JULY 12 2017

Challenges in Cleaning Tungsten and Cobalt for Advanced Node Post CMP and Post Etch Residue Removal Applications

Michael White. Daniela White, Thomas Parson, Elizabeth Thomas, Shining Jeng, Ruben Lieten, Volley Wang, Sean Kim, Wisma Hsu and Steve Lippy

2

01Cleaning requirements for Co and W at the advanced Node

02 Co cleaning mechanisms

03 Controlling corrosion on Co

04 Cobalt defectivity improvements

05 Cobalt wet etch & cleaning

06 W Cleaning mechanisms

07 Cleaning Si3N4 after W polishing

08 W wet etch & cleaning

09 Conclusions

AGENDA

3

CLEANING CHALLENGES FOR BULK COBALT AND TUNGSTEN

• Replace more traditional copper cleaners with rationally designed Co cleaners

• Low/No Cobalt corrosion

• Low/no galvanic corrosion

• Low/no dendritic CoOx growth

• Low/no Co pitting

• Low/no organic residues

• Low/no silica particles or clusters

• No increased roughness

• Green chemistry (TMAH free)

• Market increasing challenged by W recess

• High pH commodities (SC1, dilNH3)

• Traditional low pH cleaners

• Low W etch rates (<2 Ǻ/min)

• Low/no Organic Residue

• Nitride cleaning is particularly problematic

• Low no silica particles or clusters

• No increased roughness

• Green chemistry.(TMAH free)

Post CMP Bulk Co Cleaners Post CMP W Cleaners Post Etch Residue Remover

• Post Etch Residue Remover.- Cu, W, Co

• Multi Function Cleaner - Clean + Etch etc…

• PERR for advanced FEOL application (Ge and SiGe)

• Green chemistry (TMAH free)

4

THE RATIONAL DESIGN OF A POST CMP CLEANER PLANARCLEAN® AG COPPER CLEANING

PlanarClean® AG ‒ Advanced Generation Copper Cleaning Mechanism

Co(0)

CoO/Co2O3

O O

HO

H

Con+ Co

High pH leads to charge repulsion between negatively

charged silica and negative cobalt oxide surface

Corrosion inhibitor

package controls galvanic

corrosion

Cleaning additive disperses silica and organic residue and

prevents reprecipitation

Etchant for controlled, uniform CuOx

dissolution to undercut particles

Organic additive attacks and removes Co-organic residue

Q

SiO2

SiO2SiO2 SiO2

PLANARCLEAN AG PREVENTS SILICA AGGREGATION

◦ Particle adhesion mechanisms

◦ Physisorption (van der Waals attraction – increases with PS)

◦ Electrostatic attraction or repulsion (zeta potential)

◦ Chemisorption (chemical reaction particle-surface)

◦ Capillary condensation

AG-3XXX

Dispersed particlesHighly negatively charged

No particles agglomeration

OHOH

OH

OHOH

OH

OH

OH

SiO2

OHOH

OH

OHOH

OH

OH

OH

SiO2

OHOH

OH

OHOH

OH

OH

OH

SiO2

Post-CMP Co Post-CMP Co

O‒

OH

O‒

OHO‒

OH

O‒

O‒ SiO2

O‒

OH

O‒

OHO‒

OH

O‒

O‒ SiO2

O‒

OH

O‒

OHO‒

OH

O‒

O‒ SiO2

O+

Si Si

H

SiOH + HO- SiO- + H2O

IEP = 4

5

Zeta Potentialz = 4pg(n/E)/e

6

SOME CHALLENGES ASSOCIATED WITH CO CLEANER DEVELOPMENT

• Ideal pH range for Silica slurry removal to prevent hydroxide precipitation

Mtn+Xn-

Co

CoO + Co2O3

Co

CoO + Co2O3

OHOH OH OH OH OH OH OH OH

Surface passivation

• Co passivation by both cobalt oxide/hydroxide and/or corrosion inhibitor

• Can result in CoOx(OH)y growth without the proper complexing agent

Co2+

OH2

OH2

H2O H2O

H2OH2O

2 HO-

[O]3 HO-

Co2+

OH2

OH2HO-

H2O

H2OHO-

Co3+

OH2

OH2HO-HO-

H2OHO-

Co2+

L

LLL

L

L

Ksp = 1.6 x 10-16

Ksp = 1.6 x 10-44

Ksp = soluble

6 L

Co Pourbaix Diagram

7

SOME CHALLENGES ASSOCIATED WITH CO CLEANER DEVELOPMENT

• Well-passivated Co surfaceAFM, SEM – no CoOx surface precipitates,low surface roughness (Ra = 5 nm)

• Uniform, smooth etching (no pitting)

AFM

• Poorly passivated surface or insufficuentcomplexation

• Dendritic CoOx growth

SEM

8

POTENTIODYNAMIC REDUCTION OF CO OXIDE LAYERS CAN MEASURE THE RELATIVE CONCENTRATIONS OF CO(II) AND CO(III) OXIDE/HYDROXIDES

-1.00 -0.75 -0.50 -0.25 0-0.000075

-0.000050

-0.000025

0

E (V vs. Ag/AgCl)

I (A

)

tsmc CVD Co in pH 11.5 KOH

Co2O3

Q = 0.0066 CoulThickness = 41.95Å

CoO

Q = 0.01268 CoulThickness = 43.94Å

9

XPS FITTING SHOWS COBALT(II) AND COBALT(III) CAN BOTH BE PRESENT

10

Ref: 1. Wang, et al. SPIE Beijing 2016 Conf. Proc.2. Bard, A. J. Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications; Wiley and Sons 2001

NYQUIST PLOTS SHOW INFLUENCE OF PROPER INHIBITOR SELECTION AND CONCENTRATION ON COBALT PASSIVATION

22/12222/1

2/1

)()1(

=

ctdldl

ct

RCC

RRZ

High Inhibitor 2

No Inhibitor

When -> 0 aRCC

CRCZ

ctdldl

dlctdl

22/12222/1

2/1222/1

)()1(

)(

=

High Inhibitor 1

Low Inhibitor 2

Higher impedance storage and loss components

higher film integrity

11

AG- CO FORMULATIONS SHOW UP TO A 2X IMPROVEMENT IN DEFECTIVITY OVER COMPETITOR

Silica particle

Organic residue

Judicious selection of cleaning additives leads to lower defectivity

Silica cluster

2.5x

12Mukherjee, T. Thesis N. Texas U., 2016

TITANKLEAN MECHANISM FOR REMOVING DRY ETCH RESIDUES WHILE PROTECTING COBALT

Organic/inorganic residues

Residues from dry process

Oxidization Degradation

Etchant

Swelling & dissolution

Solvent

Residues removal

Etchant

Metal inhibitor

M complex

XCo/ESL

Co/ESL protection

Co/ESL

Etchant M complexTK 162 M3+ M2+

Chelating agent

ESL/inorganic residues removal

low-ĸ

Etchant

residues

CoESL 2 Low

-ĸ

ESL 1

CoLow-ĸ

TitanKlean

Wet Cleaning

13

PLANARCLEAN AG-W CLEAN MECHANISM FOR ALUMINA OR SURFACE TREATED SILICA (ST-SiO2)-Based CMP Slurries

Polishing produces many particles (slurry, metal, and organics)

W W W W W W W W W W W

OrganicParticle

MetalParticle

MetalParticle

Al2O3

ST(+)-SiO2

OrganicParticle

Al2O3

ST(+)-SiO2

MetalParticle

Comp B & D – modifies particles surface and creates negative surface charges

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

B

Al2O3

ST(+)-SiO2

B

B

B B

B

B

D

DD

D

D

DDB

Al2O3

ST(+)-SiO2

B

B

B B

B

B

D

DD

D

D

DD

Removed by DIW Rinse

W W W W W W W W W W W

B

Al2O3

ST(+)-SiO2

B

B

B B

B

B

D

DD

D

D

DD

Organicparticle

Metal Particle

Component A – Insures negative charges on W surface and organic particles.

Organicparticle

Metal Particle

Organicparticle

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

W

O

PC AG-W formulations:

◦ Inhibits W corrosion

◦ Controls the W etch rate

◦ Particle and surface modification

◦ Dielectric compatibility

◦ Non-TMAH additives fororganic residue removal

14

HIGHER TUNGSTEN ETCH RATES WITH INCREASING pH DUE TO DISSOLUTION AS POLYOXOTUNGSTATE KEGGIN IONS

"Hetero and lacunary polyoxovanadate chemistry: Synthesis, reactivity and structural aspects". Coord. Chem. Rev. 255: 2270–2280. 2011.

Dil NH3 (1:2850)

SC1: 1:50 > 6 A/min

Liu, et al. J. Mater. Chem A, Issue 6, 2014

WO3 Negative at all pHs of interest

MECHANISMS FOR IMPROVING ORGANIC RESIDUE REMOVAL FROM SI3N4 STUDIED BY CONTACT ANGLE AND FTIR

1.

clean, hydrophilic

dirty dirty

Si3N4

Control clean clean

Cleaning additive removes cationic Contamination form dielectric

surface and disperses

FTIR

Contact Angle

Si3N4 surface typicallyHighly contaminatedby cationic dishing and

erosion control agents

AG- W Cleaner

Electrostatic Repulsion during CMP

16

0

50

100

150

200

250

W100 SC1 W210 W210 #A W210 #B W210 P3 buff

slurry ball

slurry cluster

oxide

organic-silica

organic

# defects pareto (>= 65 nm defects)# defects pareto (≥ 65 nm defects)SiO2 – EDR Review – Defect Pareto

AG-W#1 SC-1 AG-W#3AG-W#2 AG-W#4

0

5

10

15

20

25

30

W100 W210 W210 #A W210 #B W210 P3 Buff

Slurry ball

Slurry cluster

Oxide

Organic

# defects pareto (>= 100 nm defects)# defects pareto (≥ 100 nm defects)W – EDR Review – Defect Pareto

AG-W#3 AG-W#40

5

10

15

20

25

30

W100 W210 W210 #A W210 #B W210 P3 Buff

Slurry ball

Slurry cluster

Oxide

Organic

# defects pareto (>= 100 nm defects)

AG-W#1

-10

10

30

50

70

90

110

130

150

W100 SC1 W210 W210 #A W210 #B

Slurry ball cluster

Slurry ball

Silica

Organic

# defects pareto (>= 60 nm defects)

9618 defects

# defects pareto (≥ 65 nm defects)Si3N4 – EDR Review – Defect Pareto

AG W#1 SC-1 AG-W#2 AG W#3 AG W#4

-10

10

30

50

70

90

110

130

150

W100 SC1 W210 W210 #A W210 #B

Slurry ball cluster

Slurry ball

Silica

Organic

# defects pareto (>= 60 nm defects)

9618 defects

PLANARCLEAN AG-W FORMULATIONS EXHIBIT LOWER DEFECTS AND ORGANIC RESIDUES OVER TRADITIONAL CLEANS

AG-W#2

9618 defects-SC1 or dil NH3

No cleaning on Si3N4

• PC AG-W Series show improved performance over SC-1 on all substrates

17

1. White, M. L. et al, Materials Research Society Symposium Proceedings Volume 991Issue Advances and Challenges in Chemical Mechanical Planarization Pages 207-212Journal 2007

2. Hegde, Sharath; Babu, S. V. Electrochemical and Solid-State Letters (2004), 7(12), G316-G3183. White , M. L. et al. Mat. Sc. For. 1249 E04-07 (2010).

DEFECTIVITY CORRELATED TO CHARGE REPULSION BETWEEN SILICA PARTICLES

Additive increases negative charge on

particle surface

q 1 q 2

r

Coulomb’sLaw

𝐹 = 𝑘𝑞1 ∗ 𝑞2/r2

18

TITANKLEAN® PERR AND SELECTIVE ETCH APPLICATIONS

Application: W vs. TiN selective etching

• Challenge and Requirements: Control selectivity of TiN/W; compatible with various dielectric materials

• W Etch rate controlled through selective W Inhibitors

Si substrate

Gate oxideTiN

W W

W/TiN Etch controllableetchant

W/TiN etching

Buried Wordline Formation

30.10

20.15 11.38

180.55

164.38

147.93

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

180.00

200.00

0215-5* 0215-6* 0215-7*

(A/m

in)

TiN ER(A/min) W ER(A/min)

6x8x

12x

Better W Inhibitors

19

CONCLUSIONS

◦ Proper selection of Cobalt inhibitors and complexers can virtually eliminate cobalt corrosion

◦ Certain cobalt cleaning additives improve defectivity on cobalt

◦ Additives have been found that remove and disperse organic residue from silicon nitride after W CMP

◦ Tungsten etch rate and corrosion can be controlled through the proper selection of W inhibitors

Entegris®, the Entegris Rings Design™ and Pure Advantage™ are trademarks of Entegris, Inc. ©2016 Entegris, Inc. All rights reserved.

20