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Low Temperature Curable Polynorbornene as Redistribution Layer
Sumitomo Bakelite co-authors:Etsu Takeuchi
Junya Kusunoki
Seishi Ohashi
Promerus co-authors:Chris Apanius
Ed Elce
Hendra Ng
Presented by: Brian Knapp, Ph.D.
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Outline
General Characteristics of Avatrel® Photodefinable Polymers
Chemical Structure
Low Shrinkage
Wafer Stress
Planarity
General Imaging
Applications
Redistribution Layer (RDL) Device Build
Reliability Testing
Summary
2008 Symposium on Polymers 2
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Synergies of Chemistry in Polycyclic Polyolefins
2008 Symposium on Polymers 3
Polynorbornene
High Tg From Backbone
Alkyl – Tune Modulus/Stress
Low Moisture Absorption
Isotropic Properties
Transparency
Low Dielectric Constant
Epoxy
Accepted Chemistry
Low Temperature Cure
Adhesion
Photosensitive
Epoxy
R
Alkyl
RR
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Low Film Thickness Shrinkage through Wafer Processing- 1400 rpm, Cyclopentanone develop, 180oC/2h cure
2008 Symposium on Polymers 4
9
9.2
9.4
9.6
9.8
10
10.2
10.4
10.6
10.8
11
SB Exposure PEB Develop Cure
Fil
m T
hic
kn
ess
(mm
)All changes < 1%
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Low Wafer Warpage with Simple Coatings
Wafer: 200 mm Si WaferThickness: 625 mmMeasuring span: 100 mm
2008 Symposium on Polymers 5
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Planarization of Avatrel over Topology
Avatrel has good planarization with dense feature patterns
Planarization is very good for 60 µm thick films on 7 & 15 µm topology, 100% DOP
Planarization is 85 to 96% DOP for 30 µm thick films on 7 µm topology
Planarization is 75 to 82% DOP for 30 µm thick films on 15 µm topology
d = d = a+b+c/3a+b+c/3
aa bb cc
200um200um 200um200um
15um15um
aa bb ccaa bb cc
200um200um 200um200um
15um15um
Avatrel
200um200um10010080807070
62008 Symposium on Polymers
% DOP (degree of planarization) = (1–d/step height) x 100%
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General Imaging Capability of Avatrel® Polycyclic Polyolefins
2008 Symposium on Polymers 7
63 x 325 mm 150 mm Dice Lanes
2.5 mm lines/spaces 4:1 aspect ratio 70 mm Collars
Single layer: 150 mm vias
Solv
ent
Dev
elo
pab
leA
qu
eou
s D
evel
op
able
Subsidiary of Sumitomo Bakelite Co. Ltd.
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20mm Avatrel
Silicon Beam
cavity
Avatrel®/Unity® Applications
2008 Symposium on Polymers 8
Photo-
definable
Unity
High
Temperature
Unity
Aqueous
Developable
CIS Dam
ApplicationsBackside
Interconnect
Layer
Transparent
Adhesive
300 µm
Layers
Wafer Level
Packaging
Temporary
Wafer
Adhesive
Wafer Level
MEMS
Packaging
Avatrel/
Unity
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Motivation for Redistribution Materials
A material which aids in the relocation of bond pads
Desirability stems from small package size, high-speed electrical access, and ability to accommodate standard pad layouts
RDL WL-CSP is often used in miniaturized consumer electronic products
Cell phones consume 80-90% of all WL-CSP packages
Redistribution is the most popular WL-CSP>90% of the 6.1 Bn WL-CSP packages shipped in 2007 used RDLs
As processors move to multi-core designs, clock redistribution may be required
2008 Symposium on Polymers 9
Marketing data courtesy of:
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WPR
PBO
PI
Cure Temperature (oC)400 300 200 100
Processing Shrinkage (%) 40 30 20 10
Water Absorption (%) 1.5 1.0 0.5 0.0
Residual Wafer Stress (MPa) 40 30 20 10
Dielectric Constant (1 MHz) 3.5 3.0 2.5 2.0
Tensile Modulus (GPa) 1.0 2.0 3.0 4.0
Tensile Strength (MPa) 20015010050
Elongation to Break (%) 10 20 30 40
Tg (oC via TMA) 200 250 300 350
CTE (ppm/oC)100 75 50 25
BCB
PI
PI
PI
PI
PI
PI
PI
BCB
BCB
BCB
BCB
BCB
BCB
BCB
BCB
PNB
PNB
PNB
PNB
PNB
PNB
PNB
BCB
PI
PBO
PBO
Property Comparison of Redistribution Materials
2008 Symposium on Polymers 10
PBO
PBO
PBO
PBO
PBO
PBO
*Source: Manufacturer websites
WPR
WPR
WPR
WPR
WPR
WPR
WPR
WPRPI PNB
PNB
PNB
HD-4000
WPR-1201
Cyclotene 4026-46
CRC-8650
Avatrel-RDL
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Process Flow for RDL Device Build
Metal-11a) Passivated Copper Wafers
1b) Coat with Resist
1c) Photo/Etch
Polymer-12) Pattern Layer-1 of Avatrel-RDL
Metal-23a) Copper Seed Layer Deposition
3b) Coat with Plating Resist
3c) Copper Electroplating
3d) Resist Strip and Seed Layer Etch
Polymer-24) Pattern Layer-2 of Avatrel-RDL
Metal-35a) Deposition of Nickel/Gold
5b) Photo/Etch
2008 Symposium on Polymers 11
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Step 1a: Copper Wafers over Passivation Layer- Copper (5000Å) on SiOx or Si3N4
2008 Symposium on Polymers 12
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
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Step 1b: Copper Wafer Coated with Resist- Shipley 1813 PT Resist
2008 Symposium on Polymers 13
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 1c: Metal-1 Patterned with Photo and Cu-Etch- Transene APS-100 Etchant
2008 Symposium on Polymers 14
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
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Step 2: 1st Layer of Avatrel Processed
2008 Symposium on Polymers 15
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
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Standard Process for the Imaging of Avatrel® Redistribution Material
Wafer Process Conditions
Dehydration Hydration Bake: 130oC/2 min
Plasma Pretreatment: 50/50 Ar/O2, 300 W, 30 sec
Spin-coat
Prebake: 120oC/5 min
Exposure: 300-800 mJ/cm2
Post-Exposure Bake: 90oC/4 min
Develop: Cyclopentanone, 20 sec
Cure: 180oC/2h
Inducing Sidewall Slope
Proximity
DOF
Polymer
Formulation
2008 Symposium on Polymers 16
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Step 2 Details: Sidewall Imaging in Proximity Mode on Aligner- 300 mJ/cm2 on Copper
2008 Symposium on Polymers 17
Contact Mode
Proximity Mode
30
40
50
60
70
80
90
0 20 40 60 80 100 120
Sid
ewal
l An
gle
(°)
Proximity (µm)
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Step 2 Details: Tunable Sidewall using Depth of Focus on Stepper
2008 Symposium on Polymers 18
60
65
70
75
80
85
90
Depth of Focus (mm)
Sid
ewal
l an
gle
(deg
rees
)
Above the surface Below the surface
84o
78o
81o
77o
86o80o
74o72o
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Step 2: 1st Layer of Avatrel Processed
2008 Symposium on Polymers 19
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 3a: Deposited Conductive Seed Layer for Electroplating- Sputtered Copper, 1000Å
2008 Symposium on Polymers 20
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 3b: Patterned Metal-2 with Plating Resist- AZ 9260: Thick Film, Positive-Tone
2008 Symposium on Polymers 21
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 3c: Subjected to Copper Electroplating (3-7 mm)
2008 Symposium on Polymers 22
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 3d: Stripped Resist and Etched Seed Layer- Acetone/IPA, Transene APS-100 Copper Etchant
2008 Symposium on Polymers 23
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 4: 2nd Layer of Avatrel Processed
2008 Symposium on Polymers 24
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 5a: Deposited Metal-3 for UBM- Sputtered 3000Å Nickel, 500Å Au
2008 Symposium on Polymers 25
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
Top Down
~150 mm
Cross-section
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Step 5b: Metal-3 Patterned with Photo/Etch- AZ 9260 Resist, Transene Gold Etch TFA & Nickel Etch TFG
2008 Symposium on Polymers 26
Cross-section
Top Down
~150 mm
150 mm
75 mm
25 mm
Si-waferPassivationCopperPhotoresistAvatrel
NickelGold
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24
23
22
21
20
19
18
17
16
15
14
13
37
38
39
40
41
42
43
44
45
46
47
48
36 35 34 33 32 31 30 29 28 27 26 25
1 2 3 4 5 6 7 8 9 10 11 12
Device Layout on Die (6.3 mm x 6.3 mm)
2008 Symposium on Polymers 27
Metal-1
Metal-2
Metal-3
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SEM Image of Full Device
Metal-1Titanium: 100Å
Copper: 5000Å
Avatrel-110 mm
Metal-2Copper: 4 mm
Avatrel-210 mm
Metal-3Nickel: 3000Å
Gold: 500Å
2008 Symposium on Polymers 28
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SEM Image of Metal-3 Bond Pad
2008 Symposium on Polymers 29
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SEM Image of Buried Metal-2 Copper Trace
2008 Symposium on Polymers 30
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SEM Image of Metal-1 and Metal-2
2008 Symposium on Polymers 31
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Reliability Testing
2008 Symposium on Polymers 32
Thermal Cycling (T/C)
-55oC -> 125oC JEDEC 22, A104-A
Thermal Reflow
260oC
Pressure Cooker (PCT)
125oC, 2.3 atm, 100% RH JEDEC 22B, A102-B
High Temperature Storage (HTS)
150oC in air JEDEC 22B, A103-A
Pending
0 Cycles1000500200100
24096480
Hours10004501680
Passed
Cycles 10530
Hours
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90%
95%
100%
105%
110%
115%
120%
CRC-8650 Competitor A Competitor B Avatrel-RDL
No
rmal
ized
Wit
hin
Mat
eria
l Set
0 h HTS 100 h HTS
Stability of Tensile Modulus post-HTS- 150oC in Air
2008 Symposium on Polymers 33
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Stability of Tensile Strength post-HTS- 150oC in Air
2008 Symposium on Polymers 34
90%
95%
100%
105%
110%
115%
120%
CRC-8650 Competitor A Competitor B Avatrel-RDL
No
rmal
ized
Wit
hin
Mat
eria
l Set
0 h HTS 100 h HTS
Subsidiary of Sumitomo Bakelite Co. Ltd.
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Summary
Avatrel® Redistribution Material
Thermal Properties: high Tg, good stability
Electrical Properties: low CTE and low dielectric constant
Wafer Properties: low shrinkage and low residual stress
Imaging: thick film, high aspect ratio, tunable sidewall angle
Low Temperature Curability
RDL devices have been successfully fabricated with positive
reliability results
Commercial qualification is ongoing
Aqueous versions are being developed
2008 Symposium on Polymers 35