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Sputtering is a method of depositing thin layers of material onto a surface by bombarding a source material with electrons or other particles. It is used in various industries, including nanotechnology, and there are different types of sputtering methods, including gas flow, reactive, and magnetron sputtering. Magnetron sputtering works by placing a magnetic field around the source material, while ion beam sputtering works without a magnetic field. Reactive sputtering relies on chemical reactions between the target material and gases pumped into the vacuum of the chamber.
Sputtering is a method of depositing very thin layers of a material onto a surface by bombarding a source material in a sealed chamber with electrons or other energetic particles to expel the source atoms as aerosols which then settle on all surfaces in the chamber . The process can deposit extremely fine film layers down to the atomic scale, but it also tends to be slow and is best used for small areas. Applications include the coating of biological samples for imaging in scanning electron microscopes (SEM), the deposition of thin films in the semiconductor industry, and the deposition of coatings for miniaturized electronics. The nanotechnology industry in medicine, information technology, and materials science research often relies on sputter deposition to design new composites and devices at the nanoscale, or one-billionth of a meter.
Several types of sputter methods are in common use, including gas flow, reactive, and magnetron sputtering. Ion beam and ion-assisted sputtering are also widely used due to the variety of chemicals that can exist in an ionic state. Magnetron sputtering is further divided into direct current (DC), alternating current (AC), and radio frequency (RF) applications.
Magnetron sputtering works by placing a magnetic field around the source material which will be used for deposition of layers on the target. The chamber is then filled with an inert gas, such as argon. As the source material is electrically charged with AC or DC current, the ejected electrons are trapped in the magnetic field and eventually interact with the argon gas in the chamber to create energetic ions composed of both the argon and the source material. These ions then escape the magnetic field and strike the target material, slowly depositing a thin layer of source material on its surface. RF sputtering is used here to deposit different varieties of oxide films on insulating targets by varying the electrical polarization between the target and the source at a high rate.
Ion beam sputtering works without the source needing a magnetic field. Ions ejected from the source material interact with electrons from a secondary source so that they bombard the target with neutral atoms. This makes for an ion sputter system capable of coating both conductive and insulating material and target parts, such as thin-film heads for computer hard drives.
Reactive sputter machines rely on chemical reactions between the target material and the gases that are pumped into the vacuum of the chamber. Direct control of the deposition layers occurs by altering the pressure and amount of gas in the chamber. Films used in optical components and solar cells are often made by reactive sputtering, as stoichiometry or chemical reaction rates can be precisely controlled.
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