1. PML Semiconductor Electronics Division, NIST
Application of Time-Domain Reflectometry To Detect Interconnect Failures
-Binayak Kandel
Mentors
Dr. Yaw Obeng
Dr. Chukwudi Okoro
PML Semiconductor Electronics Division, NIST

2. Outlines Introduction Project Goal Procedure Conclusion
How far we have come?
3-D stacking and Interconnects
Project Goal
Procedure
Conclusion

3. How Far Have We Come?
Electronic Numerical Integrator And Computer (ENIAC) -1946
17,468 vacuum tubes
~1800 square feet
~150 kW of power
-This led to a rumor that whenever the computer is switched ON, lights in Philadelphia dimmed.

4. 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.
-50% less power consumption at the same consumption level as 2-D planer transistors

5. 3-D Stacking Advantages: Increased portability Increased Functionality
TSV Connections
Advantages:
Increased portability
Increased Functionality
Increased Transmission Speed
IBMs new 3D manufacturing technology

6. Through-Silicon Via (TSV)
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)
Talk abt NIST at the end of this slide
..But the reliability of these interconnects are not studied well enough 6

7. Reliability Challenges of TSV
Void occurred at the bottom of TSV, on the connecting Cu pad due to electromigration
What is electromigration?
It is just one of the causes of the void formation
Deformation or voids means it
*Y.C. Tan et al, Electromigration performance of Through Silicon Via (TSV) – A modeling approach
**T. Frank et al, IRPS, 2011

8. Reliability Challenges Contd….
Rambient = 13.3xx Ω
Rinitial = 26.3xx Ω
Rfinal = 30.6xx Ω
FAILURE
V = I*R…same current applied but voltage increased exponentially. That means Resistance increased.
…How do we find out the location of these failures?

9. Project Goal
Determine the failure locations in interconnects using Time-Domain Reflectometry (TDR)

10. 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.
Discontinuities
Time
Amplitude T
D = Distance
vρ = Velocity of Propagation
T = Time

11. Why TDR (1)?
Easy and accurate to locate failures like open termination or any kind of discontinuities.
Daeil et al ,Early Detection of Interconnect Degradation using RF Impedance 2008

12. Why TDR (2)? Non destructive method to pinpoint failures
Daeil et al ,Early Detection of Interconnect Degradation using RF Impedance 2008

13. Reliability Challenges Contd….
Rambient = 13.3xx Ω
Rinitial = 26.3xx Ω
Rfinal = 30.6xx Ω
FAILURE
V = I*R…same current applied but voltage increased exponentially. That means Resistance increased.
…How do we find out the location of these failures in the sea of TSVs? Use TDR.

14. 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
LeCroy WaveExpert 100h 14
S. Vahanen et al, 3D integration activities at CERN 2010

15. 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

16. Thank You!