Heteroleptic Cyclopentadienyl-Amidinate Precursors for Atomic Layer Deposition (ALD) of Y, Pr, Gd, and Dy Oxide Thin Films

Thin films of rare-earth (RE) oxides (Y 2 O 3, PrO x, Gd 2 O 3, and Dy 2 O 3 ) were deposited by atomic layer deposition from liquid heteroleptic RE( i PrCp) 2 ( i Pr-amd) precursors with either water or ozone as the oxygen source. Film thickness, crystallinity, morphology, and composition were studied. Saturation was achieved with Gd 2 O 3 when O 3 was used as the oxygen source at 225 °C and with Y 2 O 3 with both oxygen sources at as high temperature as 350 °C. The growth rates were 0.90–1.3 Å/cycle for these processes. PrO x was challenging to deposit with both oxygen sources but with long, 20 s purges after the water pulses uniform films could be deposited. However, saturation was not achieved. With Dy 2 O 3, uniform films could be deposited and the Dy( i PrCp) 2 ( i Pr-amd)/O 3 process was close to saturation at 300 °C. The different oxygen sources had an effect on the crystallinity and impurity contents of the films in all the studied processes. Whether ozone or water was better choice for oxygen source depended on the metal oxide material that was deposited.