APPROACH—Two main cleaning approaches:

(1) W surface charge reversal, using cleaning additives able to adsorb at the W surface.Other cleaning additives prevent residue redeposition.

(2) Particle charge reversal and electrosteric protection using organic additives à stronglynegative charged surfaces à best cleaning.

SUMMARY—• Two main approaches followed: (1) reverse W surface charge; (2) particle charge reversal.

• Latter approach results in strongly negative charged surfaces and best cleaning.

• AG W-100 represents a significant improvement in cleaning.

• CIP2 shows the best performance on W, SiN and SiO2 blankets.

• This feature enables advanced node W cleaning for memory devices.

Post-CMP cleaners for tungsten at advanced nodesRuben R. Lieten, Daniela White, Thomas Parson, Shining Jenq, Don Frye, Michael White — Entegris, Inc.

Lieve Teugels, Herbert Struyf — imec

SCOPE OF WORK—• Design of formulated post-CMP cleaners for W plugs with TiN as barrier liner,

dielectrics SiO2 and Si3N4, for use at 10 nm technology node (40 nm metal pitch)

INTRODUCTION—• W bulk and barrier CMP slurries consist of:

— (a) abrasive particles (fumed alumina or silica: fumed or colloidal)

— (b) oxidizer (usually H2O2): W à W(VI)O3 for removal by slurry abrasive

— (c) H2O2 decomposition accelerator

— (d) W corrosion protection additive

• Particle charge in low pH W CMP slurries are usually positive (isoelectric point, pHIEP Al2O3 = 6-8and pHIEP SiO2 = 2-4).

• W surface is always negatively charged at pH >3 (pHIEP W = 2-3, ) à strong electrostatic attractionW surface and residual particles during PCMP cleaning.

Significant surface contamination after CMP: abrasive particles, organic residue, pad debris, metal cations.

RESULTS AND DISCUSSION—• Corrosion: Minimized Galvanic corrosion by using new and specific ligands that adsorb

on metal or barrier liner à additional passivation less noble material

• Particle cleaning: Upon mixing with AG-W100, all nanoparticle dispersions reversedcharges from positive to negative (Al2O3, WO3, SiN) or became more negatively charged(SiO2, SiC) à strong repulsion (from Zeta Potential)

• Organic residue cleaning:

— Contamination takes place during post-CMP rinsing with DI water

— Organics disappeared after 1‘ cleaning of SiN with AG-W100 (FTIR-ATR)

• Defectivity: 300 mm CMP + brush cleaning

— AMAT Reflexion® LK polishing tool with integrated brush cleaner (Desica)

— IC1010 pad, silica abrasive slurry (100 nm particle size), PVA brushes

— Defect inspection by laser light scattering (SP3, KLA-Tencor Corp.)

— dAmmonia as reference (W and other metals are significantly etched)

— dAmmonia dissolves some of the SiO2 surface and particles

— Significant progress in removal of organic residues

— AG W-100 represents a significant improvement in cleaning

— CIP2: unique cleaning additive designed to disperse silica and prevent reattachmentto SiO2 surface

Component

TABLE 1: PLANARCLEAN® AG-W100 FORMULATION ADDITIVES LIST – FUNCTION AND MECHANISM

A

B & C

D

Function

Non-TMAH pH adjustor

Complexing agents

Dispersing agents

Mechanism

W surface hydroxylation and good wetting

Negative surface charge surface of wafer and contamination

Surface modification of particles to preventagglomeration and re-precipitation

Prevent aggregation and control etch rate

Entegris®, the Entegris Rings Design™ , Pure Advantage™ and PlanarClean® are trademarks of Entegris, Inc.Reflexion® is a registered trademark of Applied Materials, Inc.

©2016 Entegris, IncUCPSS–2016 www.entegris.com

AG-W100-1

AG-W100-2

CIP2W105 CIP1 dAmmonia

16000

14000

12000

10000

8000

6000

4000

2000

0

Figure 1: Number of defects (particles and organic residue) pareto on silicon-nitride blanket wafers (bobom figure is a zoom in of top figure).

Figure 2: Number of defects (particles and organic residue) pareto on W blanket wafers.

Figure 3: Number of defects (particles and organic residue) pareto on SiO2 blanket wafers.

Number of defects pareto (≥60 nm defects)

2D organicTopographySlurry ball clusterSlurry ball2D cluster

AG-W100-1

AG-W100-2

CIP2W105 CIP1 dAmmonia

40

35

30

25

20

15

10

5

0

Number of defects pareto (≥100 nm defects)

2D silicaSlurry clusterSlurry ball2D flat2D cluster

AG-W100-1

AG-W100-2

CIP1 CIP2

350

300

250

200

150

100

50

0

Number of defects pareto (≥60 nm defects)

AG-W100-1

AG-W100-2

CIP2W105 CIP1 dAmmonia

200018001600140012001000800600400200

0

Number of defects pareto (≥65 nm defects)

2D organicSlurry ball clusterSlurry ball2D cluster

Slurry ballSlurry clusterSilicaOrganic-silicaOrganic

Si sub. Si sub.

Figure 4: W post-CMP cleaning formulation – mechanistic design concepts

CMP slurry abrasive:• Al2O3 ζ> 0 mV;

• Surface-treated silica(ST-SiO2)–ζ > 0 mV;

• Silica (ζ > 0 mV)

• W ζ reversal

• Non-TMAH additive fororganic residue removal

Post-CMP surfacePrimary approach

(1) (2)

Figure 5: Tunability of the galvanic corrosion W/TiN for PlanarClean AG W-100 type formulations

abs

(1) [

A]

CIP-2

-100 -0.75 -0.50 0.50-0.25 0.25-0.00

W

TiN

W passivating layer

abs

(1) [

A]

CIP-10.001

0.0001

0.00001

0.000001

0.0000001

0.00000001

0.001

0.0001

0.00001

0.000001

0.0000001

0.00000001

-100 -0.75 -0.50 0.50-0.25 0.25-0.00

W

TiN

Di�erent ph organic solvent pH adjustor

ζm

V

3020100

-10-20-30-40-50

Al203 SiO2 WO3 Si3N4 SiC

z, mV, control z, mV in AG-W100

Figure 6: Zeta Potential, ζ , (mV) for slurry abrasives (alumina, silica), W and dielectrics surfaces in contact with AG-W100 formulation.

Si3N4 control (clean)

Baseline

Form

amid

e co

nta

ct a

ng

le (d

egre

es) 14

12

10

8

6

4

2

0AGW-100

z% DAGW-100 baseline

AGW-100 y% D

AGW-100 x% D

Post-CMP (slurry con-taminated)

Clean hydrophilic D

irty

Figure 7: Formamide contact angle measurements on contaminated and cleaned SiN surfaces.