Synthesis and characterization of DyScO films deposited on Si and Si-rich SiN by atomic layer deposition for blocking layer replacement in TANOS stack

In the view of improving standard TANOS stacks, a possible route is the replacement of Al 2 O 3 blocking oxide with materials with higher dielectric constant κ, as this would increase the electric field across the tunnel oxide. A possible solution is to integrate rare earth scandates. Among the scandates, DyScO 3 appears as an attractive material due to the reported high- κ value. Films with 10-30 nm nominal thickness were grown by atomic layer deposition (ALD) on Si substrates for process optimization and structural characterization. Sc (thd) 3 and Dy (thd) 3 were used as Sc and Dy precursors and O 3 as oxidizing agent. First, Sc 2 O 3 and Dy 2 O 3 growth process was optimized by changing growth temperature (T g ) and ALD cycle. The best conditions for the deposition of the ternary DyScO films were found to be T g =350 °C and Dy:Sc=1:1 pulsing ratio. Optimized films were also grown on Si-rich SiN for integration as blocking oxide. After deposition, films were subjected to rapid thermal annealing up to 1030 °C to check their thermal stability. Film thickness was checked by x-ray reflectivity, together with roughness and electron density. Film crystallinity was investigated by grazing incidence x-ray diffraction. Film uniformity and thermal stability were explored by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles. Dielectric constant κ was extracted from capacitance-voltage (C-V) electrical measurements. As deposited amorphous DyScO films on silicon remain amorphous after annealing up to 900 °C. Film electron density reduces while thickness increases with annealing, surface roughness remaining at ∼1.5 nm. The measured Sc:Dy atomic ratio by total x-ray fluorescence analyses is 1.33 in the as deposited film. ToF-SIMS depth profiles showed that film uniformity and composition is not preserved at 900 °C, in films deposited on Si, as major Si diffusion affects the ternary oxide. Only at 600 °C the diffusion phenomena and film composition are preserved. The extracted DyScO dielectric constant is κ∼20 in films annealed at 600 °C on Si. When deposited on Si-rich SiN, DyScO uniformity remains well preserved up to 900 °C, with an improvement of the thermal stability with respect to deposition on Si. Si diffusion is evident at 1030 °C only. The κ -value extracted from C-V resulted to be κ∼20