Impact of Ferroelectric Layer Thickness on Reliability of Back‐End‐of‐Line‐Compatible Hafnium Zirconium Oxide Films

Abstract

Due to its ferroelectricity, hafnium oxide has attracted a lot of attention for ferroelectric memory devices. Amongst different dopant elements, zirconium is found to be beneficial due to the relatively low crystallization temperature of hafnium‐zirconium‐oxide (HZO), thus it is back‐end‐of‐line (BEoL) compatible. The thickness of HZO has a significant impact on ferroelectric device reliability. High operation temperatures and high endurance are important criteria depending on the application. Herein, various HZO thicknesses (7, 8, and 10 nm) in MFM (metal‐ferroelectric‐metal) capacitors are investigated at varying operation temperatures (25 to 175 °C) at varying electric fields (±3 to ±5.4 MV cm−1) with respect to polarization, leakage current, endurance, and retention. 7 nm HZO showed promising results with an endurance of 107 cycles, with a low leakage current density, and almost no retention loss after 10 years. Extrapolated results at operation conditions (±2 MV cm−1 and 10 MHz) showed an endurance of 1010 cycles.

A Study on Imprint Behavior of Ferroelectric Hafnium Oxide Caused by High‐Temperature Annealing

“…While breakdown occurs after around 2 Â 10 6 cycles at nonannealed samples, it occurs after around 10 5 cycles after annealing at 200 °C for 12 h. Therefore, it is seen that higher temperatures of annealing result in earlier breakdowns, as the high temperatures cause an acceleration of defect movement, consequently resulting in earlier breakdowns. [18] In addition to the breakdown behavior, loss in polarization can be observed which is in good agreement with the polarization loops in Figure 3.…”

“…This is mostly driven due to the increased generation and/or movements of defects in the FE material at higher temperatures. [18,32]…”

“…Stabilization of this phase can be achieved by doping with various dopants such as Si, [ 11 ] Zr, [ 12 ] and Al. [ 13 ] Zr doping has been found favorable due to back‐end‐of‐line (BEoL) compatible crystallization temperatures (≈400 °C) [ 9,14–18 ] and therefore hafnium–zirconium–oxide (HZO) films are investigated in this work here.…”

Ferroelectric Enhancement in a TiN/Hf1–xZrxO2/W Device with Controlled Oxidation of the Bottom Electrode

“…An IL breakdown can result in a shift in the electric field, concentrated solely on the HZO layer. This abrupt shift in material behavior can lead to a rapid increase in polarization, accompanied by a notable surge in current leakage and elevated temperatures . The minimal wake-up effect observed at the WO x interface greatly enhanced polarization stability, which helped to maintain current leakage within acceptable thresholds.…”

Integration of ferroelectric devices for advanced in-memory computing concepts

“…Common strategies involve exploring various dopant elements, 4,5) concentrations, 6) and film thicknesses. 7,8) Several device implementation options of the FE-memory material can be considered, such as ferroelectric FET (FeFET) 9,10) or ferroelectric random access memory (FRAM). 11) In case of FeFET, the FE-material is integrated in Front-End of Line (FEOL) process module directly in the Gate-stack of a transistor with the advantage of direct field effect of the FE material and therefore no destructive read operation.…”