sic @ infineon - freephilippe.perdu.free.fr/workshops/workshop2012/smartfa/pdf/3 - fa... · etching...

SiC @ Infineon

An insight in the analysis for SiC

André KabakowInfineon Technologies [email protected]

Copyright © Infineon Technologies 2011. All rights reserved.

Content

General information

Examples of analysis

6/19/2013

Summary and Outlook


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 ). SiC is about 30 years behind Si (taking wafer size as a basis ).

fundamental research is still ongoing

6/19/2013

Material properties

very hard

high temperature stability

high thermal conductivity

excellent chemical and radiation resistance

more than 250 known polytypes

more than 250 known polytypes

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

4H structure - ABCB

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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

SiC market and potential

SiC power technology has the potential tostart to play a major role next to conventionalSi 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 solarconverter)

switching power supplies

uninterruptable power supplies

drives

key drivers

efficiency

low system costs

power density

6/19/2013 Copyright © Infineon Technologies 2011. All rights reserved.

SiC related issues

defect density (104-105 cm-2) affects the performance andreliability of SiC devices

influence of crystal defects on functionality and reliability ofSiC devices is barely understood

characterization and analysis necessary to develop failure

characterization and analysis necessary to develop failuremechanisms

formation of a MOS structure not as easy as for Si

new challenges for FA

6/19/2013

Content

General information


6/19/2013

Summary and Outlook


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

Electrical characterization

partial backside opening of the device forfurther characterization

¬ BS contact with probe needle not necessary

¬ ensures a good BS contact

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package

leadframe

solder

die


Emission Microscopy - EMMI

SiC is transparent not only to IR, but alsoto the visible light spectrum

SiC merged pn-Schottky-Diode

Schottky diode for normal current

pn diode for surge current


Emission Microscopy - EMMI

higher Vf after extreme stress at high current densities beyondspecification

EMMI shows a reduced effective area

EMMI signature points to extensive crystal defects


reference fail

Bipolar Degradation

Stacking faults can grow at high current densities triggered byelectron hole recombination.

p+

forwardcharacteristics

before and

curr

entdensi

ty[A

/cm

2]

400

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J.P. Bergmann et al., Mat. Sci. For. Vols. 353-356 (2001), pp 299-302

n- drift layer

cathode

n+ substrate

BPD

growth of stacking faults triggeredby electron-hole-recombination

growth of stacking faults triggeredby electron-hole-recombination

before andafter stress

curr

entdensi

ty[A

/cm

voltage[V]

10 2 3 4

100

0

200

300


Crystal defect etching

etching in molten KOH at 500°C under a fume hood


bigger Ni cupsmaller Ni cup withmolten KOH

Ni foil

Ni wire

Ni cage with thesample

tube furnace at IFX

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 edgedislocation


Yukari Ishikawa et al., Mat. Sci. For. Vols. 645-648 (2010), pp 351-354

threading screwdislocation

basal planedislocation

dislocation

mechanical cross section is required

saves further investigation with e.g. SCM (ScanningCapacitance Microscopy)

SEM to visualize p doped areas


misaligned p doping of a JFET

Content

General information


6/19/2013

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 betterunderstanding of the material and its failure mechanisms.

Summary and outlook

What is the correlation between the EMMI signature of “bipolardegraded” devices and the triggered crystal defects?

Find an easier method for defect etching


Picture credits

page 4:

http://www.nature.com/nature/journal/v430/n7003/images/430974a-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://apec-conf.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/Us-nasa-columbia.jpg

http://www.greenology.co.za/images/windturbine.jpg


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