Appeal No. 1998-2311
Application No. 08/401,869
a surface on which a workpiece may be supported and with
which it is in electrical contact, the lateral axis
being substantially orthogonal relative to the
longitudinal axis;
biasing the control electrodes with a first bias
voltage that includes a negative dc component to control
the plasma potential so that the plasma potential is
positive with respect to the control electrodes;
restricting electron flow in the plasma to a
longitudinal flow that substantially parallels the
longitudinal axis, while at the same time allowing a
lateral negative ion flow or a lateral negative
particulate flow in the plasma, wherein said step of
restricting the flow of electrons in the plasma
comprises applying a magnetic field of a specified
magnitude to the plasma formation chamber that has
magnetic field lines that substantially parallel the
longitudinal axis, the specified magnitude of the
magnetic field restricting the movement of electrons to a
direction that substantially parallels the magnetic
field lines, while at the same time allowing negative
ions and negatively-charged particulates to
laterally cross the magnetic field lines; and
biasing the reference electrodes with a second bias
voltage that is more positive than the plasma, whereby
the plasma potential becomes negative relative to the
reference electrodes;
whereby negative ions and negatively-charged
particulates in the plasma are laterally drawn out of
the plasma across the magnetic field lines to the
more positively charged reference electrodes
and are not allowed to become trapped within the
plasma.
The Examiner relies on the following prior art:
O’Donnell 4,657,619 Apr. 14,
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