“Plasma” FIB
Transcript of “Plasma” FIB
Site-specific Failure
Analysis and Reliability
Testing of 3D Systems using
“Plasma” FIB
Richard Young,1 C. Rue,1 R. Routh,1
G. Franz,2 L.F.Tz. Kwakman,2
P. Ramm,3 A. Klumpp,3 and M.M.V Taklo4
1FEI Company, Hillsboro, OR, USA
2FEI Electron Optics, Eindhoven, The Netherlands
3Fraunhofer EMFT, Munich, Germany
4SINTEF, Oslo, Norway
SEMATECH 3D Interconnect Metrology Workshop: July 13th, 2010© FEI Company 2011
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Outline
Introduction to focused ion beams (FIB)
Technologies for faster material removal
Plasma FIB technology
3D integration – performance and reliability drivers
Use case examples:
• Plated bumps
• Stacked die with “TSV” and “SLID” bond technology
• Anisotropic conductive adhesive for wafer-to-wafer bonding
Summary
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What a focused ion beam (FIB) system can do:
Remove Material
• Sample is sputtered
where beam is scanned,
sometimes with a
reactive gas
Add Material
• A gas is decomposed where
beam is scanned
Form an Image
• Secondary electrons or ions are
collected to assemble an image
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Focused ion beam sample prep
Excellent for site-specific sample preparation
• Localized – positioning to nm level
- Leave rest of device intact
- Multiple locations on single device
• Any orientation
• No mechanical shock or tearing/smearing
Generally uses gallium liquid metal ion source (LMIS)
Typical beam current range 1 pA to 20-65 nA
• ~103 μm3/min for silicon at 60 nA
• Short prep times for sections a few 10s of μm on a side
• 3D IC technology/packaging sections often > 100 μm
• Therefore, require new techniques focused on
throughput and efficiency300 µm wide
>12 hours with 65nA Ga-FIB
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10 µm wide
20 mins (Ga-FIB)
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Enhancing FIB capabilities
High-speed silicon removal with XeF2
• Gas assisted etching (e.g. I2, XeF2, Cl2)
• Enhancement varies by material (1-15X)
• Special case: XeF2 + Si → 5-10 μm3/min
• Already used in backside circuit edit for “trenching”
• Limited mainly to bulk silicon removal
Larger beam currents with Ga LMIS
• Latest systems already use 65 nA from 21 nA
New source technology for higher beam currents (> 1 μA)
• Inductively coupled plasma (ICP) source
• Improvement > 20X over Ga-FIB
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0.001
0.01
0.1
1
10
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0.001 0.01 0.1 1 10 100 1000 10000
Spo
tsiz
e [µ
m]
Beam Current [nA]
Xe Plasma
Ga LMIS
Why Plasma FIB: 20x faster than current FIBs
High volume milling / high beam
current
Ga-FIB loses size advantage to
plasma source as beam current
goes above 50-60 nA
Xe has high sputter yield, high
brightness, and low energy spread
No Ga contamination
A system that provides unique and fast ion milling capabilities
for rapid cross sectioning of features from 50 to 1000 microns.
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Inductively coupled plasma (ICP) ion source
• Gas flows into plasma cell
• Helical antenna couples energy into plasma cell
• Electrons removed from atoms to form Xe+ ions
• Extraction optics accelerate ions into FIB column
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Comparison of FIB sources
LMIS
ICP
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Outline
Introduction to focused ion beams (FIB)
Technologies for faster material removal
Plasma FIB technology
3D integration – performance and reliability drivers
Use case examples:
• Plated bumps
• Stacked die with “TSV” and “SLID” bond technology
• Anisotropic conductive adhesive for wafer-to-wafer bonding
Summary
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Cross-sectioned bump
•Bump test wafer (Courtesy SEMATECH)
•80 µm wide and 100 µm tall
•Cross-sectioned and imaged in 20 min.
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Stacked die with “TSV” and “SLID” bond
technology
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Three-die reliability test chip
•TSV: Through silicon via (Cu or W)
•SLID: Solid-liquid interdiffusion
bonding (Cu-Sn-Cu)
•IMC: intermetallic compounds
Ref: P. Ramm, A. Klumpp, G. Franz, and
L. Kwakman, Proc. IMAPS Device
Packaging Conf., Scottsdale, Arizona,
2011
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Cross sectioning three-die stack
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Details of the SLID bonding (Cu-Sn-Cu)
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Anisotropic conductive adhesive for Wafer-
to-Wafer bonding
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Ref: M.M.V. Taklo, T. Bakke, H.R. Tofteberg, L.G.W. Tvedt and H. Kristiansen, Proc. IMAPS Device Packaging Conf.,
Scottsdale, Arizona, 2011
Metal coated polymer spheres (4 µm diameter) Electrical contacts
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Anisotropic conductive adhesive for W2W
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Box: 200 x 50 x 600 μm3
Time: 30 min
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Summary
3D IC technology needs metrology and root cause analysis down to the
sub-micron level for development and failure analysis
• But it takes too long with traditional Ga-FIB
Plasma FIB technology brings site specific advantages of Ga FIB to
chip/package scaled problems
• More than 20x faster than traditional FIB
• Capable of high-precision final cuts and high-resolution (sub-30 nm) imaging
• Provides faster development feedback and failure analysis
Acknowledgements: A part of the work has been performed in the project JEMSiP_3D, which is funded
by the Public Authorities in France, Germany, Hungary, The Netherlands, Norway and Sweden, as well as
by the ENIAC Joint Undertaking.
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