Appeal No. 2005-0585
Application No. 09/821,478
increases (col. 1, lines 15-20). The examiner states that Tao
teaches that photoresist trimming to achieve gate CD control
becomes difficult to implement (col. 1, lines 26-29). The
examiner states that Tao teaches that the prior art shows that
polymer deposition during etching (from organic materials such
as photoresists and anti-reflective coatings (ARC)) contributes
to etch rate differences (col. 1, lines 44-51). Tao's solution
comprises an inorganic ARC, which also serves as one layer of a
hard mask (col. 2, lines 6-9), and trimming the photoresist with
an O-plasma (col. 2, lines 14-17). The photoresist is removed
after transferring the trimmed pattern to the hard mask layers.
The examiner states that, thus, Tao clearly addresses gate CD
control in nested features. Answer, page 9.
The examiner states that Tao does not explicitly address
differential etching between nested and isolated features. The
examiner states, however, that the CD of isolated features is
controlled by the same etch as used for nested features, and it
would be illogical to control one feature dimension at the
expense of another. The examiner states that one of ordinary
skill in the art would recognize the inconsistency of the logic.
The examiner states that this has also been explicitly stated by
Horak. The examiner states that Horak teaches that it would be
deleterious to the device to trim only isolated features without
considering nested features (col. 6, lines 31-35). This is
further explained, stating “the nested to isolated etch bias
cannot be adjusted without causing the nested etch bias to also
decrease” (col. 6, lines 43-46). The examiner finds that Horak
states “In addition, both nested and isolated lines will be
etched at the same time the isolated lines are etched faster
than are nested lines, but both are etched” (col. 2, lines 17-
20). Answer, pages 9-10.
8
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Next
Last modified: November 3, 2007