ENTEGRIS PROPRIETARY AND CONFIDENTIAL

AUGUST 11, 2017

Future Development Challenges for Post-CMP Cleaning

Michael White, Daniela White, Volley Wang, Elizabeth Thomas, Jun Liu, Ruben Lieten, Thomas Parson, Atanu Das, Roger Luo, Don Frye

2

FUTURE CHALLENGES IN PCMP CLEANING

01 Introduction

02 Future trends and challenges

03 Cu PCMP

04 Co PCMP

05 W/dielectric/silica PCMP

06 CeO2 PCMP

07 Summary

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POST-CMP CLEANING CHALLENGES

1. New materials/film types

◦ Diversification of dielectric materials

◦ New barrier materials

2. Feature size decreasing

◦ 10 nm ubiquitous

◦ Working on 3-5 nm for most customers

3. Increasingly complex CMP slurries

◦ New particle types

◦ Small particles

◦ Advanced organic additives

4. Defect detection thresholds decreasing

◦ Current state of the art 18 nm

5. Environmental laws/customer EHS more stringent

◦ Country to country variations

◦ Customer EHS requirements vary

◦ Tetramethylammonium hydroxide increasingly forbidden

Graphic source: http://www.azom.com/article.aspx?ArticleID=12527

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INCREASING USE OF NEW MATERIALS CORRESPONDS TO INCREASING CLEANING COMPLEXITY

◦ Conductors

◦ Copper

◦ Barrier/liners (Ta, TaN, TiN, Co, Ru, Mn)

◦ Tungsten

◦ Cobalt

◦ Ruthenium

◦ Aluminum

◦ Dielectrics

◦ TEOS

◦ Thermal oxide

◦ Si3N4◦ Low-k dielectric, SiC (SiOC, SiON, etc.)

◦ Polysilicon, single crystal silicon (wafer, various doping)

◦ Doped glass (BPSG, PSG, etc.)

Graphic source: International Roadmap for Semiconductors ITRS press conference, Dec 2004, 25.

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COMPLICATED 4-WAY INTERACTIONS PRESENT CHALLENGES FOR POST-CMP CLEANING

Slurry Brushes

PCMP cleaner

Wafer surface/

film types

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6

CMP SLURRY DESIGN ‒ MANY POTENTIAL SOURCES OF CONTAMINATION

◦ Surface active nanoparticles ‒ Abrasives

◦ Silica (SiO2)

◦ Fumed silica

◦ Colloidal silica

◦ Surface treated silica

◦ Anionic

◦ Cationic

◦ Ceria (CeO2)

◦ Alumina (Al2O3)

◦ Titania (TiO2)

◦ Zirconia (ZrO2)

◦ Mechanical particles

◦ Diamond

◦ SiC

◦ Alumina

◦ Chemistries used in CMP Slurries

◦ Rate additives

◦ Corrosion inhibitors

◦ Counterions, pH modifiers

◦ Chelators

◦ Oxidizers

◦ Biocides

◦ Colloidal stabilizers

◦ Selectivity or self-stopping additives for dishing/erosion control

◦ Surfactants

◦ Passivating agents

◦ Water soluble and dispersible polymers

◦ Dispersion of particles

◦ Impart surface functionality

◦ Rheology modifiers

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Advanced defect metrology has enabled detection of smaller defect sizes

TYPES OF ORGANIC RESIDUE ENCOUNTERED IN POST-CMP CLEANING

1. Corrosion-inhibitor ‒ metal complexes (i.e., Cu-BTA)

2. Surfactant residues

3. Interactions between slurry additives and cleaning additives

4. Pad debris (polyurethane ‒ hydrophobic or hydrophilic)

5. Brush debris (crosslinked PVA ‒ hydrophilic)

6. Plating additives

7. Filter or tubing shedding/residues

8. Biological debris (bacterial, skin cells, etc.)

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8

CHALLENGES IN SILICA PARTICLE CLEANING

◦ Fumed silica

◦ Synthesized by burning SiCl4

◦ Highly branched structure

◦ High surface area

◦ Classically used for oxide and tungsten

◦ High solids and high pH needed

◦ Microscratches lower yield market share decreasing

◦ Colloidal silica based slurries

◦ Synthesis

◦ Controlled growth from “silicic acid”

◦ High purity particles via Stober process –controlled hydrolysis of Tetraalkylorthosilicate

◦ Preferred particle for copper CMP, buff applications and many advanced products

◦ Surface functionalization possible

◦ Anionic functionality (carboxyl or sulfonic acid)

◦ Cationic (amines, quaternary ammonium)

O+

Si Si

H

SiOH + HO- SiO- + H2O

IEP = 4

Zeta potentialζ = 4πγ(ν/E)/ε

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Advanced defect metrology has enabled detection of smaller defect sizes

Many more particles at the same silica concentration and higher surface free energy/attractive forces for small particles

SILICA PARTICLE DEFECTS

◦ Particle adhesion mechanisms

◦ Physisorption (van der Waals attraction)

◦ Electrostatic attraction or repulsion (zeta potential)

◦ Chemisorption (chemical reaction particle-surface)

◦ Capillary condensation

Dispersed particlesHighly negatively chargedNo particle agglomeration

OHOH

OH

OHOH

OH

OH

OH

SiO2

OHOH

OH

OHOH

OH

OH

OH

SiO2

OHOH

OH

OHOH

OH

OH

OH

SiO2

Post-CMP Cu Post-CMP cleaning

O‒

OH

O‒

OHO‒

OH

O‒

O‒SiO2

O‒

OH

O‒

OHO‒

OH

O‒

O‒SiO2

O‒

OH

O‒

OHO‒

OH

O‒

O‒SiO2

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1. White, M. L. et al, Mater. Res. Soc. Symp. Proc. 991, 0991-C07-02 (2007)2. Hedge, S. and Babu, H. V. 2Eelectrochem. Soc. St. Lett. V7, pp. 316-318 (2008)3. 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 silica surface

q 1 q 2

r

Coulomb’sLaw

0

20

40

60

80

Silica slurry Older tech AG #1 AG #2 AG #3

Part

icle

siz

e (n

m)

Particle Size of 60 nm Silica CMP Slurry in Various Cleaners

No silica aggregation for AG formulae

-50

-40

-30

-20

-10

0

Older tech AG #1 AG #2 AG #3

ζ(m

V)

Zeta Potential of 60 nm Silica CMP Slurryin Various Cleaners

Zeta potential of all AG formulations is

highly negative

F = kq1 ∗ q2 / r2

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11

THE RATIONAL DESIGN OF POST CMP CLEANER PLANARCLEAN® AG COPPER AND COBALT CLEANERS

PlanarClean® AG ‒ Advanced Generation Cu or Co Cleaning Mechanism

M(0)

MOx

O O

HO

H

Mn+ M

High pH leads to charge repulsion between negatively

charged silica and negative metal oxide surface

Corrosion inhibitor

package controls galvanic

corrosion

Cleaning additive disperses silica and organic residue and

prevents reprecipitation

Etchant for controlled, uniform MOxdissolution to

undercut particles Organic additive attacks and removes metal-organic residue

SiO2

SiO2SiO2 SiO2Q:

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CHALLENGES IN COPPER PCMP

1. Advanced generations requiring very low or no defects

◦ Organic residue

◦ Silica particles

◦ Metal particles

2. Minimal/zero corrosion to exposed metals (Cu, TaN, Co, Ru)

◦ No galvanic corrosion or barrier attack

◦ Low Cu recess/etch rates 3‒10 nm technology

3. Minimal Cu surface roughness

4. Extended queue time

5. EHS friendly/green chemistry

◦ No TMAH

6. Low CoO

◦ Higher POU dilution

◦ Low chemical consumption

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BREAK-UP AND DISPERSION OF Cu(I)-BTA COMPLEXES

0%

20%

40%

60%

80%

100%

Older tech AG #1 AG #2

% B

TA r

emo

ved

Cu-BTA Film Removal for Various Cleaners

Cu(I)-BTA can redeposit ifCu is not properly complexed or dispersed

Additive tailored to attack Cu(I)BTA and similar films

◦ Fast kinetics◦ Thermodynamically favored◦ (Higher Cu binding constant

than BTA)

Cu(I)

Cu(I)

M(0)

MOx

Cu(I)-BTA film

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ADVANCED ADDITIVES ENABLE SILICA CLEANING

Cu(O)CuOx

SiO2

SiO2Cleaning additive disperses

silica and prevents reprecipitation/aggregation

Surface additive forms weakly interactingfilm that prevents silica (re)attachment

SEMI Defect Review# defects pareto (≥100 nm defects)

Pit

2D Al

2D Si

2D organic

AG #1 AG #2 AG #3Competitor0

50

100

150

200

250

300

AG #5

Silica Silica cluster Organic residue

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△V = - 0.343

15

CONTROLLING GALVANIC PROPERTIES IS THE KEY TO METAL-BARRIER/LINER CORROSION PERFORMANCE

△V = 0.005

Controlled electrochemical properties✓ Ligands to control potential gap✓ Passivation to modify resistivity

eCoCo 22

OHeOHO 225.0 22

Cu Co

OH- OH-O2

e- e- CO2+

e-

e-

Co OCP < Cu OCP-: Co not protected

Anodic Co corrosion(Co 1.329 Ǻ/min)

Nearly zero galvanic corrosion(Cu 0.078 Ǻ/min)

High Galvanic CorrosionNo Galvanic Corrosion ‒

Matched OCP

Copper

Cobalt

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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

PLANARCLEAN AG FORMULATIONS PROVIDE BETTER PASSIVATION ON BOTH Cu AND Co

When w -> 0 22/12222/1

2/1

)()1(

www

w

ctdldl

ct

RCC

RRZ a

RCC

CRCZ

ctdldl

dlctdl

22/12222/1

2/1222/1

)()1(

)(

www

www

Impedance Spectroscopy

CopperCobalt

Older formulation

AG #1AG #1

Older formulation

Additional Novel Cu Inhibitor Improves Cu Passivation

0

5000

10000

15000

20000

25000

Older tech AG #1 AG #2 AG #3

R r

esis

tan

ce (

mic

ro-o

hm

s)

Calculated Cu Film Resistance for Various PCMP Formulation

Evolution of AG surface passivation

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Sematech® is a trademark of Sematech, Inc.

ELECTRON MICROSCOPY SHOWS SIGNIFICANTLY IMPROVED Cu/Co CORROSION PERFORMANCE FOR PLANARCLEAN AG

TEM on 45 nm Cu/Co WafersSEM on Sematech® 754 Wafers

Older technology PlanarClean AG #1

PlanarClean AG #3PlanarClean AG #2

Older Technology

PlanarClean AG #2

PlanarClean AG #1

PlanarClean AG #3

Minimal corrosion nearCu-Co interface

Controlled, smooth etching with minimal galvanic/edge corrosion

Corrosion near Cu-Co interface

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CLEANING CHALLENGES FOR BULK COBALT

◦ Post-CMP bulk Co cleaners

◦ 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)

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

◦ Uniform, smooth etching (no pitting)

SEM

AFM

◦ Poorly passivated surface or insufficient complexation

◦ Dendritic CoOx growth

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Proper complexation and inhibitors can control dendritic cobalt corrosion

SOME CHALLENGES ASSOCIATED WITH CO CLEANER DEVELOPMENT

Ideal pH range for silica slurry removal to prevent hydroxide precipitation

Co Pourbaix Diagram

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

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

Mtn+Xn-

OHOH OH OH OH OH OH OH OH

Co

CoO + Co2O3

Surface passivation

Co

CoO + Co2O3

Co2+

H2O

H2O

H2O

H2O

OH2

OH2

Co2+

H2O

H2O

HO-

HO-

OH2

OH2

Ksp = 1.6 x 10-16

Co3+

HO-

H2O

HO-

HO-

OH2

OH2

Ksp = 1.6 x 10-44

Co2+

L

L

L

L

L

L

Ksp = soluble

2 HO-

[O]3 HO-

6 L

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

Component A – Ensures negative charges on W surface and organic particles

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

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

W W W W W W W W W W W

O- O- O- O- O- O- O- O- O- O- O-

Organicparticle

Metal Particle

Organicparticle

W W W W W W W W W W W

OrganicParticle

MetalParticle

MetalParticle

Al2O3ST(+)-SiO2

OrganicParticle

Al2O3ST(+)-SiO2

MetalParticle

W W W W W W W W W W W

O- O- O- O- O- O- O- O- O- O- O-

Al2O3ST(+)-SiO2

Al2O3ST(+)-SiO2

D- B-

B-

B-B-

B-

B-

B-D-

D-

D-D-

D-

D-

D- B-

B-

B-B-

B-

B-

B-D-

D-

D-D-

D-

D-

W W W W W W W W W W W

Removed by DIW Rinse

Al2O3ST(+)-SiO2

Organicparticle

Metal Particle

D- B-

B-

B-B-

B-

B-

B-D-

D-

D-D-

D-

D-

Post CMP W Cleaners

◦ Market increasingly challenged by W recess

◦ High pH commodities (SC1, dil NH3)

◦ Traditional low pH cleaners

◦ Low W etch rates (

21

Top right graph: Liu, et al. J. Mater. Chem A, Issue 6, 2014Lower right graphics: "Hetero and lacunary polyoxovanadate chemistry: Synthesis, reactivity and structural aspects". Coord. Chem. Rev. 255: 2270–2280. 2011

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

Dil NH3 (1:2850)

SC1: 1:50 > 6 A/min

WO3 negative at all pHs of interest

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

Contact Angle

Dirty Dirty

Si3N4control

Clean Clean

Clean, hydrophilic

Silica NP

Organic residue

FTIR

Cleaning additive removes cationic contamination from dielectric surface and disperses

Si3N4 surface typically highly contaminated by cationic dishing

and erosion control agents

AG- W cleaner

Electrostatic repulsion during CMP

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

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

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

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

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

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

9618defects

Slurry ball clusterSlurry ballSilicaOrganic

10

30

50

70

90

110

130

150

AG-W#1 SC-1 AG-W#3AG-W#2 AG-W#40

50

100

150

200

250

Slurry ballSlurry clusterOxideOrganic-silicaOrganic

Slurry ballSlurry clusterOxideOrganic

AG-W#2 AG-W#3 AG-W#4AG-W#10

5

10

15

20

25

30

23

9618 defects ‒SC1 or dil NH3

No cleaning on Si3N4

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CHALLENGES FOR CERIA POST-CMP CLEANING FORMULATIONS

1. Many different ceria types

1. Calcined

2. Precipitated/colloidal

2. Organic additives vary depending on goals

1. Rate additives (ILD)

2. Polymeric or small molecule selectivity additives

1. Stop on nitride or poly

2. Reduce feature size dependence

◦ Highly toxic ◦ Unformulated◦ Environmentally unfriendly◦ Damage to dielectric

Entegris AG Ce-XXXX formulations◦ Improved particle and metal removal◦ Replace toxic commodity cleaners◦ Environmentally friendly◦ No damage to dielectric surfaces◦ Ce residue post-CMP cleaning < 1010 atoms/cm2

Negative CeriaPositive Ceria

CeO2 CeO2

Current industrial POR (commodity clean): inefficient and environmentally unfriendly ◦ DHF◦ SC-1◦ SC-1 + DHF◦ SPM (H2O2 + H2SO4)◦ TMAH + SC-1

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UNDERSTANDING THE CERIA PARTICLE SURFACE CHEMISTRY ENABLES THE DESIGN OF EFFICIENT CERIA CLEANERS

Ce3+2O3Few carbonates physisorbed

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

0 2 4 6 8 10 12 14

Zeta

po

ten

tial

(m

v)

CeO2

+pHIEP

_

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CERIA POST-CMP CLEANING FORMULATION – MECHANISTIC DESIGN CONCEPT

Formulation Design Options

1. High pH hydrolysis of -Ce-O-Si-bonds by HO- nucleophilic attack to Ce-center + additives needed to stabilize –Ce-OH species and prevent redeposition

2. High pH partial etch/dissolution of the surface –Si-O-Ce- groups + redeposition prevention

3. Bond-breaking additives, followed by CeO2 complexation, and particles stabilization and dispersion

Si

O‒

Si

OH

Si

OH

Si

O‒

Si

O‒

Si

O‒

Si

O‒

Si

O‒

CeO2 CeO2 CeO2

Si

O‒

Si

O‒

Si

O‒

Si

O

Si

O‒

Si

O

Si

O‒

CeO2 CeO2CeO2 CeO2

CeO2-SiO2 Surface Interactions

Chemical bondCe – O – Si

Electrostatic attraction

Si Si SiSi Si Si Si Si

O‒H+

O‒H+

O‒H+

O‒H+

O‒H+

O‒H+

O‒H+

O‒H+

Si

O‒

Si Si

O‒ O‒

HO‒

-Ce-OH+

-Si-OH HO‒

SiO2

Bond-breaking

regent

2

Ce-O-Si Bond-Breaking Mechanisms

31

CeO2 CeO2 CeO2

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SEM AND ICP-MS CHARACTERIZATION

◦ ICP-MS supports the dark field microscopy data and it shows ˃150× improvement over SC-1

◦ SEM data strongly supports DFM and ICP data

250

200

150

100

50

0

Ce

ion

(p

pb

)

SC-1 (1:1:5) A1-42 AG-CeXXXX

[Ce]/cm2 = 1.23 × 1016 [Ce]/cm2 = 2.36 × 1013

Dark field microscopy

250

200

150

100

50

0

Ce

tota

l are

a

SC-1 (1:1:5) A1-42 AG-CeXXXX

150× improvement

ICP-MS data

Si3N4

TEOS

SC-1 (1:1:5)

AG-CeXXXX

PETEOS

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FUTURE DEVELOPMENT CHALLENGES FOR POST-CMP CLEANING

◦ Particle removal is becoming increasingly difficult

◦ Charge repulsion shown to be a key driver towards cleaning performance

◦ Covalent bonds must be broken to remove particles

◦ Selection of bond breaking agents is critical for ceria particle removal

◦ Organic residues of various types are often a significant contributor to defectivity

◦ Rate of attack on Cu(I)-BTA polymer, dispersion and complexation important for removal and preventing re-deposition of organic residues and particles

◦ Surfactant and slurry residue is increasingly challenging and requires tailored solutions for cleaning

◦ Corrosion for advanced nodes (3‒10 nm) is increasingly an issue

◦ Impedance spectroscopy and Tafel plots have been used to optimize corrosion inhibiting package

◦ OCP gap must be minimized by optimal ligand selection to minimize galvanic corrosion

◦ Proper complexation and inhibitors can control dendritic cobalt corrosion

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Entegris®, the Entegris Rings Design™, Pure Advantage™, and other product names are trademarks of Entegris, Inc. as listed on entegris.com/trademarks. ©2018 Entegris, Inc. All rights reserved.

29 | CONFIDENTIAL

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