Paper TF-TuA2
Reactive Intermediates during Atomic Layer Deposition of Aluminum Oxide from Ozone and an Oxygen Plasma

Tuesday, October 19, 2010, 2:20 pm, Room Ruidoso

In this presentation, the authors will elucidate the surface reaction mechanisms during the atomic layer deposition (ALD) of aluminum oxide from trimethyl aluminum (TMA) in conjunction with O₃ and an O₂ plasma. The deposition mechanism was explored over a substrate temperature range of 70–200 °C using in situ attenuated total reflection Fourier transform infrared spectroscopy. Our IR data show that both –OH groups and carbonates are formed on the surface during the oxidation cycle. Gas-phase IR data indicate that oxidizer-assisted combustion of methyl ligands in chemisorbed TMA produces CO₂ and H₂O, which react simultaneously on the Al₂O₃ surface to produce carbonates. The origin of the –OH groups was attributed to the reaction of the uncombusted methyl ligands with gas-phase H₂O. While the type of surface sites are common to both oxidizing agents, in the case of O₂-plasma-assiated ALD, surface carbonates are simply reactive intermediates, which completely decompose upon prolonged plasma exposure. The ratio of carbonates to –OH groups is strongly dependent on the oxidizing agent, and its dose in case of plasma-assisted ALD. Surface reactions such as chemisoption of TMA, formation of –OH groups and Al₂O₃ were pseudo first order. On the other hand, the kinetic behavior of the carbonates suggests a series reaction of the type, A (CH₃) → B (carbonates) → C (Al₂O₃). Although carbonate sites contribute to Al₂O₃ growth, their contribution was determined to be insignificant.