1 1 1 LOCK-IN THERMOGRAPHY - Fraunhofer IISB · due to improper bond wire process parameters 1...

F R A U N H O F E R I N S T I T U T E F O R I N T E G R AT E D S Y S T E M S A N D D E V I C E T E C H N O L O G Y

LOCK-IN THERMOGRAPHY Non-destructive localization of electric active defects

Description of lock-in thermography analysis

• Detecting of failed power electronic devices such as IGBT, MosFETs, diodes and

resistors

• Analysisofshortcircuits,ESDdefects,oxidedamages,edgeterminationdefects,

avalanchebrakedown,whiskersandelectricalconductivecontamination

• HighsensitivityforhotspotdetectionwithaheatdissipationintheμWrange

• 2D/3Ddefectlocalizationforfurtherdestructiveanalysistoidentifythefailure

mechanism

Special features

• MeasurementvoltagefrommVupto10kV

• Decapsulationofmoldcompoundsaswellassiliconegels

• Chemicalremovalofchiptopsidemetallizationandcontactsforinstancebond

wiresandribbonsoutofdifferentmaterials

• Followupinvestigationssuchascrosssections,scanningelectronmicroscopy,

microsectionswithfocusedionbeam

• Interpretationoftestresultsandfailuremechanisms

• Consultancyonthedifferentinvestigatedfailuremodesforinstancechipdamage

duetoimproperbondwireprocessparameters

1 Lock- In Thermo graphy

in act ion

Fraunhofer Institute for

Integrated Systems and

Device Technology IISB

Landgrabenstraße 94

90443Nürnberg

Germany

Contact:

AdamTokarski

Phone: +4991123568157

Fax: +499112356812

adam.tokarski@iisb.fraunhofer.de

www.iisb.fraunhofer.de

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Analysis principle

• Thedeviceundertestispulsedwiththerectangularvoltageby

arbitrarylock-Infrequency(typical:1to25Hz)

• Electricaldefectdissipatethermalpower

• Thermalpowerheatsupthesurface

• Measurementofinfraredsignalwithinfraredcamera

• Acquisitionofamplitudeimageaswellasresultingtime

dependentstepresponse(phaseimage)

Advantages

• Differentialmeasurementprinciple

• Bestsuitedfordifferentemissioncoefficientsofthe

devicesurfacematerials

• Noinfluenceoftheambient(temperature,reflections)

• Threedifferentzoomlensestoinvestigatestructuresfrom

completepowermoduletosingleIGBTcells

Application example

• Afterfabrication,apowermodulefailedthefinalelectricalqualitytest(e.g.

gate-emitterleakagecurrent)

• Lock-inthermographyhelpstodetectwhichsemiconductorisresponsible

fortheleakagecurrentanddetermindstheexactpositionofthedefecton

the device

• Nextstepconsistsofremovingbondwiresandaluminium-metalizationof

thesemiconductorfollowedbyasecondlock-inthermographyanalysisto

getthemicroscalelocationofthedefect

• Anadditionalinvestigationcanbeafocusedionbeaminvestigationwith

scanningelectronmicroscopytodetectthecauseoffailure(e.g.damaged

gatestructure)

2 Opt i ca l Micro scopy of IGBT

3 Lock- In Thermo graphy Ampl i tude of IGBT

4 Lock- In Thermo graphy Phase of IGBT

Demolded dev ice Topography

Cross sect ion Focused ion beam

Power modul

Lock- in overv iew

2 3 4

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