96
P. Kumar et al.
Fig. 4.27 (a) Focused ion beam (FIB) image of the cross-section of the region near the top of
a TSV subjected to a current density of 1.5 × 10 5 A/cm 2 at 200 °C for 20 days. The electrons
flow upwards through the TSV into the metal-1 (M1) layer, and turn 90 o to leave the plane of the
micrograph. (b) Sn Ka x-ray map of the same TSV, showing Sn concentrations at the dark features
of the ion image
these experiments were much more severe than those TSV-containing packages are
subjected to, but suggest the types of damage to which 3D packages may be subjected
with rising current densities and temperatures (ambient or due to Joule heating).
4.4 Towards Atomistically-Informed Reliability Modeling
of TSVs
As discussed in Sects. 4.2.2.4 and 4.3.1.2, more robust modeling techniques are
needed to complement the FEA and advanced experimental characterization in order
to provide a complete picture of the microstructure and stress inside the TSVs. This
section introduces two methods, i.e., the crystal plasticity FEA (CPFEA) and the
phase field crystal (PFC) method, and discusses their capabilities for atomisticallyinformed reliability modeling of TSVs.
4.4.1 The CPFE Method
The challenge of managing mechanical stress is not new, and a number of simulators
do exist and have a long track record of use in the electronics industry. Most of the
proven simulators are based on FEA, or derivatives of that class of modeling technique. The established FEA stress simulators have typically been used for addressing
the traditional chip-package interactions, and have therefore mostly modeled physical deformations, such as cracking, delaminating, or fracturing [66]. In this class
of analyses Si dies and TSV fillers are typically modeled as monolithic bricks and
P. Kumar et al.
Fig. 4.27 (a) Focused ion beam (FIB) image of the cross-section of the region near the top of
a TSV subjected to a current density of 1.5 × 10 5 A/cm 2 at 200 °C for 20 days. The electrons
flow upwards through the TSV into the metal-1 (M1) layer, and turn 90 o to leave the plane of the
micrograph. (b) Sn Ka x-ray map of the same TSV, showing Sn concentrations at the dark features
of the ion image
these experiments were much more severe than those TSV-containing packages are
subjected to, but suggest the types of damage to which 3D packages may be subjected
with rising current densities and temperatures (ambient or due to Joule heating).
4.4 Towards Atomistically-Informed Reliability Modeling
of TSVs
As discussed in Sects. 4.2.2.4 and 4.3.1.2, more robust modeling techniques are
needed to complement the FEA and advanced experimental characterization in order
to provide a complete picture of the microstructure and stress inside the TSVs. This
section introduces two methods, i.e., the crystal plasticity FEA (CPFEA) and the
phase field crystal (PFC) method, and discusses their capabilities for atomisticallyinformed reliability modeling of TSVs.
4.4.1 The CPFE Method
The challenge of managing mechanical stress is not new, and a number of simulators
do exist and have a long track record of use in the electronics industry. Most of the
proven simulators are based on FEA, or derivatives of that class of modeling technique. The established FEA stress simulators have typically been used for addressing
the traditional chip-package interactions, and have therefore mostly modeled physical deformations, such as cracking, delaminating, or fracturing [66]. In this class
of analyses Si dies and TSV fillers are typically modeled as monolithic bricks and