Improvement in nonvolatile memory operations for metal–ferroelectric–insulator–semiconductor capacitors using HfZrO 2 and ZrO 2 thin films as ferroelectric and insulator layers

Metal–ferroelectric–insulator–semiconductor (MFIS) capacitors were characterized to elucidate the optimum design schemes for the ferroelectric field-effect transistor applications. The Hf 1− x Zr x O 2 (HZO) thin films (18 nm) were prepared on the SiO 2 and ZrO 2 insulator layers (ILs) with different film thicknesses. The choice of 10 nm thick ZrO 2 IL was found to be an optimum condition to properly balance between the values of electric fields applied to the HZO ( E HZO ) and ZrO 2 ( E IL ) layers, leading to effective improvement in capacitance coupling ratio and to suppression of charge injection for the MFIS capacitors. Furthermore, the crystalline natures of the crystallized HZO films were also found to be strategically controlled on the ZrO 2 ILs, which can additionally enhance the E HZO with reducing the E IL . As consequences, the MFIS capacitors using 10 nm thick ZrO 2 IL exhibited the ferroelectric memory window as large as 2.5 V at an application of ±5 V, which corresponds to 2.7 times wider value, compared to that obtained from the device using 2 nm thick SiO 2 IL. Long-time memory retention and robust program endurance were also verified for the fabricated MFIS capacitors.