Overview of my PhD research, for those who are not engineers or scientists.

1. Doctoral Research Overview
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
Amount of assumed background knowledge and information:
Assumed knowledge areas: Basic chemistry and physics

2. Outline
Why are new ways of
making thin layers of
materials important?
What is chemical
vapor deposition?
What needs figuring out?
Key findings

3. Why are new ways of making thin layers of materials
important?

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. Integrated circuits are made layer by layer by
depositing thin layers or films of materials
http://www.rigalab.com/Images/cross_section.jpg
webmedia.national.com/ gallery/52/52_rgb.jpg
Every material needed for an integrated circuit needs to be
deposited as a thin film.

7. 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 making smaller chips,
thin films of new materials are required.

8. What is chemical vapor deposition?

9. What is Chemical Vapor Deposition?
Precursor 1 2 3 4 5
Precursor Reactant Chemical Volatile product Atom of film Atom of film
reaction
Substrate
A main starting The precursor The precursor and New molecules are Whatever isn’t the film
molecule, called molecule may ‘meet’ reactant react. now attached to the leaves the surface.
precursor, arrives at another molecule it Sometimes the warm substrate, one of Here we are growing a
the hot growth needs to react, called surface alone can which is hopefully the film of purple balls
surface, the substrate, a reactant. cause this step by material we wanted to rather than green.
inside a vacuum making the precursor grow.
chamber. decompose.
Substrate Thermometer
A substrate up close, outside the chamber.
Chemical Vapor Deposition (CVD) is a way of
growing thin layers of materials, also called films.

10. What needs figuring out?

11. The two major constraints for circuits are
temperature and obtaining uniform coatings
Deep features need coating,
Dopants diffuse with heat
but this is difficult to do evenly
Dopants
Si
Δ
Si Dopants
If dopants do not stay where
they were put, the chips cease
to function. http://www.pressebox.de/pressemeldungen/infineon-technologies-ag/boxid-28544.html
How do you deposit the films at low temperature
and do it evenly?

12. Deep holes need uniform coatings, but this is often
slow
} ttop
The ideal: completely uniform (conformal), fast coating.
Conformality = (ttop/tbottom)·100%
} tbottom
Conformal coating.
The problem: the hole ‘clogs’ at the top - pinch-off.
Pinch-off.
The impractical compromise: grow slowly so that the
hole doesn’t have time to pinch off.
Conformal coating, but slow growth.
An opportunity exists to find a process that is fast
but retains the uniformity of the coating.

13. If the incoming molecules do not stick where they
land first, conformality is possible
High sticking probability Low sticking probability
Precursor Nearly conformal
Precursor The deposited
atoms quickly molecules bounce coverage.
molecules react
cause pinch-off. off the walls into
or stick nearly
the trench.
instantly
If the incoming molecules don’t stick immediately,
coatings are more likely to be uniform.

14. Traditional CVD has a high reaction probability
Traditional CVD O
(at high temperatures) C
O
Ru C C
C C O
O O
C
C O
C
C
O
Ru
O
Ru
O
Traditional CVD often leads to pinch-off.

15. With the right starting molecule, temperatures can
be kept low and improve the conformality
High temperatures C
C C
O
Ru
O O
Si Dopants
Dopants diffuse, ruining chip
Incoming molecules react as soon as
they reach the surface, causing pinch-off
Low temperature
Dopants
Si
Incoming molecules do not react
Dopants stay
immediately enabling conformality

16. Precursor design is key to novel CVD process
development
Enhance CVD conformality: Appropriate precursor stability:
Low sticking probability Stable during handling
L M L
Reactive at low T
Precursor Nearly conformal L
molecules bounce coverage.
off the walls into L M M
the trench.

17. Competitive advantage: collaboration with the
Girolami chemistry group
Girolami group: Innovative new chemistry
Abelson group: State of the art vacuum
chamber for growth
State of the art analysis techniques at the
Center of Microanalysis of Materials

18. Key finding

19. Precursor design is key to novel CVD process
development
Choose ligands purposefully: Choose clever co-reactant:
Ruthenium project Manganese nitride project
Siteblocking by ligands Lability enables low-T CVD
t-Bu t-Bu
N Mn N + NH3
t-Bu t-Bu
Ru
C
C C
O
O O 80 ºC and up
t-Bu H t-Bu
N Mn N + H N
L L L
t-Bu H t-Bu