No abstract

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 40 mV/decade, a low off‐state leakage current of 190 fA μm−1, and a large on/off current ratio of >107 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.

In this work, we report a novel multi-PNPN-channel junctionless transistor with short channel length of 60nm. The multi-PNPN junctionless transistor exhibits the larger drive current of >1μA/μm, the steeper turn-on switching of 77 mV/decade, and the higher on/off current ratio of >10 7 than the hybrid PN channel device under the same gate overdrive. The improved performance is mainly attributed to the enhanced depletion effect of multi-PNPN channel to optimize the electric field modification of surface p-channel. The stronger immunity to constant-voltage stress is also obtained for multi-PNPN channel due to the lower lateral electric field near drain side to reduce the impact ionization ratio.

A ferroelectric negative‐capacitance (NC) transistor using aluminum‐doped hafnium oxide (HfAlOx) with fluorine passivation is successfully demonstrated. The fluorine‐passivated device shows a nearly hysteresis‐free forward/reverse swing of sub‐30 mV dec−1 for symmetric switch, a wide sub‐60 mV (dec·swing)−1 range over 4 decades of drain current, an ultralow off‐leakage current of 4 fA μm−1, and a high on/off current ratio of >108. The fluorine defect passivation (FP) reduces oxygen vacancies of ferroelectric HfAlOx to mitigate interface depolarization field and thereby reinforce surface potential amplification effect during NC operation.

We investigated a short-channel ferroelectric FinFET using a ferroelectric HfZrO thin film as gate dielectrics, and scaled down the channel length to 60 nm to study the short-channel effect and the ferroelectricity. The HfZrO FinFETs exhibited improved short-channel performance including subthreshold swing improvement and reduced drain-induced barrier lowering effect. By using pulsed I-V measurement method, we confirmed that the thickness tradeoff between HfZrO ferroelectric layer and buffered layer are critical to alleviate the influence of interface traps and simultaneously obtain the ferroelectricity in HfZrO FinFET devices with the consideration of sidewall traps. Interface traps may cause unwanted off-state leakage current and mismatching negative capacitance.Here, we demonstrated that the ferroelectric behavior can be achieved by simultaneously increasing HfZrO thickness to obtain the optimized polarization and adopt appropriate buffered layer to screen the traps effect under ferroelectric domain switching.