Investigation of Low-Frequency Noise in
High-k First/Metal Gate Last HfO 2 and ZrO 2 nMOSFETs
San Lein Wu
1, Bo Chin Wang
2, Yu Ying Lu
1, Shih Chang Tsai
2, Jone Fang Chen
2, Shoou Jinn Chang
2, 3, Sheng Po Chang
2, 3, Che Hua Hsu
4, Chih Wei Yang
4, Cheng Guo Chen
4, Osbert Cheng
4, and Po Chin Huang
2, 3*1
Department of Electronic Engineering, Cheng Shiu University, No.840, Chengcing Rd., Niaosong Dist., Kaohsiung City 833, TAIWAN
2
Institute of Microelectronics and Department of Electrical Engineering, National Cheng Kung University, Tainan City 70101, TAIWAN
3
Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan City 70101, TAIWAN
4
Central R&D Division, United Microelectronics Corp. (UMC), Tainan City 74147, TAIWAN
Phone: +886-6-2757575 ext.62400-1223 Fax: +886-6-2761854
*E-mail: pchuang@mail.ncku.edu.tw
The oxide trap density (Nt) is extracted from the measured 1/f noise results using the following formula.
where λ is the tunneling attenuation length for carriers penetrating in to the insulator and corrected by the XT extracted in RTS using XT = λ∙ln(1/2πfτ0).
The increase of interface trap (Nit) in HfO2 device is rapider than that of ZrO2 counterpart as the pulse period raised, suggesting the higher defects in internal HfO2 gate stack.
Acknowledgement The authors would like to thank the Advanced Optoelectronic Technology Center of NCKU for the financial support under Contract HUA103-3-15-178, the National Science Council of Taiwan for the financial support under Contract numbers NSC102-2221-E-230-015 and NSC102-2221-E-006-259, and UMC staffs for their helpful supports.
1/f Noise Characteristic
Random telegraph signal (RTS) noise
Device Fabrication & DC Characteristic
S
ID/I
D2vs frequency at various V
G- V
T Frequency exponential factor (γ)
Mechanism of 1/f noise
Process flow & Device structure
I
D-V
Dcharacteristics ＆ Electrical parameters
Hooge’s parameter ( α
H)
Gate stacks quality
Gate Stack
EOT
(nm) VFB (V) JG (A/cm2)
Hysteresis (mV)
eWF (V)
HfO
21.250 -0.666 0.253 11.478 4.436
ZrO
21.250 -0.793 7.793 -0.636 4.320
−
=
∂
∂
| I
| 1 g
X V
ln
D m T
G q
kT t
kT q
ox
τe
r D, f
D,
g r
D, r
f T
T V V
L ) V
/ (
) /
ln ( Y X
+
×
+
= c e
e c
tox
q kT
τ τ
τ τ
The vertical (XT) and lateral locations (YT) of trap can be extracted from RTS results using
following formulas. t
2
0 2
D
ID 1 N
I
S
+
= fWL N N
kT
µC
µ λ
The SID/ID2 of ZrO2 device is lower than those of HfO2 device, implying the smaller oxide trap density (Nt) in ZrO2 device.
The γ values (f -γ) of ZrO2 device are smaller than those of HfO2 device at all VG – VT, suggesting that trap density ratio of interior trap to interface trap is smaller in ZrO2 gate stack than that of HfO2 one
The obvious “hump” shaped SID/ID2 of HfO2 is explained by the serious electron trapping and detrapping behaviors.
The dominant 1/f noise mechanisms are carrier number fluctuation and correlated number mobility fluctuation (unified model) for HfO2 and ZrO2 devices, respectively.
The αH is calculated by below.
2 D
ID T
G OX
I
S
| V V
| WLC
q f
H
= − α
