Electrostatic clamping method and apparatus for dielectric workpieces in vacuum processors

In combination, a vacuum plasma processor chamber for applying gaseous ions having a potential substantially equal to a reference potential to an exposed surface of a workpiece including a dielectric substrate, an electrostatic chuck in the chamber for contacting the dielectric substrate and holding the workpiece in situ in the chamber, the electrostatic chuck having an electrode, means for maintaining the electrode at a potential substantially different from the reference potential;

• the potential at which the electrode is maintained being such, and the electrode being positioned relative to the workpiece surface while the plasma is being applied to the exposed workpiece surface so that electric charge applied to the exposed surface by the plasma forms part of an electrically conducting path from the exposed surface to a terminal at the reference potential via the plasma so the charge on the surface is at a potential substantially equal to the reference potential and a substantial voltage is established between the electrode and the charge on the surface, the substantial voltage establishing an electrostatic clamping force from the electrode through the substrate to the charge on the surface for holding the workpiece in situ on the chuck and overcome other forces having a tendency to move the workpiece relative to the chuck, and means for feeding a fluid through the chuck for controlling the workpiece temperature.

Apparatus for clamping a workpiece including a dielectric substrate in a vacuum plasma processor chamber comprising an electrostatic chuck in the chamber for contacting the dielectric substrate and holding the workpiece, the chuck including an electrode, means for applying the plasma to a surface of the workpiece exposed to the plasma, a relatively high single polarity voltage source connected to the electrode of the chuck, the electrode being physically arranged so it is at a high voltage which differs substantially from that of the plasma, the electrode being in close proximity to a portion of the substrate not exposed to the plasma so (1) the electrode is at a DC voltage substantially different from the plasma, (2) a DC electrostatic charge is applied to the exposed workpiece surface by the plasma, and (3) an electrically conductive path is provided via the plasma from the exposed substrate surface to a terminal at a potential substantially different from the voltage applied to the electrode, the electrostatic charge and the electrically conducting path being such that they cause an electrostatic force to be developed between the workpiece the chuck electrodes, the electrostatic force being applied from the electrostatic charges through the thickness of the dielectric substrate to the electrode by a voltage difference between the DC voltage applied to the electrode and charge applied by the plasma to the exposed face to hold the workpiece on the chuck.