614
Y. Li and D. Goyal
exponent. As illustrated in Fig. 18.37c, d, E a and n are estimated as 0.36 eV and 1.4,
respectively based on transported Cu volume calculated from 3D X-ray CT images on
samples with different temperatures and current density levels. Both the simulation
results and experimental data indicate that the void migration could happen at room
temperature with relatively low current density, while no new void is created in the Cu
vias not having any preexisting voids. Thus void free Cu vias are desired especially
for packages designed to carry high currents [72].
18.5.4 Conclusions
Advanced fault isolation and failure analysis techniques for 3D microelectronic
packages are reviewed along with FA strategies and efficient FI-FA flow design
to demonstrate their applications. It has been illustrated that TDR is a low cost
and effective fault isolation tool for locating open failures with spatial resolution of
500 μm. EOTPR could be used to precisely (~10 μm resolution) estimate the failure
location with correct data interpretation. Both techniques have been successfully
demonstrated for the detection of open and high resistance failures in 3D packages.
LIT and SSM are very promising non-destructive techniques that could provide
fault isolation capabilities not just in the X-Y plane but also through the depth of
packages, which is critical for isolating short and leakage failures in 3D packages.
High resolution non-destructive imaging techniques like SAM, IR imaging, 2D Xray imaging, and 3D X-ray CT could be applied to reveal defects in 3D packages
either before or post the fault isolation, depending on different cases.
Sample preparation techniques, like plasma-FIB, ultra-short pulse laser milling
combined with conventional FIB and SEM, and broad-beam ion milling are very
efficient to provide artifact free cross sections of interconnects in 3D packages.
EDX, FTIR, AFM-IR, XPS, TOF SIMIS, and EBSD have been demonstrated to be
very valuable material analysis techniques for root cause understanding of failures
by providing information about chemical composition, interface contamination, and
crystal orientation of defects.
Understanding details of assembly process, various reliability tests, and failure rate
distribution is the first key step of 3D package failure analysis. A systematic, artifact
free, and efficient FI-FA flow well designed to save both time and cost is essential
to quickly identify defects led to electrical failures. In-depth failure mechanism and
root cause understanding to provide solution paths of failures is the ultimate goal of
failure analysis. Direct observation of the initiation and propagation of defects by
non-destructive and in-situ techniques are proven to be effective for thorough root
cause studies.
Acknowledgements The editors would like to thank Frank Altmann and Sebastian Brand from
Fraunhofer-Institute for Microstructure of Materials and Systems IMWS in Germany for their
critical review of this chapter.
Y. Li and D. Goyal
exponent. As illustrated in Fig. 18.37c, d, E a and n are estimated as 0.36 eV and 1.4,
respectively based on transported Cu volume calculated from 3D X-ray CT images on
samples with different temperatures and current density levels. Both the simulation
results and experimental data indicate that the void migration could happen at room
temperature with relatively low current density, while no new void is created in the Cu
vias not having any preexisting voids. Thus void free Cu vias are desired especially
for packages designed to carry high currents [72].
18.5.4 Conclusions
Advanced fault isolation and failure analysis techniques for 3D microelectronic
packages are reviewed along with FA strategies and efficient FI-FA flow design
to demonstrate their applications. It has been illustrated that TDR is a low cost
and effective fault isolation tool for locating open failures with spatial resolution of
500 μm. EOTPR could be used to precisely (~10 μm resolution) estimate the failure
location with correct data interpretation. Both techniques have been successfully
demonstrated for the detection of open and high resistance failures in 3D packages.
LIT and SSM are very promising non-destructive techniques that could provide
fault isolation capabilities not just in the X-Y plane but also through the depth of
packages, which is critical for isolating short and leakage failures in 3D packages.
High resolution non-destructive imaging techniques like SAM, IR imaging, 2D Xray imaging, and 3D X-ray CT could be applied to reveal defects in 3D packages
either before or post the fault isolation, depending on different cases.
Sample preparation techniques, like plasma-FIB, ultra-short pulse laser milling
combined with conventional FIB and SEM, and broad-beam ion milling are very
efficient to provide artifact free cross sections of interconnects in 3D packages.
EDX, FTIR, AFM-IR, XPS, TOF SIMIS, and EBSD have been demonstrated to be
very valuable material analysis techniques for root cause understanding of failures
by providing information about chemical composition, interface contamination, and
crystal orientation of defects.
Understanding details of assembly process, various reliability tests, and failure rate
distribution is the first key step of 3D package failure analysis. A systematic, artifact
free, and efficient FI-FA flow well designed to save both time and cost is essential
to quickly identify defects led to electrical failures. In-depth failure mechanism and
root cause understanding to provide solution paths of failures is the ultimate goal of
failure analysis. Direct observation of the initiation and propagation of defects by
non-destructive and in-situ techniques are proven to be effective for thorough root
cause studies.
Acknowledgements The editors would like to thank Frank Altmann and Sebastian Brand from
Fraunhofer-Institute for Microstructure of Materials and Systems IMWS in Germany for their
critical review of this chapter.