Enhancement of the film growth rate by promoting

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Enhancement of the film growth rate by
promoting iodine absorption in the
catalyst-enhanced chemical vapor deposition of Cu
Oh-kyum Kwon, Hyun-Bae, Sang-Won Kang
(KAIST) Hyung-Sang Park (Genitech)
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Introduction
The metalorganic chemical vapor deposition(MOCVD)
of Cu has been extensively studied as an
essential element for realizing it high potential
for conformal film formation on complex shaped
surfaces. Hwang and Lee reported that iodine was
also able to act as a catalytic surfactant in
Cu MOCVD. ? Iodine enhances the film growth rate
by weakening the ionic Cu - (?-diketonate)-
bond and the surface roughness of the deposited
Cu films. 20nm Cu / 45nm TaN / 100nm SiO2 /
n-Si(100) Cu(I)(hfac)(vtms) Cu(I)
hexafluoroacetylacetonate-vinyltrimethylsilane Eth
yl iodine (C2H5I) Type of sample 1) An iodine
adsorption with H2 plasma treatment rf
plasma power was 50W, for 0-600s at a temperature
of 150oC and a chamber pressure of 1Torr. 2)
A brief iodine adsorption (without H2 plasma
treatment) 3) No treatment with iodine or H2
plasma.
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Results and Discussion
Pressure 1Torr Liquid delivery rate
0.2cc/min Partial pressure of Cu
100mTorr Vaporization 60oC Carrier gas
100sccm of Ar gas
High
Low
Low
High
At a lower temperature, surface-reaction-controlle
d region At a higher temperature, mass-transport-
controlled region
This result indicates that the adsorbed iodine on
the Cu seed layer acts as a catalyst to activate
the modify the reaction rate limiting step of the
thermal decomposition of the molecule of the Cu
precursor on the film surface.
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The initial iodine adatoms on the Cu seed
layer continuously float out onto the surface of
the growing Cu film during the film deposition
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C2H5Iad Had ? Iad C2H6 ? 2C2H5Iad ? 2Iad
2C2H4 ? H2?
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364Å
156Å
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Conclusions
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Solid particle production in fluorocarbon plasma.
I. Correlation with polymer film deposition
K. Takahashi, K. Tachibana Kyoto Univ. JVST A
(2001)
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Introduction
C4F8 is being applied to plasma etching and CVD
processes. Polymerized molecules may have high
sticking probability, and may cause formation
of powder and dust particles in the gas phase as
well as thin film on the surface. In this work,
the particle production is examined by direct
observation of solid particles dropped on the
wafer prepared in the fluorocarbon plasmas.
Octafluorocyclobutane (c-C4F8)
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Experimental Methods
Electrode diameter 15cm The space of electrodes
3cm Power density 0.15W/cm2 Flow rate
1.7sccm Residence time a few (1-10)
min Pressure 23 - 250mTorr CF4 ?3 mode at
1283cm-1 C2F6 ?7 mode at 1250cm-1 by infrared
laser absorption spectroscopy(LAS)
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Results
The particles were spherical and their diameter
was Distributed between 0.5 and 2.3um The shape
of the particles means that the particles were
generated in the gas phase.
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In the high pressure region where a large
number of the particles were produced, the
deposition rate decreased with rising pressure.
The depression meant the depletion of gas species
due to polymerization reaction, that is, the
transformation of gaseous components into solid
matter.
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CF4 and C2F6 molecules were measured by
FTIR. The density of these molecules was
measured by infrared laser absorption
spectroscopy at steady state after the initial
pressure depression. It did not change
monotonously but changed drastically as the feed
gas pressure increased above a critical value of
50mTorr for the particle Formation.
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250mTorr
on the surface
particles produced in the gas phase
The particles include a larger amount of C-CFx
bond than the films, implying that the particles
were formed by cross-linked molecules.
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Discussion
The pressure dependence of the rate was changed
drastically by the pressure of the particles in
the pressure region higher than 50mTorr.
Especially, the deposition rate was reduced by
the particle production. This fact indicates that
polymer film precursors can be consumed mainly in
the particle formation in the gas phase. CF3 F
M ? CF4 M, k 2.8X1021 cm6/mol2s CF3 CF3
M ? C2F6 M, k 1.0X1025 cm6/mol2s A chain
termination reaction forming a non-reactive site
for polymerization
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Particle formation during low-pressure
chemical vapor deposition from silane and
oxygen Measurement, modeling, and film properties
T. Kim, S-M. Suh, S. L. Girshick, M. R.
Zacharian, P. H. McMurry Department of Mechanical
Engineering, U of Minnesota, R. M. Rassel, Z.
Shen, and S. A. Campell Department of Electrical
and Computer Engineering, U of Minnesota, JVST A
(2002)
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Introduction
Low-pressure chemical vapor deposition(LPCVD) can
be used to produce various thin fims, including
poly-Si, SiO2, and Si3N4, and is prone to
particle contamination problems. PECVD has
largely replaced LPCVD for SiO2 deposition
because it provides higher growth Rates and step
coverages, and is less prone to particle
contamination.
Whitby and Hoshino (1996) Particle nucleation
rates vary as P, Where P is the total pressure,
and that Below 5Torr(667Pa), particle nucleation
rates become negligible.
particle beam mass spectrometer(PBMS)
surface morphology, dielectric constant, C-V
characteristics
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Results and Discussion
The actual pressure undergoes small
fluctuations at 1.2Torr and larger fluctuations
at 1.3Torr
These pressure fluctuations start at 1.2Torr and
become more intense as the pressure is increased
to 2.0Torr The stability of a mixture for a
given temperature and pressure with respect to
explosion limits is a competition between chain
branching reactions which serve to accelerate the
formation of the radical population(H, O, and OH)
and chain termination processes which remove
radicals.
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Langmuir-Hinshelwood surface kinetics
The clustering reactions among a few gas
species, SiO, SiO2, HSiOOH, SiH2O At pressures
below 0.8Torr(107Pa), diffusion prohibits local
accumulation of the clustering species, thereby
suppressing particle formation. For pressures
above 0.8Torr, particle generation becomes
relatively insensitive to pressure
since diffusion becomes less significant at high
pressures. The changes in total reactor pressure,
even when the precursor concentration is held
constant, can lead to significant changes in
particle production.
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0.6Torr, 500oC
1Torr, 300oC
Nonparticle generation domain
0.3Torr, 800oC
1.5Torr, 300oC
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Since SiO2 is amorphous, increasing temperature
increases admolecule mobility without faceting.
This increased admolecule energy should lead to
film smoothing by surface diffusion.
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At 800oC
They contain less oxygen than SiO2
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They are crystalline. This supports the
argument that the embedded particles are rich in
silicon.
More Si-rich particles in SiO2 films can cause
higher leakage currents.
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Due to the lower electron energy states of
Si-rich particles compared to the
surrounding SiO2 film, electrons can be trapped
at Si-rich particles. The electron field
generated by these trapped electrons reduces the
transport of electrons, which results in a
decrease of leakage current.
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Conclusion
1) In the explosion domain, the pressure was
unstable and periodic emission of light was
observed. only a small amount of particle
generation is observed during operation in this
region. 2) In the unsteady region, the particle
concentration fluctuates in a seemingly random
manner. 3) Only in the steady region does the
generated particle concentration reach steady
state. ? Size analysis was performed only in the
steady region and a bimodal distribution with
modal sizes of 7 and 20nm was observed at 800oC
and 1.5Torr (200Pa) ? Film property measurements
show that the surface of the films investigated
by using AFM is rougher when films are deposited
in a particle-rich domain. ? The dielectric
constant of the films is higher when the films
are deposited in a particle-rich domain, which
suggests that the composition of the particles
embedded in the film is closer to Si than to
SiO2. ? The leakage currents are also higher due
to the embedded particles when the films are
deposited in the particle-rich domain. These
particles can also be a site for charge trapping,
which is used To manufacture nonvolatile memory
devices.