Ex Parte YOON et al

Patent Trial and Appeal Board

Sep 29, 2016

12950952 (P.T.A.B. Sep. 29, 2016)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE
12/950,952 11/19/2010
119049 7590 10/03/2016
MPG, LLP and Lam Research Corp.
Albert Penilla
710 Lakeway Drive
Suite 200
Sunnyvale, CA 94085
FIRST NAMED INVENTOR
Hyungsuk Alexander YOON
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www .uspto.gov
ATTORNEY DOCKET NO. CONFIRMATION NO.
LAM2P583.DIV1 8762
EXAMINER
CHI, SUBERR L
ART UNIT PAPER NUMBER
2829
NOTIFICATION DATE DELIVERY MODE
10/03/2016 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address( es):
lamptomail@mpiplaw.com
mpdocket@mpiplaw.com
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte HYUNGSUK ALEXANDER YOON and
FRITZ REDEKER1
Appeal2014-004856
Application 12/950,952
Technology Center 2800
Before CHUNG K. PAK, MARK NAGUMO, and
CHRISTOPHER C. KENNEDY, Administrative Patent Judges.
PAK, Administrative Patent Judge.
DECISION ON APPEAL
Appellants timely appeal under 35 U.S.C. § 134(a) from the Final
Action2 rejecting claims 1-20, which are all of the pending claims in the
above-identified application. We have jurisdiction. 35 U.S.C. § 6.
We affirm.
1 The real party in interest is listed as Lam Research Corporation. (Appeal
Brief filed October 23, 2013 ("App. Br."), 3.)
2 Final Action entered December 19, 2012 ("Final Act.").
Appeal2014-004856
Application 12/950,952
STATEMENT OF THE CASE
The subject matter on appeal relates to"[ m ]ethods of depositing a
barrier layer[, such as a metal nitride layer, with a step-wise decreasing
nitrogen concentration] on an interconnect structure [formed on a dielectric
layer] in an atomic deposition environment" and then forming a copper layer
(conductive layer) over the barrier layer. (Spec. ,-i,-i 6 and 31.) Figures 3D
and 3C, which show a barrier layer with a step wise decreasing nitrogen
concentration, are reproduced below:
c,
Co::~:::,m Ci ---Eb:
Cs , , , -:.- , , '
' '
................................ ~ .................................... : ................................................................................................................................................ ...
FiG. 30
TarCTst~~
ti
Cc:1G;}:1trs;~cn
FIG. 3C
"Figure 3D shows that the nitrogen concentration [step-wisely] decreases
with film thickness in three steps." (Id. ,-i,-i 40 and 18.) Figure 3C shows a
nitrogen concentration profile which can be formed "[ w ]hen the steps in
Figure 3D is numerous[.]" (Id.) "However, the number of steps [employed]
could be two or greater than three." (Id.) This deposition method allows the
highest nitrogen concentration part of the barrier layer to be located where
the barrier layer is in contact with the dielectric layer and the lowest nitrogen
concentration part of the barrier layer to be located where the barrier layer is
in contact with the copper layer. (Id. ,-i,-i 5-7.) The barrier layer "can yield
good adhesion with the dielectric layer surrounding the interconnect
2
Appeal2014-004856
Application 12/950,952
structure and also with the copper layer that covers the barrier layer to
improve yield and electro-migration performance and to reduce the risk of
stress-induce voiding of copper interconnect." (Id. iii! 4.)
Figure 2, which shows a dual damascene interconnect structure with a
barrier layer and cooper layer, is reproduced below:
FIG. 2
Figure 2 shows an interconnect structure having "a dielectric layer 115,
which was previous fabricated to form a metallization line 101 therein." (Id.
iJ 32.) "The metallization line [101] is typically fabricated by etching a
trench into the dielectric [layer] 106 [(sic, 115)] and then filling the trench
with a conductive material, such as copper [material 122]." (Id.) A barrier
layer 120 in the trench is used to prevent the copper material 122 from
diffusing into the dielectric layer 115. (Id. iJ 33.) "A [dielectric] barrier
layer 102 is deposited over the planarized copper material 122 to protect the
copper material 122 from premature oxidation when via holes 114 [and
trenches 116] are etched through overlying dielectric material 106 to the
dielectric barrier layer 102." (Id. iJ 34.) "The dielectric barrier layer 102 is
3
Appeal2014-004856
Application 12/950,952
also configured to function as a selective etch stop and a copper diffusion
barrier." (Id.) Once the via holes 114 and the trenches 116 are etched, a
barrier layer 130 is deposited. (Id. iJ 36.) A copper layer 132 is then
deposited to fill the via holes 114 and the trenches 116. (Id.) The barrier
layers 120 and 130 can be made of refractory metals, including tantalum
nitride (TaN), tantalum (Ta), and a combination of these films. (Id. iii! 33
and 36.) "Atomic layer deposition (ALD), pulsed CVD, or cyclic layer
deposition processes can be used to achieve good step coverage of the
barrier layer." (Id. iJ 36.)
Details of the appealed subject matter is illustrated in representative
claim 1 which is reproduced below from the Claims Appendix of the Appeal
Brief:
1. A method of depositing a barrier layer on an interconnect
structure in an atomic deposition environment, comprising:
(a) depositing a barrier layer on the interconnect structure with a first
nitrogen concentration during a first phase of deposition in the atomic
deposition environment, the interconnect structure being formed on and in
contact with a dielectric layer; and
(b) continuing the deposition of the barrier layer on the interconnect
structure with a second nitrogen concentration during a second phase
deposition in the atomic deposition environment, wherein the nitrogen
concentration step-wisely decreases from the first nitrogen concentration in
the first phase of depositing the barrier layer to the second nitrogen
concentration in the second phase of depositing the barrier layer, and the
first nitrogen concentration is highest where the barrier layer is in contact
with the dielectric layer, upon concluding the deposition of the barrier layer,
applying a barrier flash layer over the barrier layer; and
( c) forming a copper layer over the barrier flash layer, such that a
nitrogen concentration in the barrier layer is lowest where the barrier layer is
in contact with the copper layer;
the atomic deposition environment implements a sequential pulsing of
process gases to form the barrier layer.
4
Appeal2014-004856
Application 12/950,952
(App. Br. 15, Claims Appendix; disputed limitations highlighted in
italicized form. )3
The Examiner maintains, and Appellants seek review of, the
following grounds of rejection:
I. Claims 1-6 and 8-20 under 35 U.S.C. § 103(a) as unpatentable over
the combined teachings of Lee et al. (US 2005/0156316 Al, published
July 21, 2005) ("Lee"), Seutter et al. (US 2005/0164487 Al,
published July 28, 2005) ("Seutter"), and Besling et al. (Copper alloy
seed integration for reliability improvement, 82 Microelectronic
Engineering 254-260 (2005)) ("Besling"); and
II. Claim 7 under 35 U.S.C. § 103(a) as unpatentable over the combined
teachings of Lee, Seutter, Besling, and Werkhoven et al. (US
6,933,225 B2, issued Aug. 23, 2005) ("Werkhoven"). 4 (Final Act. 1-
3 Appellants only argue common limitations present in independent claims 1
and 14, the only independent claims on appeal, as a basis for the
patentability of all of the claims on appeal. Thus, for purposes of this
appeal, we select claim 1 as representative and decide the propriety of the
Examiner's§ 103(a) rejections of record. See 37 C.F.R. § 41.37(c)(l)(iv)
(2013).
4 Although the Examiner inadvertently omits Besling in rejecting claim 7 in
the statement of rejection, it is clear from the record that the Examiner relies
upon all three references (Lee, Seutter, and Besling) used in rejecting
independent claim 1, together with an additional reference, Werkhoven, to
reject dependent claim 7. (Non-Final Action entered on August 1, 2012
("Non-Final Act.") 2-13; the Amendment filed November 14, 2012; Final
Act. 2-13; and App. Br. 13.) Moreover, Appellants only rely on the same
arguments advanced in connection with claim 1 to impart patentability to
claim 7. (App. Br. 13.) Appellants do not argue that the limitation
"applying a barrier flash layer over the barrier layer" in claim 1, which
5
Appeal2014-004856
Application 12/950,952
13; Examiner's Answer entered January 14, 2014 ("Ans.") 2-5; App.
Br. 5-6; and Reply Brief filed March 14, 2014 ("Reply Br.") 3.)
DISCUSSION
Upon consideration of the evidence on this appeal record in light of
the respective positions advanced by the Examiner and Appellants, we
determine that a preponderance of the evidence supports the Examiner's
determination that the applied prior art would have rendered the subject
matter recited in claims 1-20 obvious to one of ordinary skill in the art
within the meaning of 35 U.S.C. § 103(a). Accordingly, we sustain the
Examiner's§ 103(a) rejections of the above claims essentially for the
reasons set forth in the Final Action and the Answer. We add the following
primarily for emphasis and completeness.
The Examiner finds, and Appellants do not dispute, that Lee teaches
depositing a barrier layer 24 on an interconnect structure being formed on
and in contact with a dielectric layer l 6a, l 6b, 20a, and 20b and forming a
copper layer 26 or 26a over the barrier layer 24. (Compare Final Act. 3 with
App. Br. 6-12; see also Lee ,-i,-i 36, 39--47 and Figs. 1-3.) The Examiner
also finds, and Appellants do not dispute, that Lee discloses depositing a
refractory metal nitride material, preferably a tantalum nitride, to form a
barrier layer 24 having a graded concentration of nitrogen so that a lower
nitrogen concentration part of the barrier layer 24 is adjoining the copper
layer 26 or 26a and a higher nitrogen concentration part of the barrier layer
24 is adjoining the dielectric layers 16a, 16b, 20a, and 20b. (Compare Final
Act. 3-4 with App. Br. 6-12; see also Lee ,-i,-i 21, 52 and Figs. 1-3.)
according to the Examiner, is taught by Besling, imparts patentability to
claim 7. (Id.)
6
Appeal2014-004856
Application 12/950,952
According to paragraphs 19 through 22 of Lee, this barrier layer can be
readily fabricated and can provide "inhibited interdiffusion and enhanced
performance" to a microelectronic fabrication.
Appellants contend that Lee, Seutter, and/or Besling would not have
taught or suggested using ALD (atomic layer deposition) involving a
sequential pulsing of process gases (e.g., a tantalum precursor gas and a
nitrogen-containing gases) to deposit a metal nitride barrier film with a step-
wisely decreasing nitrogen concentration, as recited in claim 1. (App. Br.
6-12.) In support of this position, Appellants focus on Seutter's ALD
involving the use of a sequential pulsing of process gases (e.g., a tantalum
precursor gas and a nitrogen-containing gas) to form a tantalum nitride
barrier layer that does not have a graded nitrogen concentration. (Id. at
7-12.) However, we are not persuaded of any reversible error.
Although Lee generally prefers using reactive sputtering physical
vapor deposition (PVD) methods as indicated by Appellants, it does not
preclude using other conventional depositing methods known in the art to
deposit a metal nitride barrier layer 24 having a graded or step wise
decreasing concentration of nitrogen. (Ans. 3; Lee iii! 23, 54-55.) In
particular, Lee, at paragraphs 54 and 55, teaches that:
[0054] A nitrogen graded refractory metal nitride
material for use within the blanket conductor barrier layer 24 in
accord with the present invention may be formed employing
any of several methods as are conventional in the art of
microelectronic fabrication ....
[0055] The nitrogen graded refractory metal nitride
material for use within the blanket conductor barrier layer 24
may be continuously graded (through appropriate continuous
adjustment of deposition parameters (i.e., nitrogen flow rate), or
7
Appeal2014-004856
Application 12/950,952
discontinuously graded (through appropriate step wise
adjustment of deposition parameters).
In other words, Lee teaches forming a metal nitride barrier layer 24 having a
graded or step wise decreasing concentration of nitrogen via appropriately
adjusting deposition parameters of conventional deposition methods, which
according to paragraph 10 of Seutter, includes ALD.
The Examiner also finds, and Appellants do not dispute, that:
Seutter impliedly suggests that ALD has few side effects for
barrier layer integration (Seutter: paragraph [0009]), and also
teaches that ALD has good step coverage and conformality
(Seutter: paragraph [0052]), precision controlled thicknesses
(Seutter: paragraph [0052]), and a reduction in the generation of
unwanted particles (Seutter: paragraph [0052]).
(Compare Ans. 3 with App. Br. 6-12 and Reply Br. 3-8.)5
The Examiner further finds, and Appellants do not dispute, that
Seutter teaches using atomic layer deposition (ALD) employing a sequential
pulsing of process gases, namely a barrier metal precursor gas and a
nitrogen-containing precursor gas, to react with one another to deposit a
5 Page 255 of Besling also teaches that "[a]pplying atomic layer deposition
(ALD)[,] in place of conventional PVD, enlarges the copper volume in the
lines by more than 10% for the 65 nm node, resulting in a significant
improvement in RC behavior." However, because "the adhesion of copper
on ALD TaN is poor and this could result in easy delamination, poor yield,
and reduced reliability behavior ( electromigration life time, stress induced
voiding)[,]" Besling teaches depositing a PVD Ta-flash layer over the ALD
TaN barrier, which will "ensure[] a good electromigration behavior." (Final
Act. 5; Besling pp. 255-256.) Indeed, there is no dispute that one of
ordinary skill in the art would have been led to apply a Ta-flash layer (the
barrier flash layer recited in claim 1) directly over the ALD TaN barrier
layer, as taught by Besling, in the method of manufacturing a
microelectronic fabrication suggested by Lee and Seutter. (Compare Final
Act. 5 with App. Br. 6-12.)
8
Appeal2014-004856
Application 12/950,952
metallic nitride barrier layer, such as a tantalum nitride barrier layer.
(Compare Final Act. 4 and Ans. 3 with App. Br. 6-12 and Reply Br. 3-8.)
The fact that Seutter teaches using an excessive amount (more than a
stoichiometric amount) of a nitrogen-containing gas6 to chemisorb nitrogen
onto a tantalum layer to form a nitrogen-rich (tantalum nitride) barrier layer
does not detract one of ordinary skill in the art from forming Lee's
advantageous metal nitride barrier layer having a graded or step wise
decreasing concentration of nitrogen via appropriately adjusting deposition
parameters of the advantageous conventional ALD taught by Seutter.
(Compare Final Act. 4-5 and Ans. 2-5 with App. Br. 7-8 and Reply Br
3-8.) Lee, by virtue of teaching the employment of appropriate deposition
parameters for conventional deposition methods, including ALD, to deposit
a metal nitride barrier layer having a gradient or step wise concentration of
nitrogen as indicated supra, implies that the determination of the optimum
deposition parameters for conventional depositing methods, including ALD,
for such purposes is well within the ambit of one of ordinary skill in the art.
See In re Aller, 220 F.2d 454, 456 (CCPA 1955) ("where the general
conditions of a claim are disclosed in the prior art, it is not inventive to
discover the optimum or workable ranges by routine experimentation.")
6 According to Appellants, Seutter teaches using an excessive amount (more
than a stoichiometric amount) of a nitrogen-containing gas such that after
reacting or saturating all of the available reaction sites in tantalum with
nitrogen, there is still an unreacted excess amount of nitrogen-containing gas
that needs to be removed. (App. Br. 8.) When substantially less than a
stoichiometric amount of a nitrogen-containing gas is used, one of ordinary
skill in the art would have reasonably expected that there is leftover tantalum
or metal reaction sites which have not reacted with nitrogen (thereby
forming a less nitrogen-rich metal nitride barrier layer).
9
Appeal2014-004856
Application 12/950,952
Under the above circumstances, we concur with the Examiner that the
collective teachings of the applied prior art references would have rendered
the subject matter recited in claims 1-20 obvious to one of ordinary skill in
the art within the meaning of 35 U.S.C. § 103(a).
ORDER
It is ORDERED that the Examiner's decision rejecting claims 1-20
under 35 U.S.C. § 103(a) is AFFIRMED.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § l.136(a).
AFFIRMED
10