Appeal No. 2006-2344
Application No. 10/408,890
Now, the question before us is what APA, Akimoto and Subramanian would have taught
to one of ordinary skill in the art? To answer this question, we find the following facts:
1. At pages 2 and 3 of Appellants’ specification, APA states:
[0009] In the prior-art measuring equipment, the wafers are rotated during measurement.
During this process, the wafer is usually supported on a wafer table that is equipped with a
rotary drive.
[0010] To avoid uncontrolled shifting during rotation, the wafer must be fixed. A vacuum
suction system may be used for this purpose, which pulls the wafer flat on a very plane
surface. This also produces a high degree of planarity of the wafer, which is required for
accurate measurement. Vacuum suction systems, however, have the drawback that the
contact can cause contamination on the rear side of the wafer, which can reduce the yield.
[0011] Attempts have therefore been made to replace such systems with other devices.
However, the elimination of vacuum suction systems presumes that the position and the
distance of the wafer do not have a negative influence on the measurement of the wafer, or
that the measuring head automatically corrects its position, as it is described, for instance in
DE 198 16 974. This makes it possible to dispense with an active alignment of the wafer
table and the planarization by means of a complex vacuum suction system to save costs and
weight. As a result it is possible to use wafer holding systems that grasp the wafer only
along its periphery. These are so-called edge gripping systems, which are provided with
rollers to roll the wafer along its edges. The drawback of these systems, however, is that
abrasive wear on the friction rollers can produce particulates that should be avoided in
semiconductor production.
[0012] Such edge gripping systems are also used to align the wafers. These are self-contained
units, referred to as notch aligners, which align the wafer by means of its recess or notch in
the wafer edge. Before such an alignment is possible, the position of the wafer and that of its
notch must be determined, which requires an additional device called a notch aligner. With
the notch detector and the notch aligner, the coordinate systems of the wafer and the
measuring system are aligned, so that the measurements can subsequently be carried out at
precisely determined locations of the wafer. A notch aligner is disclosed, for instance, in U.S.
Pat. No. 5,102,280.
2. At column 6, line 28 through column 7, line 4, Akimoto states:
The interface section 13 has the same length in the direction of depth (in the direction
of X) as that of the processing station 11 but is shorter in the direction of width. On the base
8
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