synchrotron x-ray topography for laser- drilled vias kevin wang, march 9, 2009
TRANSCRIPT
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Synchrotron X-Ray Topography for Laser-Drilled
ViasKevin Wang, March 9, 2009
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Through Silicon Via
Via connecting one side of silicon wafer to another
Reduce connection length
Drilling options Mechanical Deep Reactive Ion Etching (DRIE) Laser pulses
DRIE Vias, Source: Albany Nanotech
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Paper
Laser Drilled Through Silicon Vias: Crystal Defect Analysis by Synchrotron X-ray Topography Landgraf, R., Rieske, R., Danielewsky, A., Wolter, K. Technische Universtät Dresden, Germany
Synchrotron Source: ANKA (Karlsruhe, Germany) 2.5 GeV,current 80-180 mA: white radiation 2Å
Presented at: 2nd Electronics System-Integration Technology
Conference, Greenwich, UK (2009-09-01)
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DRIE vs. Laser Drilling
DRIE Vias, Source: Lam Research
Laser Via, Source: Landgraf
Sidewall Scalloping, Source: Aviza Technology
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Laser Via Fabrication
525μm thick Si wafer (100) 4in. (100mm)
Target via diam: 50 μm
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Laser Drilling Methods
Single Pulse
Trepanning (cut an annulus)
Percussion (high power pulsing)
Conventional drilling patterns, Source: Verhoeven, K.
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X-ray Diffraction Setup
Section Transmission (15μm slit), Lang Method
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Results – Strain Imaging
ns laser: 540 μm strain zone
ps laser: 290 μm strain zone
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Trend with Laser Pulse Width
Strain affected region: Distance from via edge to
strain edge
fs laser: 220 μm strain zone
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Conclusion
Transmission topography by synchrotron source successfully imaged strain near vias, nondestructively
Strain affected zone decreased with pulse width Electron-phonon relaxation time in Si, 400fs
Femtosecond lasers should be considered for commercial production Depth remains to be improved
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Motivation: Multi-Chip Packages
Wirebonding Longer paths Failure due to fatigue,
bond lifting
Flipchip bumps Reduce path length Still require redistribution layer (RDL) Thermal cycling failure
Flipchip Die, Source: IMEC
Wirebonded Die, Source: Aspen Tech.