What is Vacuum Thin Film Deposition (PVD):


Vacuum Thin Film Deposition is commonly known as Physical Vapour Deposition (PVD), which covers Evaporation from Thermal or Electron Beam Sources, Sputtering from Diode or Magnetron Sputtering Cathodes and Plasma from RF Plasma Sources. All of which is carried out in a high vacuum environment in various size and configured vacuum systems with a single batch or multiple chambers.


The vacuum systems can vary from small batch type systems for R&D purposes to extremely large in-line systems that can continually process sheets of glass 4 meters wide x 4 meters long, 24 hours/day, 7 days/week. The industries today that use PVD include, Universities, R&D, Semiconductor, Flat Panel Display, Opto-Electronics, Precision Optics, Hard Disk and Thin Film Head, Aerospace, Defence, Automotive, Machine Tool, Flexible Material Coating (Food Packaging Industry), Astronomical Telescopes and Industrial Glass Coating from Automotive to Architectural Glass.




What is Evaporation Deposition:


Evaporation when applying it to vacuum deposition is the process of converting a liquid to a vapour under high vacuum conditions, typically from 1 x 10-4 torr to 1 x 10-7 torr. This is accomplished by melting a material, metal or a dielectric material within a high vacuum chamber. The material can be melted either using a simple filament or tungsten boat, which is heated using a high current power supply, or an electron beam source that uses a high voltage beam that is magnetically focused and directed on to the material to be evaporated. As the material to be evaporated melts it evaporates into a vapour and settles onto any surface within it's path. High vacuum reduces the temperature required for evaporation and removes the potential for collisions with ambient molecules by the evaporant molecules. This makes their paths predictable and allows the control of the eventual condensate. Most important, it enables the unimpeded flow of energized particles. The substrates to be coated can be placed in various types of substrate fixtures above the evaporation sources to insure very good film thickness uniformity.





What is Sputtering Deposition:


The material to be deposited (the target) is placed on to a sputtering cathode within a high vacuum chamber. DC or RF high voltage is applied to the target. Argon gas is emitted into the chamber to bring the chamber pressure to around 3 x 10-3 torr. At this pressure a glow discharge is created. The planar magnetron cathode sputters efficiently because the magnetic field below the target is arranged to trap secondary electrons emitted from the target surface. The figure below shows a view of the cathode and the general direction of the magnetic field lines. Charged particles are trapped in the purple shaded region, because a magnetic mirror is created in front of the cathode. Thus, the electric and magnetic fields in this configuration, trap charged particles allowing ions to be created by collision of gas atoms with electrons. The substrates to be coated are generally placed approximately 3”- 4” away from the target surface and for larger substrates the substrates will be continually moved past the targets to insure very good film thickness uniformity.





What is RF Plasma Deposition:


RF Plasma Deposition is based upon diode-type sputtering, where no magnets are used to enhance the deposition rate. The deposition rate is enhanced by focusing a remotely-generated high density RF Plasma onto the target surface by means of two (2) electromagnets. As shown below the intensity of the plasma is magnetically enhanced using the launch magnet and bent and directed toward the target using the steering magnet. Even with plasma running, sputtering at the target does not occur unless a negative DC or RF voltage is applied to it. The sputtered material then deposits onto the electrically earthed substrate. As with evaporation and magnetron sputtering, the substrates can be held in a variety of moving or static substrate fixtures to insure very good film thickness uniformity.