Slide 1Through Silicon ViaPaperDRIE vs. Laser DrillingLaser Via FabricationLaser Drilling MethodsX-ray Diffraction SetupResults – Strain ImagingTrend with Laser Pulse WidthConclusionMotivation: Multi-Chip PackagesSynchrotron X-Ray Topography for Laser-Drilled ViasKevin Wang, March 9, 2009Through Silicon ViaVia connecting one side of silicon wafer to anotherReduce connection lengthDrilling optionsMechanicalDeep Reactive Ion Etching (DRIE)Laser pulsesDRIE Vias, Source: Albany NanotechPaperLaser Drilled Through Silicon Vias: Crystal Defect Analysis by Synchrotron X-ray TopographyLandgraf, R., Rieske, R., Danielewsky, A., Wolter, K.Technische Universtät Dresden, GermanySynchrotron Source: ANKA (Karlsruhe, Germany)2.5 GeV,current 80-180 mA: white radiation 2ÅPresented at:2nd Electronics System-Integration Technology Conference, Greenwich, UK (2009-09-01)DRIE vs. Laser DrillingDRIE Vias, Source: Lam ResearchLaser Via, Source: LandgrafSidewall Scalloping, Source: Aviza TechnologyLaser Via Fabrication525μm thick Si wafer (100)4in. (100mm)Target via diam: 50 μmLaser Drilling MethodsSingle PulseTrepanning (cut an annulus)Percussion (high power pulsing)Conventional drilling patterns, Source: Verhoeven, K.X-ray Diffraction SetupSection Transmission (15μm slit), Lang MethodResults – Strain Imagingns laser: 540 μm strain zone ps laser: 290 μm strain zoneTrend with Laser Pulse WidthStrain affected region: Distance from via edge tostrain edgefs laser: 220 μm strain zoneConclusionTransmission topography by synchrotron source successfully imaged strain near vias, nondestructivelyStrain affected zone decreased with pulse widthElectron-phonon relaxation time in Si, 400fsFemtosecond lasers should be considered for commercial productionDepth remains to be improvedMotivation: Multi-Chip PackagesWirebondingLonger pathsFailure due to fatigue,bond liftingFlipchip bumpsReduce path lengthStill require redistribution layer (RDL)Thermal cycling failureFlipchip Die, Source: IMECWirebonded Die, Source: Aspen
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