Sputtering is the use of argon ions to bombard the target, knocking out target atoms into the gas phase and depositing on the substrate. Sputtering has a wide range of applications and almost any material can be deposited.
1. The advantages and limitations of sputtering
● Good adhesiveness
● The manufacture of the targets is limited.
● Damage of the target materials, such as ceramic targets, limits the range of energy used.
● Low deposition rate.
2. Classification of sputtering coating system
(1) Planar bipolar: The target material is negative and the base material is positive.
(2) Three-pole: The system consists of three electrodes: anode, cathode, and external electron source. An external electron source generates electric field to accelerate the ionization of positive gas molecules. The three pole system cannot be used for reactive sputtering, because electrons can affect the reaction gas.
(3) Magnetron sputtering coating: Using magnetic field to increase the sputtering rate.
(4) Reaction sputtering: The reaction gas is introduced into the vacuum chamber and the metal atoms are used to produce compounds to deposit.
3. The sputter of the insulator
The insulating film can be sputtered by RF or reactive sputtering. If DC sputtering is used, surface charge will rapidly build up and sputter will fail.
(1) RF sputtering
Using a radio frequency power supply with a frequency of 13.56 MHz, the surface of the target and the substrate can be alternately bombarded by ions and electrons to avoid charge accumulation.
(2) The advantages of RF sputtering
(a) The efficiency of electron bombardment ionization is higher and the operating pressure is relatively low.
(b) Reduce the arc (The generation of arc is caused by dust or heated vaporized gases).
(3) Reactive sputtering
The reactive gas is added to argon, such as Ar + H2S, and cadmium sulfide is formed with sputtering atoms, such as cadmium. For example, titanium nitride will be formed when titanium is spun in argon or nitrogen.