Application of Time-Domain
Reflectometry To Detect
Interconnect Failures
-Binayak Kandel
Mentors
Dr. Yaw Obeng
Dr. Chukwudi Okoro
PML Semiconductor Electronics Division, NIST
Outlines
• Introduction
 How far we have come?
 3-D stacking and Interconnects
• Project Goal
• Procedure
• Conclusion
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How Far Have We Come?
Electronic Numerical Integrator And Computer
(ENIAC) -1946
• 17,468 vacuum tubes
• ~1800 square feet
• ~150 kW of power
http://www.fi.edu/learn/case-files/eckertmauchly/team.html
3
How Far Have We Come?
Ivy Bridge Processors -2012
• 1.4 billion transistors (Tri “3-D” Transistors)
• 160 mm2 die size
• 50% less power
consumption than its
predecessor.
http://www.digitaltrends.com/computing/getting-ready-to-cross-ivy-bridge-the-laymans-guide-to-intels-latest-processors/
4
3-D Stacking
TSV
Connections
Advantages:
• Increased portability
• Increased Functionality
• Increased Transmission Speed
IBMs new 3D manufacturing technology
5
Interconnects
Back-End-of-Line(BEOL)
 Connects individual
components like
transistors and
capacitors
Through-Silicon Via(TSV)
 Vertical connections
that pass through
wafer or die
Through-Silicon Via (TSV)
..But the reliability of
these interconnects are
not studied well enough
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Reliability Challenges of TSV
• Void occurred at the bottom of TSV, on the
connecting Cu pad due to electromigration
*Y.C. Tan et al, Electromigration performance of Through Silicon Via (TSV) – A modeling approach
**T. Frank et al, IRPS, 2011
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Reliability Challenges
Contd….
0.92
FAILURE
Voltage (Volts)
0.87
Rambient = 13.3xx Ω
0.82
Rinitial = 26.3xx Ω
0.77
Rfinal = 30.6xx Ω
0.72
0.67
0.62
1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200
Time (min.)
…How do we find out the location of these
failures?
8
Project Goal
• Determine the failure locations in interconnects
using Time-Domain Reflectometry (TDR)
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TDR
• Works on the same principle as radar
• TDR transmits a short rise time pulse along the conductor.
• Any discontinuities in the impedance causes signal to
reflect back.
Discontinuitie
s
Amplitude
D = Distance
vρ = Velocity of Propagation
T = Time
T
Time
10
Why TDR (1)?
• Easy and accurate to locate failures like open
termination or any kind of discontinuities.
11
Daeil et al ,Early Detection of Interconnect Degradation using RF Impedance 2008
Why TDR (2)?
• Non destructive method to pinpoint failures
12
Daeil et al ,Early Detection of Interconnect Degradation using RF Impedance 2008
Reliability Challenges
Contd….
0.92
FAILURE
Voltage (Volts)
0.87
Rambient = 13.3xx Ω
0.82
Rinitial = 26.3xx Ω
0.77
Rfinal = 30.6xx Ω
0.72
0.67
0.62
1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200
Time (min.)
…How do we find out the location of these
failures in the sea of TSVs? Use TDR.
13
My Task
•
•
•
•
•
Prepare sample
Learn to use LeCroy WaveExpert 100h
Take TDR measurements
Locate where failure occurred
Correlate data measured from Vector Network
Analyzer (VNA) with the TDR data
Test Sample
S. Vahanen et al, 3D integration activities at CERN 2010
LeCroy WaveExpert 100h
14
Acknowledgement
• Society of Physics Students
 Entire SPS and AIP Family
• National Institute of Standards and
Technology(NIST)
 Dr. David Seiler, Dr. Yaw Obeng, Dr. Chukwudi Okoro, Dr. John Suehle
Dr. Yaqub Afridi
 Entire PML Semiconductor and Electronics Division Family
• Fellow Summer Interns
15
Thank You!
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