Sputtering is a technique used to deposit a variety of high purity materials. The operation can be as easy as installing the desired target material and running a standard procedure to deposit the material onto a substrate. Sputtering becomes challenging when the desired material is unnatural. Nonetheless material scientists and engineers have developed sputtering knowledge and techniques to guide nature towards the development of new materials.
Vacuum
Sputtering is performed in a vacuum chamber. The vacuum chamber is pumped down to a low base pressure, typically below 1×10-6 [Torr]. The low base pressure provides a clean environment for deposition. Materials that react easily with oxygen and/or water may require much lower base pressure.
Process Gas
After the vacuum chamber has reached an appropriate base pressure, a process gas is injected into the chamber. Gases used for sputtering is research grade pure such as 99.9999% purity Argon or 99.999% purity Oxygen. The process gas may contain a single element such as Argon or a mixture such as Argon and Oxygen at a specified ratio. Argon is a noble gas and will not react with the target material, but including oxygen may produce an oxide of the target material to be deposited. The process gas pressure is typically 2.5 [mTorr], as low as possible while able to start a plasma. Higher gas pressures may be used to ignite the plasma before reducing to a lower pressure for deposition.
Sputtering Gun
The target is installed inside of a sputtering gun. When powered, the sputtering gun atomizes the target and sprays it out of the barrel. The sputtering gun orientation can be adjusted to control the spray pattern on the sample. The sputtering gun is powered by either a DC or RF power supply depending on the requirements of the target material. A minimum amount of power is needed to start the gun, after which, additional power increases the deposition rate. Using excessive power will overheat the gun and potential damage the target and/or gun.