Work holders – With fluid means – Vacuum-type holding means
Reexamination Certificate
1998-05-15
2001-07-10
Hail, III, Joseph J. (Department: 3723)
Work holders
With fluid means
Vacuum-type holding means
C451S388000
Reexamination Certificate
active
06257564
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor manufacturing and, more specifically, to vacuum chucks for handling wafers during semiconductor manufacturing.
2. Description of Related Art
During the semiconductor chip manufacturing, a semiconductor wafer undergoes various processing to create a plurality of chips on the wafer. Additionally, in such various phases of the manufacturing the wafer, undergoes various inspection and quality checks to assure success of the production line. It is known in the art to use vacuum chucks to hold the wafer during the manufacturing, inspection and testing stages.
A conventional vacuum chuck generally comprises a flat plate having a support structure and provisions for delivering vacuum to the back side of the wafer in order to secure the wafer to the support structure. An exemplary conventional chuck
10
is shown in FIG.
1
. It comprised substantially of a plate
20
, having circular vacuum tunnels
30
having vacuum holes
40
at the bottom thereof. The wafer is placed on the surface of the plate
20
, and is secured to the surface by the vacuum delivered to tunnels
30
via holes
40
. the chuck is secured to a stage via holders
50
. Examples of such chucks can be seen in U.S. Pat. Nos. 5,191,218 and 5,534,073.
The present inventors have identified certain disadvantages in the vacuum chuck of the prior art. First, it has been determined that the chuck can be a source for back-side contamination of the wafer. With the rapid reduction in design rules, the importance of previously irrelevant contaminants has been increasing, including backside contamination of the wafer.
Additionally, due to the cautious acceptance of 300 mm wafer processing by the industry, there may be a need to provide processing equipment capable of processing both 200 mm and 300 mm wafers. Such processing equipment would require chucks capable of handling both 200 mm and 300 mm wafers. Therefore, simply scaling the prior art chuck to accept 300 mm wafers may provide an inadequate solution for the industry.
The introduction of 300 mm wafer also raises the importance of the forces exerted by the chuck on the wafer. Specifically, because of the increased diameter, a warped chuck may cause warpage of the wafer, while a perfectly flat chuck may exert an unwanted pressure on slightly warped wafers.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a vacuum chuck which avoids the above noted disadvantages of the prior art chuck and, additionally, provides solutions to problems presented or heightened by the introduction of 300 mm wafers.
The basic concept of the invention is to use vacuum nipples for the support and retaining of the wafer on the chuck. The vacuum nipples reduce the contact area of the chuck with the wafer. In its preferred embodiment the novel chuck includes both vacuum nipples and non-vacuum nipples which have smaller contact area than the vacuum nipples.
Two provisions are made in order to avoid warpage: one assists in avoiding warpage of the chuck, while the other assists in preventing the chuck from exerting undesirable pressure on a warped wafer. In order to avoid warpage of the chuck, the chuck is secured to the stage using special supports. This can be done in one or two degrees of freedom, depending on the slots cut. In order to avoid exertion of excessive force on warped wafers the nipples are provided with a mechanism which blocks the vacuum to any particular nipple if the wafer does not rest on that particular nipple.
REFERENCES:
patent: 3923251 (1975-12-01), Flournoy
patent: 4684113 (1987-08-01), Douglas et al.
patent: 5707051 (1998-01-01), Tsuji
patent: 5923408 (1999-07-01), Takabayashi
patent: 63-93536 (1988-04-01), None
Avneri Israel
Duzi Eyal
Keren Dvir
Regev Avner
Applied Materials Inc
Hail III Joseph J.
Shanley Daniel
Thomason, Moser and Patterson
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