Novel Particles and Matching Chemistry in CMP Slurries for 22 nm … · Ta MRR (A/min) Ta MRR...
Transcript of Novel Particles and Matching Chemistry in CMP Slurries for 22 nm … · Ta MRR (A/min) Ta MRR...
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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
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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
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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
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For effective material removal, surface
tribochemical reactions must take place
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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
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Correlation between surface hydroxyl
groups and Ta removal rate
50
60
70
80
90
Ta M
RR
(n
m/m
in)
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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.
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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
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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
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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
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Uniform Surface Chemical Reactions
Lower Planarization Efficiency
Upon exposure to
Chemical Etchant
Initial Step Height
Uniform attack
Uniform attack
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No step height reduction => No Planarization
Chemical reactions:
High MRR
Chemical reactions:
High MRR
Pad Pad
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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
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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
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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”
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Free vs. Fixed Complexing Agent:
Functionalized Particles
SiO2
complexant
C
C
complexant
free complexant
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CuO
Cu
Cu2+
Cu2+
Cu2+
complexant
C complexant
free complexant
free complexantfree complexant
Y. Li, CMP-MIC Short Course on Metal CMP, 2003
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Functionalized Silica for Cu CMP
150
200
250M
RR
or
SE
R (
nm
/min
)
SiO2
SiO2 + complexant
complexant on silica
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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
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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
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Wafer
Compressed during CMP
Compressed during CMP
Compressed during CMP
Pad
No deformation
DeformationDissociation Wafer
Pad
Wafer
Pad
©KT 2008
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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
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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
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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
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Adaptive Particle Design Minimize corrosion
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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
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Move from die stacking to 3D IC
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Advantages:
•Form factor: to increase density (capacity/volume ratio)•Electrical performance: to shorten interconnect length
•Heterogeneous integration (RF, memory, logic, MEMS, etc)
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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
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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
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� 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
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Particulate adsorption
SiO2
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Cu
Cu2+
Cu2+
Cu2+
CuO
Yuzhuo Li, CMP-MIC 2004 Short Course
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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)
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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)
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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