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Ivan Zyulkova,b, Ekaterina Voroninac,d, Mikhail Krishtaba,b, Dmitry Voloshind, BT Chanb, Yuriy Mankelevichd,

Tatyana Rakhimovad, Silvia Arminib and Stefan De Gendta,b

Area-selective Ru ALD by aC modification using H plasma:

from atomistic modelling to sub 50 nm patterned structures

a KU Leuven, Department of Chemistry, Faculty of Science, B-3001 Leuven, Belgium.b Imec, Kapeldreef 75, B-3001 Leuven, Belgium.c Lomonosov Moscow State University, Faculty of Physics, Leninskie Gory, GSP-1, Moscow 119991, Russian Federation.d Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Leninskie gory, GSP-1, Moscow 119991, Russian Federation.

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Briggs, Basoene, Ivan Zyulkov, and Katia Devriendt, "Method of patterning target layer."

U.S. Patent Application No. 15/975,611.

Advanced patterning- tone-inversion

Sacrificial

material

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PVD Cu deposition without (left) and with (right) Ru liner Ishizaka, Tadahiro, et al., Microelectronic Engineering 92 (2012): 76-78

3-dimensional model for low-pressure chemical vapor deposition step coverage in trenches and circular vias, M. Islamraja, et al., J. Appl. Phys., Volume 70, 1991, 7137

Filling of narrow structures

▪ Bottom-up metal deposition can be used for defect-free fill

▪ BU requires selectivity to the trench bottom vs sidewall material

Conventional top-down depositionBottom-up deposition

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Amorphous carbon film –ALD inhibitor Amorphous carbon (aC) film

Ru

aC

SiCN

10 seconds H2 plasma pre-treatment:

ELD Cu

Zyulkov Ivan, et al., Joint EuroCVD 21 – Baltic ALD 15

Conference Linköping, Sweden, 11 – 14 June, 2017.

Robertson, J. "Material science and

engineering." R 37 (2002): 129.

• Amorphous carbon films are commonly used as pattern transfer layers

sp2/ sp3 hydrogenated carbon

• Amorphous carbon can be used as a sacrificial dielectric for low-k replacement

L. Zhang, J. F. De Marneffe, N. Heylen, G. Murdoch, Z. Tokei, J.

Boemmels, S. De Gendt, M. R. Baklanov, Appl. Phys. Lett. 2015,

092901.

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Intrinsic selectivity aC vs SiCN/ low-k

aC

SiCN/ low-k

aC

SiCN/ low-k

H2 plasma pre-treatment

+

ambient

SiOx surface, hydrophilic

Hydrophobic surface,

CH2/CH3 passivation

Zyulkov, Ivan, et al. "Selective Ru ALD as a catalyst for sub-seven-

nanometer bottom-up metal interconnects." ACS applied materials &

interfaces 9.36 (2017): 31031-31041.

Non-growth area

Growth area

ASD ALD Ru IMEC 10 seconds H2 plasma pre-treatment:

Zyulkov Ivan, et al., Joint EuroCVD 21 – Baltic

ALD 15 Conference Linköping, Sweden, 11 –

14 June, 2017.

ALD Ru

H2 plasma results in ALD Ru inhibition on aC vs SiCN

Downsides:

• ALD Ru defectivity

• aC etch (50 nm / min)

aC

SiCN

aC

SiCN

aC

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ASD ALD Ru IMEC 10 seconds H2 plasma pre-treatment:

Zyulkov Ivan, et al., Joint EuroCVD 21 – Baltic

ALD 15 Conference Linköping, Sweden, 11 –

14 June, 2017.

ALD Ru

H2 plasma results in ALD Ru inhibition on aC vs SiCN

Master-plan:

N-free etch of aC

aC pre-

treatment by

H radicals

ASD

ALD of Ru

MD

modeling of

aC

modification

in H2 plasma

Remote He/H2 etch of aC (hydrogen radicals only)

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SE measurements of aC etch

• The etch rate is close to zero @ 65

• Clear etch rate increase is observed with the etch

process temperature increase, which indicates C-C

bonds breaking

• Activation energy ~ 28.4 kJ/mol

• Etch is performed in He/H2 plasma

2000 W

• Only radials can reach the sample

surface due to the tool

configuration (downstream plasma

source)

Remote He/H2 etch of aC (hydrogen radicals only)

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Pristine aC WCA is 67.5 ± 1.6 degrees

WCA measurements of aC etch

• Significant modification of aC @ low plasma temperature (65 ºC), no etch, carbon reduction

• Hight process temperature – aC etch, dangling bonds formation, impurities for the chamber sidewalls

XPS C1s

ALD Ru at 250 C

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RBS Ru areal density• Clear benefit in ALD inhibition after cold

He/H2 plasma (H radicals only)

• To be tested on a patterned structure

Plasma T ºC decrease

MD modeling of aC exposed to H ions

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Power,

W

Ne, cm-

3

Vrf Te,

eV

H flux, cm-2s-1 H3+ flux, cm-2s-1 H2

+ flux, cm-2s-

1

H+ flux, cm-

2s-1

150 1.3∙1010 180 2 1.8∙1016 1.5∙1015 3.1∙1014 1.5∙1014

300 2.7∙1010 270 1.6 2.6∙1016 2.5∙1015 5.7∙1014 3.3∙1014

Discharge parameters obtained in PIC MCC simulation- 300 mm CCP plasma reactor

(Particle‐in‐cell with Monte Carlo Collision)

Modeling of

the plasma

discharge

MD

modeling of

aC exposed

to H ions

MD

modeling of

aC exposed

to H radicals

• H radicals are the main species in H2 plasma

• Concentration of H3+ ions is 10 times lower in comparison with the concentration of H radicals

MD modeling of aC exposed to H ions

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Ion energy distribution function

Mean energy of H ions:

300 W – ion energy of 120 eV

60 W – ion energy of 50 eV

• H radicals energy increases with the plasma power increase

• 300 W – H ion energy of 120 eV

MD modeling of aC exposed to 120 eV H ions at different ion fluences

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• aC layer thickness increases by 3.2 nm, no etch is observed. Etch requires both: H ions and radicals

• H penetrates into aC film, C-C bonds scission

• Hydrogenation occurs in the bulk of aC

Starting ratio of sp/sp2/sp3 is 4/65/31

H ion fluences

MD modeling of aC exposed to 120 eV H ions at different ion fluences

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a-C density before and after exposure to

H ions at the fluence of 3.2·1016 cm-2

• Hydrogenation occurs mainly in the bulk of the aC film

• The average density of H-modified a-C layer is ~1.4 g/cm3 (initial a-C density is 2.5 g/cm3)

Relative concentrations of C and H atoms

after exposure to H ions at the fluence of

3.2·1016 cm-2

MD modeling of aC exposed to 120 eV H ions at different ion fluences

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sp sp2

sp3

• CH/CH2 groups are present in 80/20 proportion

• Most of CHx groups are inside of the film

Distribution of CHx groups

300 W (120 eV) vs 60 W (50 eV)

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• Plasma power decrease results in lower H ion energy

• Low H ion energy results in surface-confined modifications of aC

H concentration

aC density

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MD modeling of aC exposed to H radicals

MD modeling of aC exposed to H radicals

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• H radicals do not break C-C bonds, but they break C=C

• Surface hydrogenation and increase sp2 at the expense of sp

Carbon hybridization fractions before and after

exposure to H radicals

Relative concentrations of carbon and hydrogen in a-

C before and after exposure to H radicals

sp

CONCLUSIONS

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Experiment

• Downstream He/H2 plasma (H radicals) at 65 ºC does not etch aC. H radicals provide surface

hydrogenation and hydrophibisation (WCA = 97º)

• Downstream He/H2 plasma treatment results in more than 500 cycles ALD inhibition (corresponds to ~

5 nm Ru on SiCN)

MD modeling

• H ions break C-C bonds. H ions combined with H radicals are needed to etch aC

• H radicals do not break C-C bonds at room temperature, however the can transform C=C bonds into

C-C bonds forming CHx groups

• Near-room temperature H radicals treatment (remote H2 plasma) is the best treatment for aC to

maximize the number of CHx groups and minimize layer damage

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