Effect of UV-wavelength on Hardening Process of Porogen-containing and Porogen-free Ultra-low-k PECVD Glasses A.M. Urbanowicz*, K.Vanstreels, P.Verdonck, E.Van Besien, Ch. Trompoukis, D. Shamiryan, S. De Gendt and M.R. Baklanov *also at Semiconductor Physics Department , Katholieke Universiteit Leuven
AVS 2010 17-22 October
Outline Introduction
Ultra low-k dielectrics fabricated by PECVD and porogen residue problem New PECVD curing approach: UV-curing of porogen-free films UV-curing as a photochemical process
Experimental setup Results
Organic residues content in low-k matrix studied by UV-spectrocopic ellipsometry Effect of UV-curing wavelength on mechanical properties of porogen-free films Effect of UV-curing wavelength on dielectric constant of the films
Conclusions
Adam Urbanowicz, AVS 57th Oct 17-22, 2010, Albuquerque, NM
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Ultra-low-k PECVD dielectric and porgen residue challange Porogen residue removal degrades mechanical properties of ultra-low-k PECVD
k~ 2.5 Prior Art
UV curing Film hardening
k<2.3
Porogen removal
Porogen
Porogen residue
A. M. Urbanowicz, K. Vanstreels, D. Shamiryan, S. De Gendt and M. Baklanov, Electrochem. Solid State Lett., 12, H292 (2009).
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Ultra-low-k PECVD dielectric and porgen residue challange
Porogen residue degrades electrical properties
PECVD (k=2.3) – high residue content PECVD (k=2.3)+ H2-AFT - no residue PECVD (k=2.5) – low residue content PECVD (k=2.5)+ H2-AFT no residue
E. Van Bensien, L. Zhao, M. Pantouvaki, D. De Roest, I. Ciofi, K. Croes, A. M. Urbanowicz et. al Electrical Evaluation of Low-k Dielectrics with Various Degree of Porosity in Planar Capacitor Structures, in Core Partner Workshop, IMEC, Leuven (2010). Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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New curing technology of PECVD ultra-low-k dielectrics
Prior Art
UV curing
?
New curing technology
Film hardening
Porogen removal
Porogen removal Gas inlet
He/H2
UV curing
Porogen fully
Skeleton
removed
hardening
Plasma area Grid : electrical neutralization
H H
H Reactive species
Wafer at 280 °C
Porogen
Porogen residue
A.M. Urbanowicz, K. Vanstreels, P. Verdonck, D. Shamiryan, S. De Gendt and M. Baklanov, J. Appl. Phys., 107 (2010).
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Goal: Study of the effect of the UV-curing wavelength on porogenfree films
~172 nm
>200 nm
0.22 0.20
Porogen
as deposited
0.18
Only light that is absorbed can be effective in producing photochemical change. (Grotthus-Draper Law: 1817, 1843).
0.16 0.14 0.12
One particle is excited for each quantum of radiation (photon) absorbed (Stark-Einstein Law: 1912)
0.10 0.08
Energy of an absorbed photon must be equal to or greater than the weakest bond in the molecules (Bolton)
0.06 0.04
H2-AFT L. Prager, P. Marsik, L. Wennrich, M. R. Baklanov, S. Naumov, L. Pistol, D. Schneider, J. W. Gerlach, P. Verdonck and M. R. Buchmeiser, Microelectronic Engineering, 85, 2094 (2008). S. Eslava, F. Iacopi, A. M. Urbanowicz, C. E. A. Kirschhock, K. Maex, J. A. Martens and M. R. Baklanova, Journal of the Electrochemical Society, 155, G231 (2008). A. M. Urbanowicz, B. Meshman, D. Schneider and M. R. Baklanov, Physica Status Solidi a-Applications and Materials Science, 205, 829 (2008).
extinction coefficient
Laws of Photochemistry:
0.02 0.00 -0.02
600
500
400
300
Wavelenght [nm]
200 Si-CH3 Photodissotiation threshold
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Experimental setup Experimental setup UV curing (166 s) Deposition of 130 nm films
Porogen removal
1
Gas inlet
He/H2
350 s
2a
172±15 nm
Plasma area Grid : electrical neutralization
H H
Skeleton
H Reactive species
Wafer at 280 °C
Porogen
NB
hardening
2b
BB >200 nm
BB= broad band NB= narrow band Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Curing of porogen-containing films results in porogen residues generation As deposited
Porogen residue (a-C) contains sp2 orbitals (C=C) which have transition band ~4.5 eV (275 nm)
UV-cured Porogen residue
UV Spectrocopic Ellipsometry 0.22
1.65
0.20
1.60
as deposited
refractive index
1.55
0.18 0.16
as deposited
0.14
1.50
0.12
1.45
UV ~ 172 nm
UV ~ 172 nm 1.40
0.10 0.08
1.35
0.06
UV>200 nm
UV>200 nm
extinction coefficient
Porogen
0.04
1.30
0.02 1.25 1.20 900
0.00
750
600
450
300
Wavelenght [nm]
150 900
750
600
450
300
-0.02 150
Wavelenght [nm]
P. Marsik, P. Verdonck, D. De Roest and M. R. Baklanov, Thin Solid Films, 518, 4266 (2010). Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Curing of porogen-free films results in porogen-residue-free films As deposited
Porogen removal Gas inlet
He/H2
Porogen fully
Skeleton
removed
hardening
Plasma area Grid : electrical neutralization
H H
Porogen
UV curing
H Reactive species
Wafer at 280 °C
0.22
1.65
0.20
as deposited
refractive index
1.55
0.16
as deposited
0.14
1.50
0.12
1.45
UV ~ 172 nm
UV ~ 172 nm 1.40
0.10 0.08
1.35
0.06
UV>200 nm UV>200 nm
1.30 1.25
0.18
0.04
H2-AFT+ UV ~ 172 nm
H2-AFT + UV>200 nm
0.02
H2-AFT + UV>200 nm
1.20 900
0.00
H2-AFT+ UV ~ 172 nm 750
600
450
extinction coefficient
1.60
300
Wavelenght [nm]
150 900
750
600
450
300
-0.02 150
Wavelenght [nm] Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Greater thickness loss after 172 nm NB UV than for >200 nm BB UV
Thickness loss (shrinkage), %
cured without porogen (after H2-AFT) 18 16
UV ~ 172 nm UV > 200 nm
cured with porogen (conventional)
14 12 10 8 6 4 2
H2-AFT
0
Observations: More thickness loss for films without porogen for 172 nm UV curing (improved cross-linking)
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM 10
172 nm UV curing of porgen-free low-k results in greater YM than 200 nm UV Nano-indentation and Ellipsometric porosimetry
8 .0
Young's Modulus [GPa]
7 .5 7 .0
F i lm s c u r e d w ith p o ro g e n
6 .5
m 2 n 7 1
F il m s c u r e d w it h o u t p o r o g e n
UV
6 .0 5 .5 20
5 .0 4 .5
0 n m
UV
4 .0 3 .5 3 .0
H2-AFT
2 .5 2 .0 20
25
30
35
40
45
50
O p e n p o r o s it y [ % ] Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Pore radius is greater for 172 nm UV due to more efficient Si-O-Si matrix cross-linkage Ellipsometric porosimetry H2-AF H2-AFT + UV >200 nm H2-AFT + UV ~ 172 nm
25
dV/dr
20 15 10
micropores
5 Matrix can be x-linked
0 1.0
1.5
2.0
2.5
3.0
Pore radii [nm]
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Improved cross-linkage of Si-O-Si skeleton for ~172 nm UV-cure
Methyl Oxygen Silicon
Normalized absorbance, a.u.
optimal cross-linking only T-groups
0.25
T CH3
O
0.20
Si
cross-linking with D-groups
FTIR
O
H2-AFT
Si-CH3
H2-AFT + UV~172 nm
O
H2-AFT + UV>200 nm
D
0.15 0.10
O
0.05
CH3 Si
CH3
O
0.00 1300
1290
1280
1270
1260
1250
-1
Wavenumber, cm
A.M. Urbanowicz, K. Vanstreels, P. Verdonck, D. Shamiryan, S. De Gendt and M. Baklanov, J. Appl. Phys., 107 (2010). Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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UV-curing of porogen-free films results in its lower k-values 3.0 2.8 2.6
cured with porogen (conventional)
k at 100 kHz (metal dots) k at 4 GHz (near-field probe)
cured without porogen (after H2-AFT)
k k-value
2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0
Observation for porogen free-films: >200 nm UV-curing results in lower k-value than ~172 nm UV Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Summary: UV-curing wavelength vs achieved characteristics of the porogen-residue-free films
IMEC’s data base for various organo-silica low-k
3 2.8
UV>200 nm
2.6 2.4
50
UV>200 nm
10
5
1
2.2
UV ~172 nm
0.5 2 1.8
Elastic modulus (GPa)
100
Pore size (nm)
k value
3.2
UV ~172 nm 0
10
20
30
40
50
60
Porosity (vol. %)
0.1 1.8
2
2.2
2.4
2.6
2.8
3
k value
50 40 30 20
UV >200 nm
UV ~172 nm
10 8 5 4 3 2 1 1.8
2
2.2
2.4
2.6
2.8
k value
Green area – ITRS requirements W. Volksen, D. M. Miller and G. Dubois, Chem. Rev., 110, 56 (2010). K. Maex, M. R. Baklanov, D. Shamiryan, F. Iacopi, S. H. Brongersma and Z. S. Yanovitskaya, J. Appl. Phys., 93, 8793 (2003). Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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3
Conclusionscuring technology Conclusions UV-curing in the presence of porogen results in: porogen residue generation comparable mechanical properties and k-values for both UV-sources used UV-curing after porogen removal with H2-AFT results in: narrow band (~172 nm) YM of 6.64±0.61 GPa k of 2.2±0.01 broad band (<200 nm) YM of 3.85±0.38 GPa k of 2.0±0.01
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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Future planscuring technology Conclusions Optimization of porogen residue-free ultra low-k PECVD films different UV-cure times combined narrow-band and broadband UV-curing Electrical evaluation of achieved films using planar capacitor structures CMP tests of porogen-residue-free films
Adam Urbanowicz, AVS 57th , Oct 17-22, 2010, Albuquerque, NM
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