Vacuum deposition
Encyclopedia
Vacuum deposition is a family of processes used to deposit layer
s atom-by-atom or molecule-by-molecule at sub-atmospheric pressure
(vacuum
) on a solid surface. The layers may be as thin as one atom to millimeters thick (freestanding structures). There may be multiple layers of different materials (e.g. optical coating
s). A thickness of less than one micrometre
is generally called a thin film
while a thickness greater than one micrometre is called a coating. The vacuum environment may serve one or more purposes including:
Condensing particles may come from a variety of sources including:
When the vapor source is from a liquid or solid material the process is called physical vapor deposition
(PVD). When the source is from a chemical vapor precursor the process is called low pressure chemical vapor deposition
(LPCVD) or, if in a plasma
, plasma enhanced CVD (PECVD) or "plasma assisted CVD" (PACVD). Often a combination of PVD and CVD processes are used in the same or connected processing chambers.
In reactive deposition the depositing material reacts either with a component of the gaseous environment (Ti + N → TiN) or with a co-depositing species (Ti + C → TiC). A plasma environment aids in activating gaseous species (N2 → 2N) and in decomposition of chemical vapor precursors (SiH4 → Si + 4H). The plasma may also be used to provide ions for vaporization by sputtering or for bombardment of the substrate for sputter cleaning and for bombardment of the depositing material to densify the structure and tailor properties (ion plating
).
Layer
Layer may refer to:* A layer of archaeological deposits in an excavation* A layer hen, a hen raised to produce eggs* Stratum, a layer of rock or soil with internally consistent characteristics...
s atom-by-atom or molecule-by-molecule at sub-atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
(vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
) on a solid surface. The layers may be as thin as one atom to millimeters thick (freestanding structures). There may be multiple layers of different materials (e.g. optical coating
Optical coating
An optical coating is one or more thin layers of material deposited on an optical component such as a lens or mirror, which alters the way in which the optic reflects and transmits light. One type of optical coating is an antireflection coating, which reduces unwanted reflections from surfaces, and...
s). A thickness of less than one 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...
is generally called 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....
while a thickness greater than one micrometre is called a coating. The vacuum environment may serve one or more purposes including:
- reducing the particle density so that the mean free path for collision is long
- reducing the particle density of undesirable atoms and molecules (contaminants)
- providing a low pressure plasma environment
- providing a means for controlling gas and vapor composition
- providing a means for mass flow control into the processing chamber.
Condensing particles may come from a variety of sources including:
- thermal evaporation, Evaporation (deposition)Evaporation (deposition)Evaporation is a common method of thin film deposition. The source material is evaporated in a vacuum. The vacuum allows vapor particles to travel directly to the target object , where they condense back to a solid state...
- sputteringSputteringSputtering is a process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic particles. It is commonly used for thin-film deposition, etching and analytical techniques .-Physics of sputtering:...
- cathodic arc vaporizationCathodic Arc DepositionCathodic 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...
- laser ablationLaser ablationLaser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma...
- decomposition of a chemical vapor precursor, chemical vapor depositionChemical vapor depositionChemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
When the vapor source is from a liquid or solid material the process is called physical vapor deposition
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...
(PVD). When the source is from a chemical vapor precursor the process is called low pressure chemical vapor deposition
Chemical vapor deposition
Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. In a typical CVD process, the wafer is exposed to one or more volatile precursors, which react and/or...
(LPCVD) or, if in a 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...
, plasma enhanced CVD (PECVD) or "plasma assisted CVD" (PACVD). Often a combination of PVD and CVD processes are used in the same or connected processing chambers.
In reactive deposition the depositing material reacts either with a component of the gaseous environment (Ti + N → TiN) or with a co-depositing species (Ti + C → TiC). A plasma environment aids in activating gaseous species (N2 → 2N) and in decomposition of chemical vapor precursors (SiH4 → Si + 4H). The plasma may also be used to provide ions for vaporization by sputtering or for bombardment of the substrate for sputter cleaning and for bombardment of the depositing material to densify the structure and tailor properties (ion plating
Ion plating
Ion plating is a physical vapor deposition process that is sometimes called ion assisted deposition or ion vapor deposition and is a version of vacuum deposition. Ion plating utilizes concurrent or periodic bombardment of the substrate and depositing film by atomic-sized energetic particles...
).
Applications
- Electrical conduction: metallic films, transparent conductive oxides (TCO), superconducting films & coatings
- SemiconductorSemiconductorA semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
devices: semiconductor films, electrically insulating films - Solar cellSolar cellA solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
s. - Optical films: antireflective coatings, optical filters
- Reflective coatings: mirrorMirrorA mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
s, hot mirrorHot mirrorA hot mirror is a specialized dielectric mirror, a dichroic filter, often employed to protect optical systems by reflecting infrared light back into a light source, while allowing visible light to pass...
s - Tribological coating: hard coatings, erosion resistant coatings, solid film lubricants
- Energy conservationEnergy conservationEnergy conservation refers to efforts made to reduce energy consumption. Energy conservation can be achieved through increased efficient energy use, in conjunction with decreased energy consumption and/or reduced consumption from conventional energy sources...
& generation: low-E glass coatings, solar absorbing coatings, mirrors, solar thin filmThin filmA 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....
photovoltaic cells, smart films - Magnetic films: magnetic recording
- Diffusion barrierDiffusion barrierA diffusion barrier is a thin layer of metal usually placed between two other metals. It is done to act as a barrier to protect either one of the metals from corrupting the other....
: gas permeation barriers, vapor permeation barriers, solid stateSolid-state physicsSolid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from...
diffusion barrierDiffusion barrierA diffusion barrier is a thin layer of metal usually placed between two other metals. It is done to act as a barrier to protect either one of the metals from corrupting the other....
s - CorrosionCorrosionCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
protection: - Automotive applications: lamp reflectors and trim applications
See also
- Ion platingIon platingIon plating is a physical vapor deposition process that is sometimes called ion assisted deposition or ion vapor deposition and is a version of vacuum deposition. Ion plating utilizes concurrent or periodic bombardment of the substrate and depositing film by atomic-sized energetic particles...
- Sputter depositionSputter depositionSputter deposition is a physical vapor deposition method of depositing thin films by sputtering, that is ejecting, material from a "target," that is source, which then deposits onto a "substrate," such as a silicon wafer...
- Cathodic arc depositionCathodic Arc DepositionCathodic 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...
- Spin coatingSpin coatingSpin coating is a procedure used to apply uniform thin films to flat substrates. In short, an excess amount of a solution is placed on the substrate, which is then rotated at high speed in order to spread the fluid by centrifugal force...
- Metallised filmMetallised filmMetallised films are polymer films coated with a thin layer of metal, usually aluminium. They offer the glossy metallic appearance of an aluminium foil at a reduced weight and cost...