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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