RESUMO
Hafnium oxide (HfOx) films have a wide range of applications in solid-state devices, including metal-oxide-semiconductor field-effect transistors (MOSFETs). The growth of HfOx films from the metal precursor tetrakis(ethylmethylamino) hafnium with La(NO3)3·6H2O solution (LNS) as an oxidant was investigated. The atomic layer deposition (ALD) conditions were optimized, and the chemical state, surface morphology, and microstructure of the prepared films were characterized. Furthermore, to better understand the effects of LNS on the deposition process, HfOx films deposited using a conventional oxidant (H2O) were also prepared. The ALD process using LNS was observed to be self-limiting, with an ALD temperature window of 200-350 °C and a growth rate of 1.6 Å per cycle, two times faster than that with H2O. HfOx films deposited using the LNS oxidant had smaller crystallites than those deposited using H2O, as well as more suboxides or defects because of the higher number of grain boundaries. In addition, there was a difference in the preferred orientations of the HfOx films deposited using LNS and H2O, and consequently, a difference in surface energy. Finally, a film growth model based on the surface energy difference was proposed to explain the observed growth rate and crystallite size trends.
RESUMO
Resistive switching characteristics of insulating Y2O3 films grown by an atomic layer deposition technique have been investigated with their growth temperature range of 250 °C to 350 °C. Ru/Y2O3/Ru resistors reveal the bi-stable unipolar resistive switching behaviors. Resistive switching behaviors are related to the chemical bonding states of Y2O3 insulating films. As the insulating film growth temperature increases, Y2O3 film becomes much stoichiometric and little contaminated with impurities. Moreover, the resistance ratio high resistance state to low resistance state increases at growth temperature over 300 °C.
