www.imb-cnm.csic.es

Wide and Ultra-wide

bandgap power devicesKey technologies to undertake the

electrification and decarbonisation challenge

X. Jordà, P. Godignon, O. Aviñó, X. Perpiñà, M. Vellvehi

S. Busquets

J-C. Crebiere

E. Gheeraert

Clustering and Global Challenges (CGC21) April 7, 2021

Motivation

Power electronics is a key enabling technology in the new energy transition scenario using:

• Renewable sources

• Deep electrification

Barcelona and Grenoble research groups have been collaborating in this field for years

We will show some relevant recent examples turning around WBG/UWBG semiconductors

Decarbonisation objectives for 2050 based on different approaches

Transition to renewable sources and improvement of efficiency allow major CO2 reductions

Electrification (replacement of fossil fuels by electric energy) is an optimum way for

implementing this transition in more efficient systems

Centralised demand-driven power grid Multi-modal decentralised smart-grid

Replacement of fossil fuel based power plants in traditional power grids is not the solution…

Renewables are distributed and can be scaled from kW to MW plants

Bidirectional power flow is required for managing renewables fluctuations

Electrified processes require more flexibility Smart-Grids

Power electronics circuits are found in the smart-grid between all the required conversion

interfaces of the generation - transport / distribution - use value chain

Semiconductor power devices are the key elements of power converters

They operate in switching mode at relatively high switching frequencies

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0

200

-500,0n 0,0 500,0n 1,0µ 1,5µ

-2

-1

0

1

2

3

4

Anode

curr

ent

(A)

time (s)

Anode-

to-c

athode

volt

age

(V)

-1600

-1400

-1200

-1000

-800

-600

-400

-200

0

200

-500,0n 0,0 500,0n 1,0µ 1,5µ

-12

-10

-8

-6

-4

-2

0

2

4

Anode

curr

ent

(A)

time (s)

Anode-

to-c

athode

volt

age

(V)

ETH-Zurich

7kV-400V

Solid State Transformer

Power module

SiC MOSFET die

SiC diode die

Wide bandgap (WBG, such as SiC and

GaN) and ultra-WBG (Diamond, Ga2O3)

semiconductors have broken the limits

of Silicon in terms of switching speed,

breakdown voltage, temperature, etc.

Diodes turn-off process at 1500V – 2A

SiC JBS Si PiN

Wide Band-Gap Semiconductors at

GaN-on-Si process development

SiC power devices fabrication

SiC process developement

SiC sensors development & fabrication

SiC flight components for space applications

Diamond Devices

Ga2O3 Technology

High temperature IC and diodes

1993

2020

25 mm2 >6kV SiC diodes

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0

1m

10m

100m

1

10

JF (

mA

/cm

2)

VF (V)

D22X4Y6_C

D22X4Y6bis_C

D22X4Y6bis2_C

D22X4Y6bis3_C

D22X4Y6bis4_C

D22X4Y6bis5_C

D22X4Y6bis6_C

D22X4Y6bis7_C

D22X4Y6bis8_C

D22X4Y6bis9_C

D22X4Y6bis10_C

Patented MOSFET based on lateral Diamond growth

Vertical Schottky diodes on epitaxied <100> Ga2O3 (Ni Schottky contact)

RIE/ICP of Ga2O3 : identification of a new defect

Present UWBG activities…

Diamond power devices

H2020 “Low Carbon Energy” Project

4M€

15 partners from 5 countries

2015 - 2020

Development of diamond-based power devices (MOSFETs, Schottky), their

packaging, characterization tools, industrialisation issues and final

applications. Analysis of the different technological bottlenecks at each level

Quasi-vertical power MOSFET concept studied Complete (passivated) Schottky diodes

Packaging of WBG and UWBG power devices: the GreenDiamond case

Providing mechanical, termal and electrical interface to the devices

Power module

Cross-section

Main parts

Assembling sequence

Main characteristics:

• High voltages (10kV) • High temperatures (250-300ºC)• Low termal resistance• CTE mismatches• Cost-effective

Not-limiting semiconductor performances!

1,00E-08

1,00E-07

1,00E-06

1,00E-05

1,00E-04

1,00E-03

TO220M TO257 TO254 VACTRON Raw DCB Silicone1 Silicone2 Silicone3 Epoxy1 Ceramic

Ileak at 1000V and 300ºC (uA)Leakage current @ 1000V & T = 300ºC

1,00E-10

1,00E-09

1,00E-08

1,00E-07

1,00E-06

1,00E-05

1,00E-04

1,00E-03

TO220M TO257 TO254 VACTRON Raw DCB Silicone1 Silicone2 Silicone3 Epoxy1 Ceramic

Ileak at 1000V and 25ºC (uA)Leakage current @ 1000V & T = 25ºC

1,00E-08

1,00E-07

1,00E-06

1,00E-05

1,00E-04

1,00E-03

TO220M TO257 TO254 VACTRON Raw DCB Silicone1 Silicone2 Silicone3 Epoxy1 Ceramic

Ileak at 1000V and 300ºC (uA)Leakage current @ 1000V & T = 300ºC

Example of a critical material: the encapsulant

Dielectric filler to protect the die and top contacts

Lack of suitable materials for HV/HT applications such as WBG/UWBG packaging

0 1k 2k 3k 4k 5k 6k 7k

0,0

5,0n

10,0n

15,0n

20,0n

Bare DCB

QSiL550

Epoxies 20-1650

Circalok 6710/6731

Curr

ent

(A)

Voltage (V)

Silicones are a promising cost-effective solution…

Test structure breakdown voltage

… but there are critical issues to be considered in terms of:

Aging

0,50

0,60

0,70

0,80

0,90

1,00

0,01 0,1 1 10 100 1000

Wei

ghtf

inal

/Wei

ghTi

nit

ial

Ageing time (hours)

Weight loss (250C)

0,50

0,60

0,70

0,80

0,90

1,00

0,01 0,1 1 10 100 1000

Wei

ghtf

inal

/Wei

ghTi

nit

ial

Ageing time (hours)

Weight loss (300C)

Thermo-mechanical behaviour (thermally induced stress to the wire-bondings)

Displacement Stress

In the framework of GreenDiamond we developed two families of HV/HT packages

2.5 kV – 250ºC

>6 kV – 210ºC: developed from 6 kV 25 mm2 SiC diodes manufactured at IMB-CNM

Empty package characteristics SiC diode blocking characteristics SiC diode conduction characteristics

Other approaches for implementing power converters in grid applications with LV devices:

Multi-step Packaging Concept developed by G2ELAB: “smart” series connection of devices (managing parasitic C’s)

Switching Cell

Switching Cell Array approach: Building converter legs from an array of standard cells (multi-level converters)

Building converters by series/parallel association of elementary Power Electronics Building Bloks (PEBB)

d

c 1

dc 2

dc 3

ac

3x

4x

4x

3x

2x

2x

Physical failure signature: gate oxide

local breakdown (FIB Millings and SEM)Failure physical signature located

1.2 kV SiC MOSFETs

IR-LIT detects physical

failure signature

(VDS homodinally modulated, VGS=0V)

Test: switching at 10 kHz under 500 V / 250-300ºC

Reliability issues in WBG materials specific characterization tools available at IMB-CNM

Example: Gate Oxide Degradation of SiC MOSFET in Switching Conditions

Based on an IR laser probe beam through the device under test

Advanced optical techniques for depth-resolved electro-thermal characterization:

Internal IR-laser Deflection (IIR-LD): thermal gradients determination (heat flux)

Fabry-Perot Interference thermometry (FPI): temperature measurements

Free-Carrier Absorption (FCA): free-carrier concentration measurements

Automated

setup view

Operation

principle

Advanced characterization optical techniques for depth-resolved analysis at chip level

Advanced optical techniques for depth-resolved electro-thermal characterization:

Internal IR-laser Deflection (IIR-LD): thermal gradients determination (heat flux)

Fabry-Perot Interference thermometry (FPI): temperature measurements

Free-Carrier Absorption (FCA): free-carrier concentration measurements

IGBT temperature profile

Measurement by FPI

0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.00

5

10

15

20

25

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

(b)

T

[K

]

Time [s]

(a)

Inte

rfe

ren

ce

sig

na

l [a

.u.]

Heating Cooling

Inspection depth

Laser beam

Free-carrier concentration

measurement by FCA

I

Tiempo

0 (pn-junction)

0

0

Concentración

(1016 cm-3)

0

1

2

3

4

5

6

7

8

9

10

PIN Diode

Free-carrier & thermal Gradient

measurements by IIR-LD

Laser beam

IGBT

𝜵𝒗𝒏 ≈𝝏𝒏

𝝏𝑻𝑻

𝜵𝒗𝑪

Y=300

Y=336

Dopant

incomplete

ionization

Dopant

incomplete

ionization

𝝏𝒏

𝝏𝑪𝑻

< 𝟎

𝜵𝒗𝒏 < 𝟎

under dopant incomplete ionization,

Application to WBG semiconductors: IIR-LD SiC Schottky diodes

Singular phenomena not observed in Silicon

Simulation results

Conclusions

Power electronics is a key enabling technology allowing the implementation of efficient smart-

grids, which are crucial for a deep electrification of industry, transportation, buildings, etc.

This electrification is one of the main tools for achieving the decarbonisation and a neutral

carbon society for the 2050 horizon

There is a very complementary combination of research groups in Grenoble and Barcelona

focusing their efforts on investigating more efficient and reliable power devices and converters

Strengthening their collaboration and including new groups from other fields (materials,

electrical and magnetic systems, EMC, transportation, etc.) will result in one of the most

singular research poles in Europe

Thanks for

your attention

C/ del Til·lers s/n

Campus de la Universitat Autònoma de Barcelona (UAB)

08193 Cerdanyola del Vallès (Bellaterra)

Barcelona · Spain

www.imb-cnm.csic.es

Follow us on @imb_cnm Acknowledgements: This work was partly funded by the SpanishMinistry of Science and Innovation / FEDER (Project HIPERCELLS no. RTI2018-098392-B-I00), the EC project GREEN- DIAMOND (H2020-LCE-2014-3 GA no. 640947), the Generalitat de Catalunya (AGAUR Contract no. 2017-SGR-1384) and Consejo Superior de Investigaciones Científicas (Project POWERPACK no.202050E037).