Dielectric on Dielectric Area-Selective Deposition by a Combination of

Atomic Layer Deposition and Organic Film Passivation for Self-Aligned

Via Patterning

M. Pasquali1,2, S. De Gendt1,2, S. Armini2

A. Illiberi3, S. Deng3, G. A. Verni3, M. Givens4

1Department of Chemistry, Faculty of Science, KU Leuven, Leuven, Belgium. 2Semiconductor Technology and System, IMEC, Heverlee, Belgium.

3ASM Belgium, Leuven, Belgium. 4ASM Microchemistry, Helsinki, Finland.

Outline

▪ Introduction and motivation

▪ Study of SAM-passivation on blanket substrate

▪ Surface preparation, SAM density, thermal stability

▪ Area-Selective Deposition of AlOx ALD on SiO2 lines

▪ ALD blocking on passivated samples

▪ ASD down to 50nm Half-Pitch

▪ Conclusions

2

Outline

▪ Introduction and motivation

▪ Study of SAM-passivation on blanket substrate

▪ Surface preparation, SAM density, thermal stability

▪ Area-Selective Deposition of AlOx ALD on SiO2 lines

▪ ALD blocking on passivated samples

▪ ASD down to 50nm Half-Pitch

▪ Conclusions

3

Area Selective Deposition for self-aligned film growth

▪ Intrinsic Selectivity

▪ Area Deactivation → extending selectivity

4

Different strategies all based on ALD surface sensitivity

Growing Area

Deposited MaterialNON-Growing Area 21 3

1 2 3

1 2 3

Passivation

ASD demonstration on pattern substrate

5

SiO2

Cu

TaN/Ru

ODT

AlOx

Initial Substrate:Cu Lines

TaN/Ru:

Diffusion barriers / Liners

SiO2 Lines

ASD demonstration on pattern substrate

6

SiO2

Cu

TaN/Ru

ODT

AlOx

Cu lines passivation:

1-Octadecanethiol derived SAM

CH3-(CH2)17-SH

C18

Thiol

ASD demonstration on pattern substrate

7

SiO2

Cu

TaN/Ru

ODT

AlOx

AlOx ALD: AlOx ALD on SiO2 lines:• Temperature: 150 °C

• Thicknesses: 2, 4, 6, 8 and 10 nm

ASD demonstration on pattern substrate

8

SiO2

Cu

TaN/Ru

ODT

AlOx

Post ALD Cleaning:

Acetic Acid aqueous solution.

ODT residues and ALD defects

removal

Outline

▪ Introduction and motivation

▪ Study of SAM-passivation on blanket substrate

▪ Surface preparation, SAM density, thermal stability

▪ Area-Selective Deposition of AlOx ALD on SiO2 lines

▪ ALD blocking on passivated samples

▪ ASD down to 50nm Half-Pitch

▪ Conclusions

9

Overview SAM deposition (immersion) experiments

SAM by

immersion

coating

Octadecane-thiolCu after CMP

and planarization

50mM

5mM

1mM

0.5mM 10

CH3-(CH2)17-SH

+

Cu oxide etching

0. EtOH Contamination cleaning

1. Citric Acid

2. Diluted HF

3. UVO3 10’

Oxidation + cleaning

4. UVO3 5’

Surface

Preparation

(prior to dipping)

Comparative study (ex-situ) on Cu surface preparation treatment

11

Understanding pretreatment-induced modification on Cu surface

Thickness increase

Reference Cu (after CMP)

RMS ~ 0.8nm

RMS roughness and morphology of copper surfaces after different pretreatments

(no ODT deposition) by AFMSpectroscopy Ellipsometry (raw data)

▪ Roughness to be avoid since it is a source of distortion

for SAMs’ semi-crystallinity

▪ Acid-based = Oxide removal

▪ UVO3-based = Oxide growth

▪ The least thickness variation for EtOH pretreatment

Overall, one kinetics emerged from all the experimental conditions

▪ Very fast kinetics:

▪ System immediately saturate (already

after 10min)

▪ Monolayer formation

▪ Only exception: Citric A.-treated Cu

12

50mM

5mM

1mM

WCA of dense monolayer [1]

[1] Graupe et al. Langmuir14(17), 1999

Average

Spectroscopy Ellipsometry (50mM – EtOH)

WCA (EtOH pretreatment)

CV measurement to evaluate ODT coverage

Ag/AgCl-reference electrode

Pt counter electrode

NaOH 0.1M aqueous

solution - electrolyte

Sweep rate: 0.01 V/s

Cell area: 1cm2

Cu0→Cu1+

Cu1+→Cu2+

Cu2+→Cu1+

Cu1+→Cu0

13

▪ EtOH-ODT-Cu:

▪ Flat current curve throughout potential range

→ ODT full-coverage and pinhole-free

▪ Stable up to 10x V sweeping (-1 – 0V vs

Ag/AgCl range)

▪ Cu treated by HF or UVO3 (10’) close to pinhole-free passivation but remarkably less stable

EtOH-ODT thermal stability assessment via FTIR and CV measurements

14

Passivation stable up to 150C, higher temperature causes massive degradation

Saf

e T

em

pera

ture

Win

dow

ODT degradation

▪ Stability ODT on Cu (EtOH pretreatment) till ~150 °C

▪ Degradation starts at 150 °C till complete desorption 250 °C

Anneal T

FTIR-ATRDetermine from CV data

°

°

°

°

(°C)

Outline

▪ Introduction and motivation

▪ Study of SAM-passivation on blanket substrate

▪ Surface preparation, SAM density, thermal stability

▪ Area-Selective Deposition of AlOx ALD on SiO2 lines

▪ ALD blocking on passivated samples

▪ ASD down to 50nm Half-Pitch

▪ Conclusions

15

ASD effectiveness from XPS surface characterization on blanket Cu/ODT

16

ODT blocking towards AlOx ALD is not broken up to10nm thick film

▪ ODT effectively prevents Al oxide growth up to 10 nm on blanket.

▪ Al absence for ODT-passivated samples confirmed by ERD inspection (detection limit 0.1% at. conc.)

▪ S, C, O and Cu at. conc. do not change as a function of ALD cycles

No ODT + ALD ODT + ALD

Defectivity evolution prior to and after acetic acid cleaning

17

Top-Down SEM: ODT Copper / Si oxide 50nm wide lines; prior to / after cleaning

Acetic acid

solution

Sonication

10 min.

6nm

8nm

10nm

AlO

x A

LD

tar

get

thic

kness

100nm

▪ ALD blocking on patterned structures not as effective as on blanket Cu

▪ Effective defect removal achieved only for 6 nm AlOx ALD

Defectivity evolution prior to and after acetic acid cleaning

18

Top-Down SEM: ODT Copper / Si oxide 50nm wide lines; prior to / after cleaning

Acetic acid

solution

Sonication

10 min.

6nm

8nm

10nm

AlO

x A

LD

tar

get

thic

kness

100nm

▪ ALD blocking on patterned structures not as effective as on blanket Cu

▪ Effective defect removal achieved only for 6 nm AlOx ALD

Effective ASD proven by TEM. However, ALD extend over Cu barriers

19

TEM x-section: ODT Cu / Si oxide 50nm lines after acetic acid cleaning + 6nm AlOx ALD

CuSi oxide

Al oxide 5.3 nm

CuSi oxide

Al oxide 5.3 nm

▪ 5.3 nm Al oxide (nominal ALD thickness 6nm) layer present on top of Si oxide between the Cu lines

▪ Al oxide layer extends over the Ru/TaN barriers → ODT does not passivate TaN

EDX elemental mapping supports previous conclusions

20

Cu + ODT - 6 nm ALD Al oxide target + acetic acid defect removal

▪ No Al oxide present on

the Cu lines

▪ Continuous Al oxide

layer present on top of

Si oxide and barriers

Outline

▪ Introduction and motivation

▪ Study of SAM-passivation on blanket substrate

▪ Surface preparation, SAM density, thermal stability

▪ Area-Selective Deposition of AlOx ALD on SiO2 lines

▪ ALD blocking on passivated samples

▪ ASD down to 50nm Half-Pitch

▪ Conclusions

21

Conclusions

▪ Ideal pinhole-free monolayer achieved on Cu blanket surface

▪ Fast kinetics emerged with all the surface preparation tested but citric-acid based one

▪ Cu treated with EtOH allows the deposition of the most stable ODT layer

▪ ODT-passivation inhibits AlOx growth up to 10 nm (Al below XPS/ERD detection limits)

▪ ASD on 50 nm Cu/Si oxide HP lines

▪ Perfect ASD demonstrated for 5-6 nm Al oxide on 50 nm HP lines (Al below TEM-EDX

detection limits on Cu)

▪ Defect removal via SAM wet lift-off effective under certain defectivity conditions

▪ ODT does not passivate TaN barriers

22