About sputtering coating of PVD vacuum coating machine
The sputtering coating of the PVD vacuum coating machine is a technique in which high-energy particles bombard the surface of the target in a vacuum chamber. Atoms and other particles in the target are knocked down by the momentum transfer of the particles, and are deposited on the substrate to form a thin film. The process has the advantages of small sputtering area, strong sputtering material controllability, and fast sputtering speed. Therefore, it has been rapidly developed and widely used in recent years.
There are many deposition methods in sputtering technology, such as DC bipolar sputtering, tripolar (or quadrupole) sputtering and magnetron sputtering.
1. Bipolar sputtering
Bipolar sputtering is an early and relatively simple basic sputtering method.
The device consists of a cathode and an anode. A target made of thin film material (conductor) is used as the cathode, and the workpiece frame is used as the anode (grounded). The distance between the two poles is usually between a few centimeters and ten centimeters. When the electric field intensity in the vacuum chamber reaches a certain value, abnormal glow discharge occurs between the two electrodes. Ar+ ions in the accelerated plasma bombard the cathode target, and target atoms are deposited on the substrate to form a thin film.
Using the radio frequency power supply as the target cathode power supply, a bipolar radio frequency sputtering device can be made, and the insulating material can be sputtered with a magnetron.
2. Triode sputtering
Although the method of bipolar sputtering is simple, the discharge is unstable and the deposition rate is low. In order to improve the sputtering rate and film quality, on the basis of the bipolar sputtering device, a heating cathode was added to prepare a triode sputtering device.
The plasma density can be controlled by changing the electron emission current and accelerating voltage. The target voltage can control the ion bombardment energy of the target, and solve the contradiction between the target voltage, the target current and the target voltage in dipole sputtering.
The disadvantages of triode sputtering are uneven plasma density, unstable discharge, and uneven film thickness. For this reason, an auxiliary anode is added on the basis of tripolar sputtering to form quadrupole sputtering.
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