sputters

Sputtering is a physical vapor deposition process in which atoms are ejected from a solid target as energetic ions strike its surface. In a typical chamber, a plasma (often argon) is sustained by applying dc or rf power. Positive argon ions are accelerated toward the target, transferring momentum to surface atoms. If the transferred energy exceeds the surface binding energy, those atoms are ejected into the gas phase and subsequently condense on a nearby substrate to form a thin film.

The sputtering yield, defined as the average number of atoms ejected per incident ion, depends on ion energy, mass, target material, and incidence angle. Yield generally increases with energy up to a material-specific maximum and then saturates. The energy distribution of sputtered atoms is broad, and their angular distribution is typically peaked near the target normal.

Types of sputtering include DC sputtering for conducting targets and RF sputtering for insulating targets. Magnetron sputtering uses magnetic fields to trap electrons near the target, enhancing plasma density and deposition rate. Reactive sputtering introduces a reactive gas (for example, oxygen or nitrogen) to form compounds such as oxides or nitrides on the substrate. Co-sputtering uses multiple targets to tailor film composition. Sputtering can also be used for etching when ions remove material from a surface instead of depositing it.

Applications are widespread: metal and ceramic thin films, hard coatings (such as TiN), optical coatings, diffusion barriers and contact layers in microelectronics, solar cells, and MEMS devices. Deposition rates range from tenths to tens of nanometers per second depending on conditions; film properties depend on substrate temperature, pressure, and gas composition. Challenges include target poisoning in reactive sputtering, redeposition, and control of film stoichiometry and stress. Sputtering is favored for its uniformity, adhesion, and compatibility with large-area substrates.