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A balanced SW source contains a conventional type of 2 pole magnetic array which generates an efficient magnetic trap over the target surface and minimises electron and plasma loss from the source.
The term balanced reflects the nature of the magnetic field trap. The field lines are well confined around the target racetrack and electron loss is reduced to minimum. This encourages low voltage operation and a minimum of plasma release to the substrate. Substrate temperatures are lower for this type of array compared to unbalanced types since electron and ion bombardment is lower.
A balanced magnetic field is related to the magnetic field shape over the target surface and the magnetic interaction with the anode. The other variable is the magnetic field strength. A balanced magnetron can be manufactured in low, standard, or high strength versions, depending upon the application. For higher field strength versions there is a reduced possibility of electron loss from the magnetron plasma since the escape is more difficult. This reduces the discharge voltage and increases the discharge current and also has a benefit for low-pressure operation, see high strength magnetic array options.
Conversely if the system pressure is higher than standard (>7 x 10-3 mbar), then the magnetic field strength should be reduced to allow the plasma to 'spread' across the target and to maintain normal performances.
The careful positioning of the magnetic field in front of the target and control of its shape reduces the possibility of arcing in difficult applications and improves target use. An Gencoa optimised 2 pole magnetic design can produce target use of greater than 30% at the same time as reducing the re-deposit area in the middle and outer edge of the target. For higher target use more complicated multipole (HY) or moving (FFE) magnetics are used.
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