Toroidal Plasma Processing Apparatus for Diamond Deposition
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Solution Overview
Problem
Existing plasma deposition technologies face inefficiencies and high costs due to limited electrode lifetimes, contamination, and difficulties in maintaining uniform discharges and high plasma density, especially in high-pressure applications for producing diamond and carbon-based materials.
Innovation Solution
A toroidal plasma processing apparatus with a shaped workpiece holder and multiple gas inlet ports is used to generate a high flux of atomic hydrogen efficiently, allowing for high-quality diamond deposition with reduced contamination and increased deposition rates, utilizing a toroidal plasma source that operates at high pressures and temperatures, eliminating the need for supplemental heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plasma deposition technology is used, then diamond materials can be produced, but electrode lifetime is limited and contamination occurs
Solution Approach 1:
The patent removes electrodes from the plasma generation system entirely, replacing them with a radio frequency (RF) powered plasma source. This extraction of the electrode component eliminates the source of contamination and extends system reliability by removing the limiting factor of electrode lifetime.
Solution Approach 2:
The patent replaces the mechanical/electrical electrode-based plasma generation system with an RF electromagnetic field-based plasma source. This substitution eliminates direct physical contact between electrodes and plasma, reducing contamination and improving reliability.
2Productivity
If high pressure plasma is used, then dissociation efficiency increases, but maintaining uniform discharge becomes difficult
Solution Approach 1:
The patent utilizes RF power delivery to fundamentally change the plasma generation parameters, enabling stable operation at high pressures (1-760 Torr). The RF field configuration and matching network are specifically designed to maintain discharge uniformity across the workpiece surface while operating at pressures that maximize dissociation efficiency.
Solution Approach 2:
The patent employs a planar RF coil geometry that creates a distributed plasma field across the workpiece surface, rather than using point-source electrode discharge. This dimensional approach to plasma generation maintains uniformity across the entire processing area while operating at high pressures.
3Manufacturing precision
If high plasma density is maintained, then deposition quality improves, but system complexity and cost increase
Solution Approach 1:
The RF-powered plasma source serves multiple functions simultaneously: it generates high plasma density for quality deposition, provides uniform heating of the workpiece, and maintains stable operation across a wide pressure range. This multi-functionality is achieved through a relatively simple RF coil and matching network configuration.
Solution Approach 2:
The RF-powered plasma source inherently provides workpiece heating through resistive heating of the plasma and direct energy transfer, eliminating the need for separate supplemental heating systems. This self-heating capability maintains deposition quality while reducing system complexity.
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
The toroidal plasma processing apparatus achieves high-quality diamond deposition with increased deposition rates and reduced contamination, enabling the growth of thick single-crystal diamond materials and improving the efficiency and cost-effectiveness of the process.
Implementation Method 1
A toroidal plasma processing apparatus with a shaped workpiece holder and multiple gas inlet ports is used to generate a high flux of atomic hydrogen efficiently
Implementation Method 2
At low pressure, dissociation mainly occurs due to electron impact on molecules
Implementation Method 3
Heating of the gaseous species plays a relatively minor role in the dissociation processes. Generally, the most efficient dissociation occurs when the pressure and gas temperature are both relatively high. Gas temperatures can exceed several thousand degrees Centigrade when the gas pressure is 1 Torr or greater and the electrical power absorbed in the plasma is greater than 10 W cm−3. At these high gas temperatures, thermal effects begin to play an important role in maintaining a highly dissociated gas.
Implementation Method 4
allowing for high-quality diamond deposition with reduced contamination and increased deposition rates
Data Source
AI summary
A plasma processing apparatus includes a toroidal-shape plasma vessel comprising a process chamber. A magnetic core surrounds a portion of the toroidal-shape plasma vessel. An RF power supply having an output that is electrically connected to the magnetic core energizes the magnetic core, thereby forming a toroidal plasma loop discharge in the plasma chamber. A workpiece holder is positioned in the toroidal-shape plasma vessel and includes at least one face. A plasma guiding structure is shaped and dimensioned so as to constrain a section of plasma in the toroidal plasma loop to travel substantially perpendicular to a normal to the at least one face.