Burn-in & Test Socket Workshop - BiTS Workshop

Burn-in & TestSocket WorkshopIEEEMarch 4 - 7, 2001Hilton Mesa Pavilion HotelMesa, ArizonaIEEECOMPUTERSOCIETYSponsored By The IEEE Computer SocietyTest Technology Technical Council

COPYRIGHT NOTICE• The papers in this publication comprise the proceedings of the 2001BiTS Workshop. They reflect the authors’ opinions and are reproduced aspresented , without change. Their inclusion in this publication does notconstitute an endorsement by the BiTS Workshop, the sponsors, or theInstitute of Electrical and Electronic Engineers, Inc.· There is NO copyright protection claimed by this publication. However,each presentation is the work of the authors and their respectivecompanies: as such, proper acknowledgement should be made to theappropriate source. Any questions regarding the use of any materialspresented should be directed to the author/s or their companies.

Technical ProgramSession 8Wednesday 3/07/01 10:30AMTest And Burn-in At The Wafer Level“Wafer Level Burn-in And Test”Teresa McKenzie - MotorolaWalid Ballouli - MotorolaJohn Stroupe - Stroupe Consulting“Some Scenarios On Wafer-Level Test & Burn-in”Robert Y. Million – Yamaichi Electronics USA, Inc.

Agenda / Outline• Purpose for Developing Wafer Level Burn-in• Overview of Wafer Level Burn-in Methodology• Design Considerations• Accomplishments• Process Improvement Work• SummaryBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe2

KGD Sacrificial Metal WLBI• Definition of Known Good Die (KGD)– Die having the same quality and reliability level asthat of an equivalent packaged part.• Definition of Sacrificial Metal (SM)– Metal which is temporarily deposited on a wafer toprovide electrical signal paths to a die andsurrounding die during wafer level burn-in and test.The sacrificial metal is etched away after burn-inand test is complete.BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe3

KGD Sacrificial Metal WLBI• Definition of Wafer Level Burn-In (WLBI)– Simultaneous burn-in of all die on a wafer to screenout marginal devices for infant mortality bydynamically stressing the integrated circuit atelevated temperature and voltage.BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe4

Purpose For DevelopingWafer Level Burn-In• Industry Requirements– Packaging miniaturization technology drivingneed for Known Good Die (KGD).– Use of flip chips in multi-chip modules (MCM),direct chip attach (DCA), and chip-on-board(COB).BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe5

Purpose For DevelopingWafer Level Burn-In• WLBI Known Good Die (KGD) Benefits– Lower cost method than die level burn-in.– Use of KGD flip chips in multi-chip modules(MCM), direct chip attach (DCA), and chip-onboard(COB).– Reduction in process steps when compared topackaged-level and die-level burn-in.– Reduction of wafer test insertion and probe time.– Faster test result feedback to the fab.BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe6

Wafer Level Burn-in MethodologyPackage Burn-in / Die-Level Burn-inWafer ProbeSacrificial Metal Wafer Level Burn-inDicingWLBI andDynamic TestAssemblyCarrierLoadWafer Probe(Reduced Time)TestAssemblyDicingPackageBurn-inBCarrierBurn-inTestTestPackaged UnitsKGDCarrierUnloadPackaged UnitsKGDBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe7

Wafer Level Burn-in MethodologyIC design1X BI metal maskLoad in BI fixtureBI circuit designFinished wafersDeposit sacrificialmetal and patternBI circuitKGDBurned-In wafersand ready fortesting and die prepRemove sacrificialmetalWLBI and Test ChamberBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe8

5 inch Wafer Level Burn-In MethodologyM2 Main Bus Line "Ti-W-Cu "Cu MiniBumpPolysil iconResistorFieldOxid eM1/M2InterconnectSCRIBEScribe Grid EdgeGRIDM 2 Main Bus Line "Ti-W-Cu "VSSVDDRECEIVERESETCLOCKBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe10

5 inch Wafer Level Burn-In SystemsFirst PrototypeCurrent ProductionBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe11

8 inch WLBI MethodologyPost wafer fab process (with polyimide)• Deposit, pattern and etch sacrificial metal• Parallel electrical bussing of all die in a cluster• Wafer level burn in (24 hours @ 125 °C)• Data Retention Bake (24 hours @ 270 °C)• Remove sacrificial metal• Bump (flip chip only)• Wafer probe• Visual, dice and T&R• Ship to customerBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe12

8” WLBI Methodology91 BN 2 AN 2 G E C D N 1 N81C D N A N12N1N710BNE21GBG12NAN1E C N N1 E2N C D1211NG B1D A N N E C12N2N1 B D N A 1 1 G B N D A 12 2612E C 1 NN 1 E BA1N G2N 2E C N N A1N G 1C D N N2 2N G B 1 D N N 1 G B C N N2 25NGECDA21N2ENDA11312B N N N 1 B G2D A NN2E C D A 1 N E N C 2 141 G B N N2G N N12314N1N22B N 1 E C D AG B C N A 1NN21E N D21Cluster Arrangement - Viewed Looking at the Wafer FaceBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe13

8 inch Wafer Level Burn-In SystemCurrent Production SystemBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe14

WLBI Design Considerations● Additional scribe area to support burn-in circuitinterconnect and current limiting resistors● Proper burn-in metal width and space to supportphoto and etch process● Proper pogo pin pad size for gross waferalignmentBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe15

WLBI Design Considerations● Minimum die per cluster defined by the number ofrequired signals, power lines, and grounds.● Metal bus width is designed to support currentdensity requirement● Proper adhesion between burn-in circuit metal andpolyimide at elevated temperature (Burn-In 125°C/Data Retention Bake 270°C)● Polyimide to support burn-in contact over activecircuit● Maintain aluminum pad integrity after burn-inmetal removalBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe16

Verification of Aluminum Pad IntegrityMechanical Test Engineering Wafer Control WaferBall Shear (gmf)Average 43.8 43.2High 54.3 51.3Low 31.2 36.7Std Dev 5.1 3.7Tensile Pull (gmf)Average 9.6 8.7High 11.0 10.2Low 7.6 7.3Std Dev 0.8 0.8BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe17

System Design Considerations● Maximum wafer power dissipation undernatural and forced convection● Effect of heatsink thickness and shape● Thermal transfer between wafer and heatsink● Inlet air temperature● Airflow speed and circulation pattern● Temperature uniformity across the waferBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe18

Accomplishments•5 inch Wafer Program✔Development began in 1992✔Eighteen wafer capacity system built in 1994✔Production started in 1995✔Full lot capacity production system built in1997✔Over 2 million KGD delivered since 1995 withno documented non-volatile memory (NVM)field failuresBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe19

Accomplishments•8 inch Wafer Program✔Single engineering wafer system built in1997✔Successful 8 inch Wafer Level Burn-In in1997✔Prototype Production system built in1998✔Production system built in 1999BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe20

Accomplishments•Reliability Studies on WLBI die✔Life stress tests (op life, data retention bake(DRB), temperature cycle, etc …)✔Bump shear tests✔Under-fill adhesion testsBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe21

Accomplishments•Reliability Studies on WLBI fixture✔Uniform temperature control✔Power and signal integrity✔Pogo pin characterizationBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe22

Process Improvement Work• Coefficient of Thermal Expansion Matching• Uniform Thermal Control• Cluster Yield Improvement• Wafer Cold TestBiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe23

AcknowledgmentsThe authors would like to acknowledge theteamwork from various Motorola SPS groups andDelta V Instruments that contributed to thedevelopment and continuous improvement of thissacrificial metal wafer level burn-in program(AVSD, SMD, FMTC, MOS12, and MOS5).BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe25

Reference Articles• W. Ballouli, T. McKenzie, and N. Alizy, “Known Good DieAchieved Through Wafer-Level Burn-In and Test”, 26thIEEE/CPMT IEMT Symposium, October 2000, pp. 153-159.• W. Ballouli, C. Beddingfield, F. Carney, and R. Nair, “Wafer-Level KGD Technology for DCA Applications”, AdvancedPackaging, September 1999, pp. 26-30.• T. McKenzie, “Wafer Level Burn-in (WLBI) Workshop”,Motorola Internal Publication, November 5, 1997.• W. Ballouli, J. Stroupe, “TSM Approach to Wafer Level Burnin”,Motorola Internal Publication, Motorola AMT Symposium,January 25, 1995.BiTS 2001 WorkshopT. McKenzie / W. Ballouli / J. Stroupe26

For Bits 2001 Workshop on Test & Burn-InSOME SCENARIOS ON WAFER-LEVEL TEST & BURN-INRobert Y. MillionMarketing ManagerYamaichi Electronics U.S.A., Inc.1

Chip Scale Packages (CSP)Chip Scale Packages (CSP) have been thedesign darlings of advanced packaging, butstarting last year 1999, the trend is on waferlevelpackaging. The following five areashave seen significant breakthroughs whichcollectively provide a unique technicalfoundation for a new type of electronicspackage:! Copper metallurgy and low dielectricmaterials for IC development! Wafer-level test & burn-in (WLBI)! The use of integrated passives (IPDs)! Design automation tools! Wafer bumping servicesThis presentation will define and describesome of the current technologies whichaddress the issues involving Wafer-level test& burn-in, a key element for the entire backendassembly/test function in IC production.2

Wafer-Level Test & Burn-InWafer-level test & burn-in = the ‘ultimateinterconnect’? Why? Some significantobstacles to overcome in realizing a trulyviable Wafer-level test & burn-in system:! A lot of Z-axis bumps and high-densityinterconnects! CTE matching of contactor to silicon underhigh temperature for long duration! Heavy loads or high-forces to makeelectrical connection! Uniform forces to all of the bumps orcoplanarity issues! A low cost contactor systemThese obstacles only relevant to probe orcontactor portion - just first step towardspractical WLBI system. Subsequently, wehave other issues:3

KGD (Known Good Die)! MCC’s interest in KGD began in late 1980s! DARPA funding led to joint-effort withSematech and MCC Consortia5

Became nucleus for such KGD socket/carriertechnologies as:T.I./M.M.S.’s DieMate® - AehrTest’s DiePak®Yamaichi’s KGD/Gold Dot® Program- Bear Technology/Micron Technology - EPITechnologies EPIK® SystemChip Supply’s TAB system - etc.! Goal of these technologies was to get KGD(test & burn-in) down to less than $0.01/pin= about parity with that of typical TSOPmemory package.Never reached that goal for numerousreasons:! ‘Handling’ (loading/unloading) of singulatedbare die in carriers proved too cumbersomeand unwieldy6

High volume throughput, or an automatedKGD system, to achieve KGD at a price ofbelow $25 per site on a Burn-In Board (BIB)could never be realized - actual cost wasmore like $40 ~ $125 / site with lots of toolingfor substrates, carriers and sometimessockets - vendors tried to standardize on thesockets.Curtailed the growth of MCMs (Multi-ChipModules) as a major marketMay have actually led to present dayonslaught of CSPs (Chip Scale Packages)! CSPs growing at 108% from 1997 ~ 2002! More rugged and easier to handle than KGD- eliminates yield losses! Burn-in sockets cost $25 ~ $45 per site onBIB for lower I/O count memory! High-speed test contactors, if required, cost$1,500 ~ $5,000 each7

! Over 65 different CSP packages from over40 different companies - really hard tostandardize on test & burn-in socketsMCC’s commercial project in 1995 to evaluatefeasibility of wafer-level burn-in for reliabilityscreening of KGD - several of the WLBIsystems to be shown next were germinatedfrom DARPA/MCC/Sematech consortia effort.8

MotorolaWafer-Level Burn-In at Motorola - A JointDevelopment Project between Motorola,Tokyo Electron Ltd.(TEL), and W.L. Gore &Associates! Motorola - process development, integrationand qualification! W.L. Gore - supplying wafer contactormaterials in the form of GoreMateIIContactor and Inferno IC Board! Tokyo Electron Ltd. - supplying burn-inequipment and automation! Project located at BAT-1 (Bump, Assembly,and Test) - Motorola’s integrated back-endfactory in Austin, TX - all operations fromunit probe through final test are under oneroof.9

MotorolaCurrent Final Manufacturing Flow; WLBIAdvantages; and WLBI FinalManufacturing FlowCurrent Final Manufacturing FlowPackaged UnitsKnown Good DieCarrierUnload❏ WLBI Advantages– Product Cost Reduction– Cycle Time Reduction– Capital Cost ReductionWLBI Final Manufacturing FlowPackaged UnitsKnown Good DiePackageBurn-inTestCarrierBurn-inTestAssemblyTestAssemblyTestCarrierLoadDicingWafer ProbeDicingWafer ProbeWaferLevelBurn-in10

MotorolaWLBI Wafer-Contactor AssemblyWLBI Wafer-Contactor AssemblyInferno TM IC BoardGoreMateII TMContactorChuckDiameter about 50umPitch about 100um11

MotorolaWLBI Beta Development SystemWLBI Beta Development System❏Beta Development system is a 7-wafer system including– 7-chamber burn-in rack– Aligner for wafer-contactor assembly– WLBI Electronics– System Control ModuleSystem Control ModuleWLBI ElectronicsBurn-In Rack& LifterAlign and Assemble ModuleAligner12

MotorolaWafer Maps at Temperature13

MatsushitaMatsushita WLBI System Overview14

Three Part Structure Probe (TPS):Matsushita! Contactor which provides complianceby utilizing multi-layeredinterconnecting wire board, conductiverubber, and a membrane with Z-axisbumps! Control CTE of bumped membrane15

MatsushitaIn conclusion, a first step towards practicalWLBI technology has been realized:! CTE matching of contactor to silicon! The absorption of bump height differences! Uniform pressure with the atmosphericcassette! Firm contacts have been achieved on 2,756bumps which have remained stable up to125-C! Goal on membrane/substrate life is 1,000cycles, but they are not there yet.16

FormFactorFormFactor Inc. - Using MicrospringContacts for Wafer-Level Packaging & TestFormFactor has invented a new contacttechnology called a MicroSpring suited forelectronic applications of a low force, low profile,z-axis, wiping, gold on gold contact.! These are true springs requiring around onegram of compression force for every one mil ofdisplacement and exhibit low contact resistance,typically below 30 milliohm5 per contact pair.! They can be used as a fine pitch contact downto pitches of 225 microns, ie., as in currentproduction of contacting C4 (Flip chip) arrays of1000's of contacts.! They have been profiled as being ideally used inLGA production sockets and have been used inFormFactor’s own Probe Cards to test DRAMsor CPUs at the wafer level.17

FormFactorThe ultimate extension of theirMicroSpring technology comes in the formof their WOW technology or Wafer OnWafer. WOW is the IC industry’s first backendprocess that provides full wafer levelpackage, burn-in, test and module assembly -all steps to be performed on a whole waferthereby reducing costs.The key element in FormFactor’s success isthe MicroSpring contact which is formed byplacing a specifically designed and shapedwire bond at the desired pad or contactlocation, and then plating up with a proprietaryprocess the wirebond, transforming it into aspring.18

FormFactorMicrospring Contacts on SiliconRe-route TraceMicrospringSilicon•Microsprings provide:Temporary (pressure) connection during test and Burn-inPermanent Interconnect in the final product•Microsprings can be located anywhere on the die surface includingdirectly on the bond pads19

FormFactorThe WOW Process: A Wafer Level Flow forLow Cost KGDSort 1Laser RepairSort 2AttachSpringsWafer LevelBurn-in andlong cycletestShort cycle &High FrequencyFinal Test usingFFI Probe CardInterfaceDicing(Saw)ModuleAssembly& Test20

FormFactor’s WLBI SolutionFormFactor Design Approach: “Don’t fight the mechanics”Compliant Contacter: Conform to the waferUse positive pressure to drive contacterClamping and Cooling MechanismWafer Under TestFormFactor Whole Wafer ContacterAir Pressure PlenumUse Compression stop to nullify variations21

FormFactorWLBI Clamping and Cooling System22

FormFactorCurrent Projects with Three Alternative Test Flows:! WLBI and Wafer-Level at speed test - demonstratedwith Teradyne Aires tester and Infineon’s Rambus dietested at 800MHz (12x faster than any other waferleveltest reported)! Dicing after CSP packaging at wafer-level and usingexisting CSP handlers and test boards with $10~20Yamaichi sockets (x-y registration frame and lid - themicrospring contact is on the die) instead of high-cost,and high-speed test contactors ($1500~4000).! Package, dice, then assemble into modules - do allburn-in and test at the module level. No underfillrequired which makes repair simple. Since themicrosprings are self-socketing, one can utilize a usea pressure mounted connection and elimininate solderor conductive epoxies altogether.23

GryphicsGryphics®, Inc.In Development: A Controlled Compliance Probewith Generic Applications as a Wafer ProbeAnother Company with quite innovative technologyis Gryphics, Inc., located in Plymouth, MN. Gryphicsis developing a patented group of products whichincorporate low cost and high performance into whatare referred to as Removeable Chip Modules(RCM). These high-density modules can accept awide variety of devices in many applications witheach device being interconnected by a very lowinductance Multi-mode Compliance contact system,which is solderless and demateable.The RCM can be used as a prototyping, test & burnin,and production IC socket as well as productsintegrating removeable ICs into high volumeconnector applications.24

GryphicsThe suggested interface below consists of acontrolled compliance Module having asuspended contact set to interface with abumped device by means of several contactmembers. The module is to act as theinterface to the device, which can be dematedfrom the substrate without solder reflow andsubsequently moved to another location suchas a tester or additional circuit board:25

The following is an example ofsuch controlled compliance finepitch interconnect utilized in thesame probe module for testingand burning-in multiple devicesites:27

GryphicsUsing this approach, a flex circuit exit routingcoming off the probe module can lead to edgecard connection or mate directly to testelectronics:28

Aehr Test SystemsAehr Test Systems - Wafer Level Burn-Inand Test SystemRecently Aehr Test Systems announceddevelopment agreements with NHK SpringCo., Ltd. of Yokohama, Japan for Full-Waferprobe contactors for WLBI and Electroglas,Inc. for a complete Wafer-Level Burn-in andTest solution. Aehr Test has been working inthis area for several years with cofunding fromDARPA. This section will describe therequirements for a comprehensive WLBTsystem and the solutions Aehr Test Systemshas developed.29

WLBT System RequirementsAehr Test Systems30

Aehr Test SystemsThe economics and time requirements of thealignment and burn-in processes dictate theWLBT System Architecture:! Wafer alignment is short duration but usesexpensive hardware! Burn-In process is time extensive! Cartridge based system separates the twoprocesses for best cost effectivenessTest Electronics and Software are critical toensure that effective contact is being made tothe devices:! Must test to ensure electrical connection! Additional time for test is insignificantcompared to burn-in time! Functional test can be cost effective at thisstep of the process31

Aehr Test System’ s WLBT system is able tosupport different contactors into its cartridgesystem - experimenting with NHK Spring probes(12K ~13K), Goremate, and Nano Plexus's fab'd'Electronic Membrane'.Manufacturing Integration and Automation Support isnecessary to integrate the WLBT system into theproduct flow of the manufacturing line:! Cassette-to-cassette wafer handling required! Cartridge handling in fab requires precision fixturesand is best not handled manually! Aehr WLBT system offers semi-automatic handlingat first but automation decisions are on a perinstallationbasis32

Motorola Inc. / SPS GroupSacrificial Metal Wafer Level Burn-in KGDMotorola has been developing and evaluating WLBItechnologies since the early ‘90s as seen in the earlierpresentation on the Motorola/TEL/Gore alliance. Thisparticular development and implementation of 127mmand 200mm Sacrificial Metal Wafer Level Burn-In KGD atMotorola is a strategic enabling technology that allowsMotorola to maintain a competitive edge in the electronicpersonal communications, computer and automotivemarketplace.This has been a joint effort between teams at:! Motorola Austin - TSG (Transportation Systems Group)! Motorola Chandler - SMD (Strategic ManufacturingDeployment)! Motorola Chandler - MOS 12 Group33

Motorola Inc. / SPS GroupThe WLBI process flow at the wafer-level:! WLBI process flow is identical to packagelevel devices all the way to Metal-3 at theMOS! The special passivation mask enable contactalong the scribe grid whose contactsaccommodate excercising of the deviceduring burn-in! A final polyimide over-layer acts as a stressbuffer in aggressive environments (ie.,automotive) - need to be free of unstablecomponents to prevent outgassing! Wafer-level burn-in circuit removalcomprised of wet etch processes withchemistries identical to that used in definingthe WLBI circuit - TiW and/or Cu must becompletely removed34

Test System Design:Motorola Inc. / SPS Group35

Motorola Inc. / SPS GroupThe test system consists of:! Two separate chambers containing 14individual slots for accepting DUT boards! HDI connector provides signal path betweenthe DUT board and its respective driverboard located internal to the test platform! All necessary power and drive signals aremade available to the wafer via this interface36

Fixture Design and Contact Technology:The wafer, with the WLBIcircuitry (sacrificial metallayer) applies, sits in a fixturewhich supplies properalignment, thermal stress andcreates the electrical testpath.Motorola Inc. / SPS Group! Die on the wafer areelectrically grouped intoclusters and share powerand drive signals incommon37

! Electrical contact is made with the waferthrough the use of pogo pins interfacing withtest pads provided through the WLBIcircuitry applied earlier! Pogo pins specially designed to providerobust electrical and mechanical contact -pins are replaceable in the eventperformance becomes degradedMotorola has used this system for severalyears to provide KGD for use as Flip Chip orwire-bonded die in the automotive industryand for providing non-volatile memory chips.38

Die Product ConsortiumDie Products Consortium (DPC) - KGD Testand Reliability Screens MethodsDemonstration ProjectThe Die Products Consortium (DPC) is acooperative effort among several leadingmicroelectronics companies to advance thedevelopment of a support infrastructure thatwill accelerate the adoption of die products byelectronic system manufacturers worldwide.Currently, there are seven membersinvolved with the Test MethodsDemonstration Project - these include ChipSupply, IBM, Lucent, Intel, T.I., NationalSemiconductor, and CypressSemiconductor. The Consortium is beingmanaged by MCC, recognized as a globalleader in KGD technology.39

The goal of the Test Methods DemonstrationProject is to demonstrate that wafer level testand stress screening methods are effective forthe acceleration and detection of varioustypes of defects.This project will provide a baseline formembers to compare defectivity of their fabswith other members’ experience on a strictconfidential basis.The Project will develop the tools and provideunderstanding of the industry’s “best practice”,enabling members to determine the most costeffective means to achieve their particularreliability goals.40

Contributors1. Flynn, Greg W., “Wafer Level Burn-In (WLBI) at Motorola -Outline” for Fleck Research Chip Scale International 1999.2. Mosko, John, “Full Wafer Burn-In and Test” from Sixth AnnualKGD Workshop, W.L.Gore & Associates, Inc.3. Nakata, Yoshiro and Kawai,Makoto, “A Wafer-Level Burn-inTechnology” from ULSI Process Technology DevelopmentCenter, Matsushita Electronics Corporation.4. Whitten, Ralph, “Using Microspring Contacts for WaferLevel Packaging and Test” from FormFactor, Inc.5. Rathburn, James, “In Development: Controlled ComplianceProbe with Generic Applications for Wafer Probe” fromGryphics, Inc.6. Carbone, Mark C., “Wafer Level Burn-In and Test System(WLBT)” presented at Semicon West, 1999 by Aehr TestSystems.41

Contributors7. Godavarti, Prasad and Ivy Jr., Wilburn, “Sacrificial Metal WaferLayer Burn-In KGD” presented at ECTC, 2000 from MotorolaIncorporated8. Gilg, Larry, “ Die Products Consortium - KGD Test andReliability Screens Methods Demonstration Project” for 6thAnnual KGD Workshop, co-sponsored by MCC.42