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
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-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).