Thin Film Deposition is the technology of applying a very thin film of material – between a few nanometers to about 100 micrometers, or the thickness of a few atoms – onto a “substrate” surface to be coated, or onto a previously deposited coating to form layers. Thin Film Deposition manufacturing processes are at the heart of today’s semiconductor industry, solar panels, CDs, disk drives, and optical devices industries.
Thin Film Deposition is usually divided into two broad categories – Chemical Deposition and Physical Vapor Deposition Coating Systems.
Chemical Deposition is when a volatile fluid precursor produces a chemical change on a surface leaving a chemically deposited coating. One example is Chemical Vapor Deposition or CVD used to produce the highest-purity, highest-performance solid materials in the semiconductor industry today.
Physical Vapor Deposition refers to a wide range of technologies where a material is released from a source and deposited on a substrate using mechanical, electromechanical or thermodynamic processes. The two most common techniques of Physical Vapor Deposition or PVD are Thermal Evaporation and Sputtering.
Thermal Evaporation involves heating a solid material that will be used to coat a substrate inside a high vacuum chamber until it starts to boil and evaporates producing vapor pressure. Inside the vacuum deposition chamber, even a relatively low vapor pressure is sufficient to raise a vapor cloud. This evaporated material now constitutes a vapor stream which the vacuum allows to travel without reacting or scattering against other atoms. It traverses the chamber and hits the substrate, sticking to it as a coating or thin film.
There are two primary methods of heating the source material during Thermal Evaporation. One is known as Filament Evaporation, as it is achieved with a simple electrical heating element or filament. The other common heat source is an electron beam or E-Beam Evaporation where an electron beam is aimed at the source material to evaporate it and enter the gas phase.
Thin Film Evaporation systems can offer the advantages of relatively high deposition rates, real time rate and thickness control, and (with suitable physical configuration) good evaporant stream directional control for processes such as Lift Off to achieve direct patterned coatings.
Sputtering involves the bombardment of a target material with high energy particles that are to be deposited on a substrate like a silicon wafer or solar panel. The substrates to be coated are placed in a vacuum chamber containing an inert gas – usually Argon – and a negative electric charge is placed on the target material to be deposited causing the plasma in the chamber to glow.
Atoms are “Sputtered off” the target by collisions with the Argon gas atoms, carrying these particles across the vacuum chamber and are deposited as a thin film. Several different methods ofplasma vapor deposition coating systems are widely used, including ion beam and ion-assisted sputtering, reactive sputtering in an Oxygen gas environment, gas flow and magnetron sputtering.
Magnetron sputtering uses magnets to trap electrons over the negatively charged target material so they are not free to bombard the substrate, preventing the object to be coated from overheating or being damaged, and allowing for a faster thin film deposition rate. Magnetron Sputtering systems are typically configured as “In-line” where the substrates travel by the target material on some type of conveyor belt, or circular for smaller applications. They use several methods of inducing the high energy state including direct current (DC), alternating current (AC) and radio frequency (RF) magnetron sources.
Compared to Thermal Evaporation that utilizes more conventional heating temperatures, Sputtering takes place in the plasma “Fourth state of nature” environment with much higher temperatures and kinetic energies allowing a much purer and more precise thin film deposition on the atomic level.
Which approach is the right choice for your specific thin film deposition coating system needs can depend upon many complex factors - and more than one approach can be taken to reach similar ends. You always want to get the help of competent vacuum engineering expert to assess your exact needs and offer you the optimum outcome at the best price.
Matt Hughes is President of Semicore Equipment Inc, a leading worldwide supplier of sputtering equipment for the electronics, solar energy, optical, medical, military, automotive, and related high tech industries. Please let our helpful support staff answer any questions you have regarding “What is Thin Film Deposition?” and how to implement the best techniques for your specific Thin Film Vapor Deposition Equipment needs by contacting us at email@example.com or by calling 925-373-8201.
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