Experimental Observation of Negative Capacitance Switching Behavior in One‐Transistor Ferroelectric Versatile Memory

Abstract

In this work, we investigated the negative capacitance behavior of novel ferroelectric versatile memory with low-voltage-driven and fast ferroelectric switching. The combined storage mechanism strengthened the stability of ferroelectric polarization by interface aligned dipoles. The simulation results of first principle calculation indicated that the monoclinic-like orthorhombic phase of ferroelectric hafnium oxide facilitated the occurrence of S-shaped negative capacitance behavior. Furthermore, the control of phase transition may affect ferroelectric property and negative capacitance effect during program and erase states.The ferroelectric memory using CMOS-compatible hafniumoxide-based materials [1][2][3][4][5][6][7][8][9][10] is the potential candidate among emerging memories because of its fast switching speed, long endurance and low voltage operation. Recently, the ferroelectric transistor also has made significant progress due to negative capacitance effect. [11,12] The negative capacitance effect in ferroelectric dielectrics has been proposed, [11][12][13][14][15][16][17] but experimental observation based on ferroelectric characteristics and physical mechanism model is less revealed in ferroelectric transistor memory device. Our previous study reported a versatile ferroelectric memory, [18][19][20] which is a promising candidate for next-generation dynamic random access memory (DRAM) or nonvolatile memory (NVM). To improve the stability of ferroelectric polarization, we choose a top charge-trapped zirconium-silicon oxide (ZrSiO) because of its large band gap to strengthen the spontaneous polarization of hafniumzirconium oxide (HfZrO) during memory switching operation. According to previous study on polarization degradation, the migration of charged oxygen vacancies through electric field is key factor in polarization fatigue, especially for those along the polarization axis. [4][5][6] Thus, oxygen vacancy may impact fast ferroelecrtric switching. To prevent this issue, we adopt a chargetrapping approach forming the interface aligned dipoles between top ZrSiO trapping layer and bottom HfZrO ferroelectric layer to reduce the migration effect of charged oxygen vacancies. [18] After a series of trials, we successfully demonstrated that the memory property of ferroelectric memory can be effectively improved by the combined storage mechanism of charge-trapping and ferroelectric domain. In this work, we further investigated ferroelectric negative capacitance behavior and underlying physical mechanism of ferroelectric versatile memory, which is very important for energyefficient switching of next-generation memory technology.Experiments: The fabrication procedure of memory device is simply described as follows. First, a 3.6-nm SiO 2 grown by dry oxidation process of vertical furnace was used as a bottombuffered oxide. Then the 21-nm-thick HZO ferroelectric layer and 7.5-nm-thick ZSO trapping layer were deposited by a evaporation and a sputter system, respectively. To make a performance comparison, a control ferr...

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

“…This novel ferroelectric material with a preferred orthorhombic phase exhibits a good ferroelectric property at a 10‐nm thickness . As reported in previous studies, the phase transformation from paraelectric monoclinic phase to ferroelectric orthorhombic phase can be modulated by different kinds of dopants, such as Si, Al, and Zr . It is worth mentioning that the Zr‐doped HfO 2 (Hf 1−x Zr x O 2 ) material attracts much attention due to its broad tunability of dopant concentration.…”

“…[7,8] As reported in previous studies, the phase transformation from paraelectric monoclinic phase to ferroelectric orthorhombic phase can be modulated by different kinds of dopants, such as Si, [8] Al, [9,10] and Zr. [11][12][13][14][15][16][17][18][19][20] It is worth mentioning that the Zr-doped HfO 2 (Hf 1Àx Zr x O 2 ) material attracts much attention due to its broad tunability of dopant concentration. However, the Zr diffusion issue [18] possibly causes the deterioration of interface layer and an unwanted leakage current, which gives rise to the instability of negative capacitance and poor transistor performance.…”

Gamma‐Ray Irradiation Effect on Ferroelectric Devices with Hafnium Aluminum Oxides

“…[3] Subsequently, many experimental studies for ferroelectric devices using HfO 2 -based materials were proposed and evaluated. [4][5][6][7][8][9][10][11][12][13] However, the irradiation effect on electrical properties of HfO 2 -based ferroelectric film was still less discussed. Although Y-doped HfO 2 -based FeRAM with high immunity from gamma-ray radiation has been reported, [14] there are less studies on complementary metal-oxide-semiconductor (CMOS)-processfriendly dopant such as Al and Si until now.…”

“…In 2011, ferroelectric memory with Si‐doped HfO 2 has been demonstrated using 28 nm high‐k/metal‐gate (HK/MG) approach . Subsequently, many experimental studies for ferroelectric devices using HfO 2 ‐based materials were proposed and evaluated . However, the irradiation effect on electrical properties of HfO 2 ‐based ferroelectric film was still less discussed.…”

Improved Negative‐Capacitance Switch of Ferroelectric Field Effect Transistor Using Defect Passivation Engineering

“…Recently, the ferroelectric FETs with negative capacitance (NC) effect have attracted considerable attention as possible alternatives for the present CMOS techniques due to the steep turn‐on property featuring a sub‐60 mV dec −1 subthreshold swing (SS) operated at a low supply voltage. Furthermore, the advanced NC FETs with various HfO 2 ‐based ferroelectric materials have been reported for the applications of ultralow‐power logic and memory devices. Unfortunately, the NC effect could be significantly influenced with further thickness scaling of ferroelectric layer due to unstable polarization domain switching and interface depolarization field .…”