Development of an Advanced NodeHigh Selectivity Tungsten Slurry

James SchlueterBlake Lew, Hongjun Zhou, and Tom Shi

Air Products and ChemicalsElectronics Division, Planarization Platform

Tempe, AZTempe, AZ

CMP Users Group Meeting

Albany, NY

15-May-2013

5/10/20131

Agenda

•Tungsten Background / Overview

•Tungsten Polish Mechanism

•Performance Targets

•Key Slurry Component Selection

•Polishing Performance Results

•Summary

5/10/20132

Tungsten CMP Overview

•Tungsten History:- CMP replaced RIE for Tungsten plug overburden removal

CMPTungsten

•Other Applications Followed:- Local Interconnect Lines

- High K Metal Gate (HKMG)

5/10/20133

H2O2 Based Tungsten Slurry Mechanism

• H2O2 (hydrogen peroxide) is used as an oxidant and has a standard redox potential of 1.68eV.

H2O2 + HO* + OH-Solid

StateCatalyst

Solid State

Catalyst

4

• Addition of a metal oxide solid state (heterogeneous) catalyst decomposes H2O2 into hydroxyl radicals and anions.

• Hydroxyl radicals (*OH) have a much stronger oxidizing potential than H2O2.- 1.68 vs > 2.60eV

H2O2 Based Tungsten Slurry Mechanism

• Hydroxyl radicals rapidly form a WO3 and WO42- mixture on the metallic W surface.

• WO42- exists as H2WO4 at acidic pH.

• H2WO4 and WO3 films are removed from the surface under applied mechanical force during polishing.

5

under applied mechanical force during polishing.

WWO3/H2WO4/WO4

2-

Tungsten Slurry MechanismeV-pH Equilibrium Diagram for Tungsten in Water

5/9/20126

Oxidation

pH

Tungsten High Selectivity Slurry Performance Targets

•High Removal Rate (>4000Å/min.)

• Low WIW NU (< 3% 1s)

•High or Tunable Selectivity (>100:1) *

• Low Defectivity

• Low Oxide Loss and Array Erosion *• Low Oxide Loss and Array Erosion *

• Long Shelf Life (> 1 yr)

• Low Cost of Ownership

*High Selectivity is required to minimize overalldielectric loss and array erosion (topography)

5/10/20137

Key Base Slurry Components

Key Component Purpose Result

Oxidizer (H2O2)Oxidize Metallic W into WO3

and WO42- Create/Support W Removal Rate

CatalystCreate Super Oxidizing Hydroxyl Radicals (*OH)

Support/Increase W Removal Rate

Abrasive Mechanical Removal of WO3 Increase W Removal Rate

• Tungsten CMP mechanism has unique slurry formulation requirements- Unique catalytic oxidation process

5/10/20138

Corrosion Inhibitor Protect W MetalLow Static Etch Rate (SER)

Eliminated/Minimized W Corrosion

pH Adjustor Adjust pH of Formulation Modulation of Film Selectivity

Experimental Setup

• AMAT Mirra 200mm Polisher (Titan head)

• Dow IC1000 Pad

• Diamond Disc Pad Conditioning

• 3 psi Downforce• 3 psi Downforce

• 120 rpm Platen Speed

•Base Slurry: Medium-High Selectivity

5/10/20139

Key Slurry ComponentspH Adjustor

• Base Tungsten Formulation: Medium-High Tungsten : TEOS Selectivity• W Removal Rate: > 5000 Å/min.• TEOS Removal Rate: 250 Å/min.

• W : TEOS Selectivity: ~20:1

Removal Rates Selectivity

300

350

5000

6000

TE

OS

Re

mo

va

l Ra

te (

A/m

in.)

Tun

gst

en

Re

mo

va

l Ra

te (

A/m

in.)

Tungsten and TEOS Removal Rate by pHMirra, IC1000 Pad, 3psi

200

250

Tun

gst

en

: T

EO

S R

R S

ele

ctiv

ity

Tungsten and TEOS Selectivity by pHMirra, IC1000 Pad, 3psi

Control

5/10/201310

• Increasing pH decreased TEOS RR and increased W : TEOS Selectivity

0

50

100

150

200

250

0

1000

2000

3000

4000

TE

OS

Re

mo

va

l Ra

te (

A/m

in.)

Tun

gst

en

Re

mo

va

l Ra

te (

A/m

in.)

Increasing pH

W RR

TEOS RR

Control

20 2229

37 42

0

50

100

150

200

Tun

gst

en

: T

EO

S R

R S

ele

ctiv

ity

Increasing pH

Key Slurry ComponentsSolid State Catalyst Selection

Removal Rates Selectivity

40

60

80

100

120

140

160

2000

3000

4000

5000

6000

Tun

gst

en

Re

mo

va

l R

ate

(A

/min

.)

Tungsten and TEOS Removal Rate by Catalyst TypeMirra, IC1000, pH, 3psi

W RR

TEOS RR

6371

100

150

200

250

Tun

gst

en

: T

EO

S

RR

Se

lect

ivit

y

Tungsten to TEOS Selectivity by Catalyst TypeMirra, IC1000, 3psi

5/10/201311

• Type C Solid Catalyst provides:- Highest W RR

- Lowest TEOS RR

- Highest W:TEOS Selectivity (>70:1 in Base Formula)

- Also provides WIW NU benefit (later slide)

0

20

40

0

1000

Type A Type B Type C

Tun

gst

en

Re

mo

va

l R

ate

(A

/min

.)

Catalyst Type

Control

34

0

50

Type A Type B Type C

Tun

gst

en

: T

EO

S

RR

Se

lect

ivit

y

Catalyst Type

Control

Key Slurry ComponentsCorrosion Inhibitor Selection

Static Etch Rate (SER)

3

4

5

6

7

8

Tun

gst

en

Sta

tic

Etc

h R

ate

(N

orm

ali

zed

)

Tungsten Static Etch Rate by Corrosion Inhibtor Type40C

• High Static Etch Rate (SER) has been correlated to tungsten corrosion.

• Some Corrosion Inhibitors can reduce SER, but often also decrease tungsten Removal Rate.

5/10/201312

0

1

2

3

None Type A Type B Type C Type D

Tun

gst

en

Sta

tic

Etc

h R

ate

(N

orm

ali

zed

)

Corrosion Inhibitor

Control

Key Slurry ComponentsCorrosion Inhibitor Selection

Removal Rates Selectivity

40

60

80

100

120

140

160

2000

3000

4000

5000

6000

TE

OS

Re

mo

va

l R

ate

(A

/min

.)

Tun

gst

en

Re

mo

va

l R

ate

(A

/min

.)

Tungsten & TEOS Removal Rate by Corrosion Inhibtor TypeMirra, IC1000, 3psi

W RR

TEOS RR137

109

86

110

203

100

150

200

250

Tun

gst

en

: T

EO

S

RR

Se

lect

ivit

y

Tungsten to TEOS Selectivity by Corrosion Inhibtor Type

Mirra, IC1000, 3psi

• Corrosion Inhibitor Types A, B, & C reduce tungsten RR & Selectivity.

• Corrosion Inhibitor Type D:- Does not reduce tungsten RR

- Reduces TEOS RR

- Increases W to TEOS Selectivity

- Suppresses SER (previous slide)

5/10/201313

0

20

40

0

1000

None Type A Type B Type C Type DT

EO

S R

em

ov

al

Ra

te (

A/m

in.)

Tun

gst

en

Re

mo

va

l R

ate

(A

/min

.)

Corrosion Inhibitor

Control0

50

None Type A Type B Type C Type D

Tun

gst

en

: T

EO

S

RR

Se

lect

ivit

y

Corrosion Inhibitor

Control

Key Slurry ComponentsPrimary Abrasive Selection

Removal Rates Selectivity

40

60

80

100

120

140

160

2000

3000

4000

5000

6000

TE

OS

Re

mo

va

l R

ate

(A

/min

.)

Tun

gst

en

Re

mo

va

l R

ate

(A

/min

.)

Tungsten & TEOS Removal Rate by Abrasive TypeMirra, IC1000, 3psi

W RR

TEOS RR

182

90 93

50

100

150

200

250

Tun

gst

en

: T

EO

S

RR

Se

lect

ivit

y

Tungsten & TEOS Removal Rate by Abrasive TypeMirra, IC1000, 3psi

• Presence of primary Abrasive, in addition to Solid Catalyst, is critical for providing tungsten removal rate.

• Abrasive Type A or Type B show similar performance

5/10/201314Air Products Internal Use Only

0

20

40

0

1000

None Type A Type BT

EO

S R

em

ov

al

Ra

te (

A/m

in.)

Tun

gst

en

Re

mo

va

l R

ate

(A

/min

.)

Abrasive Type

0

50

None Type A Type B

Tun

gst

en

: T

EO

S

RR

Se

lect

ivit

y

Abrasive Type

Tungsten Removal Rate Profiles60 sec. Polish Time

3000

4000

5000

6000

W R

em

ov

al

Ra

te(A

/60

se

c.)

W Removal Rate Profile (40 sec.)Mirra, IC1000 Pad, 3 psi

Control - wafer 1

Control

New Formulation

5/10/201315

0

1000

2000

-100 -80 -60 -40 -20 0 20 40 60 80 100

W R

em

ov

al

Wafer Radius (mm)

Control - wafer 1

Control - wafer 2

New Formulation - wafer 1

New Formulation - wafer 2

• New Formulation shows improve performance vs Control• Higher W Removal Rate• Improved WIW NU• Higher W : TEOS Selectivity (previous slides)

Tungsten Removal Profiles (40 sec.)Corrosion Inhibitor Type B vs Type D

Catalyst Type A vs Type C

Type C Catalyst

Type A Catalyst

Type B Corrosion Inhibitor Type D Corrosion InhibitorType C Catalyst

Type A Catalyst

Rem

oval A

mount

(Å/40 s

ec.)

Rem

oval A

mount

(Å/40 s

ec.)

5/10/201316

Wafer Radius (mm) Wafer Radius (mm)

• Corrosion Inhibitor Type D increases tungsten removal rate and improves RR non-uniformity (lower center to edge delta)

• Catalyst Type C increases tungsten removal rate at the edge- Allows process tuning for the achievement of a potentially desirable fast edge

removal rate

Rem

oval A

mount

(Å/40 s

ec.)

Rem

oval A

mount

(Å/40 s

ec.)

Summary• Tungsten was the First Metal Based CMP Process

Implemented by the Semiconductor Industry.

• CMP of Tungsten Films is a Unique Mechanism Requiring a Specialized CMP Slurry Formulation.

• High Selectivity of W to SiO2 is Required to Minimize Dielectric Loss and Topography.Dielectric Loss and Topography.

• Selection of Key Slurry Formulation Components is Critical for Achieving:- High Tungsten and Tunable Dielectric Removal Rates

- Desired Tungsten Removal Rate Profile (WIW NU)

- High or Tunable Selectivity

- Low Corrosion (Defects)

5/10/201317