Novel Particles and Matching Chemistry in CMP Slurries for 22 nm

Technology Node

7/24/2008 CMPUG July 20081

Technology Node

Yuzhuo Li

BASF SE CAE/ED

Ludwigshafen, Germany

Presentation Outline

� Why functionalized particles?

� Increase removal rate?

�Enhance planarization efficiency?

� Lower defect level?

CMPUG July 2008 2

� Lower defect level?

� Why matching chemistry?

�Allow surface functionality to express

�Balance the need for material removal and transport

� Lower defect level

Ta Removal Using Various Particles: Silica, Alumina, Diamond, h-BN, and Abrasive Free System (AFS) Vesicles

500

600

700

800

Ta

MR

R (

A/m

in)

Ta MRR (A/min)

Hint 1: Hardness: Diamond>Alumina> Silica>h-BN

CMPUG July 2008 3

0

100

200

300

400

500

Diamond Alumina Silica BN AFS Vesicle

Ta

MR

R (

A/m

in)

Ref: N. Wang, J. Keleher, Y. Li, BN particles for Cu CMP, VMIC 2003

Abrasive free System

Hint 2: Alumina is rarely used as abrasive for barrier CMP

For effective material removal, surface

tribochemical reactions must take place

CMPUG July 2008 4

Tetsuya Hoshino, Yasushi Kurata, Yuuki Terasaki, Kenzo Susa, Mechanism of polishing of SiO2 films by CeO2 particlesJournal of Non-Crystalline Solids 283 (2001) 129-136

A. Vijayakumar, T. Du, K.B. Sundaram, V. Desai, Polishing mechanism of tantalum films by SiO2 particles, Microelectronic

Engineering 70 (2003) 93-101

Using Ceria to Polish SiO2 Using silica to polish Ta (Ta2O5)

Form efficient multiple bonds between the abrasive particle and polished surface

Correlation between surface hydroxyl

groups and Ta removal rate

50

60

70

80

90

Ta M

RR

(n

m/m

in)

CMPUG July 2008 5

0

10

20

30

40

50

0 20 40 60 80 100

Relative Hydroxyl Content (%)

Ta M

RR

(n

m/m

in)

Y. Li et al Thin Solid Films, 497, 1-2, 2, 2006, pp 321-328.

Ta MRR (A/min) and surface OH content

and NMR relaxation time slopes

5

6

7

8

Ta M

RR

(A

/min

)/100

Ta MRR (A/min)/100

T1 Slope

CMPUG July 2008 6

R. Mackay, J. Zhang, Q. Wu and Y. Li, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004, 250, 1-3, pp343-348.

0

1

2

3

4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

[OH] on surface (mmol/g)

Ta M

RR

(A

/min

)/100

Tribochemical Reaction Enhances

Planarization Efficiency

Upon exposure to

Slurry Abrasives

Initial Step Height

Uniform adsorption

Uniform adsorption

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Step height reduction =>Planarization

More tribochem events:

High MRR

Fewer tribochem events:

Low MRR

Pad

Uniform Surface Chemical Reactions

Lower Planarization Efficiency

Upon exposure to

Chemical Etchant

Initial Step Height

Uniform attack

Uniform attack

CMPUG July 2008 8

No step height reduction => No Planarization

Chemical reactions:

High MRR

Chemical reactions:

High MRR

Pad Pad

For oxide CMP, silica is abundantly

functionalized with hydroxyl groups

OH-

OH-OH-

OH

OH

CMPUG July 2008 9

OH

Bare abrasiveEtchant if freely

In solution phase

OH

Functionalized abrasive

Other factors to be considered, for examples:

• How close these functionalized particles can get to the surface to be polished?

• Relative surface charges: silica vs. ceria• Relative thickness of protective sphere: variation in hydrated layer on silica

• How rigid the multiple contacts between the particles and surface has to be?• Relative force distribution: polyvinyl alcohol vs. silica

Functions of Key Components in Copper CMP

Too weak: dishing, corrosionOxidizer (white): promotes subsequent

surface film formation

Passivation against

Initial Step Height

Activator (red) and passivator (yellow)

jointly form a softer film

Too strong: low RR, Cu residue

CMPUG July 2008 10

Step height reduction =>Planarization

High MRR

Low MRR

Passivation against

Static dissolutionjointly form a softer film

Abrasive (blue)

assists mechanical removal

of the soft film

Pad

When “balanced”

Free vs. Fixed Complexing Agent:

Functionalized Particles

SiO2

complexant

C

C

complexant

free complexant

CMPUG July 2008 11

CuO

Cu

Cu2+

Cu2+

Cu2+

complexant

C complexant

free complexant

free complexantfree complexant

Y. Li, CMP-MIC Short Course on Metal CMP, 2003

Functionalized Silica for Cu CMP

150

200

250M

RR

or

SE

R (

nm

/min

)

SiO2

SiO2 + complexant

complexant on silica

CMPUG July 2008 12

0

50

100

150

Cu MRR Cu SER

MR

R o

r S

ER

(n

m/m

in)

Y. Li, CMP-MIC Short Course on Metal CMP, 2003

Effective Removal of

Cu Containing Soft Film

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Particle Mophorlogy Change on Demand for Cu CMP

Silica Particle Polymer Particle BASF Adaptive Organic Particle

Stress-free Stress-free Stress-free

CMPUG July 2008 14

Wafer

Compressed during CMP

Compressed during CMP

Compressed during CMP

Pad

No deformation

DeformationDissociation Wafer

Pad

Wafer

Pad

©KT 2008

Adaptive Organic Particles

� Particle delivers necessary functions at the right place and time!Pad

Adaptive Organic Particles activatedReactive components released

©KT 2008

reversible

CMPUG July 2008 15

Device

High-stress region

(High RR)

High-stress region

(High RR)

Low-stress region

(Low RR)

Adaptive Organic Particle

Reactive components

Potential Advantages

� Reactive molecules are caged

� Avoid using harsh activating agent in solution

� Minimize corrosion

� Particles are deformable

� No hard abrasive particles needed

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� No hard abrasive particles needed

� Lower damage to fragile materials

� Particles can be fractured into much smaller particles on demand

� Increase surface area to deal with polishing debris

� Lower LPC

� Particles are also responsive to temperature

� Elevated temperature and dilution dissolve small AP

� Easy to clean after CMP

SEMATECH 854 Patterned Wafer DataAverage dishing on 100/100 um lines

Copper thickness8.00E+03

1.00E+04

1.20E+04

Th

ick

ne

ss

& S

tep

He

igh

t(A

)

CMPUG July 2008 17

0.00E+00

2.00E+03

4.00E+03

6.00E+03

0 10 20 30 40 50 60 70 80 90 100 110 120

Time(sec)

Th

ick

ne

ss

& S

tep

He

igh

t(A

)

Thickness

Step Height

Dishing =298

Dishing=583

StepHeight=198

Adaptive Particle Design Minimize corrosion

CMPUG July 2008 18

A Good Cu CMP Slurry

� MRR = 8,000A/min to start with

� 100% Planarization Efficiency

� Short or no induction period

� With soft landing

� final dishing at 100/100 um lines: 200A (The Ratio is 40:1)

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� final dishing at 100/100 um lines: 200A (The Ratio is 40:1)

� No

– Corrosion spots

– Pitting

– Scratch

– Stain

– EOE

– Particle residue

– Pattern dependency

For TSV applicationsIf MMR = 36,000A/min

40:1 ratio gives 900A dishing

30:1 ratio gives 1200A dishing

Move from die stacking to 3D IC

CMPUG July 2008 20

Advantages:

•Form factor: to increase density (capacity/volume ratio)•Electrical performance: to shorten interconnect length

•Heterogeneous integration (RF, memory, logic, MEMS, etc)

800

1000

1200

1400

Dis

hin

g/E

rosio

n (

A)

100/100 um

Representative Patterned Wafer Polishing Results

CMPUG July 2008 21

0

200

400

600

0 1 2 3 4 5 6 7 8 9

Die Position

Dis

hin

g/E

rosio

n (

A)

50/50 um

10/10 um

9/1 um

Total polishing time to clear 1.0 um over burden copper: 20 secondsRemoval rate for the first 10 sconds: 3.6 um/minRemoval rate for the remaining 10 seconds: 2.4 um/min

LPC and Surface Defects

� Significant effort and progress have been made on

� LPC reduction in incoming slurry

� LPC minimization during slurry delivery (pumps, containers, etc)

� POU filtration serves as a last defense

� The importance of LPC generated during polishing has received

CMPUG July 2008 22

� The importance of LPC generated during polishing has received

some attention lately

� Low abrasive content slurry more vulnerable

– Ceria based slurry

– Copper is typically low abrasive

� How is functionalized particle handle polishing debris?

� Fractured particles give great surface area

Particulate adsorption

SiO2

CMPUG July 2008 23

Cu

Cu2+

Cu2+

Cu2+

CuO

Yuzhuo Li, CMP-MIC 2004 Short Course

Fresh and Spent Slurry LPC

250000

300000

350000

Pa

rtic

le C

on

c.

(>0.7

5 u

m,

#/m

l)

CMPUG July 2008 24

0

50000

100000

150000

200000

NiP slurry (fresh) NiP slurry (spent) Cu slurry (fresh) Cu slurry (spent)

Pa

rtic

le C

on

c.

(>0.7

5 u

m,

#/m

l)

LPC Sources for Cu and NiP CMP

100000

120000

140000

160000

LP

C>

.07

5u

m (

#/m

l)

CMPUG July 2008 25

-20000

0

20000

40000

60000

80000

0 2 4 6 8 10 12

LP

C>

.07

5u

m (

#/m

l)

Cu slurry (fresh)

Cu slurry (spent)

NiP slurry (fresh)

NiP slurry (spent)

Summary

� Why functionalized particles?

� Increase removal rate? Not really

�Enhance planarization efficiency? Yes

� Lower defect level? Yes

CMPUG July 2008 26

� Lower defect level? Yes

� Why matching chemistry?

�Allow surface functionality to express

�Balance the need for material removal and transport

� Lower defect level