Appeal No. 96-1805
Application 08/200,432
The Hoshi reference is directed to a method for bonding
semiconductor wafers in such a manner as to eliminate gas bubbles
between the two bonded surfaces. The examiner focuses on the
embodiment illustrated in Figures 3A through 3F. In this system,
first and second flat wafers 50A and 50B are pulled by vacuum
upon a pair of curved chucks 6A and 6B, whereupon they assume a
warped configuration (Figures 3A and 3B). Each chuck is mounted
in a cover (22A and 22B) and, as shown in Figure 3C, the covers
are folded over upon one another to form a chamber having a gas
outlet 29. There is no gas inlet. At this point in the Hoshi
process, the warped wafers are held spaced from one another. As
explained in column 4, chuck 6B then is raised to the position
shown in Figure 3D, in which the protruding center portions of
the wafers are placed in contact with each other (column 4, line
22). The next step is to subject the interior of the chamber to
a vacuum greater than that which holds the wafers upon the
chucks, whereupon they are released to flatten and make full
contact with one another, as shown in Figure 3E, so that they
bond together along their entire surfaces (column 4, lines 25
through 31). This is intended to eliminate the presence of gas
bubbles between the bonded wafers.
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