Appeal 2007-0908
Application 10/152,077
Ueno
17. Ueno teaches a method for spin cleaning substrates such as
semiconductor wafers. (Ueno at 1:5-7.)
18. Ueno teaches two general spin cleaning methods. (Ueno at 2:33ff.)
19. The first method comprises a rinsing step followed by a replacing step
that replaces the rinsing liquid with a liquid that is mixable with the rinsing
liquid and that has a lower surface tension than the rinsing liquid, followed
by a removing step in which the replacement liquid is spun off the substrate.
(Ueno at 2:35-47.)
20. The second method is similar except that the replacing step comprises
supplying a replacing medium vapor onto the surface of the substrate. The
replacing medium vapor is chosen to be mixable with the rinsing liquid and
to have a lower surface tension than the rinsing liquid. (Ueno also sets
conditions on the relative temperatures of the rinsing liquid and the replacing
medium, which we need not describe as they have not been the subject of
dispute between the Examiner and Christenson.) (Ueno at 2:50-65.)
21. Although the principal and simplest implementations of Ueno's
invention introduce the replacement medium vapor at the "substantial
center" of the surface of the substrate (e.g., Ueno Figure 5 and associated
text), Ueno also teaches that "it is important to allow the vapor to uniformly
spread on the wafer." (Ueno at 12:3-4.) We shall return to this issue infra.
22. According to Ueno, the use of the replacement fluid having a lower
surface tension than the rinsing fluid takes advantage of the "Marangoni
effect." (Ueno at 8:46-48.)
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