What is radio frequency sputtering

In the 1960s, radio frequency glow discharge was used to prepare thin films of any material from conductors to insulators, so it became popular in the 1970s. DC sputtering is an effective method for making thin films using metal and semiconductor targets. However, when the target is an insulator, the ions that hit the target will charge the target, and the potential of the target will rise. As a result, the ions cannot continue to bombard the target. 

Radio frequency refers to the frequency of the radio wave emission range. In order to avoid interference with the work of the radio station, the special frequency for sputtering is specified as 13.56MHz. Under the action of the alternating electric field of the radio frequency power supply, the electrons in the gas oscillate and ionize the gas into plasma.

Since the two electrodes of radio frequency sputtering are connected to an alternating radio frequency power supply, there seems to be no distinction between a cathode and an anode. In fact, the two electrodes of the RF sputtering device are not symmetrical. The electrode on which the substrate is placed is connected to the chassis and grounded. This electrode is a large-area electrode relative to the electrode on which the target is installed. Its potential is similar to that of plasma, and it is almost immune to ion bombardment. The other electrode is at a negative potential for the plasma, which is the cathode, which is bombarded by ions and is used to set up the target.

The disadvantage is that the high-power radio frequency power supply is not only expensive, but also a problem for personal protection. Therefore, radio frequency sputtering is not suitable for industrial production applications.