HMDS

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HMDS
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HMDS / O2
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Characterization of carbon-doped SiO2 low k thin
films Preparation by plasma-enhanced chemical
vapor deposition from tetramethylsilane(4MS)
CH3
Si
CH3
H3C
CH3
L. M. Han, J.-S. Pan, S.-M. Chen, N.
Balasubramanian, J. Shi, L. S. Wong, and P. D.
Foo J. Electrochem. Soc., 148(7) (2001) F148
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Introduction
Due to the lower polarizability and atomic mass
of carbon, a C-Si-O composite material is
expected to have a lower permittivity than
SiO2. Futhermore, PECVD carbon-doped SiO2 thin
films are attractive due to their similar
features with SiO2 and their easy-to-integrate
deposition process.
Si-N 105Kcal/mole Si-C 104Kcal/mole
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• Molar Polarization and Molar Volume of Various
• Functional Groups

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Experimental

• Type shower head, parallel-plate radio
  frequency(rf, 13.56MHz),
• liquid delivery systems
• Process gas Si(CH3)4( referred to as 4MS),
  SiH4, N2O, and N2
• Two different kinds of depositions were
  conducted,
• polymerization of 4MS precursor
• copolymerization of 4MS/SiH4 mixed precursor
• Deposition conditions
• Substrate temperature 400oC
• Chamber pressure 2.7Torr
• rf power 900W
• (1) For both cases, 4MS and 4MS/SiH4
• 4MS/N2O ratio varies from 0.09 to 0.25 by
  changing the 4MS flow rate.
• SiH4(100sccm), N2O(7000sccm)
• (2) For 4MS/SiH4
• N2O/4MS ratio was changed by changing the N2O
  flow rate.
• 4MS(1000sccm)

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Characterizations
(1) XPS VG ESCALAB2201-XL Mg Ka at 1253.6eV,
An electron-flood gun was employed to
neturalize (2) FTIR BioRad model 2200ME,
Brucker Vector 22 spectrometer 8cm-1
resolution (3) Opti-probe system from Therma
Wave film thickness and refractive index (4)
SSM Mercury probe CV system SSM 495 dielectric
constant (5) TGA Perkin Elmer TGA
instrument by scraping film from silicon
substrate(order of 10mg), TGA runs were carried
out under N2 atmosphere using a ramp rate
of 10oC/min up to 400oC. The samples were then
held at 400oC for 40min.
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Results and Discussion
Si0.25 O0.35 C0.40
Film concentration ratio
FTIR analysis
Si-CH3 asym 1410cm-1 sym 1270cm-1 Si-C,
Si-CH3 wagging 800cm-1 SiHn
n1-3 2300-2130cm-1 Si-O-Si 1040cm-1 Si-O-Si
in a caged structure 1130cm-1 ?microporous
structure No CO 1550-1870cm-1 C-O
1000-1200cm-1
copolymerization
polymerization
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Ladder structure
Caged structure
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The Si-CH3 peak at 1270cm-1 and the Si-C peak at
800cm-1 increases with increasing 4MS/N2O ratio.
Copolymerization of 4MS/SiH4
Polymerization of 4MS
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• Peak height ratio between Si-CH3 at 1270cm and
  Si-O-Si at 1040cm-1

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• Low to high N2O/4MS ratio

Copolymerization
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Copolymerization
Polymerization
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Caged structure Film density
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The major backbone of the network of these film
is -O-Si-Oi-Si-, which is more like a linear
polymer and has lower degree of cross-linking. It
is anticipated that these films show lower
mechanical strength such as lower hardness
compared with SiO2.
The majority of C moiety is Si-CH3 at
283.4eV, Which is in good agreement with FTIR
spectra
283.4eV
101.1eV
102.2eV
282.4eV
103.4eV
100.2eV
99.1eV