Guard ring electrostatic chuck
First Claim
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1. An electrostatic chuck system for holding, in a vacuum ambient, by electrostatic attraction of a DC potential a workpiece having a workpiece radius comprising:
- at least two circularly symmetric, concentric aluminum electrodes having a hard-coat alumina coating and together providing a planar clamping surface, at least one of said aluminum electrodes having gas feed means therein, characterized in that;
an outer electrode of said at least two circularly symmetric, concentric aluminum electrodes has an electrode outer radius less than said workpiece radius by a guard ring distance;
said outer electrode is surrounded by a conductive guard ring having a guard ring outer radius less than said workpiece radius by an overhang amount, having a guard ring top surface substantially coplanar with said planar clamping surface and being dielectrically isolated from and capacitively coupled to said outer electrode and to said workpiece, whereby said guard ring suppresses vacuum arcs between said workpiece and said outer electrode by establishing a equipotential area substantially equal in potential to said workpiece between said workpiece and said outer electrode.
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Abstract
An electrostatic chuck suppresses the formation of vacuum arcs between the back of the wafer being processed and the body of the chuck by the interposition of a guard ring that floats close to the self-bias potential induced by the plasma on the wafer, thereby capacitively dividing the voltage between the wafer and the closest electrode.
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Citations
12 Claims
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1. An electrostatic chuck system for holding, in a vacuum ambient, by electrostatic attraction of a DC potential a workpiece having a workpiece radius comprising:
- at least two circularly symmetric, concentric aluminum electrodes having a hard-coat alumina coating and together providing a planar clamping surface, at least one of said aluminum electrodes having gas feed means therein, characterized in that;
an outer electrode of said at least two circularly symmetric, concentric aluminum electrodes has an electrode outer radius less than said workpiece radius by a guard ring distance; said outer electrode is surrounded by a conductive guard ring having a guard ring outer radius less than said workpiece radius by an overhang amount, having a guard ring top surface substantially coplanar with said planar clamping surface and being dielectrically isolated from and capacitively coupled to said outer electrode and to said workpiece, whereby said guard ring suppresses vacuum arcs between said workpiece and said outer electrode by establishing a equipotential area substantially equal in potential to said workpiece between said workpiece and said outer electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- at least two circularly symmetric, concentric aluminum electrodes having a hard-coat alumina coating and together providing a planar clamping surface, at least one of said aluminum electrodes having gas feed means therein, characterized in that;
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9. An electrostatic chuck system for holding, in a vacuum ambient, by electrostatic attraction of a DC potential a workpiece having a workpiece radius comprising:
- at least two circularly symmetric, concentric aluminum electrodes having a hard-coat alumina coating and together providing a planar clamping surface, at least one of said aluminum electrodes having gas feed means therein, characterized in that;
an outer electrode of said at least two circularly symmetric, concentric aluminum electrodes has an electrode outer radius less than said workpiece radius by a guard ring distance; said outer electrode is surrounded by a conductive guard ring having a guard ring outer radius less than said workpiece radius by an overhang amount, having a guard ring top surface substantially coplanar with said planar clamping surface and being dielectrically isolated from to said outer electrode; said conductive guard ring has at least one sensing pin extending therefrom and exposed to the plasma, thereby raising said guard ring to said plasma potential, whereby said guard ring suppresses vacuum arcs between said workpiece and said outer electrode by establishing a equipotential area substantially equal in potential to said plasma between said workpiece and said outer electrode. - View Dependent Claims (10, 11, 12)
- at least two circularly symmetric, concentric aluminum electrodes having a hard-coat alumina coating and together providing a planar clamping surface, at least one of said aluminum electrodes having gas feed means therein, characterized in that;
Specification