DC magnetron

A DC magnetron is a contemporary model of the device for cathode sputtering of materials in vacuum with the use of a DC power source with the aim of application of current conducting coatings for articles. The principle of its action is based on the phenomenon of cathode physical sputtering (target material) with accelerated ions of the working gas, which bombard the target surface under action of the applied negative potential.

The use of a special magnetic system, which creates a tunnel-shaped magnetic field closed by contour, is a typical feature of magnetrons. It helps to provide conditions for obtaining the localized high density plasma and, respectively, of high density ion currents, sputtered targets. Its consequence is expressed in high productivity of the sputtered materials. The design principles of magnetron devices construction allow to rather simply fulfill the task of application of uniform coatings onto wide-format surfaces. This feature made it possible to ensure an essential progress in the modern production of coatings for architectural glass, displays, solar components, for decoration of plastics and rolled materials, etc.

DC magnetrons are mainly used for metals sputtering by using the inert gases.

AC magnetron

An AC magnetron has been elaborated for implementation of highly productive processes of application of dielectric coatings (oxides, nitrides, carbides, etc) by sputtering the current conducting materials in the reactive medium.

Performance of reactive processes at the magnetron has two peculiar features: 1 – composite film formation and growth on the target surface, 2 – deposition of the same film on the anode electrode. During application of dielectrics the growing coating is blocking the motion of electronic current in the circuit of plasma discharge it becomes unstable in time, and it is ceased in the final end. Besides, the growing thin dielectric films on the target due to charge accumulation undergo frequent micro punctures, being the source of contaminations in the film.

When АС magnetrons are used, they are to be connected to different poles of the AC power supply block having frequency of 20-80 kHz. Such connection provides alternate operation of each magnetron – in the cathode mode and in the anode mode (of sputtering). As a result, the problem of anode soiling with a non-conducting material disappears, as the anode is in the state of permanent self-cleaning. Besides, the non-conducting film on the target is subject to alternate impact by means of ion and electronic flows by providing the charge surface neutralization and it eliminates the arc formation problem. Finally, AC magnetron operation is stable in time, and it makes it possible to apply high quality dielectric coatings with a high speed.