Microwave Resonator Array Assembly for Cutoff-Density Plasma Coupling
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Solution Overview
Problem
In plasma processing using microwaves, increasing the power to enhance electron density leads to a cutoff density where the permittivity becomes negative, preventing microwaves from propagating and being absorbed, thus limiting the generation of high-density plasma in a wide range.
Innovation Solution
A plasma processing apparatus with a resonator array structure that includes a base plate with grooves and card-shaped or rectangular resonators capable of resonating with the magnetic field component of microwaves, allowing the microwaves to propagate beyond the skin depth and be efficiently absorbed by the plasma, even at cutoff density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If microwave power is increased to enhance electron density, then plasma density is improved, but permittivity becomes negative preventing microwave propagation and absorption
Solution Approach 1:
The patent divides the processing space into multiple regions by introducing a resonator array structure with multiple resonators arranged in an array. Each resonator acts as an independent unit that can locally enhance electromagnetic field interaction with plasma, allowing microwave energy to be effectively coupled to plasma even at high densities where bulk permittivity would normally prevent propagation.
Solution Approach 2:
The resonators are designed to create localized electromagnetic field enhancement at specific positions within the processing space. By placing resonators at strategic locations along the microwave propagation path, the system creates local regions where electromagnetic energy can be efficiently absorbed by plasma, overcoming the global permittivity limitation that would otherwise prevent microwave propagation throughout the entire chamber.
2Quantity of substance
If microwave power is increased beyond cutoff density, then plasma density cannot be enhanced further, but increasing power causes microwaves to be reflected rather than absorbed
Solution Approach 1:
The resonators are designed to oscillate at specific resonant frequencies that match the microwave frequency, creating strong local electromagnetic fields. This resonance effect enhances the interaction between microwaves and plasma electrons, allowing efficient energy transfer and absorption even when the overall plasma density approaches cutoff conditions, thereby preventing microwave reflection and enabling continued plasma density enhancement.
Solution Approach 2:
The system changes the effective electromagnetic parameters by introducing resonators with specific geometric configurations and materials. These resonators modify the local electromagnetic field distribution and impedance characteristics, transforming the plasma's electromagnetic response from a reflective state at cutoff density to an absorptive state that continues to accept microwave energy for plasma generation.
3Quantity of substance
If a resonator array structure is introduced to enable microwave propagation at cutoff density, then plasma density in wide range is improved, but device complexity increases
Solution Approach 1:
The resonator array structure serves multiple functions simultaneously: it acts as an electromagnetic field enhancer, a plasma density controller, and a microwave energy distributor. Each resonator can be independently tuned to work at the microwave frequency, and the array collectively provides uniform plasma generation across the processing space, eliminating the need for separate systems for each function.
Solution Approach 2:
The resonator array creates a structured pattern of resonant elements distributed throughout the processing space, similar to a porous or lattice structure. This distributed architecture allows microwave energy to penetrate and interact with plasma throughout the entire volume rather than being blocked at the surface, enabling high-density plasma generation in a wide range while maintaining relatively simple individual resonator 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
Enables the generation of high-density plasma over a wide range by ensuring microwaves can propagate and be absorbed, overcoming the limitations of permittivity and permeability at cutoff density.
Implementation Method 1
a plurality of resonators capable of resonating with a magnetic field component of the electromagnetic wave
Implementation Method 2
an electromagnetic wave generator configured to generate electromagnetic waves for plasma excitation supplied to the processing space
Data Source
AI summary
Provided is a plasma processing apparatus comprising a processing container configured to provide a processing space; an electromagnetic wave generator configured to generate electromagnetic waves for plasma excitation supplied to the processing space; a dielectric provided with a first surface thereof facing the processing space; an electromagnetic wave supply portion configured to supply the electromagnetic waves to the processing space through the dielectric; and a resonator array structure located along the first surface of the dielectric within the processing container, wherein the resonator array structure includes a base plate having a groove on a surface on the processing space side; a plurality of resonators capable of resonating with a magnetic field component of the electromagnetic wave and having a size smaller than a wavelength of the electromagnetic wave; and a pressing member configured to press the plurality of resonators.