Browsing by Author "Li, Ming-Fu"

Now showing 1 - 4 of 4

Investigation of Traps at MoS2/Al2O3 Interface in nMOSFETs by Low-Frequency Noise
(2016-04)
Yuan, Hui-Wen
;
Shen, Hui
;
Li, Jun-Jie
;
Shao, Jinhai
;
Huang, Daming
A new method is proposed to distinguish the contributions of the low-frequency noise (LFN) from the channel and the source/drain Schottky contacts in MOS devices. The method is applied to back-gated nMOSFETs with MoS2 channel and Al2O3 gate dielectric. To avoid a possible noise signal contamination from the top MoS2 surface by oxygen or water molecules absorption, the nMOSFETs with multilayer MoS2 are fabricated, and the measurements are carried out in the vacuum. The trap density Not at the MoS2/Al2O3 interface is derived for the first time using the proposed method. It is found that the Not responsible to LFN depends strongly on the surface potential, ranging from 4 x 10(10) cm(-2) in the weak over-drive region to 5 x 10(11) cm(-2) in the strong over-drive region.
PBTI Investigation of MoS2 n-MOSFET With Al2O3 Gate Dielectric
(2017-05-01)
Yuan, Hui-Wen
;
Shen, Hui
;
Li, Jun-Jie
;
Shao, Jinhai
;
Huang, Daming
For the first time, we report the positive bias temperature instability of the back gated multilayer MoS2 n-MOSFETs with Al2O3 gate dielectric. In the stress phase, the Id-Vg curve shifts to the positive gate bias. In the recovery phase, it shifts back to the negative gate bias. After 5000 s recovery, it completely recovers to that of the fresh device. The results indicate that the voltage shift is solely due to trapping and detrapping of the pre-existing border traps in the Al2O3 dielectric. The traps consist of fast and slow components with the capture time constants of 7 and 1.8 x 10(2) s and the emission time constants of 15 and 1.0 x 10(3) s, respectively. The results from first-order trapping and detrapping calculations are in overall agreements with 12 measured Delta Vg curves including six under stress voltages and six in the recovery phases. The energy densities for the fast and slow traps are derived to be in the order of 10(13) cm(- 2) eV(-1) above the bottom of the MoS2 conduction band.
Trapping and Detrapping of Oxide Border Traps in Al2O3 Gate Dielectric in MOS2 n-MOSFETs under PBTI Stress
(2016-01-01)
Yuan, Hui-Wen
;
Shen, Hui
;
Li, Jun-Jie
;
Shao, Jinhai
;
Huang, Daming
In this paper, we report the positive bias temperature instability (PBTI) effects of the back-gated MoS2 n-MOSFET with A1203 gate dielectric. Multilayer MoS2 was used and all measurements are carried in vacuum to avoid the electric signal contamination by the top MoS2 surface water or oxygen molecules absorption. In the stress phase, the Id-Vg curve shifts to the positive gate bias direction. In the recovery phase, the Id-Vg shifts back completely to the fresh device curve. This indicates that voltage shift is purely due to trapping or detrapping of the oxide border traps at the MoS2/A1203 interface and no new traps are generated during the stress time. When applying different stress voltage and measuring the Id-Vg shift, we can calculate the oxide border trap energy density 17(E), which has a peak value of 6x 1013cm-2eV-1 at 0.035eV above Ec of MoS2 conduction band.
Work function tunability of refractory metal nitrides by lanthanum or aluminum doping for advanced CMOS devices
(2007-11-01)
Wang, Xin Peng
;
Lim, Andy Eu-Jin
;
Yu, Hong Yu
;
Li, Ming-Fu
;
Ren, Chi
A lanthanum (La)-doped HfN is investigated as an n-type metal gate electrode on SiO(2) with tunable work function. The variation of La concentration in (Hf(x)La(1-x))N(y) modulates the gate work function from 4.6 to 3.9 eV and remains stable after high-temperature annealing (900 degrees C to 1000 degrees C, which makes it suitable for n-channel MOSFET application. An ultrathin high-k dielectric layer was formed at the metal/SiO(2) interface due to the (Hf(x)La(1-x))N(y) and SiO(2) interaction during annealing. This causes a slight reduction in the effective oxide thickness and improves the tunneling current of the gate dielectric by two to three orders. We also report the tunability of TaN with Al doping, which is suitable for a p-type metal gate work function. Based on our results, several dual-gate integration processes by incorporating lanthanum or aluminum into a refractory metal nitride for CMOS technology are proposed.