| 摘要 |
Apparatus and methods for plasma processing involving the gettering of particles having a high charge to mass ratio away from a semiconductor wafer are disclosed. In one aspect of the invention, magnets are used to produce a magnetic field which is transverse to an electric field to draw the negative particles away from the wafer to prevent the formation of a sheath which can trap the particles. In a second aspect of the invention, a power source is connected to the wafer electrode to maintain a negative charge on the wafer, thereby preventing negative particles from being drawn to the wafer surface when the plasma is turned off. In other embodiments of the invention, a low density plasma source is used to produce a large plasma sheath which permits particles to cross a chamber to be gettered. A low density plasma discharge followed by a pulse to a higher density is used to overcome the negative effect of an insulating layer between the wafer and the wafer electrode.
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