sputteren

Sputteren is a vacuum deposition process in which atoms are ejected from a solid target due to bombardment by energetic ions, typically in a low-pressure plasma, and then condense on a substrate to form a thin film. It can deposit a wide range of materials, including metals, oxides, and nitrides.

In a sputtering chamber, inert gas (commonly argon) is ionized to form plasma. Positive ions are accelerated toward a negatively biased target, creating collision cascades that eject target atoms. These atoms travel to the substrate and form a film. The process can be non-reactive (pure metal deposition) or reactive, where reactive gases (oxygen, nitrogen) react with sputtered atoms to form compounds, enabling oxide or nitride films. Magnetron sputtering uses magnetic fields to trap electrons near the target, enhancing ionization and deposition rates. DC sputtering is used for conductive targets, RF sputtering for insulating or mixed materials, and pulsed DC or RF can control film properties.

Parameters affecting film quality include sputtering energy, target material, gas type and pressure (typical 0.1–10 mTorr), substrate temperature, and deposition geometry. Sputtering yields and film stress can vary; reactive sputtering can cause target poisoning with compounds. Sputtering offers good step coverage, adhesion, and uniform thickness, but equipment costs are high and deposition rates may be slower than other methods.

Applications of sputtering include semiconductor devices, optical coatings, solar cells, hard coatings, and decorative finishes.