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Nano Packaging & Interconnect Lab.
Introduction - 3D Integration & Through Silicon Via(TSV)
¾Why TSV for 3D integration?
Chip 3
Chip 2
Chip 1
Interposer 2
Interposer 1
Die attach film
Substrate
Wire bonding
< 3 chips + 2 interposers stack with wire bonding>
Chip 1 TSV
Substrate
TSV
TSV
Chip 2
Chip 3Bump
Underfill
< 3 chips stack with TSV >
¾ Through silicon via (TSV)
TSV Si chip
9 Vertical electrical interconnection passing through the silicon
Source : STATS ChipPAC
9 Smaller package size
9 Short interconnect length
9 Pad area for wire bonding
9 Long looped Au wire
Nano Packaging & Interconnect Lab.
Introduction - Former TSV Interconnection Methods & Limits
TSV
Dielectric polymer
<Cu-Sn Metal bonding> < Cu-Cu Metal/polymer hybrid bonding>Chip
Metal bump
ChipTSV
Metal bump
Substrate chip
TSV Chip
Metal bump
UnderfillSubstrate chip
ChipTSV
Metal bump
Dielectric polymer
ChipTSV
Metal bump
Substrate chip
Voids Cracks
• Long bonding time(< minutes)• Repeat of under-fill• Void trap during under-fill
• Long bonding time(30min)• Additional polymer patterning• Semi-solid state after polymer patterning
Nano Packaging & Interconnect Lab.
TCA
Silicon waferSi chip with
TCA
Dicing of TCA-applied wafer
Pressure & temperature
TCASi chip
Si wafer
TSV
*Patent issued : US6518097
TCA coated on releasing film
*Wafer-level lamination of TCA on the wafer
TSV & bumped wafer
Introduction - Why TSV Conducting Adhesives(TCAs)/Solder Joint?
¾ Bonding process with TCA
¾What is TCA?
TSV Conducting Adhesive+ +TSV
Chip
Cu pillar Solder bump
• Substitution of underfill• No need of patterning
Chip to wafer bonding using TCA/solder joint
Nano Packaging & Interconnect Lab.
Introduction - Why TCA/solder Hybrid Joint?
¾ Features of TCAs
Substrate chip
TCA
ChipTSV
Solder bump
TSV
TCA Solder bump
Chip
9 Curing temperature
9 Viscosity9 Short bonding time
9 No need of underfill& patterning
9 Gap filling by resin flow
• Joint stability
• Joint formation
Substrate chip
Nano Packaging & Interconnect Lab.
Experiments – Test Vehicles (TSV simulated SnAg coated Cu post bump)
¾ Micro-bumped chip
9 Substrate chip design
9 Bonding chip design
Height : 10/10 μm
Diameter : 40 μm
Material : Cu/SnAg2.5
• Dimension : 13 mm X 13 mm
• Pads : 5 daisy resistance & 4 joint resistance circuits
Pitch : 80 μm
• Dimension : 6 mm X 6 mm
• Bump
Single Bump Joint resistanceAt the corner
Daisy resistance
Cu pillar (10 μm)
SnAg bump (10 μm)
Nano Packaging & Interconnect Lab.
Experiments – TCAs Formulation
¾ Resin system
Thermosetting epoxy Thermoplastic resin+ +
¾ TCA formulation
Curing agent
TCA1 TCA2 TCA3 TCA4
Curing temperature (oC) 160 185 160 160
Min. viscosity (Pa·s) 450(130oC)
90(160oC)
3000(130oC)
600(120oC)
Curing speed @250oC(sec) 70 70 70 10
Curing accelerator+Thermo-mechanical
propertiesViscosityCuring
temperatureCuring speed
*Tg : 100 ~ 140 oC
Nano Packaging & Interconnect Lab.
20
40
60
80
100
50 100 150 200 25010
100
1000
10000
100000
1000000
Visc
osity
(|K|
* )
Temperature (oC)
Dai
sy re
sist
ance
(:)
Results - Effects of Curing of TCAs
9 TCA/solder hybrid joints were interconnected with the viscosity of 600 Pa·s.
Bonding conditionPressure : 16.32 MPaTemperature : 40~250 oC (5 oC/s)
9 Bonding with TCA29 Bonding with TCA1
20
40
60
80
100
50 100 150 200 25010
100
1000
10000
100000
1000000
Visc
osity
(|K|
* )
Temperature (oC)D
aisy
resi
stan
ce (:
)
(160 oC, 450 Pa·s @ 130 oC) (185 oC, 90 Pa·s @ 160 oC)
No bump interconnection
600 Pa·s @ 110 oC
¾ Real time viscosity & resistance change during the bonding
590 Pa·s @ 120 oC
Nano Packaging & Interconnect Lab.
20
40
60
80
100
50 100 150 200 25010
100
1000
10000
100000
1000000
Visc
osity
(|K|
* )
Temperature (oC)D
aisy
resi
stan
ce (:
)
Results – Effects of Viscosity of TCAs
9 Bonding with TCA1 9 Bonding with TCA3
9 TCA/solder hybrid joints with high viscosity TCA were interconnected preby the softening of the TCA resin.
50 100 150 200 25010
100
1000
10000
100000
1000000
Vis
cosi
ty (|K|
* )
Temperature (oC)
50
100
150
200
Dai
sy re
sist
ance
(:)
(160 oC, 3000 Pa·s @ 130 oC)(160 oC, 450 Pa·s @ 130 oC)
No bump interconnection
¾ Real time viscosity & resistance change during the bondingBonding conditionPressure : 16.32 MPaTemperature : 40~250 oC (5 oC/s)
Nano Packaging & Interconnect Lab.
20
40
60
80
100
50 100 150 200 25010
100
1000
10000
100000
1000000
Visc
osity
(|K|
* )
Temperature (oC)
Dai
sy re
sist
ance
(:)
Results - Joint Interconnection during the BondingBonding conditionPressure : 16.32 MPaTemperature : 40~250 oC (5 oC/s)
<Before bonding>
<Physical contact of the bumps> <Increase of the contact area>
<Metallurgical bonding>No bump
interconnection
¾ Bonding with TCA1(160 oC, 450 Pa·s @ 130 oC)
Nano Packaging & Interconnect Lab.
Result – 40 μm Fine Pitch Capability of TCA/solder Joints
¾ TCAs bonding with 40 μm pitch test vehicles
9 Chip specification
Height : 10/10 μmDiameter : 20 μm
Material : Cu/SnAg
Pitch : 40 μm
• Bump
40 μm 80 μm
Contact resistance (mΩ) 1.18 2
9 Joint resistance
Successful bonding of 40 μm pitch TCA/solder hybrid joints in 10 sec!
Nano Packaging & Interconnect Lab.
Result – Humidity Test
¾ 85 oC/85 %RH test
< Cross-sectioned image of the bumps after 500 hours of 85 oC/85 %RH test>
9 No failure was found until 300 h of the humidity test for TCA/solder hybrid joints.
TCA 1 (160 oC, 450 Pa·s @ 130 oC)Pressure : 16.32 MPaTemperature : 40~250 oC (5 oC/s)
0 20 40 60 80 100
0
20
40
60
80
100 0 h 300 h 500 h
Cum
ulat
ive
dist
ribut
ion
(%)
Joint resistance (m:)
Nano Packaging & Interconnect Lab.
Conclusion & Ongoing Works
1. TCA/solder hybrid joint was demonstrated for TSV interconnection using new TCA materials.
TCA/solder as a new solution for the 3D-TSV vertical interconnection
2. TCA material properties was designed for joint interconnection.Curing temperature → joint stability Viscosity → joint interconnection @ 600 Pa·s
3. 40 μm fine pitch capability was demonstrated in 10s bonding time.
¾ Conclusion
¾ Ongoing works
1. Void elimination
2. Optimization of the TCA materials Curing agent, epoxy, & thermo-plastic polymers
3. 3D TSV chip stacking using TCAs
Process & TCA properties optimization
