440
L. Chen et al.
Fig. 15.6 Distribution of mobility changes in (a) n-type MOSFETS with the electric field and
current density in [100] direction and (b) Mobility change for p-type MOSFET with [100] channel.
(c) Mobility change for n-type MOSFET with current density in [110] direction. (d) p-type
MOSFETS with the electric field and current density in [110] direction. The dashed lines indicate
the 5% mobility change (d = 10 μm, H = 200 μm, and T = − 250 °C). [40]
Si. Further analyses by FEA show that the KOZ increases monotonically with TSV
diameter [47]. The plasticity of Cu can relax stress close to the via/Si interface to
reduce the size of KOZ, but this effect is rather localized. When the TSVs are placed
closer together, stress interaction between neighboring vias can increase the overall
stresses in Si and thus the size of KOZ, but stress interaction is negligible when the
ratio of via pitch to diameter is larger than 5.
15.2.5 Thermal Stress Induced via Extrusion
Via extrusion is the non-recoverable deformation of Cu near the top of the via after
thermal cycles. Grain growth, plastic yielding by dislocation glide, and diffusional
creep along grain boundaries and/or the via/liner interface are possible relaxation
L. Chen et al.
Fig. 15.6 Distribution of mobility changes in (a) n-type MOSFETS with the electric field and
current density in [100] direction and (b) Mobility change for p-type MOSFET with [100] channel.
(c) Mobility change for n-type MOSFET with current density in [110] direction. (d) p-type
MOSFETS with the electric field and current density in [110] direction. The dashed lines indicate
the 5% mobility change (d = 10 μm, H = 200 μm, and T = − 250 °C). [40]
Si. Further analyses by FEA show that the KOZ increases monotonically with TSV
diameter [47]. The plasticity of Cu can relax stress close to the via/Si interface to
reduce the size of KOZ, but this effect is rather localized. When the TSVs are placed
closer together, stress interaction between neighboring vias can increase the overall
stresses in Si and thus the size of KOZ, but stress interaction is negligible when the
ratio of via pitch to diameter is larger than 5.
15.2.5 Thermal Stress Induced via Extrusion
Via extrusion is the non-recoverable deformation of Cu near the top of the via after
thermal cycles. Grain growth, plastic yielding by dislocation glide, and diffusional
creep along grain boundaries and/or the via/liner interface are possible relaxation