Browsing by Author "Chang, Tun-Jen"

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Achieving High-Scalability Negative Capacitance FETs with Uniform Sub-35 mV/dec Switch Using Dopant-Free Hafnium Oxide and Gate Strain
(2018-01-01)
Fan, Chia-Chi
;
Cheng, Chun-Hu
;
Tu, Chun-Yuan
;
Liu, Chien
;
Chen, Wan-Hsin
For the first time, we successfully demonstrated that the 4-nm-thick dopant-free HfO2 NCFETs using gate strain can implement an energy-efficient switch of a low gate overdrive voltage and a nearly hysteresis-free sub-40 mV/dec swing. The gate strain favorably rearranges oxygen vacancies and boosts orthorhombic phase transition. Furthermore, the dopant-free HfO2 NCFET can be further improved by in-situ nitridation process. The 4-nm-thick nitrided HfO2 NCFETs achieve a steep symmetric sub-35 mV/dec switch, a sustained sub-40 mV/dec SS distribution, and excellent stress immunity during NC switch. The high-scalability and dopant-free NCFET shows the great potential for the application of future highly-scaled 3D CMOS technology.
Investigation on polarization characteristics of ferroelectric memories with thermally stable hafnium aluminum oxides
(2019-08-01)
Chang, Tun-Jen
;
Liu, Chien
;
Fan, Chia-Chi
;
Hsu, Hsiao-Hsuan
;
Chen, Hsuan-Han
In this work, we successfully demonstrated the 9.6-nm-thick HfAlOx ferroelectric memory using light aluminium doping of 6.5% to form ferroelectric orthorhombic phase. Compared to ferroelectric HfZrOx film with zirconium diffusion issue, the HfAlOx film showed excellent thermal stability under high temperature annealing. Besides, the ferroelectric HfAlOx also exhibited robust polarization characteristics under endurance cycling test. A > 10(6) stressed cycles with 4 MV/cm can be measured and a long endurance was sustained over 5 x 10(7) cycles under 3.6 MV/cm. Therefore, the HfAlOx film showed the great promise for integrating in high performance ferroelectric memory with thermal budget concerns.
Program/Erase Speed and Data Retention Trade-Off in Negative Capacitance Versatile Memory
(2017-01-01)
Fan, Chia-Chi
;
Chiu, Yu-Chien
;
Liu, Chien
;
Liou, Guan-Lin
;
Lai, Wen-Wei
In this work, we investigated the performance tradeoff between program/erase speed and data retention of ferroelectric HfZrO memory. The monoclinic HfNO layer with a trapping mechanism was employed to improve the data retention. Under the thickness optimization of HfNO, the HfZrO/HfNO gate stack can be functionalized with volatile and non-volatile operation.