High voltage chuck for a probe station
A chuck for testing an integrated circuit includes an upper conductive layer having a lower surface and an upper surface suitable to support a device under test. An upper insulating layer has an upper surface at least in partial face-to-face contact with the lower surface of the upper conductive layer, and a lower surface. A middle conductive layer has an upper surface at least in partial face-to-face contact with the lower surface of the upper insulating layer, and a lower surface.
1. A chuck comprising:
(a) an upper conductive layer having a lower surface and an upper surface suitable to contact and support a device under test;
(b) an upper insulating layer having an upper surface at least in partial face-to-face contact with said lower surface of said upper conductive layer, and a lower surface, wherein the upper insulating layer is horizontally distinct from the upper conductive layer; and
(c) a middle conductive layer having an upper surface at least in partial face-to-face contact with said lower surface of said upper insulating layer, and a lower surface, wherein the middle conductive layer is horizontally distinct from the upper insulating layer;
wherein the chuck is an assembly of separate parts, wherein the separate parts include the upper conductive layer, the upper insulating layer, and the middle conductive layer;
wherein the upper conductive layer includes a conductive layer vacuum path configured to apply a vacuum to the lower surface of the upper conductive layer to retain the lower surface of the upper conductive layer in at least partial face-to-face contact with the upper surface of the upper insulating layer;
wherein the upper insulating layer includes an insulating layer vacuum path configured to apply a vacuum to the lower surface of the upper insulating layer to retain the lower surface of the upper insulating layer in at least partial face-to-face contact with the upper surface of the middle conductive layer; and
further wherein no vacuum path extends between the upper surface of the upper insulating layer and the lower surface of the upper insulating layer.
2. The chuck of claim 1 wherein said upper insulating layer extends beyond an exterior surface of said upper conductive layer and an exterior surface of said middle conductive layer.
3. The chuck of claim 1 wherein said upper insulating layer extends beyond an exterior surface of said upper conductive layer and an exterior surface of said middle conductive layer, and wherein said upper conductive layer has a smaller diameter than said middle conductive layer.
4. The chuck of claim 1 wherein said upper insulating layer includes at least one recess defined therein, wherein said recess is proximate an exterior surface of at least one of said upper conductive layer and an exterior surface of said middle conductive layer, wherein said recess extends around a majority of a circumference of said upper insulating layer, and further wherein said recess is configured to absorb stresses in said upper insulating layer.
5. The chuck of claim 1 further comprising an insulated lift pin slidably extendable from a retracted position within a lift pin hole formed within said upper surface of said upper conductive layer, and an insulated lift pin sleeve further interposed between said lift pin and said upper conductive layer, wherein said lift pin sleeve includes a flange projecting radially outward from an axis of said lift pin, said flange adapted in size and shape to increase at least one of an arc distance and a creepage distance characteristic of said chuck.
6. The chuck of claim 1 wherein said middle conductive layer comprises a guard potential held to a predetermined value, said predetermined value between a signal potential and a shield potential.
7. The chuck of claim 1 , wherein said upper surface of said upper conductive layer includes thereon a vacuum distribution for holding said device under test.
8. The chuck of claim 7 , wherein said vacuum distribution comprises a plurality of vacuum holes positioned across said upper surface of said upper conductive layer and close enough to one another to have overlapping areas of full vacuum effect so as to provide uninterrupted vacuum across zones of said upper surface of said upper conductive layer.
9. The chuck of claim 7 wherein said vacuum distribution comprises a porous sintered metal layer having at least as small as one micron sized pores through which a vacuum is drawn.
10. The chuck of claim 7 wherein said vacuum distribution comprises micro-grooves at least as small as 50 microns wide and 15 microns deep, said micro-grooves formed upon said upper surface of said upper conductive layer with close enough spacing so as to provide a substantially continuous vacuum field across zones of said upper surface of said upper conductive layer.
11. The chuck of claim 1 , wherein the upper insulating layer extends entirely below the upper conductive layer.
12. The chuck of claim 1 , wherein the middle conductive layer extends entirely below the upper insulating layer.