Impact of Zirconium Doping on Steep Subthreshold Switching of Negative Capacitance Hafnium Oxide Based Transistors

In this work, it is demonstrated that the negative capacitance effect of ferroelectric Hf _1−x Zr _x O ₂ 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 >10 ⁷ can be simultaneously achieved in optimized negative capacitance Hf _1−x Zr _x O ₂ transistor. Besides, the Zr diffusion issue and non-ferroelectric phases significantly affect the multi-domain switching of polycrystalline Hf _1−x Zr _x O ₂ . Therefore, an appropriate amount of Zr substitution is more favorable for both boosting ferroelectric and implementing the negative capacitance switch.