Plasma-Assisted Atomic Layer Deposition of PtOx from (MeCp)PtMe3 and O2 Plasma†

Atomic layer deposition (ALD) using (MeCp)PtMe₃ and O₂ gas or O₂ plasma is a well-established technique for the deposition of thin films of Pt, but the potential of ALD to deposit platinum oxide (PtO_x) has not yet been systematically explored. This work demonstrates how PtO_x can be deposited by plasma-assisted (PA)-ALD in a temperature window from room temperature (RT) to 300 °C by controlling the O₂ plasma and (MeCp)PtMe₃ exposure. With increasing substrate temperature, the thermal stability of PtO_x decreases and the reducing activity of the precursor ligands increases. Therefore, longer O₂ plasma exposures and/or lower (MeCp)PtMe₃ exposures are required to obtain PtO_x at higher temperatures. Furthermore, it is established that, during the nucleation stage, PtO_x ALD starts by the formation of islands that grow and coalesce during the initial ∼40 cycles. Closed-layer thin films of PtO_x with an O/Pt ratio of 2.5 can be deposited at 100 °C with a minimal thickness of only ∼2 nm. It is also demonstrated that a conformality of ∼90% can be reached for PtO_x films in trenches with an aspect ratio of 9 when using optimized O₂ plasma and precursor exposure times.