Thin-film deposition is any technique for depositing a thin film of material onto a substrate or onto previously deposited layers. Thin films are thin material layers ranging from fractions of a Nanometre to several Micrometres in thickness "Thin" is a relative term, but most deposition techniques allow layer thickness to be controlled within a few tens of nanometers, and some (molecular beam epitaxy) allow single layers of atoms to be deposited at a time. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Molecular beam Epitaxy (MBE, is one of several methods of depositing Single crystals It was invented in the late 1960s at Bell Telephone Laboratories History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny

It is useful in the manufacture of optics (for reflective or anti-reflective coatings, for instance), electronics (layers of insulators, semiconductors, and conductors form integrated circuits), packaging (i. Reflection is the change in direction of a Wave front at an interface between two different media so that the wave front returns into the medium from which Anti-reflective or antireflection (AR coatings are a type of Optical coating applied to the surface of lenses and other optical devices to reduce Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical An insulator, also called a Dielectric, is a material that resists the flow of Electric current. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that In Science and engineering, a conductor is a material which contains movable Electric charges. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside Packaging is the science art and technology of enclosing or protecting products for distribution storage sale and use e. , aluminum-coated PET film), and in contemporary art (see the work of Larry Bell). WikipediaNaming Biaxially-oriented Polyethylene terephthalate (boPET Polyester film is used for its high Tensile strength, Chemical and dimensional Stability Contemporary art can be defined variously as art produced at this present point in time or art produced since World War II. Larry Bell (born in 1939 in Chicago Illinois) is a contemporary American artist and sculptor Similar processes are sometimes used where thickness is not important: for instance, the purification of copper by electroplating, and the deposition of silicon and enriched uranium by a CVD-like process after gas-phase processing. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Electroplating is the process of using electrical current to reduce Cations of a desired material from a solution and coat a conductive object Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the

Deposition techniques fall into two broad categories, depending on whether the process is primarily chemical or physical. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion.

Contents 1 Chemical deposition 2 Physical deposition 3 Other deposition processes 4 See also 5 External links

Chemical deposition

Here, a fluid precursor undergoes a chemical change at a solid surface, leaving a solid layer. An everyday example is the formation of soot on a cool object when it is placed inside a flame. Since the fluid surrounds the solid object, deposition happens on every surface, with little regard to direction; thin films from chemical deposition techniques tend to be conformal, rather than directional. A conformal film defines a morphologically uneven interface with another body and has a thickness that is the same everywhere along the interface

Chemical deposition is further categorized by the phase of the precursor:

• Plating relies on liquid precursors, often a solution of water with a salt of the metal to be deposited. Plating describes surface-covering where a Metal is deposited on a conductive surface Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants Some plating processes are driven entirely by reagents in the solution (usually for noble metals), but by far the most commercially important process is electroplating. A reagent or reactant is a substance or compound consumed during a Chemical reaction. Noble metals are Metals that are resistant to Corrosion or Oxidation, unlike most Base metals They tend to be Precious metals often Electroplating is the process of using electrical current to reduce Cations of a desired material from a solution and coat a conductive object It was not commonly used in semiconductor processing for many years, but has seen a resurgence with more widespread use of Chemical-mechanical polishing techniques. Chemical-mechanical planarization or Chemical-mechanical Polishing, commonly abbreviated CMP, is a technique used in Semiconductor fabrication

• Chemical Solution Deposition (CSD) uses a liquid precursor, usually a solution of organometallic powders dissolved in an organic solvent. Organometallic chemistry is the study of Chemical compounds containing bonds between Carbon and a Metal. This is a relatively inexpensive, simple thin film process that is able to produce stoichiometrically accurate crystalline phases. Thin films are thin material layers ranging from fractions of a Nanometre to several Micrometres in thickness

• Chemical vapor deposition (CVD) generally uses a gas-phase precursor, often a halide or hydride of the element to be deposited. Chemical vapor deposition (CVD is a Chemical process used to produce high-purity high-performance solid materials A halide is a Binary compound, of which one part is a Halogen Atom and the other part is an element or radical that is less Hydride is the name given to the negative Ion of Hydrogen, H− In the case of MOCVD, an organometallic gas is used. Organometallic chemistry is the study of Chemical compounds containing bonds between Carbon and a Metal. Commercial techniques often use very low pressures of precursor gas.
  • Plasma enhanced CVD uses an ionized vapor, or plasma, as a precursor. Plasma Enhanced Chemical Vapor Deposition (PECVD is a process used to deposit thin films from a Gas state ( Vapor) to a Solid state on some substrate In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound Unlike the soot example above, commercial PECVD relies on electromagnetic means (electric current, microwave excitation), rather than a chemical reaction, to produce a plasma. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0

Physical deposition

Physical deposition uses mechanical or thermodynamic means to produce a thin film of solid. An everyday example is the formation of frost. Frost is the solid deposition of Water vapor from saturated air Since most engineering materials are held together by relatively high energies, and chemical reactions are not used to store these energies, commercial physical deposition systems tend to require a low-pressure vapor environment to function properly; most can be classified as Physical vapor deposition or PVD. Physical vapor deposition (PVD 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

The material to be deposited is placed in an energetic, entropic environment, so that particles of material escape its surface. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy Facing this source is a cooler surface which draws energy from these particles as they arrive, allowing them to form a solid layer. The whole system is kept in a vacuum deposition chamber, to allow the particles to travel as freely as possible. Since particles tend to follow a straight path, films deposited by physical means are commonly directional, rather than conformal.

Examples of physical deposition include:

• A thermal evaporator uses an electric resistance heater to melt the material and raise its vapor pressure to a useful range. Evaporation is a common method of Thin film deposition. The source material is evaporated in a Vacuum. This is done in a high vacuum, both to allow the vapor to reach the substrate without reacting with or scattering against other gas-phase atoms in the chamber, and reduce the incorporation of impurities from the residual gas in the vacuum chamber. Scattering is a general physical process whereby some forms of Radiation, such as Light, Sound or moving particles for example are forced to deviate from Obviously, only materials with a much higher vapor pressure than the heating element can be deposited without contamination of the film. Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium A heating element converts Electricity into Heat through the process of Joule heating. Molecular beam epitaxy is a particular sophisticated form of thermal evaporation. Molecular beam Epitaxy (MBE, is one of several methods of depositing Single crystals It was invented in the late 1960s at Bell Telephone Laboratories
  • An electron beam evaporator fires a high-energy beam from an electron gun to boil a small spot of material; since the heating is not uniform, lower vapor pressure materials can be deposited. An electron gun (also called electron emitter) is an electrical component that produces an Electron beam that has a precise Kinetic energy and is most often Vapor pressure (also known as equilibrium vapor pressure or saturation vapor pressure) is the Pressure of a Vapor in equilibrium The beam is usually bent through an angle of 270° in order to ensure that the gun filament is not directly exposed to the evaporant flux. Typical deposition rates for electron beam evaporation range from 1 to 10 nanometers per second. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a

• Sputtering relies on a plasma (usually a noble gas, such as Argon) to knock material from a "target" a few atoms at a time. Sputtering is a process whereby Atoms are Ejected from a solid target material due to bombardment of the target by energetic Ions It is commonly used for In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound History Noble gas is translated from the German noun de ''Edelgas'' first used in 1898 by Hugo Erdmann to indicate their extremely low level of reactivity This article pertains to the chemical element For other uses see Argon (disambiguation. The target can be kept at a relatively low temperature, since the process is not one of evaporation, making this one of the most flexible deposition techniques. It is especially useful for compounds or mixtures, where different components would otherwise tend to evaporate at different rates. Note, Sputtering's step coverage is more or less conformal.

• Pulsed laser deposition systems work by an ablation process. Pulsed laser deposition (PLD is a Thin film deposition (specifically a Physical vapor deposition, PVD technique where a high power pulsed Laser beam is Ablation is defined as the removal of material from the surface of an object by Vaporization, Chipping, or other erosive processes Pulses of focused laser light vaporize the surface of the target material and convert it to plasma; this plasma usually reverts to a gas before it reaches the substrate. A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission.

• Cathodic Arc Deposition or Arc-PVD which is a kind of ion beam deposition where an electrical arc is created that literally blasts ions from the cathode. Cathodic arc deposition or Arc-PVD is a Physical vapor deposition Ion Beam Deposition (IBD is a process of applying materials to a target through the application of an Ion beam. The arc has an extremely high power density resulting in a high level of ionization (30-100%), multiply charged ions, neutral particles, clusters and macro-particles (droplets). In Engineering, the term specific power can refer to power either per unit of Mass, Volume or Area, although power per unit of Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons 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. Dissociation is a state of acute mental Decompensation in which certain Thoughts Emotions Sensations and/or memories are Ionization is the physical process of converting an Atom or Molecule into an Ion by adding or removing charged particles such as Electrons Excitation or excitement can refer to The Excited state of an atom The Excitation (magnetic provided with an electrical

Other deposition processes

Some methods fall outside these two categories, relying on a mixture of chemical and physical means:

• In reactive sputtering, a small amount of some non-noble gas such as oxygen or nitrogen is mixed with the plasma-forming gas. Sputtering is a process whereby Atoms are Ejected from a solid target material due to bombardment of the target by energetic Ions It is commonly used for Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 After the material is sputtered from the target, it reacts with this gas, so that the deposited film is a different material, i. e. an oxide or nitride of the target material.

• In Molecular beam epitaxy (MBE), slow streams of an element can be directed at the substrate, so that material deposits one atomic layer at a time. Molecular beam Epitaxy (MBE, is one of several methods of depositing Single crystals It was invented in the late 1960s at Bell Telephone Laboratories Compounds such as gallium arsenide are usually deposited by repeatedly applying a layer of one element (i. Gallium arsenide ( GaAs) is a compound of two elements Gallium and Arsenic. e. , Ga), then a layer of the other (i. Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 e. , As), so that the process is chemical, as well as physical. The beam of material can be generated by either physical means (that is, by a furnace) or by a chemical reaction (chemical beam epitaxy). A furnace is a device used for Heating The name derives from Latin fornax, Oven. Chemical beam epitaxy (CBE forms an important class of deposition techniques for semiconductor layer systems especially III-V semiconductor systems

• In Topotaxy, a specialized technique similar to epitaxy, thin film crystal growth occurs in three dimensions due to the crystal structure similarities (either heterotopotaxy or homotopotaxy) between the substrate crystal and the growing thin film material. Epitaxy refers to the method of depositing a Monocrystalline film on a monocrystalline substrate Epitaxy refers to the method of depositing a Monocrystalline film on a monocrystalline substrate Homotopotaxy is a process similar to Homoepitaxy except for the fact that the thin film growth is not limited to two dimensional growth

See also

• Materials science
• Photolithography
• MEMS
• CVD, MBE, and Sputtering
• List of coating techniques
• Thin-film thickness monitor
• VINF Virtual Institute of Nanofilms

External links

• ORNL (Oak Ridge National Laboratory)

Materials Science or Materials Engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of Science and Photolithography (also called optical lithography) is a process used in Microfabrication to selectively remove parts of a thin film (or the bulk of a substrate Microelectromechanical systems ( MEMS) is the technology of the very small and merges at the nano-scale into Nanoelectromechanical systems (NEMS and Nanotechnology Chemical vapor deposition (CVD is a Chemical process used to produce high-purity high-performance solid materials Molecular beam Epitaxy (MBE, is one of several methods of depositing Single crystals It was invented in the late 1960s at Bell Telephone Laboratories Sputtering is a process whereby Atoms are Ejected from a solid target material due to bombardment of the target by energetic Ions It is commonly used for This list contains an overview of coating techniques for Thin-film deposition, found in the field of Materials science. Thin-film thickness monitors, deposition rate controllers, and so on are a family of instruments used in high and ultra-high Vacuum systems The Virtual Institute of NanoFilms ( VINF) is a non profit organisation registered in Belgium on March 22, 2007. Oak Ridge National Laboratory ( ORNL) is a multiprogram science and technology National laboratory managed for the United States Department of Energy by

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