Title: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences
1Cracking in Interconnectsdue to Thermal
Ratcheting
- Zhen Zhang, Zhigang SuoDivision of Engineering
and Applied Sciences - Harvard University
- Jean H. Prévost
- Department Civil and Environmental Engineering
- Princeton University
MRSEC
2What is the origin of high stress?
3Ratcheting Plastic Deformation
Huang, Suo, Ma, Fujimoto, J. Mater. Res., 15,
1239 (2000)
4Ratcheting Plastic Deformation
membrane stress due to CTE mismatch
Metal yields every cycle !
What is the crack behavior?
52D Shear Lag Model
Gradual loss of constraint Stress relaxes in
crack wake, but intensifies at crack tip.
- Two challenges for simulation
- Crack growth
- Plasticity
X-FEM
Linear creep analogy
6Extended Finite Element Method (X-FEM)
- Nodal Enrichment functions
Time-saving
Moës, Dolbow, Belytschko, Int. J. Num Math. Eng,
46, 131 (1999).
7Linear Ratcheting-Creep Analogy
Time-saving
Huang, Suo, Ma, Acta Materialia, 49, 3039-3049
(2001)
8Semi-infinite Stationary Crack in Blanket Film
- Both creep and ratcheting calculation show the
same trend.
- Comparison of time cost
- Creep 1hr 20min
- Ratchet 22 hr
9Finite Stationary Crack in Blanket Film
10Crack Propagation in a Blanket Film
Initiation
Steady-state
11Simulation of Cracks Propagation in Interconnects
Tensile stress
Compressive region
12Summary
Ratcheting deformation in metal layer
High temperature packaging
Cracking in interconnects
High stress in SiN passivation film
Thermal cyclic loading
X-FEM Linear creep analogy
Simulation of cracking in interconnects becomes
feasible