Inductive Plasma Reactor Coil Segmentation for Heat Removal
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Solution Overview
Problem
Inductive plasma reactors face issues with capacitive coupling, transmission line effects, and inefficient heat removal, leading to non-uniform plasma distribution and high power losses during the processing of large wafers and panel displays.
Innovation Solution
The use of an array of ferromagnetic core antennas immersed in the plasma, with individual matching networks for each antenna cell, and a heat conductor connected to a heat sink, allows for deep immersion and efficient plasma excitation, reducing capacitive coupling and enhancing plasma uniformity while facilitating effective heat removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard resonance matching network is used to match the coil, then impedance matching conditions are achieved, but extra-large RF current and high power losses occur in the matcher network and coil
Solution Approach 1:
The patent divides the single large coil into multiple smaller coil segments (e.g., four quadrants). Each segment is matched individually with a simple resistive match, avoiding the need for a complex resonance matching network. This segmentation reduces the RF current and power losses in each individual match while achieving overall impedance matching for the plasma source.
2Ease of operation
If the conductor length becomes comparable to the coil length, then connection is achieved, but plasma azimuthal asymmetry and non-uniformity increase
Solution Approach 1:
The patent segments the coil into multiple smaller units positioned at different locations (e.g., four quadrants of the chamber). Each segment is connected to the matching network through short conductors, minimizing conductor length effects. The segmented arrangement also improves plasma uniformity by distributing the electromagnetic field more evenly across the chamber, reducing azimuthal asymmetry.
Solution Approach 2:
The patent intentionally positions the coil segments asymmetrically in specific locations around the chamber (e.g., at 45-degree intervals). This asymmetric positioning optimizes the electromagnetic field distribution and plasma uniformity while minimizing the impact of conductor lengths on plasma azimuthal symmetry.
3Power
If high RF voltage is applied between coil terminals, then plasma excitation is achieved, but capacitive coupling and ion acceleration towards the window occur
Solution Approach 1:
The patent divides the single high-voltage coil into multiple lower-voltage coil segments. Each segment operates at reduced voltage levels, significantly reducing capacitive coupling effects. The segmented configuration maintains effective plasma excitation through distributed electromagnetic fields while minimizing the harmful high-voltage capacitive coupling between the coil and plasma sheath.
Solution Approach 2:
The patent introduces a dielectric window structure as an intermediary between the coil segments and the plasma. This dielectric barrier reduces direct capacitive coupling while allowing the electromagnetic fields to penetrate and excite the plasma effectively. The window acts as a mediator that transmits energy while blocking harmful direct electrical contact and ion acceleration.
4Device complexity
If a single large coil is used, then plasma source is simplified, but plasma uniformity over large areas deteriorates
Solution Approach 1:
The patent divides the single large coil into multiple smaller coil segments arranged in specific patterns (e.g., four quadrants). Each segment generates a localized electromagnetic field that contributes to the overall plasma distribution. This segmentation enables better control and uniformity of plasma across large processing areas while maintaining a relatively simple overall device structure.
Solution Approach 2:
The patent combines multiple coil segments to create a distributed plasma source that achieves uniform plasma distribution over large areas. The electromagnetic fields from individual segments merge and overlap to produce a uniform plasma environment across the entire processing chamber, effectively combining the advantages of simple coil structures with improved plasma uniformity.
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 configuration increases power transfer efficiency, reduces capacitive coupling and transmission line effects, and achieves uniform plasma distribution across large surfaces, while efficiently removing heat from the excitation coils, leading to improved processing capabilities and reduced operational costs.
Implementation Method 1
The RF current driven in the inductor coil induces an electromagnetic RF field and RF plasma current in the activated gas of the working chamber, thus maintaining the plasma discharge inside the chamber
Implementation Method 2
a heat conductor inserted into this opening for removal of heat from the core and the coil
Data Source
AI summary
The plasma reactor of the invention is intended for treating the surfaces of objects such as semiconductor wafers and large display panels, or the like, with plasma. The main part of the plasma reactor is an array of RF antenna cells, which are deeply immersed into the interior of the working chamber. Each antenna cell has a ferromagnetic core with a heat conductor and a coil wound onto the core. The core and coil are sealed in the protective cap. Deep immersion of the antenna cells having the structure of the invention provides high efficiency of plasma excitation, while the arrangement of the plasma cells and possibility of their individual adjustment provide high uniformity of plasma distribution and possibility of adjusting plasma parameters, such as plasma density, in a wide range.