coupled capacitive tuning (TCCT) circuit for an inductively coupled plasma (ICP) chamber includes a matching circuit including a first switched capacitor circuit and a first inductor. The first switched capacitor circuit includes a first terminal, a second terminal, a first capacitor connected to at least one of the first terminal and the second terminal, a second capacitor connected to at least one of the first terminal and the second terminal, and a first switch in communication with at least one of the first capacitor and the second capacitor to vary a capacitance value between the first terminal and the second terminal. A power splitter communicates with the matching circuit and an inductive coil of the ICP chamber.