Cathodic Arc Deposition
Encyclopedia
Cathodic arc deposition or Arc-PVD is a physical vapor deposition
technique in which an electric arc
is used to vaporize material from a cathode
target. The vaporized material then condenses on a substrate, forming a thin film
. The technique can be used to deposit metal
lic, ceramic
, and composite
films.
around 1960–1970.
By the late 70's Soviet government released the use of this technology to the West.
Among many designs in USSR at that time the design by L. P. Sablev, et al., was allowed to be used outside the USSR.
, low voltage
arc on the surface of a cathode
(known as the target) that gives rise to a small (usually a few micrometre
s wide), highly energetic emitting area known as a cathode spot. The localised temperature at the cathode spot is extremely high (around 15000 °C), which results in a high velocity
(10 km/s) jet of vapourised cathode
material, leaving a crater behind on the cathode surface. The cathode spot is only active for a short period of time, then it self-extinguishes and re-ignites in a new area close to the previous crater. This behaviour causes the apparent motion of the arc.
As the arc is basically a current carrying conductor it can be influenced by the application of an electromagnetic field
, which in practice is used to rapidly move the arc over the entire surface of the target, so that the total surface is eroded over time.
The arc has an extremely high power density
resulting in a high level of ionization
(30-100%), multiple charged ions, neutral particles, clusters and macro-particles (droplets). If a reactive gas is introduced during the evaporation process, dissociation
, ionization
and excitation
can occur during interaction with the ion flux and a compound film will be deposited.
One downside of the arc evaporation process is that if the cathode spot stays at an evaporative point for too long it can eject a large amount of macro-particles or droplets. These droplets are detrimental to the performance of the coating as they are poorly adhered and can extend through the coating. Worse still if the cathode target material has a low melting point such as aluminium
the cathode spot can evaporate through the target resulting in either the target backing plate material being evaporated or cooling water entering the chamber. Therefore magnetic field
s as mentioned previously are used to control the motion of the arc. If cylindrical cathodes are used the cathodes can also be rotated during deposition. By not allowing the cathode spot to remain in one position too long aluminium
targets can be used and the number of droplets is reduced. Some companies also use filtered arcs that use magnetic fields to separate the droplets from the coating flux.
The plasma
beam from Cathodic Arc source contains some larger clusters of atoms or molecules (so called macro-particles), which prevent it from being useful for some applications without some kind of filtering.
There are many designs for macro-particle filters and the most studied design is based on the work by I. I. Aksenov et al. in 70's. It consists of a quarter-torus duct bent at 90 degrees from the arc source and the plasma is guided out of the duct by principle of plasma optics.
There are also other interesting designs such as a design which incorporates a straight duct filter built-in with truncated cone shape cathode as reported by D. A. Karpov in the 90's. This design became quite popular among both the thin hard-film coaters and researchers in Russia and former USSR countries until now.
Cathodic arc source can be made into the long tubular shape (extended-arc) or long rectangular shape but both designs are less popular.
coatings can be synthesized by this technology including TiN
, TiAlN, CrN
, ZrN, AlCrTiN and TiAlSiN.
This is also used quite extensively particularly for carbon ion deposition to create diamond-like carbon
films. Because the ions are blasted from the surface ballistic
ally, it is common for not only single atoms, but larger clusters of atoms to be ejected. Thus, this kind of system requires a filter to remove atom clusters from the beam before deposition.
The DLC film from filtered-arc contains extremely high percentage of sp3 diamond which is known as tetrahedral amorphous carbon, or ta-C.
Filtered Cathodic arc can be used as metal ion/plasma source for Ion implantation
and Plasma Immersion Ion Implantation and Deposition (PIII&D).
Physical vapor deposition
Physical vapor deposition is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the desired film material onto various workpiece surfaces...
technique in which an electric arc
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...
is used to vaporize material from a cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
target. The vaporized material then condenses on a substrate, forming a thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
. The technique can be used to deposit metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
lic, ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
, and composite
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
films.
History
Industrial use of modern cathodic arc deposition technology originated in Soviet UnionSoviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
around 1960–1970.
By the late 70's Soviet government released the use of this technology to the West.
Among many designs in USSR at that time the design by L. P. Sablev, et al., was allowed to be used outside the USSR.
Process
The arc evaporation process begins with the striking of a high currentElectric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
, low voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
arc on the surface of a cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
(known as the target) that gives rise to a small (usually a few micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s wide), highly energetic emitting area known as a cathode spot. The localised temperature at the cathode spot is extremely high (around 15000 °C), which results in a high velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
(10 km/s) jet of vapourised cathode
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
material, leaving a crater behind on the cathode surface. The cathode spot is only active for a short period of time, then it self-extinguishes and re-ignites in a new area close to the previous crater. This behaviour causes the apparent motion of the arc.
As the arc is basically a current carrying conductor it can be influenced by the application of an electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
, which in practice is used to rapidly move the arc over the entire surface of the target, so that the total surface is eroded over time.
The arc has an extremely high power density
Power density
Power density is the amount of power per unit volume....
resulting in a high level of ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
(30-100%), multiple charged ions, neutral particles, clusters and macro-particles (droplets). If a reactive gas is introduced during the evaporation process, dissociation
Dissociation (chemistry)
Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...
, ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
and excitation
Excited state
Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
can occur during interaction with the ion flux and a compound film will be deposited.
One downside of the arc evaporation process is that if the cathode spot stays at an evaporative point for too long it can eject a large amount of macro-particles or droplets. These droplets are detrimental to the performance of the coating as they are poorly adhered and can extend through the coating. Worse still if the cathode target material has a low melting point such as aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
the cathode spot can evaporate through the target resulting in either the target backing plate material being evaporated or cooling water entering the chamber. Therefore magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s as mentioned previously are used to control the motion of the arc. If cylindrical cathodes are used the cathodes can also be rotated during deposition. By not allowing the cathode spot to remain in one position too long aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
targets can be used and the number of droplets is reduced. Some companies also use filtered arcs that use magnetic fields to separate the droplets from the coating flux.
Equipment design
Sablev type Cathodic arc source, which is the most widely used in the West, consists of a short cylindrical shape electrical conductive target at cathode with one open end. This target has an electrically float metal ring surrounded working as an arc confinement ring. The anode for the system can be either the vacuum chamber wall or a discrete anode. Arc spots are generated by mechanical trigger (or igniter) striking on open end of the target making a temporarily short circuit between the cathode and anode. After the arc spots being generated they can be steered by magnetic field or move randomly in absence of magnetic field.The plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
beam from Cathodic Arc source contains some larger clusters of atoms or molecules (so called macro-particles), which prevent it from being useful for some applications without some kind of filtering.
There are many designs for macro-particle filters and the most studied design is based on the work by I. I. Aksenov et al. in 70's. It consists of a quarter-torus duct bent at 90 degrees from the arc source and the plasma is guided out of the duct by principle of plasma optics.
There are also other interesting designs such as a design which incorporates a straight duct filter built-in with truncated cone shape cathode as reported by D. A. Karpov in the 90's. This design became quite popular among both the thin hard-film coaters and researchers in Russia and former USSR countries until now.
Cathodic arc source can be made into the long tubular shape (extended-arc) or long rectangular shape but both designs are less popular.
Applications
Cathodic arc deposition is actively used to synthesize extremely hard film to protect the surface of cutting tools and extend their life significantly. A wide variety of thin hard-film, Superhard coatings and nanocompositeNanocomposite
A nanocomposite is as a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers , or structures having nano-scale repeat distances between the different phases that make up the material...
coatings can be synthesized by this technology including TiN
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
, TiAlN, CrN
CRN
CRN may refer to:* Center for Responsible Nanotechnology* Climate Reference Network a network of climate stations in the United States for future long-term standardized observations* Cognos Reportnet* CREMe Research Network...
, ZrN, AlCrTiN and TiAlSiN.
This is also used quite extensively particularly for carbon ion deposition to create diamond-like carbon
Diamond-like carbon
Diamond-like carbon exists in seven different forms of amorphous carbon materials that display some of the typical properties of diamond. They are usually applied as coatings to other materials that could benefit from some of those properties. All seven contain significant amounts of sp3...
films. Because the ions are blasted from the surface ballistic
Ballistics
Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...
ally, it is common for not only single atoms, but larger clusters of atoms to be ejected. Thus, this kind of system requires a filter to remove atom clusters from the beam before deposition.
The DLC film from filtered-arc contains extremely high percentage of sp3 diamond which is known as tetrahedral amorphous carbon, or ta-C.
Filtered Cathodic arc can be used as metal ion/plasma source for Ion implantation
Ion implantation
Ion implantation is a materials engineering process by which ions of a material are accelerated in an electrical field and impacted into another solid. This process is used to change the physical, chemical, or electrical properties of the solid...
and Plasma Immersion Ion Implantation and Deposition (PIII&D).