Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H....
-
Upload
james-crawford -
Category
Documents
-
view
216 -
download
4
Transcript of Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H....
![Page 1: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/1.jpg)
Zhen Zhang, Zhigang SuoDivision of Engineering and Applied Sciences
Harvard University
Jean H. PrévostDepartment Civil and Environmental Engineering
Princeton University
Cracking in Interconnectsdue to Thermal Ratcheting
MRSEC
![Page 2: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/2.jpg)
Time
Temperature
1500C
1250C
-550C
Packaging temperature
Loadingrange
Cyclic loading test
Silicon
Lower level interconnects (10-15 m thick)
Al-Cu 2m thick
Underfill
Polyimide(4 m thick)
SiN (0.45m thick)
underfill
Flip-chip structure
Plan view of SiN
Silicon die
Organicsubstrate
What is the origin of high stress?
![Page 3: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/3.jpg)
Ratcheting Plastic Deformation
Huang, Suo, Ma, Fujimoto, J. Mater. Res., 15, 1239 (2000)
Biased Shear Stress
Al or Cu
Silicon
10~100 µm
2 µm 0.5 µm SiN
Silica and low level interconnects (10~15µm thick)
Polymeric underfill
underfill Silicon die
Organic Substrate
Time
Temperature
1500C
1250C
-550C
Packaging temperature
Loadingrange
Packaging and loading
![Page 4: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/4.jpg)
First cycle
m
SiN film
What is the crack behavior?
membrane stressdue to CTE mismatch
Metal yields every cycle !
Many cycles
mAl / Cu pad
Stress builds up in SiN
m
m biased shear stress
Al / Cu pad
Ratcheting Plastic Deformation
p
![Page 5: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/5.jpg)
2D Shear Lag Modelstress
YE
strain
Two challenges for simulation• Crack growth• Plasticity
0
Elastic substrate
x
yzx
0
y0
Elastic film
Elastic-plastic sublayer
X-FEMLinear creep analogy
Gradual loss of constraintStress relaxes in crack wake, but intensifies at crack tip.
![Page 6: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/6.jpg)
Extended Finite Element Method (X-FEM)
Nodal Enrichment functions:
Moës, Dolbow, Belytschko, Int. J. Num Math. Eng, 46, 131 (1999).
– Displacement jumps– Singular crack tip field
– Relative coarse mesh– No remeshing required for
crack growth simulations
Benefits:
Time-saving
![Page 7: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/7.jpg)
Linear Ratcheting-Creep Analogy
Y3
/p N Strain per cycle
Uni-directional shear stress
metal filmcyclic membrane stress
substrateCycle
Temperature
125 °C
-55 °C
Cyclic loading
1 cycle
Y
strain
stress
E
p
R
d
dN
1
212(1 ) (1 )
m mR
m m
E E Twhere
v v Y
Linearapproximation
pd d
dN dt
Ratcheting-Creep analogy
Time-saving
Huang, Suo, Ma, Acta Materialia, 49, 3039-3049 (2001)
p
![Page 8: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/8.jpg)
Semi-infinite Stationary Crack in Blanket Film
• Comparison of time cost:• Creep: 1hr 20min• Ratchet: 22 hr
1/ 40~K N
Creep
Ratchet
N
0
IK
Rl hHEN Length scale
• Both creep and ratcheting calculation show the same trend.
K
l(N)
Kl(N)
![Page 9: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/9.jpg)
Finite Stationary Crack in Blanket Film
0
IK
a
Normalized cycles 2/NEHh a
Creep
Ratchet
0K a
Final stage l>>aGriffith crack limit
Early stage l<<aInfinite crack limit
1/ 4
01.05 /K NEHh
2a
Earlystage
l
2a
Finalstage
l>>a
2a
0
,K l
faa
Evolvingl ~ a
![Page 10: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/10.jpg)
Crack Propagation in a Blanket Film
a
0
IK
a
/ c
V
N
Normalized cycles / cN N
Preparation
Initiation
TransientPropagation Steady-state
Length scale2
0
ssK
HhEN c
2Cycle scale
Kss
![Page 11: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/11.jpg)
Simulation of Cracks Propagation in Interconnects
Initial state After 100 cycles
Time
Temperature
150 °C
125 °C
-55 °C
Packaging temperature
Loadingrange
Cyclic loading
Tensile stress
Compressive region
![Page 12: Zhen Zhang, Zhigang Suo Division of Engineering and Applied Sciences Harvard University Jean H. Prévost Department Civil and Environmental Engineering.](https://reader035.fdocuments.in/reader035/viewer/2022070403/56649f2f5503460f94c499f2/html5/thumbnails/12.jpg)
SummaryRatcheting
deformation
in metal layer
High stress
in SiN
passivation film
X-FEM + Linear creep analogy
Simulation of cracking in interconnects becomes feasible
High
temperature
packaging
Thermalcyclic
loading
Cracking in interconnects