Ferroelectric properties of full plasma-enhanced ALD TiN/La:HfO_2/TiN stacks

摘要

We report the possibility of employment of low temperature (≤330℃) plasma-enhanced atomic layer deposition for the formation of both electrodes and hafnium-oxide based ferroelectric in the metal-insulator-metal structures. The structural and ferroelectric properties of La doped HfO_2-based layers and its evolution with the change of both La content (2.1, 3.7 and 5.8 at. %) and the temperature of the rapid thermal processing (550-750 ℃) were investigated in detail. Ferroelectric properties emerged only for 2.1 and 3.7 at. % of La due to the structural changes caused by the given doping levels. Ferroelectric properties were also found to depend strongly on annealing temperature, with the most robust ferroelectric response for lowest La concentration and intermediate 650 ℃ annealing temperature. The long term wake-up effect and such promising endurance characteristics as 3 × 10~8 switches by bipolar voltage cycles with 30 μs duration and ± 3 MV/cm amplitude without any decrease of remnant polarization value were demonstrated.