Roomtemperature deposition of aSiC:H thin

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Room-temperature deposition of a-SiCH thin films
by ion-assisted plasma-enhanced CVD
Dong S. Kim, Young H. Lee
Department of Chemical Engineering, Drexel
Unv. Thin Solid Films, 1996
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Experimentals

• Conditions
• TMS(40oC) diluted highly with hydrogen(10 vol.
  TMS in H2)
• A constant power mode, the pressure is
  varied(50200mTorr).
• A constant pressure mode, the power is
  varied.(-200-600V)
• Temperature 20oC
• Substrate silicon, quartz, aluminum, and
  polymer such as
• polycarbonate and polyimide.
• The distance between the powered electrode and
  the top
• plate was 9.5cm.
• The diameter of the powered electrode is 10cm.

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Results and Discussion

• Constant pressure mode(50mTorr)

• Constant power mode(100W)

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The extent of Si-(CH)n-Si bond (in comparison to
the Si-C bond) increases as the apparent ion
energy flux increases.

• Constant pressure mode(50mTorr)

With the help of the energetic ions, lighter
species are likely to combine with the
Si-containing precursors already adsorbed on the
substrate sufrace to form Si-(CH2)n-Si bonds.
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When the pressure is increased at constant power,
the species containing Si-C becomes more abundant
in the plasma phase due to less breakdown of the
source gas(TMS) This leads to a lower degree of
crosslinking and that a large number of bonds are
likely to be terminated by a methyl group

• Constant power mode(100W)

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• Absorption coefficient ratio, a1000 / a780

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• Effect of ion energy flux on film properties

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• UV-Vis transmittance of films

• Chemical resistance
• in a buffered HF solution
• NH4F HF 7 1 for 15min
• SiO2 1000Å/min
• SiN 5-10Å/min
• SiON 33-400Å/min
• All films show no loss of weight.

• Adhesion on substrates
• The films did not peel off when they
• were subjected to repeated cycles
• (over 20times) of boiling(100oC) and
• cooling(4oC) in water.
• ?due to a formation of strong chemical
• bonds between the carbon species of the
• substrate and the deposited film under
• energetic ion bombardment conditions

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Preparation and characterization of Low-k Silica
film incorporated with Methylene groups
S. Sugahara, T. Kadoya, K.-I. Usami, T. Hattori,
and M. Matsumura
Department of Physical Electronics,
TIT Department of Electrical and Electronic
Engineering, MIT Journal of the Electrochemical
Society, 2001
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Introduction
The silica group including fluorinated silica,
organic siliica, and porous silica has Received
considerable attention because only these films
are compatible with the Present silicon
technology. The organic silica film incorporated
with methyl groups is a feasible candidate for
a Low-k ILD, since it k value can be made as low
as 2.7 by increasing the content of Methyl
groups in the film. It also has satisfactory
moisture tolerance. However, insufficient thermal
conductivity and poor mechanical strength (such
as Toughness and hardness) are common but
serious problems for all low-k ILDs. In the
proposed film, some of oxygen atoms in the
original Si-O-Si network are replaced by alkylene
groups. ? long phonon mean-free-path Since the
alkylene group does not break the original silica
network, sufficient mechanical strength is
expected. Alkylene groups also act to make the
dielectric constant of the silica film low as
well As the conventional organic silica film with
methyl groups. In this study, the methylene
group (CH2) was selected. This is because the
methylene Group is lilkely to replace the oxygen
atom without introducing an internal strain.
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Experimentals
Method Hot-wall-type thermal CVD Cl3Si-CH2-SiCl
3 was used as Si precursor and H2O as an
oxidizer. Since the Si-Cl bond by H2O proceeds
spontaneously at sufficiently low
temperatures Such as room temperature, oxidation
does not take place for the Si-CH2-Si
moiety During the growth. Condition wall
temperature of 80oC net H2O flow
rate of 60sccm net source gas
flow rate of 1sccm total flow
rate of 400sccm including the N2 carrier
gas. Dehydration 1) annealing under vacuum
2) XeF2 ambient condition using
the N2 carrier gas of 60sccm. Comparing the
silica films incorporated with CH3 groups with
sample with CH2 groups.
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Results and Discussion
Si C O 2 1 3
The rate dcreased rapidly with increasing
temperature, Since the sticking coefficient of
H2O molecules on the Silica surface decreases
with increasing temperature.
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900cm-1
SiCl4 H2O
It is slightly shifted from 920cm-1 for pure
silica film to 890cm-1
Cl3SiCH2SiCl3 H2O
Si-CH2-Si is the symmetrical bridged structure
and hence insensitive to IR light
1360cm-1
CH3SiCl3 H2O
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Si-CH2-Si H2O ? Si-CH3 Si-OH ?H-2eV
exothermic
This reaction is likely to proceed spontaneouly
at low temperatures, such as 400oC
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TPD spectra
Thermal dicomposition of C-H groups
CH4(m 16) _at_ 300oC Si-CH3 H2O ? Si-OH CH4
?H -1eV
The dehydration reaction between Si-OH
groups, since from the above described FTIR
experiment the H2O-related absorption disappeared
at 400oC
H2O started to desorb at around 200oC
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Sample A
dense water-related species
Film CH3SiCl3 H2O SiCl4
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XeF2 diffuses easily into the silica film
and extracts H2O molecules and OH groups
at relatively low temperatures such as
200oC, i.e., XeF2 acts as a catalyst for
low-temperature dehydration of silica films
for 2hours
The broad absorption peak around 3500cm-1 related
to H2O molecules vanishied almost completely.
However, the small absorption peak at 3680cm-1
was still observed, that is, OH groups remained
in the film
The unwanted decomposition of Si-CH2-Si
groups and the resulting formation of Si-CH3
groups at low temperatures such as 300oC were
suppressed compared with results shown in Fig. 4.
Although the absorption intensity related to
Si-CH2-Si groups decreased above 500oC, Si-CH3
groups were not formed clearly.
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Isothermal conditions at 200oC
From 200 to 400oC with the heating rate of 1.7oC/s

• The absorption peak related to OH groups
• was eliminated completely after the XeF2
• dehydration at 400oC for 120min. However,
• there appeared the undesirable Si-CH3
• absorption in the FTIR spectrum after such
• a high temperature dehydration treatment.

• For the case of ramp mode (b),
• The film is almost dehydrated
• at 200oC without decomposition of Si-CH2-Si
• groups and the rate constant for the decomp-
• osition of the Si-CH2-Si group increases only
• after most of the water-related species desorbs

from the film. The remaining OH groups were
excluded at higher annealing temperatures such as
400oC where the decomposition of the Si-CH2-Si
group is ruled out by the very small amount of OH
groups.
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Although the amount of OH groups is less than the
detection limit of FTIR measurements, the
considerably affect electrical properties.
The values deteriorated at annealing at more than
550oC. This originated from the
thermal decomposition of the methylene group.
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The k value increased for the temperature of more
than 550oC. This is also caused by the thermal
decomposition of methylene groups.
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Thermal conductivity
Al sputtering Silica 1?m SiO2 100nm
RR? (Ts To) /
P Thermal conductivity ? d / (R S)
R thermal resistance of the silica film R
thermal resistance of the ref. sample To
temperature of the heat sink S the area of the
Al line d the thickness of the silica film