In situ Reaction Mechanism Studies on Atomic Layer Deposition of Ir and IrO₂ from Ir(acac)₃

Reaction mechanisms in three atomic layer deposition (ALD) processes using Ir(acac) 3 as a precursor were studied: Ir(acac) 3 –O 2 process at 300 °C for Ir deposition, Ir(acac) 3 –O 3 process at 195 °C for IrO 2 deposition, and Ir(acac) 3 –O 3 –H 2 process at 195 °C for Ir deposition. Reactions were studied in situ with a quadrupole mass spectrometer (QMS) and a quartz crystal microbalance (QCM). The byproducts in all processes were CO 2 and H 2 O. Only in the Ir(acac) 3 –O 2 process these were partially released during the Ir(acac) 3 pulse (14% of CO 2 and 57% of H 2 O as compared to a complete ALD cycle). To explain this, some oxygen atoms were concluded to chemisorb on the surface during the O 2 pulse. In the other two processes, the adsorption of Ir(acac) 3 appeared to be molecular on a plain surface of the film material.