Magnetron Sputtering Theory Part 1 of 3

Magnetron sputtering is a powerful and flexible PVD coating technique which can be used to coat virtually any workpiece with a wide range of materials - any solid metal or alloy and a variety of compounds. Prior to the magnetron sputtering coating procedure a vacuum of less than one ten millionth of an atmosphere must be achieved. From this point a closely controlled flow of an inert gas such as argon is introduced. This raises the pressure to the minimum needed to operate the magnetrons, although it is still only a few ten thousandth of atmospheric pressure. A magnetron consists of a plate of the material of which all or part of the coating is to consist (referred to as the target) with magnets arranged behind it with alternating polarity. See Figure 1.

Figure 1. Schematic of a magnetron

When power is supplied to the magnetron a negative voltage of typically -300V or more is applied to the target. This attracts argon ions to the target surface at speed. When they collide with the surface two important processes take place: Atoms are knocked out of the target surface with mean kinetic energies of 4 to 6 eV- this is sputtering. These sputtered atoms are neutrally charged and so are unaffected by the magnetic trap, see Figure 1.

Figure 2. An animation depicting the collision between a positive ion and the negatively charged target surface resulting in the sputtering of a target atom.

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