Chemical Vapor Deposition or CVD (Chemical Vapor Deposition) is a chemical process used to produce high-purity, high-performance products from solid materials. The process is often used in the semiconductor industry to produce thin films. In a standard CVD process the substrate (wafer) is exposed to one or more volatile precursors, which react or decompose on the surface of the substrate to produce the desired deposit. Volatile byproducts are also frequently produced, which are removed by a gas flow passing through the reaction chamber.
CVD microfabrication processes are widely used to deposit materials in various forms, including: monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include: silicon, carbon fiber, carbon nanofibers, filaments, carbon nanotubes, SiO, silicon-germanium, tungsten, silicon carbide, silicon nitride, silicon oxynitride), titanium nitride, and various high electrical permittivity dielectrics. The CVD process is also used to produce synthetic diamonds.
Processes
There are numerous processes, depending on the field of application. These processes differ in the means by which the chemical reactions are initiated (e.g., activation process) and the process conditions.
Uses
integrated circuits
Various CVD processes are used in integrated circuits (ICs). Specific materials deposit best under specific conditions.
Polycrystalline silicon is deposited from silane (SiH), according to the following reaction:
This reaction is generally performed in LPCVD systems, with either pure silane feedstock, or a silane solution with 70-80% nitrogen. Temperatures between 600 and 650 °C and pressures between 25 and 150 Pa produce a growth rate between 10 and 20 nm per minute. An alternative process uses one based on hydrogen solutions. Hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 °C to compensate.
Polysilicon can be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine reduce it.
CVD deposit machines
Introduction
Chemical Vapor Deposition or CVD (Chemical Vapor Deposition) is a chemical process used to produce high-purity, high-performance products from solid materials. The process is often used in the semiconductor industry to produce thin films. In a standard CVD process the substrate (wafer) is exposed to one or more volatile precursors, which react or decompose on the surface of the substrate to produce the desired deposit. Volatile byproducts are also frequently produced, which are removed by a gas flow passing through the reaction chamber.
CVD microfabrication processes are widely used to deposit materials in various forms, including: monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include: silicon, carbon fiber, carbon nanofibers, filaments, carbon nanotubes, SiO, silicon-germanium, tungsten, silicon carbide, silicon nitride, silicon oxynitride), titanium nitride, and various high electrical permittivity dielectrics. The CVD process is also used to produce synthetic diamonds.
Processes
There are numerous processes, depending on the field of application. These processes differ in the means by which the chemical reactions are initiated (e.g., activation process) and the process conditions.
Uses
integrated circuits
Various CVD processes are used in integrated circuits (ICs). Specific materials deposit best under specific conditions.
Polycrystalline silicon is deposited from silane (SiH), according to the following reaction:
This reaction is generally performed in LPCVD systems, with either pure silane feedstock, or a silane solution with 70-80% nitrogen. Temperatures between 600 and 650 °C and pressures between 25 and 150 Pa produce a growth rate between 10 and 20 nm per minute. An alternative process uses one based on hydrogen solutions. Hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 °C to compensate.
Silicon dioxide (usually simply called "oxide" in the semiconductor industry) can be deposited by several different processes. The most common source gases include silane and oxygen, dichlorosilane") (SiCl H ) and nitrous oxide (NO), or tetraethylorthosilicate") (TEOS; Si (OCH) ). The reactions are as follows:
The choice of gas source depends on the thermal stability of the substrate, for example aluminum is sensitive to elevated temperature. Depósitos silano entre 300 y 500 °C, diclorosilano alrededor de los 900 °C, y TEOS entre 650 y 750 °C, resultando una capa de óxido de baja temperatura (LTO). Sin embargo, silano produce un óxido de menor calidad que los otros métodos (inferior resistencia dieléctrica, por ejemplo), y se deposita no conformemente. Any of these reactions can be used in LPCVD, but the silane reaction is also performed in APCVD. ECV óxido invariablemente tiene menor calidad que el óxido térmico, pero la oxidación térmica sólo se puede utilizar en las primeras etapas de fabricación de CI.
Oxide can also be grown with impurities (alloy or "doping (semiconductors)"). This can serve two purposes. During the process steps, in addition, that occur at high temperature, impurities can diffuse "Diffusion (physics)") from the oxide of adjacent layers (especially silicon) and dope them. Oxides containing 5-15% impurities by mass are often used for this purpose. Additionally, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth uneven surfaces. P-glass softens and flows at temperatures above 1000 °C. This process requires a phosphorus concentration of at least 6%, but concentrations above 8% can corrode aluminum. Phosphorus is deposited from phosphine gas and oxygen:.
Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; Around 850 °C is achievable with glasses containing around 5% by weight of both components, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient humidity to produce phosphoric acid. BPO crystals can also precipitate from flowing glass on cooling; These crystals are not easily etched in the standard reagent plasmas used for patterning oxides, and will lead to defects in IC circuit manufacturing.
In addition to these intentional impurities, CVD oxide may contain byproducts of the deposition process. TEOS produces a relatively pure oxide, while silane introduces hydrogen impurities, and dichlorosilane introduces chlorine.
Low temperature (350 to 500 °C) deposition of silicon dioxide and glasses from TEOS doped with ozone instead of oxygen has also been explored. Ozone glasses have excellent conformality, but tend to be hygroscopic - that is, they absorb water from the air due to the incorporation of silanol (Si-OH) into the glass. Infrared spectroscopy and temperature-dependent mechanical stress are valuable tools for diagnosing such problems.
Silicon nitride is often used as an insulating and chemical barrier in the manufacturing of integrated circuits. The following two gas phase reactions deposit nitride:.
Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress, which can crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (10 16 Ω$ cm and 10 M V/cm, respectively).
Two other reactions can be used in plasma to deposit SENOH:
These films have much less tensile stress, but worse electrical properties (resistivity 10 10 w cm, and dielectric strength 1 to 5 MV/cm).[4].
Some metals (significantly aluminum and copper) are rarely, if ever, deposited by CVD. In 2010, a commercially viable CVD process for copper did not exist, although copper formate, copper (HFAC) 2, Cu(II) ethyl acetoacetate, and other precursors had been tested. The deposition of metallic copper is mainly carried out by electroplating, in order to reduce cost. Aluminum can be deposited from tri-isobutyl aluminum (TIBAL), triethyl/methyl aluminum (TEA, TMA), or dimethyl aluminum hydride (DMAH), but physical vapor deposition methods are generally preferred.
However, CVD processes are widely used with molybdenum, tantalum, titanium, nickel, tungsten. These metals can form useful silicides when deposited on silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorates. Nickel, molybdenum and tungsten can be deposited at low temperatures from their carbonyl precursors. In general, for an arbitrary metal M, the reaction is as follows:
The usual source of tungsten is tungsten hexafluoride, which can be deposited in two ways:
Diamonds
CVD can be used to produce synthetic diamonds by creating the conditions necessary for the carbon atoms of a gas to settle on a substrate in crystalline form.
Diamond CVD receives a lot of attention in materials science, as it enables many new diamond applications that had been considered too difficult to do economically. ECV growth of diamond typically occurs under low pressure conditions (1-27 kPa; 0.145-3.926 psi; 7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for the growth of diamonds on the substrate. Gases always include a carbon source, and typically also include hydrogen, although the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament"), microwaves, and arc discharges"), among others. The energy source is intended to generate a plasma in which gases break down and produce more complex chemistries. The actual chemical process of diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.
The advantages of CVD diamond growth include the ability to grow diamonds over large areas, the ability to grow on a substrate, and control over the properties of the diamond produced. In the past, when high pressure, high temperature (HPHT) techniques were used to produce diamonds, the diamonds were typically very small permanent free diamonds of different sizes. CVD diamond growth areas of more than six inches in diameter have been achieved and much larger areas are likely in the future. Improving this capability is key to enabling several important applications.
The ability to grow diamonds directly on a substrate is important because it allows the addition of many of diamond's qualities to other materials. Since diamond has the highest thermal conductivity of any bulk material, coatings of diamond on high-heat electronics (such as optics and transistors) allow diamond to be used as a heat sink.[5][6] Diamond films form on valve rings, cutting tools, and other objects that benefit from diamond's hardness and its very low wear rate. In each case the growth of the diamond must be done carefully to achieve the necessary adhesion on the substrate. Diamond's very high resistance to scratching, its thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (polytetrafluoroethylene) and strong lipophilicity would make a nearly ideal non-stick coating for cookware if large areas of substrate can be economically coated.
The most important attribute of diamond ECV growth is the ability to control the properties of the diamond produced. In the area of diamond growth the word "diamond" is used as a description of any material composed primarily of SP3 bonded carbon, and there are many different types of diamond included in this. By regulating the transformation parameters, especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the plasma generation method many different materials that can be considered diamond can be realized. Single crystal diamond can be made containing various dopants.[7] Polycrystalline diamonds can be formed consisting of grain sizes from several nanometers to several micrometers.[8][9] Some polycrystalline diamond grains are surrounded by fine carbon and non-diamonds, while others are not. These factors affect the diamond's hardness, smoothness, conductivity, optical properties and much more.
Find more "CVD deposit machines" in the following countries:
[3] ↑ Schropp, R.E.I.; B. Stannowski, A.M. Brockhoff, P.A.T.T. van Veenendaal and J.K. Rath. «Hot wire CVD of heterogeneous and polycrystalline silicon semiconducting thin films for application in thin film transistors and solar cells». Materials Physics and Mechanics. pp. 73-82. La referencia utiliza el parámetro obsoleto |coauthors= (ayuda).: http://www.ipme.ru/e-journals/MPM/no_2100/schropp/schropp.pdf
[4] ↑ S.M. Sze (2008). Semiconductor devices: physics and technology. Wiley-India. p. 384. ISBN 81-265-1681-X.
[6] ↑ Sun Lee, Woong; Yu, Jin (2005). «Comparative study of thermally conductive fillers in underfill for the electronic components». Diamond and Related Materials 14 (10): 1647-1653. doi:10.1016/j.diamond.2005.05.008.: https://dx.doi.org/10.1016%2Fj.diamond.2005.05.008
[7] ↑ Isberg, J (2004). «Single crystal diamond for electronic applications». Diamond and Related Materials 13 (2): 320-324. doi:10.1016/j.diamond.2003.10.017.: https://dx.doi.org/10.1016%2Fj.diamond.2003.10.017
Polysilicon can be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine reduce it.
Silicon dioxide (usually simply called "oxide" in the semiconductor industry) can be deposited by several different processes. The most common source gases include silane and oxygen, dichlorosilane") (SiCl H ) and nitrous oxide (NO), or tetraethylorthosilicate") (TEOS; Si (OCH) ). The reactions are as follows:
The choice of gas source depends on the thermal stability of the substrate, for example aluminum is sensitive to elevated temperature. Depósitos silano entre 300 y 500 °C, diclorosilano alrededor de los 900 °C, y TEOS entre 650 y 750 °C, resultando una capa de óxido de baja temperatura (LTO). Sin embargo, silano produce un óxido de menor calidad que los otros métodos (inferior resistencia dieléctrica, por ejemplo), y se deposita no conformemente. Any of these reactions can be used in LPCVD, but the silane reaction is also performed in APCVD. ECV óxido invariablemente tiene menor calidad que el óxido térmico, pero la oxidación térmica sólo se puede utilizar en las primeras etapas de fabricación de CI.
Oxide can also be grown with impurities (alloy or "doping (semiconductors)"). This can serve two purposes. During the process steps, in addition, that occur at high temperature, impurities can diffuse "Diffusion (physics)") from the oxide of adjacent layers (especially silicon) and dope them. Oxides containing 5-15% impurities by mass are often used for this purpose. Additionally, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth uneven surfaces. P-glass softens and flows at temperatures above 1000 °C. This process requires a phosphorus concentration of at least 6%, but concentrations above 8% can corrode aluminum. Phosphorus is deposited from phosphine gas and oxygen:.
Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; Around 850 °C is achievable with glasses containing around 5% by weight of both components, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient humidity to produce phosphoric acid. BPO crystals can also precipitate from flowing glass on cooling; These crystals are not easily etched in the standard reagent plasmas used for patterning oxides, and will lead to defects in IC circuit manufacturing.
In addition to these intentional impurities, CVD oxide may contain byproducts of the deposition process. TEOS produces a relatively pure oxide, while silane introduces hydrogen impurities, and dichlorosilane introduces chlorine.
Low temperature (350 to 500 °C) deposition of silicon dioxide and glasses from TEOS doped with ozone instead of oxygen has also been explored. Ozone glasses have excellent conformality, but tend to be hygroscopic - that is, they absorb water from the air due to the incorporation of silanol (Si-OH) into the glass. Infrared spectroscopy and temperature-dependent mechanical stress are valuable tools for diagnosing such problems.
Silicon nitride is often used as an insulating and chemical barrier in the manufacturing of integrated circuits. The following two gas phase reactions deposit nitride:.
Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress, which can crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (10 16 Ω$ cm and 10 M V/cm, respectively).
Two other reactions can be used in plasma to deposit SENOH:
These films have much less tensile stress, but worse electrical properties (resistivity 10 10 w cm, and dielectric strength 1 to 5 MV/cm).[4].
Some metals (significantly aluminum and copper) are rarely, if ever, deposited by CVD. In 2010, a commercially viable CVD process for copper did not exist, although copper formate, copper (HFAC) 2, Cu(II) ethyl acetoacetate, and other precursors had been tested. The deposition of metallic copper is mainly carried out by electroplating, in order to reduce cost. Aluminum can be deposited from tri-isobutyl aluminum (TIBAL), triethyl/methyl aluminum (TEA, TMA), or dimethyl aluminum hydride (DMAH), but physical vapor deposition methods are generally preferred.
However, CVD processes are widely used with molybdenum, tantalum, titanium, nickel, tungsten. These metals can form useful silicides when deposited on silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorates. Nickel, molybdenum and tungsten can be deposited at low temperatures from their carbonyl precursors. In general, for an arbitrary metal M, the reaction is as follows:
The usual source of tungsten is tungsten hexafluoride, which can be deposited in two ways:
Diamonds
CVD can be used to produce synthetic diamonds by creating the conditions necessary for the carbon atoms of a gas to settle on a substrate in crystalline form.
Diamond CVD receives a lot of attention in materials science, as it enables many new diamond applications that had been considered too difficult to do economically. ECV growth of diamond typically occurs under low pressure conditions (1-27 kPa; 0.145-3.926 psi; 7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for the growth of diamonds on the substrate. Gases always include a carbon source, and typically also include hydrogen, although the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament"), microwaves, and arc discharges"), among others. The energy source is intended to generate a plasma in which gases break down and produce more complex chemistries. The actual chemical process of diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.
The advantages of CVD diamond growth include the ability to grow diamonds over large areas, the ability to grow on a substrate, and control over the properties of the diamond produced. In the past, when high pressure, high temperature (HPHT) techniques were used to produce diamonds, the diamonds were typically very small permanent free diamonds of different sizes. CVD diamond growth areas of more than six inches in diameter have been achieved and much larger areas are likely in the future. Improving this capability is key to enabling several important applications.
The ability to grow diamonds directly on a substrate is important because it allows the addition of many of diamond's qualities to other materials. Since diamond has the highest thermal conductivity of any bulk material, coatings of diamond on high-heat electronics (such as optics and transistors) allow diamond to be used as a heat sink.[5][6] Diamond films form on valve rings, cutting tools, and other objects that benefit from diamond's hardness and its very low wear rate. In each case the growth of the diamond must be done carefully to achieve the necessary adhesion on the substrate. Diamond's very high resistance to scratching, its thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (polytetrafluoroethylene) and strong lipophilicity would make a nearly ideal non-stick coating for cookware if large areas of substrate can be economically coated.
The most important attribute of diamond ECV growth is the ability to control the properties of the diamond produced. In the area of diamond growth the word "diamond" is used as a description of any material composed primarily of SP3 bonded carbon, and there are many different types of diamond included in this. By regulating the transformation parameters, especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the plasma generation method many different materials that can be considered diamond can be realized. Single crystal diamond can be made containing various dopants.[7] Polycrystalline diamonds can be formed consisting of grain sizes from several nanometers to several micrometers.[8][9] Some polycrystalline diamond grains are surrounded by fine carbon and non-diamonds, while others are not. These factors affect the diamond's hardness, smoothness, conductivity, optical properties and much more.
Find more "CVD deposit machines" in the following countries:
[3] ↑ Schropp, R.E.I.; B. Stannowski, A.M. Brockhoff, P.A.T.T. van Veenendaal and J.K. Rath. «Hot wire CVD of heterogeneous and polycrystalline silicon semiconducting thin films for application in thin film transistors and solar cells». Materials Physics and Mechanics. pp. 73-82. La referencia utiliza el parámetro obsoleto |coauthors= (ayuda).: http://www.ipme.ru/e-journals/MPM/no_2100/schropp/schropp.pdf
[4] ↑ S.M. Sze (2008). Semiconductor devices: physics and technology. Wiley-India. p. 384. ISBN 81-265-1681-X.
[6] ↑ Sun Lee, Woong; Yu, Jin (2005). «Comparative study of thermally conductive fillers in underfill for the electronic components». Diamond and Related Materials 14 (10): 1647-1653. doi:10.1016/j.diamond.2005.05.008.: https://dx.doi.org/10.1016%2Fj.diamond.2005.05.008
[7] ↑ Isberg, J (2004). «Single crystal diamond for electronic applications». Diamond and Related Materials 13 (2): 320-324. doi:10.1016/j.diamond.2003.10.017.: https://dx.doi.org/10.1016%2Fj.diamond.2003.10.017