Doctoral research project on depositing thin layers of manganese nitride for future computer chips.

1. Chemical Vapor Deposition
of Manganese Nitride
Teresa S. Spicer, PhD, PMP
teresa.s.spicer@gmail.com
http://www.linkedin.com/in/teresaspicer
• Doctoral research performed at the Department of Materials Science and Engineering at the University
of Illinois at Urbana-Champaign, in collaboration with chemistry students in Dr. Gregory S. Girolami’s
research group
• Submitted to Chemistry of Materials for publication, published in doctoral thesis in October 2009
Amount of assumed background knowledge and information:
Assumed knowledge areas: Basic chemistry and physics knowledge, chemical nomenclature, ball and
stick structures, lability due to spin states, the basics of chemical vapor deposition as a technique,
familiarity with a variety of materials characterization techniques and ability to interpret the raw data from
them

2. Outline
Introduction
Problem Statement
Experiments
Results
Key Findings

3. Introduction

4. Integrated circuits have created a vital industry and
enabled the telecommunications revolution
Global Semiconductors Market Value, $ billion, 2004-2013(e)
350 9
J 8
Market value (USD billions)
300
7
250 J
J J 6
J
% Growth
200 5
J
150 4
J
3
100 J
J 2
50
1
0 0
2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Source: Datamonitor
Image from http://www.textually.org/
Semiconductor industry plays an important role in globalization,
and therefore also in shaping our collective future.

5. Miniaturization drives integrated circuit development
and applications
Image from http://tunicca.wordpress.com/2009/07/21/moores-law-the-effect-on-productivity/

6. Materials and thin film processing are key to
miniaturization
2007: 30 new materials introduced into 45-nm node1
1 A Thorough Examination of the Electronic Chemicals and Materials Markets, Businesswire, August 15, 2007
Image from http://www.intel.com/pressroom/kits/45nm/photos.htm
❝The implementation of high-k and
metal materials marks the biggest
change in transistor technology
since the introduction of polysilicon
gate MOS transistors in the late
1960s.❞
Gordon Moore, Intel Co-Founder, regarding two of the 30
new materials introduced in 2007
In order to continue miniaturization,
thin films of new materials are required.

7. Manganese nitride CVD could be used in both
electronic and spintronic devices
Magnetic layers in microelectronics
• Mn4N is ferrimagnetic
• Mn3N2, MnN are antiferromagnetic
http://static.howstuffworks.com/gif/recover-data-hard-drive-2.jpg
Mn doping of GaN for spintronics
• Ga1-xMnxN is a magnetic semiconductor at RT
• Current Mn source: Manganocene, high T required
http://www.wmi.badw-muenchen.de/research/images/electron.jpg

8. Synthetic inorganic chemistry and materials
engineering are required for new CVD processes
Synthetic inorganic
Materials engineering
chemistry
Conception and synthesis of new
CVD of films from precursor
CVD precursor candidates
Process hypothesis
development
Synthesis of modified precursor Measurement of film properties
Development of novel growth processes and chemistry
are needed to develop good CVD processes.

9. Problem Statement

10. Many previous transition metal nitrides have been
deposited from amides reacted with ammonia
Tried-and-true concept:
R
R
N
N M N
+ H H
R R H
Example: Tetrakis(dimethylamido)-titanium(IV) + NH3 → TiN films1-4
1 Dubois, L. H.; Zegarski, B. R.; Girolami, G. S. J. Electrochem. Soc. 1992, 3 Prybyla, J. A.; Chiang, C. M.; Dubois, L. H. J. Electrochem. Soc. 1993, 2695–
3603–3609. 2702.
2 Dubois, L. H. Polyhedron 1994, 13, 1329–1336. 4 Fix, R. M.; Gordon, R. G.; Hoffman, D. M. Chem. Mat. 1990, 235–41.
Dialkylamide precursors in particular
have worked very well in the past.

11. Previously, few volatile precursors for Mn-N were
known
Shannon-Prewitt Crystal Ionic Radii of Cations1
Most common oxidation state shown in bold.1
Scandium Titanium Vanadium Chromium Manganese Iron Cobolt Nickel Copper Zinc
21 22 23 24 25 26 27 28 29 30
Sc Ti V Cr Mn Fe Co Ni Cu Zn
44.956 47.867 50.942 51.996 54.938 55.845 58.933 58.693 63.546 65.39
+3 +2 +2 +2 +2 +2 +2 +2 +2 +2
88 pm 100 pm 93 pm 94 pm 97 pm 92 pm 88 pm 83 pm 91 pm 88 pm
+3 +3 +3 +3 +3 +3 +3 +3
81 pm 78 pm 75 pm 78 pm 78 pm 75 pm 74 pm 87 pm
+4 +4 +4 +4 +4 +4
74 pm 72 pm 69 pm 67 pm 72 pm 67 pm
+5 +6 +7
68 pm 58 pm 60 pm
1 Wulfsberg, G. Principles of Descriptive Inorganic Chemistry. University Science Books, Sausalito, CA, 1991.
Due to the size of Mn(II), sterically bulky ligands are required to
prevent di- or polymerization of the precursor.

12. Bis[di(tert-butyl)amido]manganese(II) is a monomer
and volatile
30% probability surfaces shown.
Spicer, C. W. Synthesis, Characterization and Chemical Vapor Deposition of Transition Metal Di(tert-butyl)amido Compounds. Doctoral dissertation,
University of Illinois at Urbana-Champaign: Urbana, IL, 2008.
When reacted with ammonia, bis[di(tert-butyl)amido]Mn(II)
should give manganese nitride films.

13. Experiments

14. Films were deposited with and without ammonia
Deposition in vacuum chamber
➡ In-situ ellipsometer monitors growth
➡ Precursor heated to 40 ºC
➡ N2 carrier gas
H N H
Experiment sets: Substrates:
H
With NH3 • Si(100)
• Varying T, constant NH3 flow
• α-C TEM grids
• Varying NH3 flow, constant T
Experiment set: Substrates:
Without NH3
• Cr-coated Si(100)
• Varying T

15. Film phase, composition, roughness, and
microstructure data were collected
Deposition in vacuum chamber
➡ In-situ ellipsometer monitors growth
➡ Precursor heated to 40 ºC
➡ N2 carrier gas
With NH3 Without NH3
Atomic force microscopy X-ray diffraction
Transmission electron microscopy* Scanning electron microscopy
X-ray photoelectron spectroscopy Auger electron spectroscopy
* Select films

16. Results

17. The growth rates are high considering the low
growth temperatures
Ammonia flow: 4.3 sccm
Precursor partial pressure: 0.2 - 0.4 mTorr
Total chamber pressure: 1.6 mTorr
The reaction between bis[di(tert-butyl)]amidoMn(II)
and ammonia is very facile.

18. In the absence of ammonia, severely carbon-
contaminated films of Mn are obtained
Auger electron spectrum of Mn film grown at 300 ºC
41.5 at. % C
38.4 at. % O
20.0 at. % Mn
Ammonia is key to growing films of manganese nitride.

19. The reaction is likely a transamination
First step of tetrakis(dimethylamido)Ti(IV) transamination
Me Me Me Me
N N
Me Me Me H Me
N Ti N + NH3 N Ti N + H N
Me N Me Me N H Me
Me Me Me Me
Analogous first step of bis[di(tert-butyl)amidoMn(II) transamination
t-Bu t-Bu t-Bu H t-Bu
N Mn N + NH3 N Mn N + H N
t-Bu t-Bu t-Bu H t-Bu
The analogous results in other respects suggest
that the reaction mechanism is also analogous.

20. Films can be deposited at temperatures as low as
80ºC in the presence of ammonia
H N H
H
With NH3 Without NH3
• No growth until 400 ºC
• Even at 400 ºC, growth
rate is only 0.4 nm/min
500 nm
• Growth rate is 2.1 nm/min
The reaction between bis[di(tert-butyl)]amidoMn(II)
and ammonia is very facile.

21. The film phase and composition depend on growth
temperature
XRD diffractograms
(101) η-Mn3N2 AES-derived elemental
Mn2N1.08 compositions
(420) (422)
Mn23C6
(611)
(440) (531) (102) (110) (0 0 10)
Mn
Intensity (Arbitraty units)
N
C
35 40 45 50 55 60 65 70 75 80 85
2-theta
(103) (110) (202) (213) (206)
(006) (200)
The film grown at 300 ºC is markedly different
from those grown at 200 ºC and below.

22. 80-100 ºC: Crystalline grains of η-Mn3N2 embedded
in an amorphous matrix
XRD diffractogram Brightfield TEM image
Insets: convergent-beam
diffraction patterns from nm-
sized areas indicated in image
The extremely low growth temperature inhibits complete
crystallization of the films at 80 and 100 ºC.

23. 200ºC: Fully crystalline films of η-Mn3N2
TEM images and patterns
Left: Convergent-beam diffraction patterns
from six different nm-sized areas
Below: Brightfield image with diffraction
pattern inset
XRD diffractogram
The high-quality crystallinity at merely 200 ºC is unusual.

24. 300 ºC: 40% Mn3N2, 40% Mn2N1.08, 20% Mn23C6
XRD diffractogram
(101)
(103)
(420)
900 (422)
η-Mn3N2
800
Mn2N1.08
700
Mn23C6
Intensity (counts)
1 µm
600 (110)
(006)
500 (611)
400 AES elemental composition
300 (440) (102)
(202)
• 67% Mn
200 (531) (200) (110) (0 0 10)
100
(213) (206) • 16% N
0 • 17% C
35 40 45 50 55 60 65 70 75 80 85
2-theta
At 300 ºC, the ammonia supply may have
been insufficient to deposit a single phase.

25. The crystallinity and high growth rates can be
attributed to high-spin Mn(II)
High growth rates for low temperatures Low-temperature crystallinity
Any growth at 80ºC is surprising, especially at Convergent-beam diffraction patterns from
rates of several nanometers a minute six different nm-sized areas, all showing
diffraction through crystalline η-Mn3N2
6
J
5
Growth rate (nm/min)
J
4
J
3
2 J
1
0
0 50 100 150 200 250 300 350
Deposition temperature (ºC)
Surface species are likely to remain reactive and mobile and can
settle into low-energy ordered arrangements.

26. Key Findings

27. CVD of Manganese Nitride
• Very facile, due to the lability of high-spin Mn(II)
• Transamination of precursor with ammonia
• Films of η-Mn3N2 films can be grown at 80ºC

28. Acknowledgements
Dr. Charles Spicer, UNCC
Dr. Bong-Sub Lee, UIUC
Kristof Darmawikarta, UIUC
Dr. Angel Yanguas-Gil, UIUC
Dr. Mauro Sardela, UIUC
Nancy Finnegan, UIUC (Ret.)
Dr. Tim Spila, UIUC
Dr. Richard Haasch, UIUC
Subhash Gujrathi, Université de Montreal
Research supported by NSF grant DMR-0420768
Film characterization was carried out in the Center for Microanalysis of Materials,
University of Illinois, which is partially supported by the U.S. Department of
Energy under grant DEFG02-91-ER45439