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A Study on the Temperature-Dependent Operation of Fluorite-Structure-Based Ferroelectric HfO2 Memory FeFET: Pyroelectricity and Reliability

: Ali, T.; Kühnel, K.; Czernohorsky, M.; Mart, C.; Rudolph, M.; Pätzold, B.; Lehninger, D.; Olivo, R.; Lederer, M.; Müller, F.; Hoffmann, R.; Metzger, J.; Binder, R.; Steinke, P.; Kämpfe, T.; Müller, J.; Seidel, K.; Eng, L.M.


IEEE transactions on electron devices 67 (2020), Nr.7, S.2981-2987
ISSN: 0018-9383
ISSN: 1557-9646
Fraunhofer IPMS ()

We report on the high-temperature operation and reliability of the Si-doped hafnium oxide (HSO) ferroelectric FET (FeFET) emerging memory. In this study, we explore the role of high-temperature operation of the ferroelectric (FE) material on the FeFET in the temperature range of 40-120 °C. The inverse memory window (MW) dependence on temperature leads to a very small MW size (~300 mV) at 120 °C. The recovery of MW size at room temperature (RT) indicates a potential pyroelectric effect as a cause for MW closure upon high-temperature operation. The FeFET state readout shows pronounced effects to erase (ER) threshold voltage (Vth) shift, due to the decrease in remnant polarization and improved substrate Vth shift as the temperature increases. The endurance reliability measured for temperature range (-40 °C to 40 °C) with 105 cycles shows a maximized initial MW at low temperatures, whereas higher postcycling interface trap generation occurs as the temperature increases. The FeFET 10 h retention tests at 0 °C and 40 °C were extrapolated to ten years and indicated stable properties independent of temperature. The depolarization field (Ed) dependence on the FeFET stack parameters is studied based on an analytical formula. The Ed decreases with increased permittivity of the FE, interface layer (IL), and increased FE film thickness. Substrate doping and temperature seem to have a small impact on E d , whereas the FE-IL area ratio tuning below unity lowers the E d . The role of pyroelectric effect on the FeFET memory and operating temperature-induced endurance and retention reliability concerns are discussed.