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Ferroelectric Characterization of Hafnium-Oxide-Based Ferroelectric Memories with Remote Nitrogen Plasma Treatments
(2019-01-01)
Lee, You-Ting
;
Chen, Hsuan-Han
;
Tung, Yi-Chun
;
Shih, Bing-Yang
;
Hsiung, Szu-Yen
In this paper, we experimentally demonstrated the advantage of remote nitrogen plasma on improving interface quality of HfO2-based ferroelectric devices. The remote nitrogen plasma not only reduces leakage current of gate stack to appropriately sustain the ferroelectricity during ferroelectric domain switching, but also effectively improve the ferroelectric fatigue to enhance endurance cycling performance.
Investigation of Phase Transformation in HfO2 Ferroelectric Capacitor by Means of a ZrO2 Capping Layer
(2019-01-01)
Liu, Kuan-Wei
;
Chen, Hsuan-Han
;
Huang, Zhong-Ying
;
Wang, Wei-Chun
;
Fan, Yu-Chi
In this paper, the ferroelectric polarization effect of ZrO2 capping layer on HfO2 NUM capacitor was investigated. Based on crystallinity analysis, the phase transformation from monoclinic to orthorhombic phase in HfO2 film can be induced by a thin ZrO2 capping layer. The thickness of ZrO2 capping layer plays an important role in the ferroelectric polarization of HfO2 MFM capacitor. Compared to mixed HfZrO film, the stacked ZrO2/HfO2 film shows the advantage for suppressing the leakage issue during high-temperature ferroelectric phase transition.
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.
Interface Engineering of Ferroelectric Negative Capacitance FET for Hysteresis-Free Switch and Reliability Improvement
(2018-01-01)
Fan, Chia-Chi
;
Tu, Chun-Yuan
;
Lin, Ming-Huei
;
Chang, Chun-Yen
;
Cheng, Chun-Hu
In this work, we successfully achieve a hysteresis-free negative capacitance field effect transistors (NCFETs) by exploiting a defect passivation scheme. This research work simultaneously provides a new insight into the gate-oxide stress reliability of NCFET. The fluorine-passivated HfAlOx NCFET shows the excellent transistor characteristics including a steep subthreshold swing of sub-30-mV/dec, a negligible hysteresis-free switch of similar to 10mV and a large on/off current reatio (I-on/I-off) of >10(7). Most importantly, fluorine passivation for NC HfAlOx effectively suppress the generation of shallow traps during electrical stress test. Besides, it is favorable to maintain NC operation and SILC immunity by in-situ fluorine passivation, which has been verified by transient pulse I-V measurement.
Impact of Zirconium Doping on Steep Subthreshold Switching of Negative Capacitance Hafnium Oxide Based Transistors
(2019-05-01)
Cheng, Chun-Hu
;
Lin, Ming-Huei
;
Chen, Hsin-Yu
;
Fan, Chia-Chi
;
Liu, Chien
In this work, it is demonstrated that the negative capacitance effect of ferroelectric Hf1-xZrxO2 transistor is highly correlated with Zr doping concentration. A steep subthreshold swing of 40mV/decade, a low off-state leakage current of 190fAm(-1), and a large on/off current ratio of >10(7) can be simultaneously achieved in optimized negative capacitance Hf1-xZrxO2 transistor. Besides, the Zr diffusion issue and non-ferroelectric phases significantly affect the multi-domain switching of polycrystalline Hf1-xZrxO2. Therefore, an appropriate amount of Zr substitution is more favorable for both boosting ferroelectric and implementing the negative capacitance switch.
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 of Efficiency Droop for UV-LED with N-type AlGaN Layer
(2012-01-01)
Tu, Po-Min
;
Chang, Jet-Rung
;
Huang, Shih-Cheng
;
Yang, Shun-Kuei
;
Lin, Ya-wen
The efficiency droop in InGaN-based 380nm UV light emitting device (LED) with n-GaN and n-AlGaN underlayer grown on sapphire substrate by metal-organic chemical vapor deposition (MOCVD) was investigated. From simulation result of high resolution x-ray diffraction (HRXRD) omega-2 theta. curve by using dynamical diffraction theory, the Al composition in the n-AlGaN layer was determined to be about 3%. The experimental results of temperature dependent photoluminescence (PL) demonstrated that the internal quantum efficiency (IQE) of n-GaN and n-AlGaN UV-LEDs are 43% and 39%, respectively, which are corresponding to an injected carrier density of 8.5 x 10(17) #/cm(3). It could be explained that the crystal quality of n-GaN is better than of n-AlGaN. In addition, the observation of pit density from atomic force microscopy (AFM) surface morphology is consistent with the interpretation. It was well-known that the pits appearing on the surface in the virtue of the threading dislocations. Thus, it means that defects induce the non-radiative centers and deteriorate the IQE of the UV-LED with n-AlGaN underlayer. Therefore, the light output power of n-GaN UV-LED is slightly higher below the forward current of 250 mA. Nevertheless, the output power was enhanced about 22% as the injection current was increased to 600 mA. Furthermore, the external quantum efficiency (EQE) of n-AlGaN UV-LED was nearly retained at the 600 mA (only 20% droop), whereas the UV-LED with n-GaN exhibits as high as 33%. We attributed this improvement to the less self-absoption by replacing n-GaN underlayer with n-AlGaN.
Nearly Dislocation-free Ge/Si Heterostructures by Using Nanoscale Epitaxial Growth Method
(2012-01-01)
Luo, Guang-Li
;
Ko, Chih-Hsin
;
Wann, Clement H.
;
Chung, Cheng-Ting
;
Han, Zong-You
The selective growth of germanium into nanoscale trenches on silicon substrates was investigated. These nanoscale trenches-the smallest size of which was 50 nm-were fabricated using the state-of-the-art shallow trench isolation technique. The quality of the Ge films was evaluated using transmission electron microscopy. It was found that the formation of threading dislocations (TDs) was effectively suppressed when using this deposition technique. It was considered that for the Ge grown in nanoscale Si areas (e. g., several tens of nanometers), the TDs were readily removed during cyclic thermal annealing, predominantly because their gliding distance to the SiO2 sidewalls was very short. Therefore, nanoscale epitaxial growth technology can be used to deposit Ge films on lattice-mismatched Si substrates with a reduced defect density. (C) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of Garry Lee
Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions
(2016-01-22)
Cheng, Chih-Hsien
;
Tzou, An-Jye
;
Chang, Jung-Hung
;
Chi, Yu-Chieh
;
Lin, Yung-Hsiang
The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC1-x) buffer is demonstrated. The a-SixC1-x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC1-x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC1-x buffer. The C-rich SixC1-x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC1-x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Sirich SixC1-x buffer, the device deposited on C-rich SixC1-x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively.
AlN Surface Passivation of GaN-Based High Electron Mobility Transistors by Plasma-Enhanced Atomic Layer Deposition
(2017-04-27)
Tzou, An-Jye
;
Chu, Kuo-Hsiung
;
Lin, I-Feng
;
Ostreng, Erik
;
Fang, Yung-Sheng
We report a low current collapse GaN-based high electron mobility transistor (HEMT) with an excellent thermal stability at 150 degrees C. The AlN was grown by N-2-based plasma enhanced atomic layer deposition (PEALD) and shown a refractive index of 1.94 at 633 nm of wavelength. Prior to deposit AlN on III-nitrides, the H-2/NH3 plasma pretreatment led to remove the native gallium oxide. The X-ray photoelectron spectroscopy (XPS) spectroscopy confirmed that the native oxide can be effectively decomposed by hydrogen plasma. Following the in situ ALD-AlN passivation, the surface traps can be eliminated and corresponding to a 22.1% of current collapse with quiescent drain bias (V-DSQ) at 40 V. Furthermore, the high temperature measurement exhibited a shift-free threshold voltage (V-th), corresponding to a 40.2% of current collapse at 150 degrees C. The thermal stable HEMT enabled a breakdown voltage (BV) to 687 V at high temperature, promising a good thermal reliability under high power operation.

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