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Synchrotron X-Ray Topography for Laser-Drilled Vias. Kevin Wang, March 9, 2009. 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. - PowerPoint PPT Presentation
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Synchrotron X-Ray Topography for Laser-Drilled
ViasKevin Wang, March 9, 2009
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
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)
DRIE vs. Laser Drilling
DRIE Vias, Source: Lam Research Laser Via,
Source: Landgraf
Sidewall Scalloping, Source: Aviza Technology
Laser Via Fabrication 525μm thick Si wafer (100)
4in. (100mm) Target via diam: 50 μm
Laser Drilling Methods Single Pulse Trepanning (cut an annulus) Percussion (high power pulsing)
Conventional drilling patterns, Source: Verhoeven, K.
X-ray Diffraction Setup Section Transmission (15μm slit), Lang Method
Results – Strain Imaging
ns laser: 540 μm strain zone
ps laser: 290 μm strain zone
Trend with Laser Pulse Width Strain affected region:
Distance from via edge tostrain edge
fs laser: 220 μm strain zone
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
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.