Sputtering Deposition Coating

Sputtering deposition coating

When high energy particles are bombarded the solid surface, the particles on the solid surface can obtain energy and escape from the surface and deposit on the substrate. The sputtering phenomenon began to be used in the coating technology in 1870, and after 1930, it was gradually used in industrial production because of the increase of deposition rate. Usually, the material to be deposited is made into a plate ─ a target ─ and fixed on the cathode. The substrate is placed on the anode directly opposite the target, a few centimeters away from the target. After the system is pumped to a high vacuum, 10~1 Pa gas (usually argon) is filled, and several thousand volts are applied between the cathode and anode to produce glow discharge between the poles. The positive ions produced by the discharge fly to the cathode under the action of the electric field and collide with the atoms on the target surface. The target atoms escaping from the target surface by the collision are called sputtering atoms, whose energy ranges from 1 to dozens of electron volts. The sputtering atoms are deposited on the surface of the substrate to form a film. Different from evaporation coating, sputtering coating is not limited by the melting point of film material, and can sputter W, Ta, C, Mo, WC, TiC and other refractory materials. The sputtering compound membrane can be used by reactive sputtering method, in which the reaction gas (O, N, HS, CH, etc.) is added to Ar gas, and the reaction gas and its ions react with target atoms or sputtering atoms to generate compounds (such as oxides, nitrides, etc.), which are deposited on the substrate. High frequency sputtering can be used to deposit the insulating film. The substrate is mounted on the grounded electrode and the insulating target is mounted on the opposite electrode. One end of the HF power supply is grounded, and the other end is connected to an electrode equipped with an insulated target through a matching network and the isolated DC current capacity. After the high frequency power supply is switched on, the high frequency voltage constantly changes its polarity. Electrons and positive ions in the plasma hit the insulating target in the positive and negative half of the voltage, respectively. Because the electron mobility is higher than that of the positive ions, the insulating target surface is negatively charged. When the dynamic equilibrium is reached, the target is in a negative bias potential, so that the sputtering of the positive ions on the target continues. Using magnetron sputtering can increase the deposition rate by nearly one order of magnitude compared with non-magnetron sputtering.

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