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Consolider RUE (CSD2009-00046)
Wide Band Gap Semiconductor Devices for
Rational Use of EnergyRUE
José MillánCNM
Consolider RUE (CSD2009-00046)
Outline
• Why WBG Semiconductors?• The CONSOLIDER RUE at a glance• The RUE Consortium• The RUE WPs• Results• Future Trends of WBG Power Devices
Consolider RUE (CSD2009-00046)
“efficient processing of electrical energy through means of electronic switching devices ”
Power Electronics is:
40% of Energy consumed as electricity
Consolider RUE (CSD2009-00046)
Power Electronics: Electrical Energy Processing
Consolider RUE (CSD2009-00046)
Electrical Energy Areas
• Energy generation (1)
• Energy transmission &distribution (2,3)
• Energy storage (4)
• Energy usage & conversion (5,6)
Consolider RUE (CSD2009-00046)
• Increased power densities• Lower electromagnetic emissions• Plug-and-go systems• Extreme operating environments• Higher levels of integration• Lower cost
Moore’s Law for Power Devices:
Doubling frequency and power density every 4.5 years
Consolider RUE (CSD2009-00046)
• Si devices are limited to operation at junction temperatures lower than 200 ºC.
• Si power devices not suitable at very high frequencies.
• SiC and GaN offer the potential to overcome both the temperature, frequency and power management limitations of Si.
Why WBG Semiconductors?
Consolider RUE (CSD2009-00046)
• SiC&GaN process technologies are more “mature”.
• At present, SiC shows the best trade-off between properties and commercial maturity.
• GaN can offer better HF and HV performances, but lacks of high quality large substrates (no vertical devices).
• GaN lower thermal conductivity than SiC.
• GaN: 2DEG heterojunctions (InAlGaN alloys) grown on SiC or Si substrates.
• Currently, it is a sort of competition SiC vs GaN, in a battle of performance versus cost.
• No clear winner at the moment. They will find their respective application niches with a tremendous potential market.
Why WBG Semiconductors?
Consolider RUE (CSD2009-00046)
Physical Properties of Semiconductors for Power Devices
Material Eg (eV)@300K
µn(cm²/Vs)
µp(cm²/Vs)
Vsat(cm/s)
Ec(MV/cm )
λ(W/cm.ºK)
εr
Si 1.12 1450 450 1 × 107 0.25 1.5 11.7
4H - SiC 3.2 950 115 2 × 107 2.2 5 10
GaN 3.39 1000 350 2.2 × 107 3 1.3 8.9
Diamond 5.6 2200 1800 2.7 × 107 10 22 5.7
Consolider RUE (CSD2009-00046)
WBG-based Devices
• Wider Energy Bandgap lower leakage currents and high operating temperatures. Radiation hardness is also improved.
• Higher critical electric field thinner blocking layers and higher doping concentrations lower on-resistance. Unipolar HV devices feasible.
• Higher electron saturation velocity Higher operating frequencies.
• Higher thermal conductivity better power dissipation (improves heat spreading) - possibility of working at higher current densities – higher operating temperatures.
---------------
• 2 kV SiC Schottky diode with similar losses than a 150 V Si Schottky diode
Consolider RUE (CSD2009-00046)
Consolider RUE at a glance
• Main objective: to develop power WBG semiconductor devices aimed at• an important improvement in the performance of existing
power converters, and • the development of new power converters • In both cases seeking a more Rational Use of the electric
Energy
• SiC and GaN are the best options due to:• theoretical properties (HV capability, HT operation and HSS)• real commercial availability of the starting material (wafers)• maturity of their technological processes
Consolider RUE (CSD2009-00046)
Consolider RUE at a glance
• The development of this generation of power devices includes:• the study, design and fabrication of new power devices• design and implementation of novel packages according to the
voltage, temperature and frequency ranges of these devices. • new characterization and simulation tools • the investigation of the suitable circuitry: new drivers,
controllers, converter topologies, control strategies, etc.
• The project would not be completed if the real advantages of the new devices were not tested in real applications !!
Consolider RUE (CSD2009-00046)
Consolider RUE at a glance
> 60 PhDs
5 year duration
Funds: 4.56 M€
Consolider RUE (CSD2009-00046)
The RUE Consortium
Consolider RUE (CSD2009-00046)
The WorkPackages
The Project is split into three workpackages:
• WP1 deals with the development of SiC and GaN devices.
• WP2 develops the interface technologies to use these devices in real systems.
• WP3 includes several proofs of concepts concerning new and innovative niches for HT and HV capabilities, and HSS operation of WBG power devices.
Consolider RUE (CSD2009-00046) ApplicationsWork Package 3
Consolider RUE (CSD2009-00046) ApplicationsWork Package 3
Consolider RUE (CSD2009-00046)
Critical Packaging Elements• Hermetically sealed package• Die attach• Die bonding
Optimized for high temperature operation and -170°C/+300°C thermal cycling
Results: 300V, 5A SiC Schottky diode for ESA BepiColombo
Mission (solar panel protection)
1,9
1,95
2
2,05
2,1
2,15
2,2
2,25
0,0 100,0 200,0 300,0 400,0 500,0
T ime (hours)
Fo
rwar
d v
olt
age
(V)
Ni Schottky diode withhermetic sealing
W Schottky diode
Forw
ard
volta
ge(V
)
Vf at 5A and 270ºC
Time (hours)1,9
1,95
2
2,05
2,1
2,15
2,2
2,25
0,0 100,0 200,0 300,0 400,0 500,0
T ime (hours)
Fo
rwar
d v
olt
age
(V)
Ni Schottky diode withhermetic sealing
W Schottky diode
Forw
ard
volta
ge(V
)
Vf at 5A and 270ºC
Time (hours)
Consolider RUE (CSD2009-00046)
1.2kV & 3.5kV 25mm2 SiC Schottky Diodes
VAK= 1.78V @ 50A (25mm2 diode)
1.2kV diodes: estimated epilayer resistance, Repi = 1.5 mΩ.cm2
For these diodes’ size starting material is a must.
Starting material from CREE: 3” ultralow micropipes 4H substrate
Wafer ∅ 75 mm
Consolider RUE (CSD2009-00046)
Large area SiC JFET
• ACCUMOS vertical power device• 5mmx5mm transistors• 2 or 3 terminals devices• 7 photolitographic mask levels• 2 µm minimum feature size
Consolider RUE (CSD2009-00046)
Latest Results. Target: 10 kV
Consolider RUE (CSD2009-00046)
Latest Results: MOS gate
MOS gate:
• Surface pre-treatment ( in-situ RTA step) in H2 atmosphere
• The gate oxidation process performed in an RTP furnace in N2O
10 100 1000-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
290 oC
250 oC
150 oC
50 oC
Bias-stress + 10 Vtbs = 10, 36, 100, 360, 1000 s
Vds = 100 mVL/W = 12/150
∆Vth
[V]
Bias-Stress Time [s]
25 oC
100 oC200 oC
0 50 100 150 200 250 300-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
∆Vth
[V]
Bias-Stress Temperature [oC]
tbs = 10 s tbs = 1000 s
Consolider RUE (CSD2009-00046)
SiC Switches
• Successful demonstration of the cascode pair (a high-voltage, normally-on SiC JFET + a low-voltage Si MOSFET).
• An industrial normally-off SiC switch is expected. The SiC MOSFET (<5kV) or either the SiC MCT or the IGBT (>5kV).
• BJTs/Darlingtons are promising, they also suffer from reliability problems.
• A normally-off SiC power transistor in the BV range of 600V-1200V available within next two years.
WBG Future Trends
WBG Power Devices Future Trends
Consolider RUE (CSD2009-00046)
GaN Power Devices
• GaN is already commercialised in optoelectronics.
• Its applications in power switching still require further work in materials, processing and device design.
• GaN HEMT (5-10 A, 600-1200 V normally-off)
GaN Power HEMTs
WBG Power Devices Future Trends
Consolider RUE (CSD2009-00046)
Thanks for your attention