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Vapor Deposition of thin Films

281 bytes added, 18:22, 7 January 2012
m
Introduction: zap
{{MECH370}}
== Introduction ==
[[Image:PECVD.jpg|thumb|right|Figure 1. Schematic of a PECVD Process <ref name="two"/>]]Vapor Deposition is a processing method to lay a thin layer of a precursor material onto a substrate material to improve its mechanical and chemical properties. Vapor deposition is categorized into two major subdivisions of processing:
*(1) [[Chemical Vapor Deposition]]{{WPw|Chemical Vapor Deposition}} (CVD) *(2) [[Physical Vapor Deposition]]{{WPw|Physical Vapor Deposition}} (PVD)
Vapor Deposition is an atomistic process in which a[[precursor]]{{WPw|precursor}} material is vaporized from a solid or gaseous precursor material and transported in a vacuum in the form of excited atoms or molecules and deposited on a [[substrate]]{{WPw|substrate}}material where it condenses and is deposited as a thin film. Vapor Deposition was originally ‘coined by the authors CF Powell, JH Oxley and JM Blocher Jr. in their 1966 book “Vapor Deposition” <ref name="one"> Mark Allendorf, "From Bunsen to VLSI 150 Years of Growth in Chemical Vapor Deposition Technology", The electrochemical society '''IF3-98'''(1),
36-39</ref>.
CVD and PVD is highly popular in the semiconductor industry to enhance the conductive and magnetic properties of metals without considerable cost. Deposition films in semiconductors are so thin that the process is extremely beneficial and economic. Deposited Material can be in the form of:
*[[Polycrystalline]]{{WPw|Polycrystalline}}*[[Amorphous]]{{WPw|Amorphous}}*[[epitaxial]]{{WPw|epitaxial}}
== Physical Vapor Deposition ==
*(2)If the time of atom migration on the surface is great enough to meet another atom before being evaporated these atoms join together to form an island.
*(3)As the energy required to evaporate one atom from the pair is higher than needed for a separate atom stable islands (nuclei) start to form on the surface.
*(4)The islands [[coalesce]]{{WPw|coalesce}} and the continual growth of the film takes place.
the link below has a detailed video of the process
=== '''[[Pulses Laser Deposition]]{{wpw|Pulses Laser Deposition}}''' ===
[[Image:mech370_laser.jpg||thumb|left|Figure 3. An example of laser ablation]]
Pulsed [[laser]]{{WPw|laser}} deposition (PLD) is the use of a high power laser rotated and focused at a target in a vacuum chamber. The material will absorb this energy and lattice bonds will be broken. Surface atoms are disassociated and ejected in the form of an {WP|ablation}{WP|plume}. Layered plums travel at high speeds in this chamber and impinge on the surface of a rotating substrate. The plume and substrate make contact at high impact energies particles react on the surface, adhere and compress leaving a deposit of a thin film on the surface. Laser pulses continue to ablate more product and the film thickens. It is important to note that implantation and sputtering can occur during this process to a small degree.
=== '''[[Magnetic Sputtering]]{{wpw|Magnetic Sputtering}}''' ===
[[Image:Magnetron_mech370.jpg||thumb|left|Figure 2. Magnetron in use]][[Magnetron]]{{wpw|Magnetron}} Sputtering is a processing method that is used to coat virtually any material of any shape and orientation. Sputtering is the removal of atomized material from a solid due to energetic bombardment of its surface layers by ionized or neutral particles at high impact velocities. Magnetic Sputtering is performed in near vacuum environmental conditions. During this particles bombardment, a controlled flow of inert gas is introduced to raise the pressure to allow the [[magnetron]]{{wpw|magnetron}} to operate. A high negative voltage source is applied to the substrate material that attracts positive ions at high speeds. The impact energy, if greater than the binding energy of the lattice site create an oscillation withing the crystal plane and cause a recoiling effects; thus resulting in a sputtering effect from the surface atoms. The magnetic field within the system traps secondary electrons. The electrons flow in a helical path around a magnetic line and thus more ionizing collision occurs with the inert gas in the system.
=== '''[[Arc Evaporation]]{{wpw|Arc Evaporation}}''' ===
[[Image:mech370arc.jpg||thumb|left|Figure 3. Arc Evaporation Schematic]]
[[Arc]]{{WPw|Arc}}[[evaporation]]{{WPw|evaporation}} processing uses electricity to deposit precursor material. A high current low voltage arc is connected to a microscopic cathode. This shorted current source is highly energetic emitting area known as a cathode spot. This concentrated temperature, generally extremely high results in a high velocity (10 km/s) of vaporized cathodic material that is removed from its location creating microscopic molten chips at the surface. A plasma with ionized ions, and neutral particles are released. A reactive gas is introduced and evaporation will occur. This gas will fill the chip defect spots left by the cathode and a film will be deposited.
=== '''[[Plasma Enhanced CVD]]{{wpw|Plasma Enhanced CVD}}''' ===
Plasma Enhanced Chemical Vapor Deposition is mainly used for the deposition of dielectric films and passivation films like silicon oxide or nitride at low temperature. This type of process is driven by the heating of a gas or plasma rather than the sequestered material. This process is ideal when dopants are relatively low.
[[Plasmas]]{{WPw|Plasmas}} are formed usign a radio frequency generator. These reactive ions are subdivided into 'thermal' and 'cold' varieties.
* Thermal- High enough energy in particles to separate electrons from atoms
* Cold - Temperatures lower than ionized energies
== References ==
<references/>
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[[Category:Materials processing]]
[[Category:Materials processing]]
[[Category:Projects]]
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