81
Process-Induced Stress Engineering in CMOS Technology
Moreover, as the TSV radius increases, the stress effect becomes stronger and
finally saturates. On the other hand, when the device is located outside the
keep-out zone, the device performance is very stable and hardly affected by
the stress. Figure  3.19(b) shows the mobility variation factor changes with
TSV radius. As the radius increases, the bottom stress grows up toward saturation. This phenomenon is similar to that the stress is saturated in e-SiGe
0.4
10
–7
10
–6
r TSV (m)
10
–5
0.8
1.2
V
th
1.6
2.0
2.4
2.8
N a = 1E15 cm
–3
T ox = 50, 75, 100, 125, 125 nm
FIGURE 3.18
Threshold voltage varies with the radius of copper for different oxide thickness. (After Wang,
C.-C., Predictive Modelling for Extremely Scaled CMOS and Post Silicon Devices, PhD thesis,
Arizona State University, 2011.)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
Mobility Enhancement Factor
0
100
100 Mpa
200
Distance from TSV (nm)
(a)
300
400
500
L = 40
1.17
1.16
1.15
1.14
1.13
Mobility Enhancement Factor
100
0
200
400
300
r TSV
(b)
500 600 700 800 900
100 nm
r TSV
250 nm
500 nm
750 nm
1000 nm
FIGURE 3.19
Characteristics for a device placed (a) inside the keep-out zone and (b) outside the keep-out
zone. (After Wang, C.-C., Predictive Modelling for Extremely Scaled CMOS and Post Silicon
Devices, PhD thesis, Arizona State University, 2011.)