Design and Manufacturing of a Double-Side Cooled, SiC based, High - - PowerPoint PPT Presentation

Design and Manufacturing of a Double-Side Cooled, SiC based, High Temperature Inverter Leg

Raphaël RIVA1, Cyril BUTTAY1, Marie-Laure LOCATELLI2, Vincent BLEY2, Bruno ALLARD1

1 Laboratoire Ampère, Lyon, France 2 Laboratoire LAPLACE, Toulouse, France

15/5/14

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Outline Introduction The 3-D structure Silver migration Module Manufacturing Conclusion

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Outline Introduction The 3-D structure Silver migration Module Manufacturing Conclusion

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Active Power Devices for High Temperature

Falahi et Al. “High temperature, Smart Power Module for aircraft actuators”, HiTEN 2013

2 4 6 8 10 12 Drain-to-Source voltage [V] 10 20 30 40 50 60 70 Drain current [A]

• 50◦C -10◦C 27◦C

70◦C 107◦C 160◦C 196◦C 234◦C 270◦C 49.0 48.8 48.6 48.4 time [µs] 50 50 100 150 200 250 Vout [V] 0.2 0.0 0.2 time [µs]

310°C

Previous results show that SiC JFETs are attractive for > 200 ° C operation:

◮ rated at 1200 V (or more), several Amps ◮ Voltage-controlled devices ◮ No reliability issue related to gate oxide degradation

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High Temperature Thermal Management

Buttay et al. “Thermal Stability of Silicon Carbide Power JFETs”, IEEE Trans on Electron Devices, 2014

100 150 200 250 300 350 time [s] 30 40 50 60 70 80 power [W]

current changed from 3.65 to 3.7 A Run-away

SiC JFET:

◮ 490 mΩ, 1200 V ◮ RThJA = 4.5 K/W ◮ 135 °

C ambient

◮ On-state losses

High temperature capability = reduced cooling needs! SiC JFETs must be attached to a low-RTh cooling system.

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Double Side Cooling

◮ Standard packaging offers cooling through one side of the

die only

◮ “3-D” or “Sandwich” package performs thermal

management on both sides

◮ Requires suitable topside metal on the die ◮ Requires special features for topside contact

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Double Side Cooling

◮ Standard packaging offers cooling through one side of the

die only

◮ “3-D” or “Sandwich” package performs thermal

management on both sides

◮ Requires suitable topside metal on the die ◮ Requires special features for topside contact

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Outline Introduction The 3-D structure Silver migration Module Manufacturing Conclusion

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The proposed 3-D Structure

Vbus OUT GND JH JL

◮ Two ceramic substrates, in “sandwich” configuration ◮ Two SiC JFET dies (SiCED) ◮ assembled using silver sintering ◮ 25.4 mm×12.7 mm (1 in×0.5 in)

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Ceramic Substrates

SiC JFET Alumina

0.2 mm

0,3 mm

0.16 mm

0,15 mm

Copper

0.15 mm

Gate Source Source Drain

0.3 mm

Scale drawing for 2.4×2.4 mm2 die

◮ Si3N4 identified previously for

high temperature

◮ For development: use of

alumina

◮ Etching accuracy exceeds

standard design rules

◮ Double-step copper etching for

die contact ➜ Custom etching technique

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Bonding Material: Silver Sintering

Göbl, C. et al “Low temperature sinter technology Die attachment for automotive power electronic applications” proc of APE, 2006

Silver Paste

◮ Based on micro-scale silver

particles (Heraeus LTS-117O2P2)

◮ Low temperature (240 °

C) sintering

◮ Low pressure (2 MPa) process

No liquid phase involved:

◮ No movement of the die ◮ No bridging across terminals ◮ No height compensation thanks to

wetting

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3-D Structure: Challenges

◮ Behaviour of silver at high temperature (risks of migration) ◮ Behaviour of silver paste during assembly (bridging,

compensation of height differences)

◮ High-resolution alignment of parts ◮ Etching resolution of the DBC substrates

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3-D Structure: Challenges

◮ Behaviour of silver at high temperature (risks of migration) ◮ Behaviour of silver paste during assembly (bridging,

compensation of height differences)

◮ High-resolution alignment of parts ◮ Etching resolution of the DBC substrates

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3-D Structure: Challenges

◮ Behaviour of silver at high temperature (risks of migration) ◮ Behaviour of silver paste during assembly (bridging,

compensation of height differences)

◮ High-resolution alignment of parts ◮ Etching resolution of the DBC substrates

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3-D Structure: Challenges

◮ Behaviour of silver at high temperature (risks of migration) ◮ Behaviour of silver paste during assembly (bridging,

compensation of height differences)

◮ High-resolution alignment of parts ◮ Etching resolution of the DBC substrates

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Outline Introduction The 3-D structure Silver migration Module Manufacturing Conclusion

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Causes of Silver Migration

Source: Yang S et al. Initial stage of silver electrochemical migration degradation. Microelectron Reliab 2006;46(9):1915–21.

Silver atoms can migrate due to simultaneous presence of:

◮ High Temperature ◮ Oxygen/moisture ◮ Electric field

Silver will then form filaments across the potential differences, causing short circuits!

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Characterization Test Bench

◮ Up to 10 samples biased and monitored

simultaneously

◮ 1100 V max biasing, < 10 nA accuracy ◮ Tests performed at 300 °

C

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Test Vehicles

◮ Silver paste stencil-printed on alumina, and sintered ◮ Various gaps investigated: 0.5, 1, 1.5, 2 mm ◮ Test of vehicles:

◮ Un-protected ◮ Protected with a 20 µm layer of parylene HT

◮ 5 samples for each configuration

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Results – Un-coated samples

50 100 150 200 250 1E-8 1E-7 1E-6 1E-5 1E-4

Current (A) Time (h)

◮ Leakage current remains negligible until short circuit ◮ Large differences between similar test vehicles:

◮ shape of the silver migration ◮ time before failure 16 / 28

Results – 2

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 1E-3 1E-2

1/t (h

• 1)

Electric Field (V/mm)

Without parylene Parylene SCS HT

T = 300°C Stop parameter

◮ time before failure short without encapsulation (100–1000 h) ◮ Strong increase with parylene HT protection ◮ Tests stopped after 1000 h if no migration occured

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Conclusions on High Temperature Operation of Silver-Sintered Joints

◮ Silver migration is an issue ◮ It should be evaluated on a more representative test

vehicle (silver used for die attach only)

◮ Parylene HT is a good way to slow down migration

➜ Parylene HT will be used in the 3-D structure.

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Conclusions on High Temperature Operation of Silver-Sintered Joints

◮ Silver migration is an issue ◮ It should be evaluated on a more representative test

vehicle (silver used for die attach only)

◮ Parylene HT is a good way to slow down migration

➜ Parylene HT will be used in the 3-D structure.

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Conclusions on High Temperature Operation of Silver-Sintered Joints

◮ Silver migration is an issue ◮ It should be evaluated on a more representative test

vehicle (silver used for die attach only)

◮ Parylene HT is a good way to slow down migration

➜ Parylene HT will be used in the 3-D structure.

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Conclusions on High Temperature Operation of Silver-Sintered Joints

◮ Silver migration is an issue ◮ It should be evaluated on a more representative test

vehicle (silver used for die attach only)

◮ Parylene HT is a good way to slow down migration

➜ Parylene HT will be used in the 3-D structure.

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Outline Introduction The 3-D structure Silver migration Module Manufacturing Conclusion

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Preparation of the Substrates

plain DBC board

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching 3a - resin coating

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching 3a - resin coating 3b - Exposure and Developpment

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching 3a - resin coating 3b - Exposure and Developpment 4a - Photosentive film laminating

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching 3a - resin coating 3b - Exposure and Developpment 4a - Photosentive film laminating 4b - Exposure and Development

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching 3a - resin coating 3b - Exposure and Developpment 4a - Photosentive film laminating 4b - Exposure and Development 5 - Etching

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

plain DBC board 1a - Photosensitive resin coating 1b - Exposure and Development 2 - Etching 3a - resin coating 3b - Exposure and Developpment 4a - Photosentive film laminating 4b - Exposure and Development 5 - Etching 6 - Singulating

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Substrates

◮ Final patterns within 50 µm of desired size ◮ Two designs, for 2.4×2.4 mm2 and 4×4 mm2 dies ◮ Total copper thickness 300 µm, ≈ 150 µm per step

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Preparation of the Dies

◮ Standard aluminium topside finish

not compatible with silver sintering

◮ Ti/Ag PVD on contact areas ◮ Need for a masking solution

➜ jig with locating pockets.

Die Mask PVD

Before PVD After Ti/Ag PVD

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Preparation of the Dies

◮ Standard aluminium topside finish

not compatible with silver sintering

◮ Ti/Ag PVD on contact areas ◮ Need for a masking solution

➜ jig with locating pockets.

Die Mask PVD

Before PVD After Ti/Ag PVD

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Preparation of the Dies

◮ Standard aluminium topside finish

not compatible with silver sintering

◮ Ti/Ag PVD on contact areas ◮ Need for a masking solution

➜ jig with locating pockets.

Die Mask PVD

Before PVD After Ti/Ag PVD

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Assembly

Screen printing

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing 4 - First sintering step

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing 4 - First sintering step 5 - Removal of die- alignment jig

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing 4 - First sintering step 5 - Removal of die- alignment jig 6 - Screen printing on "drain" substrate

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing 4 - First sintering step 5 - Removal of die- alignment jig 6 - Screen printing on "drain" substrate 7 - Mounting in alignment jig

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing 4 - First sintering step 5 - Removal of die- alignment jig 6 - Screen printing on "drain" substrate 7 - Mounting in alignment jig 8 - Second sintering step

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Assembly

Screen printing 2- Mounting in alignment jig 3- Die-alignment jig, dies and spacer placing 4 - First sintering step 5 - Removal of die- alignment jig 6 - Screen printing on "drain" substrate 7 - Mounting in alignment jig 8 - Second sintering step Result

◮ Ceramic laser-cut jigs for precise alignment of dies and

substrate

◮ Two sintering steps using the same temperature profile

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Encapsulation

◮ Tests performed on a “sandwich” without dies ◮ Parylene thickness very uniform, including in intricate

areas

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Test

Complete assembly After first sintering step Die before assembly

0.08 0.06 0.04 0.02

• 30
• 25
• 20
• 15
• 10
• 5

VG (V) ID (A)

5

Measured for VDS = 10 mV

◮ Only preliminary tests performed, on a probe station ◮ Contact on Gate, Source and Drain of all JFETs ◮ No short-circuit between contacts ◮ Drop in current probably associated with test probes and

• xidation of substrate

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Prototype

Size: 25×25 mm2

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Outline Introduction The 3-D structure Silver migration Module Manufacturing Conclusion

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Conclusion

◮ 3D structure using only high-temperature-rated materials

◮ Should be able to operate continuously at 300 °

C, including passivation

◮ Silver migration is an issue

◮ It can be slowed down using encapsulation

◮ Silver sintering is suited to rigid sandwich structures. ◮ Proposed etching technique offers satisfying resolution ◮ Package for demonstration of technology, no cooling

attempted yet

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Conclusion

◮ 3D structure using only high-temperature-rated materials

◮ Should be able to operate continuously at 300 °

C, including passivation

◮ Silver migration is an issue

◮ It can be slowed down using encapsulation

◮ Silver sintering is suited to rigid sandwich structures. ◮ Proposed etching technique offers satisfying resolution ◮ Package for demonstration of technology, no cooling

attempted yet

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Conclusion

◮ 3D structure using only high-temperature-rated materials

◮ Should be able to operate continuously at 300 °

C, including passivation

◮ Silver migration is an issue

◮ It can be slowed down using encapsulation

◮ Silver sintering is suited to rigid sandwich structures. ◮ Proposed etching technique offers satisfying resolution ◮ Package for demonstration of technology, no cooling

attempted yet

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Conclusion

◮ 3D structure using only high-temperature-rated materials

◮ Should be able to operate continuously at 300 °

C, including passivation

◮ Silver migration is an issue

◮ It can be slowed down using encapsulation

◮ Silver sintering is suited to rigid sandwich structures. ◮ Proposed etching technique offers satisfying resolution ◮ Package for demonstration of technology, no cooling

attempted yet

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Conclusion

◮ 3D structure using only high-temperature-rated materials

◮ Should be able to operate continuously at 300 °

C, including passivation

◮ Silver migration is an issue

◮ It can be slowed down using encapsulation

◮ Silver sintering is suited to rigid sandwich structures. ◮ Proposed etching technique offers satisfying resolution ◮ Package for demonstration of technology, no cooling

attempted yet

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Thank you for your attention,

cyril.buttay@insa-lyon.fr

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