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

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.

Experimental Investigation of Thermal Annealing and Ferroelectric Capacitor Area Effects for Hafnium-Zirconium Oxide Devices

“…However, the HZO capacitor with a large area of 40,000 µm 2 also suffers from the leakage issue due to the existence of more defect traps. Therefore, the large polarization current also contains the contribution of a leakage-oriented component [14], which can significantly affect the ferroelectric domain switching, especially under the operation environment of high electric field or high temperature.…”

“…In recent years, the novel ferroelectric memories using HfZrO x (HZO) with zirconium doping have been reported and investigated, frequently owing to the outstanding hysteresis polarization effect and extensive process rangeability of doping concentration [7]. Although the HZO ferroelectric memory has the advantages of good device scalability and a fast switching speed of sub-100ns, the poor thermal stability of Zr doping, the leakage current issue and the small ferroelectric hysteresis window are the major concerns with the thickness scaling [8][9][10][11][12][13][14][15]. As for another ferroelectric material of HfAlO x with a light Al doping concentration (<10%), the leakage current can be improved due to the large bandgap of AlO x .…”

Antiferroelectricity in ZrO&lt;sub&gt;2&lt;/sub&gt; and Ferroelectricity in Zr, Al, La Doped HfO&lt;sub&gt;2&lt;/sub&gt; Nanoparticles

“…Furthermore, ferroelectricity was found in HfO 2 thin films doped with Zr (HZO) [1] [4] [8] [9] [10] [11] [12] as well as with Si, Y, Al, Gd, La [13]- [20]. It must be noted that pure HfO 2 and ZrO 2 are not ferroelectric.…”

Impact of Series-Connected Ferroelectric Capacitor in HfO₂-Based Ferroelectric Field-Effect Transistors for Memory Application

“…The negative capacitance effect can break the physical limitation of Boltzmann tyranny leading to a sub-60mV/decade subthreshold swing (SS) under an ultralow supply voltage, which is critical for the application in Internet of Things (IoT) [7]- [9]. Hafnium-oxide (HfO2)-based thin film with stable ferroelectric properties at the nanoscale has good scalability and compatibility with the standard complementary metal-oxide-semiconductor (CMOS) integration technology [4], [5], [10]. Adding a ferroelectric layer into the gate stack of the metal-oxide-semiconductor field-effect transistors (MOSFETs) causes a unique operation behavior of the FeFETs, that is, there is a hysteresis loop in the transfer curve due to the polarization in ferroelectric material [11].…”

“…Adding a ferroelectric layer into the gate stack of the metal-oxide-semiconductor field-effect transistors (MOSFETs) causes a unique operation behavior of the FeFETs, that is, there is a hysteresis loop in the transfer curve due to the polarization in ferroelectric material [11]. Since the memory window of conventional ferroelectric transistors with metal-ferroelectric-insulator-semiconductor (MFIS) structure can easily be affected by the undesirable interface quality, such as interface defeats, leakage current and depolarization [12], the ferroelectric domain in material cannot do a stable switching, which results in the unexpected memory window during the operation of the FeFETs [5], [13]. In this work, we demonstrated a HfO2-based FeFET by connecting an external aluminum-doped hafnium-oxide (HfAlO) ferroelectric capacitor in series, which could effectively reduce the influence of undesirable interface quality to achieve better domain switching and transistor operation.…”