Electricity: electrical systems and devices – Electric charge generating or conducting means – Use of forces of electric charge or field
Reexamination Certificate
1999-07-09
2001-07-31
Fleming, Fritz (Department: 2836)
Electricity: electrical systems and devices
Electric charge generating or conducting means
Use of forces of electric charge or field
C279S128000
Reexamination Certificate
active
06268994
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates generally to electrostatic chucks and their method of manufacture and, in particular, to such chucks that can be manufactured to relatively high standards, for relatively low costs while at the same time eliminating cumbersome manufacturing techniques.
2. Description of the Prior Art
Prior art attempts to accomplish the goals to which this invention is directed, have met with limited success.
U.S. Pat. No. 5,055,964 to Logan, et al discloses a bipolar chuck using an anodized ring insert in an anodized base.
U.S. Pat. No. 5,572,398 to Federlin, et al discloses a tripolar electrostatic chuck using separate positive and negatives electrodes housed on a non-polarized base housing.
The technologies described in U.S. Pat. Nos. 5,055,964 and 5,572,398 are relatively low-cost technologies but suffer the disadvantage that the separate clamping electrodes must be joined to a framed in careful alignment to achieve flatness. The best flatness that can be achieved in manufacturing is about +/−0.00015 inch (+/−3.75 microns) without a final mechanical grinding or lapping step, which causes insulator thickness non-uniformity. Furthermore, U.S. Pat. No. 5,055,964 has inherently unbalanced rf capacitance as well as non-uniform heat transfer for the 2 poles.
In U.S. Pat. No. 5,207,437 to Barnes, et al and U.S. Pat. No. 5,191,506 to Logan, et al, an electrostatic chuck is disclosed including fired ceramic sheets containing metallic layers within, which are then bonded to a metal cooling/heating assembly containing connections to the electrostatic chuck electrodes.
Fired ceramic sheets consisting of conductive layers embedded in a ceramic matrix can be made but must have significant thickness to maintain physical strength and rigidity. This thickness causes the thermal resistance and rf impedance to be much higher compared to sprayed ceramic layers over metal. Cost of these ceramic structures is usually high.
U.S. Pat. No. 5,691,876 to Chen, et al describes an electrostatic chuck with organic coatings, such as polyimide (Kapton) over a metal chuck assembly.
Organic insulators with metal electrodes embedded are commonly bonded to metal frames to make electrostatic chucks. These chucks have good uniform rf coupling and cooling but suffer the disadvantage that they are not robust and are easily attacked by reactive chemicals in a plasma environment and may be easily damaged by physical abrasion.
In U.S. Pat. No. 5,754,391 to Bates crystalline insulator coatings such as sapphire, usually thick sheets, are bonded to the metal chuck surface.
Crystalline insulator coatings such as sapphire have excellent insulating properties but are expensive and difficult to manufacture in thin coatings required for low operating voltage and high thermal conductivity coupling capacitance.
Watanabe, et al U.S. Pat. No. 5,151,846 discloses the fabrication of an electrostatic chuck by pressing a plurality of given ceramic sheets in the form of pastes with electrode films printed thereon, against a ceramic green sheeting serving as a base plate and then firing the laminated body.
SUMMARY OF THE INVENTION
An object of the present invention is an electrostatic chuck having high and uniform thermal conductivity between clamping surface and coolant channels.
Another object is such a chuck with exceptional flatness.
Still another object is such a chuck with high capacitance between clamping surface and the metallic chuck body.
A further object is such a chuck with balanced rf capacitance with more than one pole.
A still further object is such a chuck with a ceramic insulator or semiconductive covering and completely isolating the clamping electrodes from outside except at the connections.
Yet another object is such a chuck with backside cooling gas supply channels that do not contact the clamping electrodes internally.
Yet still another object is such a chuck that can be manufactured at low cost.
These and other objects features and advantages of the present invention are accomplished in accordance with the teachings of the present invention, one illustrative embodiment of which comprises forming an electrostatic chuck by: providing a conductive base member; machining a pattern of ridges in the top surface of the base member; providing through holes in the base member; inserting insulated contact posts into through holes and joining same to the base member in such manner that the contact posts extend above the top surface of the base member; depositing a first insulating layer over the base member top surface, ridges and the contact posts, the thickness of the insulating layer being less than the height of the contact posts above the base member surface; removing the first insulating layer from the top of the contact posts and removing a portion of contact posts in such manner that the contact posts are flush with the surrounding first insulating layer; depositing a conductive layer over the first insulating layer and the tops of the contact posts, the thickness of the conductive layer being approximately the height of the ridges; grinding the top surface of the base member flat to the point of exposing the first insulating layer over the ridges to form separate electrodes; depositing a second insulating layer over the conductive layer and first insulating layer; and, joining the conductive base member to a supporting frame.
REFERENCES:
patent: 5055964 (1991-10-01), Logan et al.
patent: 5151845 (1992-09-01), Watanabe et al.
patent: 5191506 (1993-03-01), Logan et al.
patent: 5207437 (1993-05-01), Barnes et al.
patent: 5535090 (1996-07-01), Sherman
patent: 5572398 (1996-11-01), Federlin et al.
patent: 5600530 (1997-02-01), Smith
patent: 5691876 (1997-11-01), Chen et al.
patent: 5754391 (1998-05-01), Bates
patent: 5781400 (1998-07-01), Takahashi et al.
patent: 5886863 (1999-03-01), Nagasaki et al.
patent: 5946184 (1999-08-01), Kanno et al.
Logan Joseph
Miller John R.
Tompkins Robert
Dorsey Gage, Inc.
Fleming Fritz
Spiegel Joseph L.
LandOfFree
Electrostatic chuck and method of manufacture does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrostatic chuck and method of manufacture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrostatic chuck and method of manufacture will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2488987