Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1997-04-01
2001-07-03
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S255000, C174S261000, C174S267000
Reexamination Certificate
active
06255601
ABSTRACT:
BACKGROUND OF THE DISCLOSURE
1. Field of the Invention
The present invention relates to semiconductor wafer processing equipment and, more particularly, to a conductive feedthrough extending from volume containing atmospheric pressure through a ceramic body into a vacuum chamber.
2. Description of the Background Art
A semiconductor wafer processing system generally contains a vacuum chamber within which is mounted a wafer support pedestal or susceptor. The pedestal is used to support the wafer within the chamber during processing. The pedestal contains various components which provide heating and/or cooling of the wafer as well as clamping (chucking) of the wafer to retain the wafer in a stationary position upon the pedestal surface. Such clamping is provided by either a mechanical clamp or an electrostatic chuck. Within the vacuum chamber, the space above the pedestal where the wafer is processed is generally maintained at a high vacuum. However, the space below or inside the pedestal is maintained at atmospheric pressure.
For high-temperature reactions, such as high temperature physical vapor deposition, the pedestal is fabricated of ceramic. Heretofore, there has not been a convenient nor practical solution for providing an electrically conductive, yet vacuum sealed, connection through a ceramic pedestal such that electrical current can be passed from the atmosphere side of the pedestal to the vacuum side of the pedestal without violating the integrity of the vacuum.
Therefore, there is a need in the art for apparatus that provides a conductive feedthrough connection through a ceramic body , such as a ceramic pedestal, and a method of fabricating the feedthrough.
SUMMARY OF THE INVENTION
The disadvantages heretofore associated with the prior art are overcome by the present invention of a conductive feedthrough connector for facilitating the flow of electrical current through a ceramic body. Specifically, ceramic bodies such as ceramic support pedestals are generally fabricated by stacking a plurality of layers of ceramic material (e.g., aluminum-nitride, alumina, and the like) and then sintering the stack of layers to cure the layers into a unitary, solid ceramic body. In accordance with the present invention, as each layer is positioned upon the stack, a portion of a select number of layers is silk screened with a conductive material (tungsten alloy) prior to the next layer being positioned atop the silk screened layer. Each silk screened region is coaxially aligned along a vertical axis through the ceramic body within another conductive region of another layer. The stack of silk screened layers are then sintered to form a solid ceramic body containing a plurality of stacked conductive electrodes.
Conductive vias are then formed vertically into one surface of the ceramic body to intersect the embedded electrodes. These vias are formed by drilling, bead blasting, etching, or some other process used to generate bores in the ceramic body. Using a physical vapor deposition (PVD), chemical vapor deposition (CVD) or other means of metal deposition, the vias are filled with a conductive material such that the embedded electrodes are interconnected by one or more vertical conductive vias. A top end of the vias are exposed by lapping the surface of the ceramic body. As such, electrodes and other conductors can be sputtered onto the surface of the ceramic body and connect to the exposed ends of the vias.
From the opposite side of the ceramic body (i.e., the side not containing the conductive vias), a bore is formed into the surface of the ceramic body passing through (intersecting) one or more of the layers of electrodes. An electrical connector pin is then braised into this bore such that the pin conductively connects to the intersected layers of electrode. As such, a conductive path is formed between the conductive vias on one side of the ceramic body (e.g., the vacuum side) and the electrical connector on the other side of the ceramic body (e.g., the atmosphere side). This feedthrough is completely vacuum-sealed and permits a variety of electrical connections to be made to the feedthrough on the vacuum side of the ceramic body.
Alternatively, two or more conductive electrode stacks can be fashioned in various, laterally disparate, locations in the ceramic body. These electrode stacks are laterally interconnected with one another through conductive traces deposited (silk screened) between the ceramic layers.
In one illustrative application for the invention, the inventive feedthrough is used in a PVD system where the ceramic body is a Johnsen-Rahbek electrostatic chuck, and the feedthrough connector of the present invention provides current to a surface electrode located on the vacuum side of the chuck.
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R. Cechanek, Multilayer Printed-Circuit Boards, IBM Technical Disclosure Bulletin, vol. 20 No. 11B, Apr. 1978, pp 4726-4727.
Applied Materials Inc.
Paladini Albert W.
Thomason, Moser & Patterson L.L.P.
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