Ex Parte Cha et al

Board of Patent Appeals and Interferences

Aug 21, 2003

09624025 (B.P.A.I. Aug. 21, 2003)

The opinion in support of the decision being entered today was not
written for publication and is not binding precedent of the Board.

Paper No. 14

UNITED STATES PATENT AND TRADEMARK OFFICE
__________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________

Ex parte CHER LIANG CHA,
KOK KENG ONG,
and
ALEX SEE
__________

Appeal No. 2003-0230
Application No. 09/624,025
___________

ON BRIEF
___________

Before KIMLIN, MOORE, and POTEATE, Administrative Patent Judges.

MOORE, Administrative Patent Judge.

DECISION ON APPEAL
This is an appeal under 35 U.S.C. § 134 from the final
rejection of claims 1-6, 8-12, 14-18, and 20. Claims 7, 13, and
19 have been canceled. Thus, only claims 1-6, 8-12, 14-18, and 20
are before us on this appeal.
REPRESENTATIVE CLAIM
Claim 1 is representative, and reads as follows:
1. A method of fabricating an integrated circuit isolation
region comprising:

providing a semiconductor substrate;
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Application No. 09/624,025

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forming a first oxide layer overlying said substrate;
depositing a first nitride layer overlying said first oxide
layer;

patterning and etching away a portion of said first nitride
layer and said first oxide layer forming an opening to said
substrate;

anisotropically etching said substrate in the area of said
opening to form a trench;

thermally growing a second oxide layer on the surface of said
trench;

implanting ions through said second oxide layer into said
substrate at the bottom only of said trench thereby forming an
implanted region under said trench;

depositing a second nitride layer overlying said first
nitride layer and covering the surface of said second oxide layer
on the surface of said trench;

anisotropically etching said second nitride layer and said
second oxide layer at the bottom of said trench thereby forming
nitride spacers on sidewalls of said trench and exposing said
implanted region;

depositing a third oxide layer to fill said trench; and
planarizing said third oxide layer completing fabrication of
said integrated circuit isolation region.

The References
In rejecting the claims under 35 U.S.C. § 103(a), the
examiner relies upon the following references:
Arnold 5,783,476 Jul. 21, 1998
Sheng et al. (Sheng) 5,904,540 May 18, 1999
Peidous 5,989,978 Nov. 23, 1999
Wu 6,069,057 May 30, 2000
Gardner et al. (Gardner) 6,093,611 Jul. 25, 2000
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The Rejections
I. Claims 1, 2, 4, 5, 8-10, 12, and 14 stand rejected under
35 U.S.C. § 103(a) as being unpatentable over Gardner in view of
Arnold and Sheng.
II. Claim 6 stand rejected under 35 U.S.C. §103(a) as being
unpatentable over Gardner in view of Arnold and Sheng, as applied
to claims 1 and 9, further in view of Wu.
III. Claims 3, 11, and 17 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over Gardner in view of Arnold and
Sheng as applied to claims 1 and 9, further in view of Peidous.
IV. Claims 15, 16, 18, and 20 stand rejected under 35 U.S.C.
§ 103(a) as being unpatentable over Gardner in view of Arnold,
Sheng, and Wu.
V. Claim 17 stands rejected under 35 U.S.C. § 103(a) as being
unpatentable over Gardner in view of Arnold and Sheng as applied
to claim 15, further in view of Peidous.
The Invention
The invention relates to a method of shallow trench isolation
used to isolate adjacent components in sub-micron devices in the
fabrication of integrated circuits. (Specification, page 1, lines
6-8). A trench is etched, and an oxide layer is grown along the
bottom and sidewalls of the trench. Oxygen or field isolation
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Application No. 09/624,025

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ions are then implanted in the bottom of the trench. A nitride
spacer is then formed along the bottom and sidewalls of the
trench, followed by an isotropic etch removing the nitride and
oxide from the bottom of the trench. An oxide deposition then
fills the trench, followed by a planarization step completing the
isolation structure. (Specification, page 3, line 13 - page 4,
line 2).
I. The rejection of Claims 1, 2, 4, 5, 8-10, 12, and 14 under
35 U.S.C. § 103(a) as being unpatentable over Gardner in view
of Arnold and Sheng.

The examiner has found that Gardner teaches all of the steps
of claim 1 except for implanting oxygen into the trench bottom and
forming spacers of nitride. More specifically, the examiner has
found that Gardner provides a substrate, forms a first oxide
layer, deposits a nitride layer, patterns and etches the oxide and
nitride layers to form an opening, and anisotropically etches the
substrate to form trenches. A second oxide layer is grown as the
trench liner and a nitride layer is formed over the oxide layer,
then anisotropically etched back to form spacers, exposing the
substrate at the trench bottom. (Examiner’s Answer, page 3, line
18 - page 4, line 3). The trench is then filled with oxide and
planarized (Id., page 4, lines 11-12).
The appellants have not challenged these findings of the
examiner, stating that “[I]t is agreed that Gardner teaches
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forming a shallow trench isolation but does not disclose nitride
spacers or oxygen implantation under the trench.” (Appeal Brief,
page 5, line 22 - page 6, line 2).
The examiner has found that Sheng teaches that nitride may be
used for spacers, and that nitrides and oxides are both dielectric
in nature and would protect the trench sidewall from further
processing steps. The examiner has also found that Sheng uses
nitride for temporary spacers, but that this teaching is
sufficient to suggest that the permanent oxide spacers of Gardner
may be substituted by the nitride spacers of Sheng. (Examiner’s
Answer, page 4, lines 3-11).
The examiner has also found that Arnold teaches implanting
oxygen into the substrate at the bottom of the trench to form
silicon oxide as an isolation between device regions, an
improvement for isolation trenches as dimensions decrease. The
examiner has also found that Arnold teaches the equivalence of
TEOS or HDP for trench filling. (Examiner’s Answer, page 5, lines
19-23).
The examiner then concludes that it would have been obvious
to one of ordinary skill in the art at the time the invention was
made to use the nitride spacers of Sheng, implant oxygen to
improve isolation properties, and fill the trench using HDP with
the reasonable expectation of forming an isolation trench
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structure with improved reliability.
The appellants, on the other hand, urge that the nitride
spacers of Sheng cannot be substituted into the teaching of
Gardner. The spacers, they contend, are temporary, and it is
important to Sheng that the spacers be a different material from
the oxide fill layer. (Appeal Brief, page 6, lines 2-21).
In response, the examiner states that although he agrees that
the sidewall spacers are removed, Sheng was used to show that it
was known to use nitride spacers and that the substitution of
nitride for oxide is obvious. (Examiner’s Answer, page 11, lines
16-19).
We agree with the appellants. First, we note that the
examiner has failed to provide any motivation for making the
switch of nitride for oxide. Sheng discloses that it is known to
use a nitride for a temporary sidewall spacer, which spacer is
totally removed by an isotropic hot acid etching process. (Column
4, lines 26-28). Further, the nitride layer is said to be
different from the oxide layer, in that the oxide layer is used as
an etching stop layer for the etching process (Id., lines 28-32).
The examiner has not shown why it would be desirable to replace
the oxide with the nitride.
Further, if the examiner’s position is that Sheng establishes
that they are equivalent or interchangeable, we disagree. Sheng
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clearly utilizes the nitride for its different properties than the
oxide in the hot acid etching process. The record is unclear as
to why it is different, but in establishing the prima facie case
of obviousness the burden initially falls to the examiner.1
As the initial burden has not been met, we reverse this
rejection.
II. The rejection of Claim 6 under 35 U.S.C. §103(a) as
being unpatentable over Gardner in view of Arnold and Sheng,
as applied to claims 1 and 9, further in view of Wu.

As we have reversed the rejection of claim 1, we likewise
reverse this rejection for the reasons noted above.
III. The rejection of Claims 3, 11, and 17 under 35
U.S.C. §103(a) as being unpatentable over Gardner in view of
Arnold and Sheng as applied to claims 1 and 9, further in
view of Peidous.

As we have reversed the rejection of claim 1, we
likewise reverse this rejection for the reasons noted above.
IV. The rejection of Claims 15, 16, 18, and 20 under 35
U.S.C. § 103(a) as being unpatentable over Gardner in view of
Arnold, Sheng, and Wu.

1 We additionally note that claim 1 requires the bottom of the
trench be exposed when the nitride spacers are formed. The second
oxide layer on the surface of the trench, through which the ions
are implanted, is removed. It does not appear to us that the
second oxide layer of Garner, 140, is ever removed. Consequently,
even if it were obvious to implant oxygen ions through the trench
bottom, the removal of the oxide layer does not appear to be
taught in the references.
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Application No. 09/624,025

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As we have reversed the rejection of claim 1, we likewise
reverse this rejection for the reasons noted above.
V. The rejection of Claim 17 under 35 U.S.C. §103(a) as
being unpatentable over Gardner in view of Arnold and Sheng
as applied to claim 15, further in view of Peidous.

As we have reversed the rejection of claim 1, we likewise
reverse this rejection for the reasons noted above.
Summary of Decision
The rejection of Claims 1, 2, 4, 5, 8-10, 12, and 14 under 35
U.S.C. § 103(a) as being unpatentable over Gardner in view of
Arnold and Sheng is reversed.
The rejection of Claim 6 under 35 U.S.C. § 103(a) as being
unpatentable over Gardner in view of Arnold and Sheng, as applied
to claims 1 and 9, further in view of Wu is reversed.
The rejection of Claims 3, 11, and 17 under 35 U.S.C. §103(a)
as being unpatentable over Gardner in view of Arnold and Sheng as
applied to claims 1 and 9, further in view of Peidous is reversed.
The rejection of Claims 15, 16, 18, and 20 under 35 U.S.C.
§103(a) as being unpatentable over Gardner in view of Arnold,
Sheng, and Wu is reversed. The rejection of Claim 17 under 35
U.S.C. § 103(a) as being unpatentable over Gardner in view of
Arnold and Sheng as applied to claim 15, further in view of
Peidous is reversed.
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REVERSED

EDWARD C. KIMLIN )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
JAMES T. MOORE )
Administrative Patent Judge ) APPEALS AND
)
) INTERFERENCES
)
LINDA R. POTEATE )
Administrative Patent Judge )

JTM/ki
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Application No. 09/624,025

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