SiC @ Infineon An insight in the analysis for SiC
André Kabakow Infineon Technologies AG
[email protected] 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.
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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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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
6/19/2013
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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
6/19/2013
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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 6/19/2013
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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
6/19/2013
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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 6/19/2013
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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 6/19/2013
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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 6/19/2013
fail Copyright © Infineon Technologies 2011. All rights reserved.
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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
6/19/2013
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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 6/19/2013
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