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How Much Do We Really Know About the Chemical Reactions Occurred During Cu CMP?

Prof. Dr. Yuzhuo Li

Global Electronic Business Unit

BASF, Ludwigshafen

Yuzhuo.li@basf.com

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Presentation Outline

� BASF CMP slurry development setup

� Representative results

� Innovative particles for copper slurries

� Progress in barrier slurries

� Polishing debris management for STI

� Fundamental understanding of CMP

� Conclusions and Acknowledgement

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Cu CMP for interconnect (Cu)Barrier CMP for interconnect

Shallow trench isolation (STI)

TSV for 3D chips

BASF CMP Slurry DevelopmentAccording to Application

High K metal gate

Interlayer dielectric (ILD)

Established Applications

New Applications

Type of CMP Slurry for:

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BASF CMP Slurry Development Setup

� Structured process checks chemical and applications viability

� Practical and focused approach accelerates commercialization

PolishingFormulation

BASF Chemistry

BASF R&D Lab

BASF Application LabTaiwan (200 mm)

BASF R&D Polishing Lab Germany (200 mm)

BASF Contract LabsUSA (200/300 mm)

Customers’ Needs(Process Targets)

Data packageDemo sample

Particle Technology(Internal / Outsourced)

Promising prototypes Robust prototypesCompatibility

BASF Product ManagementGlobal

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Silica Particle Polymer Particle BASF Adaptive Organic Particle

Wafer

Stress-free Stress-free Stress-free

Compressed during CMP

Compressed during CMP

Compressed during CMP

Pad

No Deformation Deformation

Dissociation Wafer

Pad

Wafer

Pad

©KT 2008

Chemistry Innovation in CMPAdaptive Organic Particle

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CONFIDENTIAL

Typical Dishing Results for PC606 (100 um lines)

~ 35 sec over-polishing under 1 psi, 95/85 rpm, 200 ml/min polishing condition

Baseline slurry PC606x21a Baseline slurry PC606x21b

Dishing of Cu Patterned Wafer

(1 psi, ~ 35 sec Over-Polishing)

0

100

200

300

400

500

600

3 (Middle) 4 5 (Center)

Die #

Dis

hin

g (

A) 100_100 Line

10_10

9_1

100_100 Pad

Dishing of Cu Patterned Wafer

(1 psi, ~ 35 sec Over-Polishing)

0

100

200

300

400

500

600

2 3 (Middle) 4 5 (Center)

Die #

Dis

hin

g (

A) 100_100 Line

10_10

9_1

100_100 Pad

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Low Erosion on 9x1 Features shown by Profilometry TracesPark System AFM Profilometer Scan

Die#2 9_1 Feature Die#3 (middle) 9_1 Feature

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Matching Surface Chemistry Increased efficiency of material removal

More effectiveLess effective

Activating / Passivating film•Generated in-situ

•To be removed

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BASF TSV Cu CMP Slurry Defy Dishing Trend Predicted by

Polishing Rates for Conventional Slurry

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 5000 10000 15000 20000 25000 30000 35000 40000

MRR (A/min)

Dis

hin

g 1

00/1

00 u

m (

A)

BASF PC501

for TSV

Polishing rate vs dishing valuefor conventional slurry

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Advanced BASF Barrier SlurryMaximize removal rate with minimal solids content

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5 6 7

Abrasive (%)

Rel. Ta MRR

Rel. Cu MRR

Rel. BD MRR

Product Generations

Abrasive content significantly reduced

Key performance characteristics retained

Benefits for the customers:

1. Lower defects

2. Lower COO

3. Lower burden on filters4. Simpler waste treatment

0.25 micron line array after barrier polish

Minimal dishing and erosion

No EOE (“tiger teeth / fangs”)

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BASF Planapur STI Products

Si Wafer

Pad oxide

Stopping Layer

Step height (P1)

SiN (P2A)

PolySi (P2B)

PS5545P2B

PS5010P2A

PS5600P1

Slurry CodeProcess

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PS5600 (P1) – High RR STI Bulk100 x 100 line

0

1000

2000

3000

4000

5000

3159 A

Th

ickn

ess (

in a

ng

str

om

s)

Time (in sec)

3.5 psi

5 psi

0 60

4947 A

New

BASF particle

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Copper Surface Oxidization/Passivation

Bulk metallic copper

Oxidized copper rich in

Cu (I) and Cu (II) ions

Copper ions diffuseinto aqueous phase

a

b

c

d

Dense passivating film

Copper ions diffusionare enhanced

Bulk metallic copper

Oxidized copper rich in

Cu (I) and Cu (II) ions

Copper ions diffuseinto aqueous phase

a

b

c

d

Dense passivating film

Copper ions diffusionare enhanced

Cu (I/II)

H2O

Cu (I/II)Cu (I/II).L2Cu (I/II).L2

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Effect of Cu Ion on Water T1

0 500 1000 1500 2000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

T1 (

se

co

nd

)

Concentration of copper ions (ppm)

0 100 200 300 400 500

0

1

2

3

4

5

0 500 1000 1500 2000

0

2

4

6

8

10

12

14

16

18

20

Concentration of copper ions (ppm)

1/T

1(s

ec-1

)

Concentration of copper ions (ppm)

y=0.0094x+0.2429

R=0.99941

1/T

1 (se

c-1)

y=0.00855x+0.3582

R=0.99965

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0.0 0.1 0.2 0.3 0.4 0.5 0.60.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

T1

(secon

d)

Weight percent (%)

Film forming

None film

forming

Why induction period?

Classification of Complexing Agent

Cu (I/II).L2

Cu (I/II).Ln

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Effect of Silica on BTA-Cu Complex

0 3 6 9 12 15

1.8

2.0

2.2

2.4

2.6

2.8

3.0

T1 (

se

cco

nd

)

BTA concentration (mM)

T1 values for water proton of 34 ppm Copper ions dependence on BTA concentration:

(■) in the presence of 0.2%N85 (●)without silica

Without silica

With silica

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Reaction Between Cupric Ions and BTA

0.0 0.1 0.2 0.3 0.4 0.5 0.62

3

4

5

6

7

Water

Water+34 ppm Cu2+

Water+250ppm Cu2+

pH

BTA (wt %)

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Reaction Between Glycine and BTA

0.0 0.1 0.2 0.3 0.4 0.5 0.62

3

4

5

6

7

8

pH

Glycine (wt %)

Water

Water+34 ppm Cu2+

Water+250ppm Cu2+

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BTA Competes with Glycine for Cupric

0.0 0.1 0.2 0.3 0.4 0.5 0.63.2

3.4

3.6

3.8

4.0

4.2

4.4

pH

BTA (wt %)

No Cu

With Cu

Contains

0.6% Glycine

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Particle size of samples containing varying amount of BTA and cupric ions

(■■■■ for 34 ppm and ●●●● for 250 ppm)

0.0 0.1 0.2 0.3 0.4 0.5 0.6

4

8

12

16

20

24

28

32P

art

icle

siz

e (

nm

)

Concentration of BTA (wt %)

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TEM images of samples containing 0.2% BTA and varying amount of cupric ions

(left: 34 ppm and right: 250 ppm).

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TEM images of samples collected from the wafer surfaces after the exposure to a solution containing hydrogen peroxide, glycine, and BTA (left) and a solution containing hydrogen peroxide and

BTA (right).

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Summary

� BASF CMP slurry development setup

� Strong global R&D organization

� Local presence to support our customers

� Significant progress made in 2008/2009

� Innovative particles for copper slurries

– Functionality and morphology design

� Progress in barrier slurries

– Lower COO and defect level

� Polishing debris management for STI

– Lower defect

� Fundamental understanding of CMP

– Important component in slurry and R&D team development

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Acknowledgment

� BASF (Germany)� Dr. Klemens Mathauer

� Dr. Michael Lauter� Dr. Mario Brands

� Dr. Vijay Raman

� Dr. Claus Poppe

� Mr. Yongqing Lan� Mr. Roland Lange� Ms. Elisabeth Seltzer

� Mr. Kennith Rushing� BASF (Asia)

� Dr. Charles Lin

� Mr. Kevin Teo (USA)

� Mr. JJ Chu� Mr. William Chiu� Mr. Daniel Shen� Mr. Robert Lo

� STLN/Clarkson University (USA)� Dr. Changxue Wang� Professor S.V. Babu

� Mr. Shyam Venkataraman� Mr. Paul Vendadi

� Mr. Ke Wang

� Mr. Harvey Pinder� Dr. Valli Ramji� Mr. Jeff Yu

� ISIT (Germany)

� Professor G. Zwicker

� Sun Yat-sen University (China)

� Professor Menglian Gong

� Ms. Yan Li