SiC @ Infineon
An insight in the analysis for SiC
André Kabakow
Infineon Technologies AG
andre.kabakow@infineon.com
Copyright © Infineon Technologies 2011. All rights reserved.
Content
 General information
 Examples of analysis
 Summary and Outlook
6/19/2013
Copyright © Infineon Technologies 2011. All rights reserved.
Page 2
Content
 General information
 Examples of analysis
 Summary and Outlook
6/19/2013
Copyright © Infineon Technologies 2011. All rights reserved.
Page 3
Purpose
 Infineon is one of the key player in SiC power technology.
 Understanding the material is essential to keep this role.
 SiC is about 30 years behind Si (taking wafer size as a basis ).
 fundamental research is still ongoing
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Material properties
 very hard
 high temperature stability
 high thermal conductivity
 excellent chemical and radiation resistance
 more than 250 known polytypes
4H structure - ABCB
 most common structures: 6H, 4H and 3C
 only 4H SiC used for IFX power devices
 100 mm (4-inch) wafers available today
 150 mm wafers available since August 2012
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Physical and electrical properties
 wide energy bandgap (eV)
 4H-SiC: 3.26
Si: 1.12
 high breakdown electric field [V/cm]
 4H-SiC: 2.2 x 106
Si: 2.5 x 105
 high thermal conductivity (W/cm · K @ RT)
 4H-SiC: 3.0-3.8
Si: 1.5
 high saturated electron drift velocity [cm/sec (@ E ≥ 2 x 105 V/cm)]
 4H-SiC: 2.0 x 107
Si: 1.0 x 107
SiC is very suitable for power devices
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SiC market and potential
 SiC power technology has the potential to
start to play a major role next to conventional
Si in the current decade
 estimated worldwide annual sales 100-150 Mio. €
 estimated growth rate 30-40% p.a.
 key applications
 hybrid and electric vehicles
 renewable energies (wind energy plants and solar
converter)
 switching power supplies
 uninterruptable power supplies
 drives
 key drivers
 efficiency
 low system costs
 power density
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SiC related issues
 defect density (104-105 cm-2) affects the performance and
reliability of SiC devices
 influence of crystal defects on functionality and reliability of
SiC devices is barely understood
 characterization and analysis necessary to develop failure
mechanisms
 formation of a MOS structure not as easy as for Si
new challenges for FA
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Content
 General information
 Examples of analysis
 Summary and Outlook
6/19/2013
Copyright © Infineon Technologies 2011. All rights reserved.
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Electrical characterization
 in principle as for Si power devices
 high current measurements
 High Power Curve Tracer (pulsed measurement)
¬ avoids overheating of the device
 partial backside opening of the device for
further characterization
¬ BS contact with probe needle not necessary
¬ ensures a good BS contact
die
solder
leadframe
package
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Emission Microscopy - EMMI
 SiC is transparent not only to IR, but also
to the visible light spectrum
 SiC merged pn-Schottky-Diode
 Schottky diode for normal current
 pn diode for surge current
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Emission Microscopy - EMMI
 higher Vf after extreme stress at high current densities beyond
specification
 EMMI shows a reduced effective area
 EMMI signature points to extensive crystal defects
reference
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fail
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Bipolar Degradation
current density [A/cm2]
 Stacking faults can grow at high current densities triggered by
electron hole recombination.
forward
400 characteristics
before and
after stress
300
p+
BPD
n- drift layer
n+ substrate
200
cathode
growth of stacking faults triggered
by electron-hole-recombination
100
0
0
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1
2
3
voltage[V]
4
J.P. Bergmann et al., Mat. Sci. For. Vols. 353-356 (2001), pp 299-302
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Crystal defect etching
 etching in molten KOH at 500°C under a fume hood
Ni wire
Ni foil
tube furnace at IFX
bigger Ni cup
smaller Ni cup with
molten KOH
Ni cage with the
sample
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crystall defect etching
 size and shape of the etch pits depend on the defect type
 no easier procedure is known to decorate crystal defects till now
threading edge
dislocation
basal plane
dislocation
threading screw
dislocation
Yukari Ishikawa et al., Mat. Sci. For. Vols. 645-648 (2010), pp 351-354
6/19/2013
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SEM to visualize p doped areas
 mechanical cross section is required
 saves further investigation with e.g. SCM (Scanning
Capacitance Microscopy)
misaligned p doping of a JFET
6/19/2013
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Content
 General information
 Examples of analysis
 Summary and Outlook
6/19/2013
Copyright © Infineon Technologies 2011. All rights reserved.
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Summary and outlook
 FA methods, well-known for Si, still applicable for SiC
 some work better:
“p doped areas under SEM”
 some work worse:
“crystal defect etching”
 Analysis, with all of its methods, can contribute to a better
understanding of the material and its failure mechanisms.
 What is the correlation between the EMMI signature of “bipolar
degraded” devices and the triggered crystal defects?
 Find an easier method for defect etching
6/19/2013
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Picture credits
 page 4:
 http://www.nature.com/nature/journal/v430/n7003/images/430974
a-f1.2.jpg
 http://atecom.en.alibaba.com/viewimg/picture.html?picture=http://
i00.i.aliimg.com/photo/v2/525568278/EPI_Ready_Polish_Wafer_4H
_6H_Silicon.jpg
 page 5:
 https://apecconf.org/2012/images/PDF/2012/Industry_Sessions/is1.5.5.pdf
 http://upload.wikimedia.org/wikipedia/commons/1/15/Toyota_Prius
_Plug-In_Hybrid_IAA_2009.jpg
 http://www.quantrimang.com.vn/photos/image/032011/29/Usnasa-columbia.jpg
 http://www.greenology.co.za/images/windturbine.jpg
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