Search

In this work, we investigate the ferroelectricity of stacked zirconium oxide and hafnium oxide (stacked HfZrO) with different thickness ratios under metal gate stress and simultaneously evaluate the electrical reliability of stacked ferroelectric films. Based on experimental results, we find that the stacked HfZrO films not only exhibited excellent ferroelectricity but also demonstrated a high performance on reliability. The optimized condition of the 45% Zr proportion exhibited a robust ferroelectric polarization value of 32.57 μC/cm2, and a polarization current with a peak value of 159.98 μA. Besides this, the ferroelectric stacked HfZrO also demonstrated good reliability with a ten-year lifetime under >−2 V constant voltage stress. Therefore, the appropriate modulation of zirconium proportion in stacked HfZrO showed great promise for integrating in high-performance ferroelectric memory. [ABSTRACT FROM AUTHOR]

Herein, the electrical characteristics of a p‐type negative‐capacitance field‐effect transistor are investigated using an ultrathin 2.5 nm‐thick HfAlOx. The optimized performance exhibits a steep subthreshold slope of 35 mV dec−1, a negligible hysteresis of 4 mV, and a low off‐state current of 3 × 10−13 A μm−1. Appropriate aluminum doping into HfAlOx film can not only improve the leakage current but also stabilize the negative‐capacitance matching. The prominent improvement on the capacitance matching and ferroelectricity can be ascribed to the reduced defect traps and less dielectric crystalline phase during annealing, which is important for the practical application of energy‐efficient logic devices. [ABSTRACT FROM AUTHOR]

Herein, the gamma‐ray irradiation effect on ferroelectric HfAlOx capacitors for biomedical and space applications is investigated. The experimental results focus on the observation of ferroelectric polarization characteristics in support of different defect mechanisms induced by annealing, endurance cycling, and gamma‐ray irradiation. It is found that the HfAlOx with low Al doping of 6.5% become more vulnerable to radiation exposure, but a remarkable improvement in 9%‐Al‐doped HfAlOx due to less oxygen vacancies is demonstrated. In addition, the results also confirm that the fatigue property of ferroelectric HfAlOx capacitor is determined by the electric‐stress‐induced defect during endurance cycling, not mainly contributed by irradiation damage, which shows the potential for memory applications in rigorous irradiation environment. [ABSTRACT FROM AUTHOR]

• Nanoscale ferroelectric domain switching of undoped HfO 2 were investigated. • Well-controlled thermal stress can enhance polarization strength of undoped HfO 2. • Ferroelectric negative capacitance effect can be improved by thickness scaling. • Undoped HfO 2 NCFET with tight hysteresis distribution can be achieved. In this work, we investigated the polarization characteristics of nanoscale undoped hafnium oxide (HfO 2) ferroelectric film. The nanoscale domain switching behavior of undoped HfO 2 is mainly dominated by mixed ferroelectric/nonferroelectric crystalline phases and interface domain pinning by oxygen vacancies or defect traps. Our experimental results confirm that these issues can be improved by film thickness scaling and well-controlled mechanical stress. We demonstrated a 4-nm-thick undoped HfO 2 negative capacitance thin film transistor (NCFET) with an energy-efficient switch characteristic of a low overdrive voltage of -0.6 V, a steep subthreshold swing of sub-60 mV/dec and a uniform hysteresis distribution of sub-60 mV. [ABSTRACT FROM AUTHOR]

• Ferroelectric characteristics of mixed and stacked HfZrO devices were investigated. • Stacked HfZrO device showed a much stronger ferroelectricity than mixed one. • A surface nitrogen plasma treatment can alleviate ferroelectric domain pinning. • Nitrogen incorporation into stacked HfZrO further improved the endurance cycling. In this work, we investigate ferroelectric characteristics of hafnium zirconium oxide (HfZrO) metal-ferroelectric-metal (MFM) devices with mixed and stacked film structure. The experimental results reveal that the stacked HfZrO MFM device has a lower dynamic leakage and stronger ferroelectric polarization value of approximately 27.3 μC/cm2, which is much higher than 17.5 μC/cm2 measured from mixed HfZrO MFM device. From endurance cycling test, we also confirm that the stacked HfZrO MFM capacitor with a remote nitrogen plasma treatment featuring a large initial hysteresis window can achieve a stable operation up to 108 cycles at an operating voltage of 2.5 V, which is even longer than that of mixed HfZrO MFM capacitor by one order of magnitude. Therefore, the stacked MFM structure with proper interface engineering provides a promising approach for the process integration of ferroelectric memory under the comprehensive consideration of device performance and endurance. [ABSTRACT FROM AUTHOR]

• Dopant-free HfO2 transistors with negative capacitance were demonstrated. • Ferroelectric HfO2 transistors successfully exhibited a SSof sub-60 mV/decade. • Transistor performancecan achieve ION/IOFF ratio of >107 and IOFF of ∼10–13A/μm. In this study, we demonstrated the hafnium-oxide negative capacitance transistors using different nitrogen plasma treatments. According to our experimental results, the electrical performance and negative capacitance switch characteristics were also affected by process temperature and ferroelectric/non-ferroelectric crystalline phases in addition to nitrogen species. The transistor device using optimal nitrogen plasma treatment exhibited the excellent performances, including a low off-state current (I OFF) of ∼10−13 A/μm, a large on/off-state current ratio (I ON /I OFF) of 107 and a steep subthreshold swing (SS) of sub-60 mV/decade with tight switching uniformity under a gate overdrive voltage of 2 V. These experimental results confirm that the negative capacitance transistor adopting hafnium oxide can be further improved by nitrogen species incorporation, which give a promising guidance for the next-generation low-power electronics. [ABSTRACT FROM AUTHOR]

• The effect of AlOxcapping layer on HfO2MFM devices wereinvestigated. • Ferroelectric polarization can be significantly improved by AlOxcapping. • Nitrogen plasma treatment on AlOxcan alleviate stress-induced defect traps. • AlOxlayer with nitrogen incorporation further improve electrical stress resistance. In this work, we investigate the effect of a capping layer of aluminum oxide (AlO x) on dopant-free hafnium-oxide (HfO 2) ferroelectric layer. According to our experimental results, the AlO x -capped HfO 2 ferroelectric capacitor exhibits the significant improvement on ferroelectric polarization strength and also presents a comparable electrical stress resistance in comparison with control HfO 2 ferroelectric capacitor with a very weak ferroelectric hysteresis. An additional nitrogen treatment on AlO x capping layer effectively alleviate the stress-induced generation of defect traps near the interface of tantalum nitride (TaN) electrode under negative-bias voltage stress. Therefore, the performance improvement can be ascribed to the introduction of AlO x capping layer and well-controlled nitrogen plasma treatment to improve interface traps and stabilize the ferroelectric phase transformation during high-temperature annealing process. [ABSTRACT FROM AUTHOR]