Abstract
The HfO2-based ferroelectric field effect transistor (FeFET) with a metal/ferroelectric/insulator/semiconductor (MFIS) gate stack is currently being considered as a possible candidate for high-density and fast write speed non-volatile memory. Although the retention performance of the HfO2-based FeFET with a MFIS gate stack could satisfy the requirements for practical applications, its memory window (MW) and reliability with respect to endurance should be further improved. This work investigates the advantage of employing ZrO2 seed layers on the MW, retention, and endurance of the Hf0.5Zr0.5O2 (HZO)-based FeFETs with MFIS gate stacks, by using fast voltage pulse measurements. It is found that the HZO-based FeFET with a ZrO2 seed layer shows a larger initial and 10-year extrapolated MW, as well as improved endurance performance compared with the HZO-based FeFET without the ZrO2 seed layer. The results indicate that employing of a direct crystalline high-k/Si gate stack would further improve the MW and reliability of the HfO2-based FeFETs.
Highlights
HfO2-based ferroelectric thin films are considered as promising gate-stack materials for ferroelectric field effect transistors (FeFETs) because of their complementary metal-oxide-semiconductor (CMOS) compatibility and scalability
One can see that the Drain current (ID)–Gate voltage (VG) curves of both FeFETs show counterclockwise switching characteristics, suggesting that the memory window (MW) of the present FeFETs are originated from the polarization switching of the HZO layers, rather than the charge trapping and injection
The MWs as well as the reliability with respect to retention and endurance of the HZO-based FeFETs with the TaN/ HZO/SiO2/Si and TaN/HZO/ZrO2/SiO2/Si metal/ferroelectric/ insulator/semiconductor (MFIS) gate stacks were characterized by fast voltage pulse measurements
Summary
HfO2-based ferroelectric thin films are considered as promising gate-stack materials for ferroelectric field effect transistors (FeFETs) because of their complementary metal-oxide-semiconductor (CMOS) compatibility and scalability. High-density and fast write speed FeFETs with MFIS gate stack structures have been successfully fabricated using HKMG processes [9, 10]. In addition to the high integration density and fast write speed, a large memory window (MW) and a high reliability with respect to retention and endurance are critical for employing FeFETs for nonvolatile memory applications [11,12,13,14]. HfO2-based ferroelectric thin films, HfO2-based FeFETs with MFIS gate stack structures exhibit reliable retention properties (10-year extrapolation) [15,16,17]. Employing of high-k insulator layers is expected to
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