Blank, T.

Caselle, M.

Colombo, F.

Husemann, U.

Kudella, S.

Leyrer, B.

Weber, M.

KITopen

KIT – University of the state of Baden-Wuerttemberg and national research institution of the Helmholtz AssociationInstitut für Experimentelle Kernphysikwww.kit.eduGold-stud bumpbondingInterconnection technology for research and development of new detectorsThomas Blank, Michele Caselle, Fabio Colombo, Ulrich Husemann, •Simon Kudella, Benjamin Leyrer und Marc WeberSimon KudellaInstitut für Experimentelle Kernphysik2Bumpbonding of pixel detectorsInterconnection-density of pixel detectors to high for wire bondingBumpbonding for vertical interconnection with high densityStandard technologies base on chemical bump depositionChemical processes need Under-Bump-Metallization (UBM)Complex and expensive wafer-processingSearch for cheap and flexible bumpbonding alternative technologies for single chip processing during R&D picture-source: L. Rossi – Pixel DetectorsGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik3Alternative bumping method (KIT) Gold-stud bumping is an evolution of ~50 years of wirebondingWire gets sheared after ball connection to substratesubstrateBall  - wedge gold wire bondingNo UBM necessarySingle-chip-bumping possibleCheap bumping process, @KIT20 bumps/sBall-wedge-BonderBond head with capillarySEM-pictures of gold-stud bumpsPicture source: J.Jordan – Gold Stud Bumps in Flip-chip ApplicationsGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik4Bumping – process operationProcess of upto 10 single steps ''Free Air Ball'' formationTouchdown onto surfaceBonding via ultrasonic bonding by ultrasonic generator (USG)Shearing of wireRe-feeding and ripping of wireProcess with large number of paramters → optimization regarding:Mechanical strengthBumpsize and -shapeLong-term stabilityBumping process-sequenceGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik5Bumping – mechanical strengthInvestigation by shearing of the bumpsLooking for: High shearforce per connection areaSeparation process: bond-shear, aluminium-shear Systematical investigation of mechanical strengthNo connection for IUSG<25 mA or Fbond<7 gDimension for mechanical strength γ=F/(Aσ), σ=standard deviationParameters in area of high stability chosen Shearforce: 8 g per bumpShear-testPicture sources: SPT & NordsonGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik6Bumping – Bumpgröße & -formBump-shaping via wire-shearing parametersCurrent status: 30 µm diameter, 15 µm heightBump-diameter comparable to lithographic process30 µm bump on30 µm opening34 µm bump on15 µm openingMinimal bump-diameter depending on opening diameter of passivation → small passivation openings cause bigger bumps30 µmSEM – 30 µm gold-stud bump15 µmGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik7Bumping – long-term stabilityLong-term stability depending on hardware parameters (condition of wire , cleaniness of wire-feed system) and bumping parametersCurrent long-term stability >4000 bumps without interruption → bumping of a CMS pixel single sensor (4160 bumps) process in <5 minGold-stud bumps on CMS pixel sensorGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik8Gold-stud bumpsBonding – process operationFlip-chip bonding by thermo-compressionBonding with Femto Fineplacer® @KITBondiung profileheatingBond-forceBond-temperatureheatingFemto FineplacerPicture source: Finetech GmbH & Co. KGTwo-step process1) Establishing planarity by gamber tool2) Bonding by thermo compressionProcess parameters1) Bond-force: 200 N (4,9 g/bump) for 60 s (necessary for bumpdeformation)2) Bond-temperature 250 °C for 60 s (no elektromigration in ROC/Sensor)BondedsensorsGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik9Bonding – test resultsPulltest:High pull force of >2,2 g per bumpSeparation process: 95% bump-to-bump, 5% aluminium-liftoff→ bumping optimized→ bonding not optimized yetChip shift due to weak vacuumCross-section:Very good connection of the gold bumps at 250 °CChip shift due to weak vacuumCrossection through bumpsBumps after PulltestGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik10Bonding – flattening of bumpsShift due to high shear-forces during the bonding→ Reduction of the shear-forces by flattening all bumpsPressing bumps onto bonding tableShift reduced All bumps seem to be connected → electrical testCross-section of bumpGold-stud surface27.03.2014DPG-Frühjahrstagung 2014Cross-section of bonded bumpsGold-stud bumpbonding - Interconnection technology for research and development of new detectorsSimon KudellaInstitut für Experimentelle Kernphysik11Bonding – electrical testFirst prototype assembledChip alive after processing and 80% of connections establishedSource test shows planarity problem→ correlated to flattening problem causing two plane structureImproving flattening process to assemble class A singles soon Gold-stud bumpbonding - Interconnection technology for research and development of new detectorsUnflattened bumps Flattened bumpsPlotted with HRPixelMap27.03.2014DPG-Frühjahrstagung 2014Two plane structureSimon KudellaInstitut für Experimentelle Kernphysik12SummaryBumpbonding necessary for hybrid pixel detectors but complex and expensiveGold-stud bumpbonding as cheap flexible alternative that enables single-chip processing in the R&D phaseSetting at KIT:Bumping with Ball-wedge bonder (@KIT)Bonding with Flip-chip bonder (@KIT)Status:Stable process producing 30-µm-bumpsVery good and strong interconnection using 250 °C bond-temperatureChip shift due to weak vacuum → flattening of bumps to avoid shear forcesUpcoming:Improvement of flattening process and produce class A singlesBumpbonding process @KITGold-stud bumpbonding - Interconnection technology for research and development of new detectors27.03.2014DPG-Frühjahrstagung 2014Simon KudellaInstitut für Experimentelle Kernphysik13Thanks for your attention!27.03.2014DPG-Frühjahrstagung 2014Gold-stud bumpbonding - Interconnection technology for research and development of new detectors

Gold-stud bumpbonding. Interconnection technology for research and development of new detectors

https://publikationen.bibliothek.kit.edu/230095670/3816538

Gold-stud bumpbonding. Interconnection technology for research and development of new detectors

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