Post on 07-Aug-2018
transcript
Post CMP Cleans Evolution and
Defect Improvement Approaches
Business of Cleans / SPCC Conference
Katrina Mikhaylichenko, Ph.D.
Applied Materials
April 9th, 2017
Applied Materials Confidential
2 Applied Materials | Presented at Business of Cleans / SPCC 2018
CMP Mechanism and Cleaning Challenges
Three-body interaction: Wafer, Pad, Slurry
Slurry: Complex suspensions containing
abrasive particles, stabilizing agents and
inhibitors
Pad & abrasive remove inhibitor(a) from high
pressure areas
Remaining inhibitor(a) protects low areas.
After polish layer cleared from stop layer,
inhibitor(b) protects stop area and inhibitor(a)
represses dishing of oxide in trenches
Polishing by-products (chemical reactants,
agglomerated slurry and pad/conditioner
debris) are present on wafer after polish and
needs to be removed during post-CMP cleans
2
3 Applied Materials | Presented at Business of Cleans / SPCC 2018
Post CMP Cleaning Challenges
3
Difficult to remove
contaminants:
► Slurry particles and polish residues
► Organic components of the slurry
► Pad debris
Corrosion
Multiple film materials
exposed and new
metals/liners/barriers
(W, TiN, Co, Ru, ULK)
Particle removal is more
difficult with time
Hydrophobic films, Philic /
phobic surface combination
Scratches on softer films
Secondary contamination
due to the “Loading” of the
cleaning media
Wafer edge cross-
contamination
Small particles become
“visible” to metrology tools
only after next film deposition
4 Applied Materials | Presented at Business of Cleans / SPCC 2018
Particle Removal and Re-Deposition
Particle removal: interaction force between the particle and the substrate has to be eliminated by shear force:
► Fluid shear flow, Brush scrub, Megasonic cleaning, Fluid jet
Chemical etching is used to assist with breaking the particle-surface bond
► Undercut on the substrate and/or wet etch of the particle
After breaking the bond, the particle has to be removed away from the surface to prevent re-attachment
4
Particle attached on wafer
surface
Breaking van der Walls forces:
Undercutting by HF
Shear force by brush scrub,
Megasonics, Fluid jet…
Lift off by repulsive forces:
Shear force by brush scrub,
Megasonics, Fluid jet…
Electrostatic forces
Diffusion of particles to surface
due to overall attraction force
and electrostatic force
Van der Walls interactions:
rapid deposition of particles
close to the surface
Particle Removal
Particle Deposition
5 Applied Materials | Presented at Business of Cleans / SPCC 2018
Addressing Post CMP Cleaning Challenges in LKP System
Cleaner: 5x Side-by-Side Cleaner Stations
► Megasonics
− Provides physical force to remove contamination form the features
− Provides full wafer immersion tank for bevel contamination removal
► Pre-Clean
− Provides means to perform chemical buff in a dedicated slurry-free module
− Vertical buff enables effective contamination removal off the surface
− Enable cleaning of top surface of the wafer bevel
► Two consecutive brush boxes provide high particle removal efficiency
and precise brush pressure control
► Vapor Dryer provides defect-free drying of hydrophilic, hydrophobic and
mixed surfaces
► Cleaner Chemical Flexibility enables particle undercut and lift-off
− HF-compatible brush box enables SiO2 substrate etching
− Proprietary chemicals often include particle etch capability
5
6 Applied Materials | Presented at Business of Cleans / SPCC 2018
Po
st
CM
P C
lean
Defe
ct
Imp
rove
me
nt
Ap
pro
ach
es
6
Post Polish Rinse Chemical Rinse in Polisher Load/Unload Station
Chemical Mechanical Buff PreClean Module High Shear Force Clean for Dielectric and Metal CMP
Brush Box Advanced Cleaning Features Chemical Coverage Uniformity Improvement
SteadyClean Brush Torque (Shear Force) Control for Consistent Roller Brush PRE
Ozonated Water Rinse for Organic Defect Reduction
BB2.0 Brush Conditioning for Extended Brush Life
Dryer High Speed Dry in VD1.5
7 Applied Materials | Presented at Business of Cleans / SPCC 2018
Post Polish Chemical Rinse Optimization for Poly CMP
Strategy:
Convert hydrophobic wafer surface to hydrophilic as soon as possible after polish step to prevent strong
bonding of residues onto surface
7
Using AMAT post polish rinse station design, wafer surface is converted from
hydrophobic to hydrophilic with very short chemical exposure
8 Applied Materials | Presented at Business of Cleans / SPCC 2018
Post Polish Rinse Effect on Poly Defects
8
Process SP2 Maps SP2 Maps SP2 Maps SP2 Maps Ave.
Counts@80nm
Optimized Post Polish Rinse
X
Un-optimized Post Polish Rinse
10X
About 10X improvement in defects from adding post polish chemical rinse
Polish: Silica poly slurry; PreClean buff: acidic cleaning solution, soft pad;
Brush scrub: acidic cleaning solution
9 Applied Materials | Presented at Business of Cleans / SPCC 2018
Po
st
CM
P C
lean
Defe
ct
Imp
rove
me
nt
Ap
pro
ach
es
9
Post Polish Rinse Chemical Rinse in Polisher Load/Unload Station
Chemical Mechanical Buff PreClean Module High Shear Force Clean for Dielectric and Metal CMP
Brush Box Advanced Cleaning Features Chemical Coverage Uniformity Improvement
SteadyClean Brush Torque (Shear Force) Control for Consistent Roller Brush PRE
Ozonated Water Rinse for Organic Defect Reduction
BB2.0 Brush Conditioning for Extended Brush Life
Dryer High Speed Dry in VD1.5
10 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean Chemical Mechanical Buff Module
Control parameters
► Wafer RPM: recipe programmable by step
► Pad RPM: recipe programmable by step
► Pad Pressure: recipe programmable by step
► Fully programmable sweep profile control on
wafer and conditioner
► Chemical and water CLC to chemical nozzle
► DIW CLC to rinse bars
► Broad range of chemical compatibility (not HF)
10
Wafer
Holder
DIW
Spray bar
PreClean has a wide range of processing capability
Vacuum
Chuck
Swing
Arm
Pad
conditioner
Chem
nozzle
Buff
pad
11 Applied Materials | Presented at Business of Cleans / SPCC 2018
Ce Slurry Cleaning Challenge for High Oxide Removal CMP
11
Ceria abrasive have significant surface
chemical action during SiO2 film polish
Oxide removal rates are tunable by
controlling ceria particle characteristics
and the surface activation components
High oxide removal characteristics of the
slurry represent significant challenge for
post CMP clean
Pad
SiO2 Film
CeO2
particle
Si(OH)3
H2O
Si(OH)4
O Ce
O
O Ce O bonding
Dissolution
of Si(OH)4
Pad direction
Polish + B1/B2
Saturated
Problem Statement:
High Ceria surface Contamination after CMP
Without Chemical Buff, ceria surface contamination remains high after conventional Brush Scrub
12 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean for FEOL: ILD0 PreClean vs. Platen Chemical Buff
12
Polish: Ceria slurry polish; Platen buff /PreClean buff: acidic cleaning solution, soft pad;
Brush scrub: acidic cleaning solution
0
20
40
60
80
100
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Sc
ale
d M
TM
Ad
de
rs,
Bla
nk
et
TE
OS
@ 9
0n
m
Wafer Count
Polish + Platen buff
Polish + Pre-Clean
0
10
20
30
40
Rela
tive
Ad
ders
ILD0 CMP
oxide stop on nitride
FEOL advantage: Move platen chemical buff to pre-clean module in the cleaner
Pre-clean extended run performance more stable than platen buff
13 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean for BEOL: Small Defect Removal on Oxide Wafers Polished with Cu
Alkaline Barrier Slurry
For defect threshold of 90nm (SP5): No significant difference in post-CMP defect count was observed with and without PreClean.
For defect threshold of 45nm (SP5): Adding PreClean significantly reduced post-CMP defect count
Oxide Wafers
PreClean is effective for small, sub 50 nm, particle reduction in BEOL N
orm
ali
ze
d P
ost
Co
un
ts @
>4
5 n
m
P3 Polish + B1B2 P3 Polish + PreClean + B1B2
No
rma
lize
d P
ost
Co
un
ts @
>9
0 n
m
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
P3 Polish + B1B2 P3 Polish + PreClean + B1B2
Polish: Alkaline Cu barrier slurry, soft pad
PreClean: Alkaline cleaning solution, soft pad
Brush Scrub: Alkaline cleaning solution
14 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean for BEOL: Small Defect Removal on Low-K Wafers Polished with Cu
Alkaline Barrier Slurry
Adding PreClean significantly reduced post-CMP defect count
through removing organic residues from hydrophobic BD3 wafers
BD3 Wafers
(SP5 at 65nm)
P3 Polish + B1B2 P3 Polish + PreClean + B1B2
No
rma
lize
d P
ost
Co
un
ts @
>6
5 n
m
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Polish: Alkaline Cu barrier slurry, soft pad
PreClean: Alkaline cleaning solution, soft pad
Brush Scrub: Alkaline cleaning solution
15 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean for W CMP: Small Defect Removal on Oxide Wafers Polished with W
Silica Slurry
For defect threshold of 65nm (SP2): No significant difference in post-CMP defect count was observed with and without PreClean.
For defect threshold of 45nm (SP5): Adding PreClean significantly reduced post-CMP defect count
PreClean is effective for small, sub 50nm, particle reduction in W CMP
SP5 at 45 nm SP2 at 65 nm Defect Adders on Blanket Oxide Wafers
No
rma
lize
d M
TM
Ad
ders
@>
65
nm
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
No
rma
lize
d M
TM
Ad
ders
@>
45
nm
Polish: W Silica Slurry
PreClean: NH4OH cleaning solution, soft pad
Brush scrub: alkaline cleaning solution
P3 Polish + B1B2 P3 Polish + PreClean+ B1B2 P3 Polish + B1B2 P3 Polish + PreClean+ B1B2
16 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean Module Flexibility: Particle Removal from Edge
16
TEOS Blanket
Polished with SS12
+ Pre-Clean with no
edge contact > 20mm
+ VD
Re-cleaned with
Pre-Clean +
BB1/BB2/VD
Edge overloaded
Small and
large defects
Re-cleaned with
BB1/BB2/VD
Re-cleaned with
Meg +
BB1/BB2/VD
61
@90nm
Edge counts
still high
Large defects
removed
Low counts & only
film defects observed
Pre-Clean effective in removing nano particles and edge defects
17 Applied Materials | Presented at Business of Cleans / SPCC 2018
PreClean Module Flexibility Edge Cleaning Capability near Bevel
17
Contaminated Bevel Pre Clean + B1/B2 + VD B1/B2 + VD
Residue belt observed at the Apex
Slurry residue on top surface near bevel
Slurry on top and bottom of bevel
Most of the residue belt is removed
Few isolated, small slurry particles on
top surface near bevel and on top and
bottom of bevel
Most of the residue belt is removed
No slurry on top surface near bevel
Remaining slurry only on bottom
portion of bevel
Pre-Clean effective in removing nano particles and edge defects
18 Applied Materials | Presented at Business of Cleans / SPCC 2018
Po
st
CM
P C
lean
Defe
ct
Imp
rove
me
nt
Ap
pro
ach
es
18
Post Polish Rinse Chemical Rinse in Polisher Load/Unload Station
Chemical Mechanical Buff PreClean Module High Shear Force Clean for Dielectric and Metal CMP
Brush Box Advanced Cleaning Features Chemical Coverage Uniformity Improvement
SteadyClean Brush Torque (Shear Force) Control for Consistent Roller Brush PRE
Ozonated Water Rinse for Organic Defect Reduction
BB2.0 Brush Conditioning for Extended Brush Life
Dryer High Speed Dry in VD1.5
19 Applied Materials | Presented at Business of Cleans / SPCC 2018
Brush Box Chemical Uniformity Improvement
Shower style HVM spray bar improves range by 3X
19
Problem Statement
Chemical etch (coverage) non-
uniformity with brush-closed
process due to brush and
chemical spray interferences
Solution
Optimized shower style spray bar
0
10
20
30
40
50
60
-150 -100 -50 0 50 100 150
Ox
ide
re
mo
ve
d (
A)
Position (mm)
POR 1500ml 50rpm
SA HVM 3.0 1500ml 30 rpm
Old Spray bar; 1500 mL/min chem flow
Shower Style HVM bar; 1500 mL/min chem flow
TOX Removal with Brush-Closed Process
20 Applied Materials | Presented at Business of Cleans / SPCC 2018
Ozonated Water Clean for Oxide and Poly Polish Organics Reduction
Objective:
► Remove organic contamination
Strategy:
► Implement DIO3 rinse in a dedicated cleaner module
Current test methodology:
► Implement Brush-open rinse with DIO3
Circular
Scratches
Defect reduction with DIO3 is due to reduction
in surface Carbon
DIW Rinse
DIO3 Rinse
in BB1
DI Water Rinse
in BB1
DIO3 Rinse
3x improvement observed with DIO3 rinse
No
rma
lize
d M
TM
Ad
de
rs
@>
65
nm
1.50
1.25
1.00
0.75
0.50
0.25
0.00
21 Applied Materials | Presented at Business of Cleans / SPCC 2018
DIO3: Surface Carbon Reduction Mechanisms on Si
21
Reduction in surface organics is due to surface conversion hydrophilic and direct oxidation reaction
BB1: HF BB2: DIO3 or DIW (brushes Open in both brush boxes)
DIO3 Rinse Effect on Surface Contact Angle DIO3 Rinse Time Effect on Oxide Film Growth on Si Substrate
60 sec DIO3 Rinse 5 sec DIO3 Rinse
60 sec DI Water Rinse
DIO3 rinsed surface shows lower
contact angle due to surface
oxidation with DIO3 exposure
Effective chemical oxide growth on
bare Si with DIO3 rinse
Contact angle >30
Contact angle <5 Contact angle <5
22 Applied Materials | Presented at Business of Cleans / SPCC 2018
Challenge :
► For small brush gap compression processes (<0.5mm),
variations in roller brushes & mechanical setup lead to
unstable particle cleaning and/or short brush lifetimes.
Approach:
► Maintain consistent brush shear force on wafer surface by
dynamically changing brush spacing to keep brush motor
torque consistent
Benefit:
► Consistent brush PRE for stable particle defect
performance and longer brush lifetimes.
SteadyClean Advanced Brush Torque Control
22
Control Shear Force for Consistent Roller Brush PRE
With SteadyClean Active
Z
z
R R
Brush Compression
Controlled by Gap motor
Challenge: Brush Shear Force Fluctuations
Approach: Consistent Brush Motor Torque
23 Applied Materials | Presented at Business of Cleans / SPCC 2018
SteadyClean Brush Torque Control – Examples
23
Keeps net brush torque stable over 2000+ wafers
Steady Clean Brush Torque Control compensates for environmental changes and brush wear by dynamically changing brush spacing
Fast Error Correction
Manually
decreased
brush gap
24 Applied Materials | Presented at Business of Cleans / SPCC 2018
BB2.0: Brush Conditioning Defect Adder Reduction
Objective:
– Extend brush life and reduce brush break-in time to reduce brush
generated defects
Strategy:
– Add conditioning plates to clean brush
– Ex-situ brush cleaning after brush-closed wafer cleaning step and wet idle
– Brush position control during conditioning
– DIW spray on conditioning bar
Status:
– Released on LK and LKP
Circular
Scratches
25 Applied Materials | Presented at Business of Cleans / SPCC 2018
Po
st
CM
P C
lean
Defe
ct
Imp
rove
me
nt
Ap
pro
ach
es
25
Post Polish Rinse Chemical Rinse in Polisher Load/Unload Station
Chemical Mechanical Buff PreClean Module High Shear Force Clean for Dielectric and Metal CMP
Brush Box Advanced Cleaning Features Chemical Coverage Uniformity Improvement
SteadyClean Brush Torque (Shear Force) Control for Consistent Roller Brush PRE
Ozonated Water Rinse for Organic Defect Reduction
BB2.0 Brush Conditioning for Extended Brush Life
Dryer High Speed Dry in VD1.5
26 Applied Materials | Presented at Business of Cleans / SPCC 2018
Weight Percent IPA
0 10 20 30 40 50 60 70 80 90 100 15
20
25
30
35
40
45
50
55
60
65
70
75
Su
rfac
e t
en
sio
n (
dyn
es
/cm
)
Water – IPA Surface Tension at 20C
DIW
Basic Principle of Surface Tension Gradient Drying Surface tension difference caused by surface IPA concentration gradient in DIW helps pull DIW from wafer surface
Marangoni drying requirement: refreshing of IPA and DIW to keep the gradient
26
[IPA]A > [IPA]B
gA(IPA+DIW) < gB(IPA+DIW) < g(DIW)
IPA
gB
g A
DIW
N2 + IPA Spray Bar
gB
g A
DIW
N2 + IPA Spray Bar
Wafer motion
IPA-rich atmosphere
near liquid-air interface – Gravity removes bulk of the liquid from the
wafer
– Tank volume exchanged with fresh DIW
(Overflow)
– IPA vapor is continuously fed to the DIW-
air interface
– Interface is kept saturated with IPA to
produce surface tension gradient drying
effect
Vertical Marangoni Tank
Vertical Marangoni Dryer provides defect-free drying of hydrophilic, hydrophobic and mixed surfaces
27 Applied Materials | Presented at Business of Cleans / SPCC 2018
Vapor Dry 1.5
Optimized IPA spray bar (VD1.5) enables high speed dry on hydrophilic substrates
Objective:
– Develop high speed vapor drying process to support short polish times
– Improve robustness of drying process
Strategy:
– Made prototype setup with which bars adjustable in position and angle
– Optimized spray bar position based on visual observation of droplets on front and back
– Validated optimal position and N2-IPA flow for defectivity on Si, TEOS and BD and FCVD
Status:
– Optimized spray bar position and N2/IPA flow for good defectivity and no residual water
– 29 sec BKM with new bars equivalent to 52 sec BKM with old bars
– Required change in angle, height and spacing of spray bars to front and back
– New geometry implemented: available on LK and LKP
Residual water
Inputs
• Angle
• Height
• Distance
• N2/IPA flow rate
H
DBS DFS
bBS bFS
Outputs
• Defects
• Wetness
• Touch-point
27
28 Applied Materials | Presented at Business of Cleans / SPCC 2018
VD1.5 Defect Validation on LKP
Demonstrated increased drying robustness
TEOS @ 65nm Si @ 45nm
28
46sec BKM 29sec BKM
0.40
0.35
0.30
0.25
0.20
0.15
0.1 N
orm
ali
ze
d M
TM
Ad
ders
on
Si
@>
45
nm
46sec BKM 29sec BKM
BSLN Short Dry
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.1
No
rma
lize
d M
TM
Ad
ders
on
TE
OS
@>
65
nm
29 Applied Materials | Presented at Business of Cleans / SPCC 2018 29
Addressing Post CMP Cleaning Challenges in LKP System
Difficult to remove
contaminants:
► Slurry particles and polish residues
► Organic components of the slurry
► Pad debris
Corrosion
Multiple film materials
exposed and new
metals/liners/barriers
(W, TiN, Co, Ru, ULK)
Particle removal is more
difficult with time
Hydrophobic films, Philic /
phobic surface combination
Scratches on softer films
Secondary contamination
due to the “Loading” of the
cleaning media
Wafer edge cross-
contamination
5 consecutive cleaning stations
High shear force Pre-Clean
Megasonic option
Two Brush Boxes
Dryer
Flexible chemistries
Inter-Platen Clean
Chemistry in HCLU Option
Flexible chemistries
Brush box recipe flexibility
Vertical Marangoni Dryer
VD1.5 Dryer enhancement
Contamination removal in Pre-Clean
Advanced brush pressure control
Buff pad conditioning in Pre-Clean
BB2.0 brush conditioning in brush box
Wafer top-bevel Clean in Pre-Clean
Bevel clean in immersion Meg tank
30 Applied Materials | Presented at Business of Cleans / SPCC 2018
Summary
Geometry shrinking and new material implementation in advanced nodes demand the
achievement of high particle removal efficiency.
To address cleaning challenges in various nodes, Applied CMP Clean technology continues to
evolve and includes broad portfolio of cleaning techniques
► Optimized post polish rinse
► High shear force Pre-Clean module for high particle removal efficiency in Dielectric and Metal CMP
► Single wafer Megasonic module for improving defect removal efficiency
► HF-compatible dual brush box module with
− Improved chemical coverage uniformity
− SteadyClean Brush Torque (Shear Force) Control for Consistent Roller Brush PRE
− Ozonated Water Rinse for Organic Defect Reduction
− BB2.0 Brush Conditioning for Extended Brush Life
► Single wafer IPA dryer for achieving water-mark free drying at high speed (with VD1.5 option)
30
31