2.4 Types of Plasmas in Manufacturing
3 min read•july 23, 2024
Plasma generation methods come in various forms, each with unique characteristics. From DC discharges to RF and microwave discharges, these techniques power a wide range of manufacturing processes. Understanding their differences is key to selecting the right method for specific applications.
Low-pressure and atmospheric-pressure plasmas offer distinct advantages in manufacturing. While low-pressure plasmas excel in semiconductor processing, atmospheric-pressure plasmas are ideal for surface treatments. Thermal and non-thermal plasmas further expand the possibilities, enabling diverse applications from welding to gentle surface modifications.
Plasma Classification and Characteristics
Classification of plasma generation methods
Top images from around the web for Classification of plasma generation methods
Frontiers | Simulation of main plasma parameters of a cylindrical asymmetric capacitively ... View original
Is this image relevant?
Frontiers | An Inductively-Coupled Plasma Electrothermal Radiofrequency Thruster View original
Is this image relevant?
Comparison of Surface Modification of CR-39 Polymer Film Using RF and DC Glow Discharges Plasma View original
Is this image relevant?
Frontiers | Simulation of main plasma parameters of a cylindrical asymmetric capacitively ... View original
Is this image relevant?
Frontiers | An Inductively-Coupled Plasma Electrothermal Radiofrequency Thruster View original
Is this image relevant?
1 of 3
Top images from around the web for Classification of plasma generation methods
Frontiers | Simulation of main plasma parameters of a cylindrical asymmetric capacitively ... View original
Is this image relevant?
Frontiers | An Inductively-Coupled Plasma Electrothermal Radiofrequency Thruster View original
Is this image relevant?
Comparison of Surface Modification of CR-39 Polymer Film Using RF and DC Glow Discharges Plasma View original
Is this image relevant?
Frontiers | Simulation of main plasma parameters of a cylindrical asymmetric capacitively ... View original
Is this image relevant?
Frontiers | An Inductively-Coupled Plasma Electrothermal Radiofrequency Thruster View original
Is this image relevant?
1 of 3
- Direct Current (DC) discharges
- Generated by applying a constant voltage between two electrodes
- Commonly used in DC glow discharges and arc discharges for applications such as plasma spraying and welding
- Radio Frequency (RF) discharges
- Generated by applying an alternating voltage in the radio frequency range (typically 13.56 MHz)
- Capacitively coupled plasmas (CCP) have electrodes placed outside the discharge chamber and are used for (PECVD) and (RIE)
- Inductively coupled plasmas (ICP) are generated by an inductive coil wound around the discharge chamber and are used for and deposition processes (plasma-enhanced atomic layer deposition)
- Microwave discharges
- Generated by applying electromagnetic waves in the microwave frequency range (typically 2.45 GHz)
- Electron Cyclotron Resonance (ECR) plasmas are created by applying a magnetic field to achieve electron cyclotron resonance condition and are used for high-density plasma etching and deposition processes (diamond-like carbon coatings)
Low-pressure vs atmospheric-pressure plasmas
- Low-pressure plasmas
- Generated at pressures below atmospheric pressure (typically 1 mTorr to 10 Torr)
- Characterized by longer of particles resulting in fewer collisions higher electron temperatures and lower ion energies
- Commonly used in semiconductor processing (silicon nitride) and ( of polymers)
- Atmospheric-pressure plasmas
- Generated at or near atmospheric pressure
- Characterized by shorter mean free path of particles resulting in more collisions lower electron temperatures and higher ion energies
- Commonly used in surface treatment () (medical devices) and (thermal barrier coatings)
Characteristics of thermal and non-thermal plasmas
- Thermal plasmas
- High gas temperature (, typically > 10,000 K)
- High ()
- (LTE) condition where the temperatures of electrons ions and neutral species are approximately equal
- Commonly used in plasma spraying () welding cutting and waste treatment (hazardous waste destruction)
- Non-thermal plasmas
- Low gas temperature (, typically < 1,000 K)
- Lower electron density compared to thermal plasmas
- Non-equilibrium condition () where the electron temperature is much higher than the ion and neutral species temperatures
- Commonly used in surface modification (hydrophilic treatment of polymers) plasma-enhanced chemical vapor deposition (PECVD) (silicon dioxide films) plasma etching (integrated circuits) and sterilization (food packaging)
Suitability of plasmas for manufacturing
- Plasma-enhanced chemical vapor deposition (PECVD)
- Uses non-thermal low-pressure RF or microwave discharges
- Allows deposition at lower substrate temperatures compared to thermal CVD enabling deposition on temperature-sensitive substrates (plastics)
- Plasma etching
- Uses non-thermal low-pressure RF or microwave discharges
- Enables anisotropic etching for high aspect ratio features in semiconductor manufacturing ()
- Plasma spray coating
- Uses thermal atmospheric-pressure DC arc or RF discharges
- Provides high deposition rates and thick coatings for wear and corrosion protection (ceramic coatings on turbine blades)
- Surface modification and cleaning
- Uses non-thermal atmospheric-pressure discharges (dielectric barrier discharges corona discharges)
- Improves wettability adhesion and printability of surfaces (plasma treatment of polyethylene)
Key Terms to Review (28)
Atmospheric-pressure plasma: Atmospheric-pressure plasma is a type of plasma generated at atmospheric pressure, characterized by its ability to operate without the need for a vacuum environment. This form of plasma is significant in manufacturing processes because it can be produced easily and cost-effectively, making it suitable for a wide range of applications including surface modification, coating, and cleaning. The versatility and accessibility of atmospheric-pressure plasma make it a valuable tool in various manufacturing sectors, enhancing efficiency and effectiveness in processes.
Capacitively Coupled Plasma: Capacitively coupled plasma (CCP) is a type of low-pressure plasma generated by applying an alternating electric field between two electrodes, which are separated by a gas. This method allows for the efficient ionization of the gas, creating a plasma that can be used for various applications in manufacturing and surface treatment. The ability to control the characteristics of the plasma through the applied voltage and frequency makes CCP particularly useful in industrial settings.
Corona Discharge: Corona discharge is a process where a gas becomes ionized around a conductor that is at a high electric field strength, leading to the creation of a plasma region. This phenomenon occurs when the electric field intensity exceeds the dielectric strength of the surrounding medium, resulting in ionization and the release of energy in the form of light or heat. Corona discharge is essential in various manufacturing processes, particularly in surface treatment and material modification, where it aids in improving adhesion properties and cleaning surfaces.
Dc discharge: DC discharge refers to the electrical discharge that occurs when a direct current (DC) voltage is applied to a gas, ionizing it and creating plasma. This type of discharge is characterized by its continuous flow of electric current, which maintains the ionization process and allows for stable plasma generation. The nature of DC discharge plays a vital role in various manufacturing applications, influencing the types of plasmas generated and their effectiveness in processes such as surface treatment, coating, and etching.
Deep Reactive Ion Etching: Deep reactive ion etching (DRIE) is a specialized etching process that uses plasma to create deep, high aspect ratio features in semiconductor materials and other substrates. This technique is crucial in microfabrication, allowing for precise control over the etching depth and profile, which is essential for producing advanced microelectronic and MEMS devices.
Dielectric Barrier Discharge: Dielectric barrier discharge (DBD) is a type of electrical discharge that occurs between two electrodes separated by an insulating dielectric material. This process allows for the generation of non-thermal plasma, which can be used for various applications in manufacturing, especially in surface modification processes that enhance material properties without damaging the substrate. DBD is crucial in creating uniform plasma conditions, making it an effective tool for improving adhesion, wettability, and chemical reactivity on surfaces.
Electron cyclotron resonance plasma: Electron cyclotron resonance plasma is a type of plasma where electrons are accelerated to high energies by an electromagnetic field that oscillates at a frequency matching the natural cyclotron frequency of the electrons in a magnetic field. This phenomenon occurs when the frequency of the applied microwave radiation matches the frequency at which electrons spiral around magnetic field lines, allowing for efficient energy transfer and heating. This unique interaction makes it valuable in various manufacturing processes, especially in semiconductor fabrication and materials processing.
Electron Density: Electron density refers to the measure of the probability of an electron being present in a specific location within a plasma or material. This concept is crucial as it influences various properties of plasmas, such as conductivity, ionization, and the overall behavior of charged particles. Understanding electron density helps in characterizing different types of plasmas, utilizing diagnostic techniques, and modeling interactions at surfaces in manufacturing processes.
High-density plasma etching: High-density plasma etching is a process that uses plasma generated at high density to remove material from a substrate, typically used in semiconductor manufacturing. This technique provides better control over etching profiles and allows for more precise patterning at smaller scales compared to traditional methods, making it essential for creating advanced electronic devices.
Hydroxyapatite coatings: Hydroxyapatite coatings are biomimetic layers applied to various substrates, primarily in biomedical applications, to enhance biocompatibility and promote osseointegration. These coatings mimic the mineral component of bone, which helps in the attachment of bone cells and supports the healing process after implantation.
Inductively Coupled Plasma: Inductively coupled plasma (ICP) is a type of plasma created by using electromagnetic fields to induce current in a gas, typically argon, to ionize it. This process generates a highly energetic plasma state that is used extensively in various manufacturing applications, such as semiconductor fabrication, surface treatment, and material analysis.
Local Thermodynamic Equilibrium: Local thermodynamic equilibrium (LTE) refers to a condition where the properties of a plasma system are uniform over small spatial scales, allowing the system to be described by local thermodynamic variables such as temperature, pressure, and density. In the context of plasma-assisted manufacturing, LTE is crucial as it influences the energy distribution among particles and affects various processes like ionization and chemical reactions, ensuring that the plasma behaves predictably in manufacturing applications.
Low-pressure plasma: Low-pressure plasma is a state of matter created when a gas is ionized at reduced pressure, typically in the range of 0.1 to 10 Torr. This form of plasma is crucial in various industrial applications due to its unique properties that allow for efficient energy transfer and reactive species generation, making it suitable for processes such as cleaning, surface modification, and synthesis of nanomaterials.
Mean Free Path: Mean free path is the average distance a particle travels between collisions in a gas or plasma. This concept is essential for understanding the behavior of particles in different types of plasmas and is particularly relevant when considering how particles interact within PECVD reactor designs, affecting deposition rates and film quality.
Microwave Discharge: Microwave discharge refers to a method of generating plasma using microwave radiation, typically within a vacuum or controlled environment. This technique allows for the efficient excitation of gas molecules, leading to the formation of plasma with unique properties suitable for various manufacturing processes. Microwave discharges are particularly beneficial due to their ability to produce uniform plasma and operate at relatively low pressures, making them an attractive choice for applications like material processing and surface modification.
Non-thermal plasma: Non-thermal plasma is a state of ionized gas where the bulk temperature is near room temperature, but the electrons within the plasma possess high energy levels. This unique characteristic makes non-thermal plasma ideal for applications in manufacturing and catalysis, as it allows for efficient processing of materials without excessive heating that could damage sensitive substrates.
Plasma activation: Plasma activation refers to the process of modifying the surface properties of materials using plasma, which enhances their reactivity, adhesion, or wettability. This technique is crucial in various applications where improved surface characteristics are needed, such as in coatings, adhesives, and surface treatments. By utilizing different types of plasma, materials can be effectively cleaned and prepared for further processing or bonding.
Plasma cleaning: Plasma cleaning is a surface treatment process that utilizes ionized gas (plasma) to remove contaminants from materials, enhancing surface properties and promoting adhesion. This technique is widely used in manufacturing to prepare surfaces for further processing, such as coating or bonding, by effectively cleaning and activating the surface at a microscopic level.
Plasma spray coating: Plasma spray coating is a thermal spray process that utilizes a high-temperature plasma jet to melt and propel powdered materials onto a substrate, forming a protective or functional coating. This technique is widely used for enhancing surface properties, improving wear resistance, and providing corrosion protection in various applications. By harnessing the unique properties of plasma, this method allows for precise control over coating thickness and composition.
Plasma stability: Plasma stability refers to the ability of a plasma to maintain its structure and behavior under various operational conditions without undergoing unwanted changes such as instabilities or disruptions. This stability is crucial in plasma-assisted manufacturing processes, where consistent plasma behavior ensures high-quality outcomes in applications like material processing and surface treatment. Proper control and monitoring of plasma stability are vital for achieving desired results while minimizing defects or variations during manufacturing.
Plasma Uniformity: Plasma uniformity refers to the consistency of plasma properties, such as density and temperature, across the volume of a plasma system. Achieving uniformity is crucial because it affects the quality and efficiency of processes like etching, deposition, and surface modification in manufacturing. Variations in plasma characteristics can lead to non-uniform treatment results, impacting the performance of the final products.
Plasma-enhanced chemical vapor deposition: Plasma-enhanced chemical vapor deposition (PECVD) is a process that uses plasma to deposit thin films of material onto a substrate through a chemical reaction. This method allows for lower deposition temperatures compared to traditional chemical vapor deposition, making it particularly suitable for delicate substrates and complex geometries while enabling precise control over film properties.
Reactive Ion Etching: Reactive Ion Etching (RIE) is a plasma-based etching process used in semiconductor fabrication to remove material from a substrate with high precision. This technique combines both physical sputtering and chemical reactions, allowing for anisotropic etching, which is essential for creating intricate patterns and features on semiconductor devices.
Rf discharge: RF discharge, or radio frequency discharge, refers to the process of creating plasma by applying an alternating electromagnetic field, typically in the radio frequency range of 3 kHz to 300 GHz. This method is widely utilized in manufacturing for processes like etching, deposition, and surface modification. RF discharge generates plasma that can be precisely controlled, allowing for specific interactions with materials to achieve desired surface properties and chemical reactions.
Sterilization: Sterilization is the process of eliminating all forms of microorganisms, including bacteria, viruses, and spores, from a surface or material. In manufacturing contexts, especially those involving medical devices or sensitive materials, sterilization is critical for ensuring that products are safe for use and free from contamination that could cause infection or other health issues.
Surface Modification: Surface modification refers to the process of altering the physical or chemical properties of a material's surface to enhance its performance for specific applications. This can involve changing surface energy, roughness, or chemical composition, enabling materials to better adhere to coatings, resist corrosion, or improve biocompatibility.
Thermal Plasma: Thermal plasma is a state of matter where the gas is ionized and exists at high temperatures, allowing for the presence of free electrons and ions that are in thermal equilibrium. This high-energy environment plays a vital role in various manufacturing processes by facilitating chemical reactions, surface modifications, and material transformations.
Thin Film Deposition: Thin film deposition is the process of depositing a very thin layer of material onto a substrate, often in the nanometer to micrometer range. This technique is essential in various applications such as electronics, optics, and surface coatings, where precise control over layer thickness and composition is required to achieve desired material properties and performance.