Journal of The Electrochemical Society, 158 ͑1͒ D1-D5 ͑2011͒
D1
0
013-4651/2010/158͑1͒/D1/5/$28.00 © The Electrochemical Society
Atomic Layer Deposition of Ni Thin Films and Application
to Area-Selective Deposition
a
b
c
e
Woo-Hee Kim, Han-Bo-Ram Lee, Kwang Heo, Young Kuk Lee,
e
e
c,d
a
Taek-Mo Chung, Chang Gyoun Kim, Seunghun Hong, Jong Heo, and
b, ,z
Hyungjun Kim *
a
Department of Material Science and Engineering, Pohang University of Science and Technology, Pohang
7
90-784, Korea
b
School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea
Department of Physics and Astronomy and Interdisciplinary Program in Nano-Science and Technology,
c
d
Seoul National University, Seoul 151-747, Korea
e
Advanced Materials Division, Korea Research Institute of Chemical Technology, Daejeon 305-600, Korea
Ni thin films were deposited by atomic layer deposition ͑ALD͒ using bis͑dimethylamino-2-methyl-2-butoxo͒nickel ͓Ni͑dmamb͒2͔
as a precursor and NH3 gas as a reactant. The growth characteristics and film properties of ALD Ni were investigated. Low-
resistivity films were deposited on Si and SiO2 substrates, producing high-purity Ni films with a small amount of oxygen and
negligible amounts of nitrogen and carbon. Additionally, ALD Ni showed excellent conformality in nanoscale via holes. Utilizing
this conformality, Ni/Si core/shell nanowires with uniform diameters were fabricated. By combining ALD Ni with octadecyl-
trichlorosilane ͑OTS͒ self-assembled monolayer as a blocking layer, area-selective ALD was conducted for selective deposition of
Ni films. When performed on the prepatterned OTS substrate, the Ni films were selectively coated only on OTS-free regions,
building up Ni line patterns with 3 m width. Electrical measurement results showed that all of the Ni lines were electrically
isolated, also indicating the selective Ni deposition.
©
2010 The Electrochemical Society. ͓DOI: 10.1149/1.3504196͔ All rights reserved.
Manuscript submitted December 15, 2009; revised manuscript received July 16, 2010. Published November 9, 2010.
As scaling continues in order to improve device integration in the
complementary metal-oxide-semiconductor ͑CMOS͒ process, the
silicidation process becomes more essential for lowering contact re-
properties of the films can be hydrophobic or hydrophilic, depending
on the end groups of the SAMs. Previous studies on AS-ALD have
been limited to research fields of some oxide materials, such as
1
16-21
sistance and increasing drive currents. TiSi and CoSi have been
ZrO2, HfO2, ZnO, and TiO2.
AS-ALD processes for metal have
2
2
extensively investigated as contact materials. However, these mate-
only been reported for Ru, Pt, and Ir, all of which are deposited
2
2-25
rials have been reported to cause increased series resistance of de-
using O2 gas as a reactant.
AS-ALD using other reactant gases
2
6
2
such as NH3 or H2 has rarely been studied. Recently, we have
vices at the sub-65 nm technology node. In addition, TiSi exhibits
2
3
reported the AS-ALD of Co using bis͑N,NЈ-diisopropyl-
the narrow line effect. Although CoSi lines depend less on the
2
acetamidinato͒cobalt͑II͒ ͓Co͑iPr-AMD͒ ͔ as a precursor and NH
sheet resistance, the greater consumption of Si is a major concern in
forming silicide with the decreased junction depth. Also, both ma-
terials require a two-step annealing process to form a low resistive
2
3
2
7
and H2 as reactants.
For this study, we developed a new Ni ALD process utilizing
Ni͑dmamb͒ as a Ni precursor and NH gas as a reactant. The ALD
3
phase. Because of these problems, NiSi is being investigated as a
2
3
contact material for application in nanoscale devices and shows no
linewidth effects, low resistivity, low Si consumption, low process
Ni films showed low resistivity and contained only a minimal
2,9
amount of oxygen and no nitrogen and carbon. Notably, nitrogen
and other impurities were not incorporated into the Ni films in spite
4
temperature, and a one-step annealing process.
of using the NH reactant. Additionally, the ALD Ni process was
The Ni metal deposition process is a key requirement in the
formation of Ni silicide contacts. Among the various thin film depo-
sition techniques, atomic layer deposition ͑ALD͒ is a promising
method which exhibits good conformality and uniformity, atomic
scale thickness controllability, and low impurity contamination at a
low growth temperature due to its growth mechanism based on a
3
applied to AS-ALD using octadecyltrichlorosilane ͑OTS͒ SAM as a
blocking layer. The ALD Ni films were selectively deposited onto
the prepatterned OTS lines, forming well-defined Ni lines.
Experimental
5-7
self-limited surface reaction. However, in spite of its importance
in nanoscale device contact applications, there are only a few reports
For this study, a commercial ALD chamber ͑Quros Plus 150͒
with a loadlock chamber was used. This system had a double shower
head system for better uniformity. Further information on the cham-
2,8-13
on the ALD of Ni films.
In an early study, Chae et al. reported
2
8
ber configuration can be found in our previous report. The Ni
precursor Ni͑dmamb͒2 was contained in a stainless steel bubbler
maintained at a temperature of 70°C to produce a suitable vapor
pressure. The Ni͑dmamb͒2 molecules generated were carried into
the main chamber by Ar carrier gas at a flow rate of 50 sccm. Ar gas
at the same flow rate was also used for purging the excess gas
molecules and by-products between each precursor and exposure
the formation of Ni films by H plasma reduction of ALD NiO films
2
using bis͑cyclopentadienyl͒nickel ͓NiCp ͔ as a precursor and water
2
9
as a reactant. Later, Do et al. reported a Ni ALD process using a
2
Ni͑dmamb͒ precursor and H as the reactant gas. However, the Ni
2
2
films deposited in these studies contain a large amount of carbon,
2
,9
which may have caused high resistivity. These results suggest that
a combination of a proper precursor and reactant should be intro-
duced to produce pure metal Ni films with low resistivities.
step. For ALD Ni, the NH gas reactant at a flow rate of 400 sccm
3
was delivered to the reaction chamber. The substrate temperature
was maintained at 300°C. One ALD deposition cycle consisted of
In addition, area-selective ALD ͑AS-ALD͒ using self-assembled
monolayers ͑SAMs͒ is attracting attention because it is simple and
requires no expensive patterning processes, such as lithography and
etching. Several groups have utilized AS-ALD for various applica-
four steps: Ni͑dmamb͒2 precursor exposure ͑t ͒, Ar purging ͑t ͒,
s
p
NH gas reactant exposure ͑t ͒, and another Ar purging ͑t ͒. The
3
r
p
1
4,15
tions, such as fuel cell and solar cell fabrication.
The surface
times ts and tp were fixed at 4 and 1 s, respectively, and tr was
systematically varied from 2 to 12 s. Si͑001͒ and SiO ͑100 nm͒/
2
Si͑001͒ substrates were used. The Si͑001͒ substrates were cleaned
by dipping in a buffered oxide etchant ͑6:1͒ for 10 s, followed by a
deionized ͑DI͒ water rinsing and N2 blowing, resulting in
*
Electrochemical Society Active Member.
E-mail: hyungjun@yonsei.ac.kr
z