development of an advanced node high selectivity tungsten ......corrosion inhibitor selection...
TRANSCRIPT
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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)
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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.)
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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