Ferroelectric switching kinetics of the Al-doped HfO2 (Al:HfO2) thin films prepared by the atomic layer deposition process were investigated by varying the dose time of oxygen precursor (O3). When the O3 dose time was reduced to 3 s, the Al:HfO2 films exhibited an enhanced remnant polarization (2Pr) of 10.2 μC/cm2 due to the suppression of the monoclinic phase and the increase in the ratio of oxygen vacancy. Double-pulse switching and the Kolmogorov–Avrami–Ishibashi model were used to obtain detailed quantitative information on the switching kinetics of the Al:HfO2 films. The estimated values of switching time and activation energy showed the strong dependence of O3 dose. This suggests that the O3 dose condition can be a key control parameter to modulate the ferroelectric polarization switching dynamics of the Al:HfO2 thin films.

We fabricated the charge-trap memory thin film transistors (CTM-TFTs) using InGaZnO (IGZO) active channel and HfO 2 /ZnO stack-structured charge-trap layer (CTL). To investigate the effects of the number and thickness of HfO 2 layers inserted between the ZnO within the stack structured CTLs on the device characteristics, 2-nm-thick HfO 2 thin films were inlaid once, twice, and four times, and 4-nm-thick HfO 2 layers were introduced twice between the ZnO layers. The CTM-TFTs using the stack structured CTLs with 4-nm-thick HfO 2 layers showed good memory characteristics, including large memory window (MW) of 25 V and rapid program/erase (P/E) speed of 500 μs because of high total trap density of HfO 2 with a sufficient thickness to provide charge-trap centers. On the contrary, relatively narrow MW of 16 V and slower P/E speed of 100 ms were obtained for memory device using the stacked CTL with four HfO 2 layers of 2 nm. The HfO 2 layer with a thickness as thin as 2 nm was supposed to act as just dielectric films deactivating the trapping or migration of electron charges due to too thin film thickness. The gate-stack structures confirmed from STEM images suggested that the modulations in memory device characteristics with different CTL structures resulted from the variations in designs of stack structured CTLs when the interface qualities within the gate-stacks were well prepared. Moreover, the detailed fabrication conditions were found to be important control parameters to reproducibly obtain reliable memory device characteristics.INDEX TERMS High-k material, HfO 2 , ZnO, ALD, IGZO charge-trap memory. SO-YEONG NA was born in South Korea in 1995. She received the B.S. degree from the

The effects of atomic layer deposition (ALD) conditions for the HfO2 gate insulators (GI) on the device characteristics of the InGaZnO (IGZO) thin film transistors (TFTs) were investigated when the ALD temperature and Hf precursor purge time were varied to 200, 225, and 250 °C, and 15 and 30 s, respectively. The HfO2 thin films showed low leakage current density of 10−8 A cm−2, high dielectric constant of over 20, and smooth surface roughness at all ALD conditions. The IGZO TFTs using the HfO2 GIs showed good device characteristics such as a saturation mobility as high as 11 cm2 V−1 s−1, a subthreshold swing as low as 0.10 V/dec, and all the devices could be operated at a gate voltage as low as  ±3 V. While there were no marked differences in transfer characteristics and PBS stabilities among the fabricated devices, the NBIS instabilities could be improved by increasing the ALD temperature for the formation of HfO2 GIs by reducing the oxygen vacancies within the IGZO channel.

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Metal–ferroelectric–metal–insulator–semiconductor (MFMIS) capacitors using Al-doped HfO2 (Al:HfO2) ferroelectrics were proposed and the effects of O3 doses were investigated. The memory window (MW) increased with increasing the areal ratios of the MIS to the MFM (SI/SF) and the largest MW was obtained at the largest SI/SF for both devices prepared with O3 doses of 3 and 5 s. Contrarily, the retention of the device prepared with O3 dose of 3 s could be improved compared with the device prepared with longer O3 doses. Thus, the SI/SF and O3 doses could be suggested as critical control parameters for the Al:HfO2 MFMIS capacitors.