245
Reliability and Degradation of Strain-Engineered MOSFETs
breakdown showed a significantly degraded Weibull shape factor, β, and
voltage acceleration factor, γ, for the multifin devices without corner rounding. When adequate corner rounding is applied, however, multigate devices
show breakdown behaviour similar to that of planar devices. In order to
decouple the effects of the Si crystal orientation from the effects of nitridation, 45° rotated structures resulting in (100) Si at both top and sidewalls
were studied (Figure 8.13).
Figure 8.14 shows BTI comparisons between reference (nonnitrided)
devices and devices with ammonia nitridation for 45° rotated notch wafers,
1
2
4
6 8
E OX [MV/cm]
2
4
6 8
E OX [MV/cm]
2
4
6 8 10
E OX [MV/cm]
10
9
10
6
10
3
10
0
Lifetime [s]
Poly-Si/SiON
TiN/HfO 2
FUSI/HfSiON
Reference
Ref. L G = 100 nm
CESL L G = 100 nm
SiGe HDD last
SiGe HDD first
SiGe HDD last + CESL
Ref. L G = 70 nm
SiGe L G = 1 μm
SiGe L G = 70 nm
FIGURE 8.12
Lifetime extrapolations for devices with process-induced strain and reference devices for
a degradation criterion of 30 mV V th shift, assuming a power law dependence on the oxide
electric field. T = 125°C. (After Shickova, A., Bias Temperature Instability Effects in Devices
with Fully-Silicided Gate Stacks, Strained-Si, and Multiple-Gate Architectures, PhD thesis,
Katholieke Universiteit Leuven, 2008.)
(100)
(110)
(100)
(100)
D
G
D
< 1 0 0 >
< 1 0 0 >
< 1 1 0 >
< 1 1 0 >
G
S
S
Standard wafer orientation
Rotated notch 45°
FIGURE 8.13
Top and sidewall Si crystal orientations (and current directions) in the cases of standard wafer
orientation and 45° rotated notch. (After Shickova, A., Bias Temperature Instability Effects in
Devices with Fully-Silicided Gate Stacks, Strained-Si, and Multiple-Gate Architectures, PhD
thesis, Katholieke Universiteit Leuven, 2008.)
Reliability and Degradation of Strain-Engineered MOSFETs
breakdown showed a significantly degraded Weibull shape factor, β, and
voltage acceleration factor, γ, for the multifin devices without corner rounding. When adequate corner rounding is applied, however, multigate devices
show breakdown behaviour similar to that of planar devices. In order to
decouple the effects of the Si crystal orientation from the effects of nitridation, 45° rotated structures resulting in (100) Si at both top and sidewalls
were studied (Figure 8.13).
Figure 8.14 shows BTI comparisons between reference (nonnitrided)
devices and devices with ammonia nitridation for 45° rotated notch wafers,
1
2
4
6 8
E OX [MV/cm]
2
4
6 8
E OX [MV/cm]
2
4
6 8 10
E OX [MV/cm]
10
9
10
6
10
3
10
0
Lifetime [s]
Poly-Si/SiON
TiN/HfO 2
FUSI/HfSiON
Reference
Ref. L G = 100 nm
CESL L G = 100 nm
SiGe HDD last
SiGe HDD first
SiGe HDD last + CESL
Ref. L G = 70 nm
SiGe L G = 1 μm
SiGe L G = 70 nm
FIGURE 8.12
Lifetime extrapolations for devices with process-induced strain and reference devices for
a degradation criterion of 30 mV V th shift, assuming a power law dependence on the oxide
electric field. T = 125°C. (After Shickova, A., Bias Temperature Instability Effects in Devices
with Fully-Silicided Gate Stacks, Strained-Si, and Multiple-Gate Architectures, PhD thesis,
Katholieke Universiteit Leuven, 2008.)
(100)
(110)
(100)
(100)
D
G
D
< 1 0 0 >
< 1 0 0 >
< 1 1 0 >
< 1 1 0 >
G
S
S
Standard wafer orientation
Rotated notch 45°
FIGURE 8.13
Top and sidewall Si crystal orientations (and current directions) in the cases of standard wafer
orientation and 45° rotated notch. (After Shickova, A., Bias Temperature Instability Effects in
Devices with Fully-Silicided Gate Stacks, Strained-Si, and Multiple-Gate Architectures, PhD
thesis, Katholieke Universiteit Leuven, 2008.)