Sputtering

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The verb to sputter is derived from the Latin word SPUTARE which means to secrete saliva with noise. Sputtering is the collisions of atoms on a surface that results in the discharge of atoms from the surface as a result of bombardments and energy transfer from the incoming particles. This process is most commonly used for thin-film deposition of various materials including metals and ceramics. The occurrence was first explained more than 150 years ago in 1852 by William Robert Grove who described vaporization and film formation of metal films by sputtering. Grove discovered “sputtering” while studying glow discharges. Grove utilized a tip of wire as the coating foundation and sputtered a deposit onto a silver surface that was close to the wire at a pressure around 0.5 Torr (1). He made a note of a coating on the silver surface when the silver surface was the cathode and the wire was the anode in an electrical circuit. . M. Faraday likewise described film deposition by sputtering in 1854. At this time sputtering was an unwanted phenomenon because it destroyed the cathode and grid in the gas discharge tube.

As early as 1585 sputtering was used to create gorgeous metallic mirror. This incident first occurred when Julius Plucker reported platinum film inside of a gas discharge tube creating the first metallic mirror via sputtering(2). Sputtering also found many other applications such as coating fabrics and phonograph wax masters. In Thomas Edison’s 1902 paten on the subject of seed coating his wax cylinder phonograph he used sputtering to deposit gold to create the gold moulded cylinder records to subsequent electroplating(3). Before 1908 it was believed that the deposits were a direct result of evaporation at hot spots on the ...

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...gnetically confined plasma. This method was used to enhance the level of ionization in the plasma but became outdated with the advancement of magnetron sputtering.

Even before Penning’s work it was known that magnetic fields had an effect on the paths of electrons. The duo of electric and magnetic fields amplified the ionization of the plasma near the surface of the target and used magnetic fields that were parallel to the sputtering target surface. Electrons can be confined near the surface in a closed pattern by utilizing magnetic fields that develop and reenter a surface in a closed loop. These magnetic fields can be created with a magnetron source. The surface magnetron sputtering configurations of the 1960s and 1970s were developed by utilizing these confined electrons which create high density plasma near the surface of the substrate.

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